Effects of ultrasonic pretreatment on drying characteristics and water migration characteristics of freeze-dried strawberry

The effects of ultrasonic pretreatment on the drying characteristics and microstructure of strawberry slices were investigated. The rehydration characteristics of freeze-dried products, which were pre-frozen at -20 °C and - 80 °C were explored, with a focus on water mobility and distribution. The ultrasonic pretreatment significantly increased the water mobility of the strawberry slices, resulting in a reduction in their water content. However, the application of ultrasound significantly decreased the rehydration speed, indicating a lower moisture absorption capacity in the pretreated sample. The micrographs revealed that the structure of the tissue was more uniform after ultrasonic treatment, and water loss was accelerated. In addition, the contact angle measurements showed that the samples were more hydrophobic after ultrasonic treatment, and the eutectic temperature and fold point of the samples increased. Therefore, this study found that ultrasonic-assisted freeze vacuum drying technology effectively reduces hygroscopicity, improves product storage, and represents a potential method for dried production.

Dynamic Study on Water State and Water Migration during Gluten-Starch Model Dough Development under Different Gluten Protein Contents

Mixing is crucial for dough quality. The gluten content influences water migration in dough development and properties, leading to quality changes in dough-based products. Understanding how the gluten protein content influences water migration during dough development is necessary for dough processing. A compound flour with different gluten protein contents (GPCs, 10-26%, w/w) was used to study the dough farinograph parameters and water migration during dough development. According to the farinograph test of the gluten-starch model dough, the GPC increases the water absorption and the strength of the dough. Water migration was determined via low-field nuclear magnetic resonance (LF-NMR). With the increase in GPC, the gluten protein increases the binding ability of strongly bound water and promotes the transformation of weakly bound water. However, inappropriate GPC (10% and 26%, w/w) results in the release of free water, which is caused by damage to the gluten network according to the microstructure result. Moreover, the changes in proteins' secondary structures are related to the migration of weakly bound water. Therefore, weakly bound water plays an important role in dough development. Overall, these results provide a theoretical basis for the optimization of dough processing.

Dynamic changes in the water and volatile compounds of chicken breast during the frying process

The influence of frying times (0, 2, 4, 6, 8, and 10 min) on the continuous changes in the water distribution and the concentrations of key volatile compounds in chicken breast during the frying process were studied. The fried chicken samples could be distinguished by PCA of E-nose and PLS-DA of GC-MS. A total of 40 volatile compounds were identified by GC-MS, and 28 compounds were verified to be the key compounds after further screening by OAVs. The T22 was increased first and then decreased, while the M22 and M23 in fried chicken were considerably decreased and increased with increasing frying time, respectively. The content of the water and the total peak area of LF-NMR in fried chicken samples during the frying process significantly decreased, and the water was transferred from high to low degrees of freedom. In addition, water content, T21, T22, M22 and L* value were positively correlated with most alcohols and aldehydes, and were negatively correlated with pyrazines, while a*, b*, M23 and all amino acids were positively correlated with pyrazines and were negatively correlated with most alcohols and aldehydes. The results may guide the production processes of fried chicken and help produce high-quality chicken products.

Dynamic changes in the water distribution and key aroma compounds of roasted chicken during roasting

The effects of roasting times (0, 2, 4, 6, 8, 10, 12, and 14 min) on the dynamic changes of the water distribution and key aroma compounds in roasted chicken during the electric roasting process were studied. In total, 36 volatile compounds were further determined by GC-MS and 11 compounds, including 1-octen-3-ol, 1-heptanol, hexanal, decanal, (E)-2-octenal, acetic acid hexyl ester, nonanal, 2-pentylfuran, heptanal, (E, E)-2,4-decadienal and octanal, were confirmed as key aroma compounds. The relaxation time of T22 and T23 was increased first and then decreased, while the M22 and M23 in roasted chicken were decreased and increased with increasing roasting time, respectively. The fluidity of the water in the chicken during the roasting process was decreased, and the water with a high degree of freedom migrated to the water with a low degree of freedom. In addition, the L*, a*, b*, M23 and all amino acids were positively correlated with all the key aroma compounds, while T22, M22 and moisture content were negatively correlated with all the key aroma compounds.

Evolution of lean meat tenderness stimulated by coordinated variation of water status, protein structure and tissue histology during cooking of braised pork

Tenderness of lean meat in braised pork is of great importance to the consumer palatability and acceptance. The influence of water status, protein structure and histological changes on lean meat tenderness during cooking was investigated. Results indicated that lean meat began to tenderize mainly after 20 min-cooking. In the early period of cooking, the decrease of total sulfhydryl content caused the protein oxidative cross-linking, leading to the gradual unfolding of the protein structure, thus resulting in a decrease of T₂₂ and an increase of centrifugal loss, which decreased the tenderness of lean meat. However, after cooking for 20 min, the β-sheet decreased and random coil increased, thus generating conversion between P₂₁ and P₂₂. The rupture of perimysium structure was observed. Changes in protein structure, water status, and tissue histology could facilitate the initiation and development of lean meat tenderness.

Effect of coagulation temperature on cooking integrity of heat and acid-induced milk gels

Heat and acid-induced milk gels do not melt or flow upon heating and thus show great potential as a dairy-based protein source for cooking, e.g. for stews. Understanding how processing, e.g. acidification, affects the cooking behavior of these gels is therefore of great industrial interest. The cooking integrity of gels produced by rapidly acidifying milk using citric acid at temperatures of 60, 75, and 90 °C, was determined by analyzing composition, texture, and spatial water distribution before and after cooking. Increasing the acidification temperature from 60 to75 °C resulted in a significant reduction of yield, due to decreased moisture content of the gels. With increasing content of solids, the gels grew harder and denser, as observed by texture profile analysis and low-field Nuclear Magnetic Resonance. Upon cooking the 60 °C gel lost a significant amount of moisture, due to the contraction of the porous protein network. The more compact gels, prepared at 75 and 90 °C, did not lose mass indicating good cooking integrity, i.e. a gel that keeps its structure during cooking. Acidification temperature thus greatly influenced cooking integrity. The effect was mainly ascribed to the density of the gel texture, a result of the speed of protein aggregation and calcium recovery.

Structural Characterization of Several Cement-Based Materials Containing Chemical Additives with Potential Application in Additive Manufacturing

The rapid increase in additive manufacturing applications in all industries has highlighted the lack of innovative technologies and processes in the construction industry. Several European and international policies are in place to guide the development of the technological processes involved in the construction industry toward a sustainable future. Considering the global concerns regarding this industry, the purpose of this study was to develop new cement-based materials that are capable of accelerated hydration and early strength development for use in additive manufacturing. Ca(NO₃)₂·4H₂O, Al₂(SO₄)₃·18H₂O and Na₂S₂O₃·5H₂O were used to obtain the accelerating effect in the hydration of Portland cement. Based on results obtained from X-ray diffraction (XRD), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX) techniques, as well as low-field nuclear magnetic resonance relaxometry (LF-NMR) techniques, it was demonstrated that all accelerators used have a quickening effect on cement hydration. The addition of Na₂S₂O₃·5H₂O or combined Na₂S₂O₃·5H₂O and Ca(NO₃)₂·4H₂O led to obtaining new cement-based materials with early strength development and fast hydration of microorganized internal structures, critical characteristics for 3D printing.

Effect of Oudemansiella raphanipies Powder on Physicochemical and Textural Properties, Water Distribution and Protein Conformation of Lower-Fat Pork Meat Batter

The effects of the addition of different amounts (0%, 1%, 2%, 3% and 4%) of Oudemansiella raphanipies powder (ORP) to lower-fat pork batter on its physicochemical, textural and rheological properties, water distribution and protein conformation were evaluated. The results showed that the addition of ORP from 0% to 4% significantly decreased the pH and L* value of pork batter (p < 0.05); however, it also increased the a* value and enhanced the cooking yield of pork batter from 77% to 92%. Pork batter with 1−2% ORP added had an improved texture profile and a higher storage modulus (G’), but the addition of 3−4% ORP resulted in an inferior texture of pork batter and G’. LF-NMR showed that the addition of ORP significantly increased the peak area ratio of immobile water and reduced the peak area ratio of free water (p < 0.05). ORP significantly affected protein secondary structure of pork batter. The α-helix content of pork batter with 1−2% ORP decreased and β-sheet content increased. Overall, the addition level of 1−2% ORP effectively improved the texture and water holding capacity of lower-fat emulsified sausage and provides a new reference for developing nutritional meat products.

[Mechanism of moistening process of Rehmanniae Radix based on kinetic process]

The moistening process of Rehmanniae Radix was characterized quantitatively by moisture phase, texture properties, and component content based on water absorption kinetics and expansion kinetics. Non-linear fitting of water absorption kinetics and expansion kinetics in the moistening process of Rehmanniae Radix was carried out. Low-field nuclear magnetic resonance and imaging(LF-NMR/MRI) technology was used to investigate the phase state and distribution changes of water during the moistening process. The Texture Analyzer was used for the determination of texture properties. The correlations between water absorption rate, expansion rate, water phase state, hardness, and compression cycle work of Rehmanniae Radix at different moistening time were analyzed. The results showed that the water absorption kinetics and expansion kinetics of Rehmanniae Radix were in accordance with the first-order kinetics. Moreover, the water absorption rate and expansion rate increased with the increase in temperature but decreased with the increase in the size of the medicinal materials.In the moistening process, the moisture was transferred from the outside to the inside, and the proportion of the moisture phase changed significantly.Within 16 hours, free water increased from 0.825% to 97.7%,while bound water decreased from 99.2% to 2.33%.Within 28 hours, the texture properties, such as hardness and compression cycle work, decreased gradually with the prolongation in moistening time.At 32 hours, water was evenly distributed throughout the whole medicinal material, and the texture properties also tended to be stable.Pearson correlation bivariate analysis showed that moistening time, water absorption rate, expansion rate, the relative content of free water and bound water, hardness, and compression cycle work were significantly correlated, suggesting that water absorption kinetics and expansion kinetics, LF-NMR/MRI,and Texture Analyzer could directly and quantitatively characterize the moistening process.This study is expected to provide a scientific basis for clarifying the scientific connotation of the moistening process of Rehmanniae Radix.

Influence of ultrasonic pretreatments on microwave hot-air flow rolling drying mechanism, thermal characteristics and rehydration dynamics of Pleurotus eryngii

BACKGROUND

In order to improve the drying efficiency and reduce the drying energy consumption of Pleurotus eryngii, microwave hot-air flow rolling drying (MHARD) coupled with ultrasonic pretreating time (0, 20, 40, and 60 min) was used to investigate the drying profile, thermal characteristics, water migration, microstructure and rehydration dynamics of P. eryngii using differential scanning calorimetry (DSC), low-field nuclear magnetic resonance (LF-NMR) analysis and scanning electron microscopy (SEM).

RESULTS

Results showed that the drying time of P. eryngii was 80, 70, 60 and 50 min, accordingly. Energy consumption was significantly reduced by ultrasonic pretreatment, and moisture effective diffusivity (D_eff ) was increased with the increase of ultrasonic pretreating time. DSC curves showed that the drying process was accelerated by ultrasonic pretreatment significantly by enhancing the heat transfer. Meanwhile, SEM images showed that the cell was broken and numbers of irregular holes appeared in the ultrasound-pretreated samples. In terms of rehydration dynamics, Page model could well model the rehydration kinetics of dried P. eryngii with R²  > 0.99.

CONCLUSION

The findings indicate that ultrasonic pretreatment is a promising method for MHARD of P. eryngii as it can enhance the drying process, and show potential for industrial application. © 2021 Society of Chemical Industry.

Effects of different modified starches and gums on the physicochemical, functional, and microstructural properties of tapioca pearls

The effects of different modified starch and gums on the physicochemical, functional, and microstructural properties of tapioca pearls were investigated. The addition of starch acetate (SA) and carboxymethylcellulose (CMC) improved the springiness, hardness, cooking properties, and overall acceptability of pearls. Samples added with CMC presented higher peak viscosities, breakdown viscosities, onset gelatinization temperature, and lower enthalpy of gelatinization values compared to control pearls. Furthermore, Rheology and LF-NMR results indicated that all five kinds of modifiers promoted the formation of tighter network structures in products. SEM showed that the addition of SA and hydroxypropyl distarch phosphate (HDP) could fill the voids in the internal gel network of the pearls, thus promoting the formation of a continuous phase network. This study proved SA, HDP, and CMC as modifiers could have tremendous potential to improve the quality of pearls before and after cooking.

Polysaccharide-based hydrogels crosslink density equation: A rheological and LF-NMR study of polymer-polymer interactions

A simple relation between pendant groups of polymers in hydrogels is introduced to determine the crosslink density of (complex) hydrogel systems (mixtures of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) modified nanocellulose, alginate, scleroglucan and Laponite in addition of crosslinking agents). Furthermore, the rheological properties and their great potential connection to design complex hydrogel systems with desired properties have been thoroughly investigated. Hydrogel structures governing internal friction and flow resistance were described by the predominant effect of ionic, hydrogen, and electrostatic interactions. The relationship between rheological properties and polymer-polymer interactions in the hydrogel network is explained and expressed in a new mathematical model for determining the crosslink density of (crosslinked) hydrogels based on single or mixture of polymer systems. In the end, the combined used of rheology and low field nuclear magnetic resonance spectroscopy (LF-NMR) for the characterization of hydrogel networks is developed.

The Process of Pasting and Gelling Modified Potato Starch with LF-NMR

Currently, society expects convenience food, which is healthy, safe, and easy to prepare and eat in all conditions. On account of the increasing popularity of modified potato starch in food industry and its increasing scope of use, this study focused on improving the physical modification of native starch with temperature changes. As a result, it was found that the suggested method of starch modification with the use of microwave power of 150 W/h had an impact on the change in starch granules. The LF-NMR method determined the whole range of temperatures in which the creation of a starch polymer network occurs. Therefore, the applied LF-NMR technique is a highly promising, noninvasive physical method, which allows obtaining a better-quality structure of potato starch gels.

LF-NMR as a tool for predicting the 3D printability of surimi-starch systems

In this study, surimi from golden pompanos was mixed with starch to form a surimi-starch system. The water properties, rheological properties, and three-dimensional (3D) printability of the surimi-starch were measured. Cluster analysis results showed that the 3D printability was closely related to the type and addition content of starch, and the water and rheological properties. The low-field nuclear magnetic resonance (LF-NMR) parameters were used to predict 3D printability using polynomial regression models. The correlation coefficients (R²) for 3D printing accuracy and stability were 0.88 and 0.93, and the root mean square error (RMSE) values were 0.20% and 4.59%, respectively. In the verification test, the R² for the two models were 0.85 and 0.89, and the RMSE values were 0.20% and 1.06%, respectively. The nonlinear surface regression fitting exhibited superior predictive performance. Therefore, LF-NMR is a good non-destructive tool for quickly and accurately predicting the 3D printability of the surimi-starch systems.

Effects of ultrasound pretreatment on the drying kinetics, water status and distribution in scallop adductors during heat pump drying

BACKGROUND

A material's physical and chemical properties during drying are influenced by water status and distribution. However, merely overall water removal is reported in many investigations, which hinders clarification of the drying mechanism. Therefore, the effects of ultrasound (US) pretreatment (0 W, CK; 90 W, US-90; 180 W, US-180) on the drying kinetics and quality of heat pump drying (HPD) scallop adductors was performed based on low-field nuclear magnetic resonance (LF-NMR).

RESULTS

Compared with CK, effective moisture diffusion coefficient was increased by 12.43% and 23.35% for US-90 and US-180, respectively. The Weibull model satisfactorily described the drying characteristics with a high r² (> 0.998), low rmse (< 0.0120) and χ² (< 0.00008). LF-NMR revealed that the immobilized water was predominant in scallop adductors. As drying proceeded, the relaxation time of free and immobilized water was decreased sharply, whereas the relaxation time of bound water scarcely changed. The time required to reduce approximately two-fifths of the original peak area of immobilized water was 720, 630 and 540 min for CK, US-90 and US-180, respectively. The amplitude of immobilized water was decreased and bound water increased significantly, although free water was kept constant (ranging 1-2%). US pretreatment reduced total color difference and hardness, but enhanced the toughness of dried scallop adductors. However, US had no significant influence on the product rehydration rate and shrinkage rate.

CONCLUSION

LF-NMR was successfully employed to evaluate the drying degree of scallop adductors. US facilitated the conversion of immobilized water to free water and, consequently, promoted water removal during HPD. © 2021 Society of Chemical Industry.

Moisture variation analysis of the green plum during the drying process based on low-field nuclear magnetic resonance

Green plums were dried at 50, 60, 70, and 80 ℃ to study the dynamic changes of internal moisture during the drying process. Low-field nuclear magnetic resonance (LF-NMR) was used to study the dynamic changes across the T₂ relaxation spectrum, while magnetic resonance imaging (MRI) provided visualization of the plums throughout the process. The results indicate a negative linear relationship between the lost moisture of the plums (p < 0.05) as drying time increased. Relaxation times T₂₁ , T_22, and T₂₃ , and the peak areas of A₂₁ and A₂₃ decreased significantly during the drying process. The MRI results also show that the brightness of the images decreased as the drying time increased, indicating that the higher the temperature, the greater the water loss inside the plums. Color measurements demonstrated that the high temperature dried plums had better sensory quality. Correlation analysis implies a strong positive relationship between A₂₃ and A_total and water content, with coefficients of 0.958 and 0.936, respectively. Principal component analysis results show that the drying temperature has a significant effect on the sample's internal moisture release. LF-NMR is a fast, convenient, and feasible technique for monitoring the moisture variation of green plums during the drying process. PRACTICAL APPLICATION: Low-field nuclear magnetic resonance (LF-NMR) was used to study the moisture dynamic changes of green plums across the T₂ relaxation spectrum, while magnetic resonance imaging (MRI) provided visualization of plums throughout the process. The drying temperature has a significant effect on the green plum's internal moisture release and may affect the quality of the plums. LF-NMR might be a complementary technique in monitoring the moisture variation of green plums during the drying process.

Effect of Structurally Different Pectin on Dough Rheology, Structure, Pasting and Water Distribution Properties of Partially Meat-Based Sugar Snap Cookies

Pectin has been widely used as a hydrocolloid in foods, but its effectiveness based on hydrodynamics radius (Rh), average side chain length (ACL) and degree of esterification (DE) has been less studied. This study investigated the effect of 4 types of pectin (with different molecular weight and structures) at a level of 1.5% w/w of wheat flour on functional, structural and water binding properties of sugar snap cookies partially substituted with fish meat. The results showed that pectin (CU-201 and CU-601) with higher ACL and Rh controlled excessive expansion, while the improved rheology of dough in terms of behavior as viscous matrix compared to control and other pectin. Texture was found to be highly dependent on Rh and ACL compared to DE of pectin. The pasting properties, especially peak viscosity and final viscosity, were significantly (p < 0.05) increased with increasing DE, as well as ACL, by entangling and increasing the interaction between starch and pectin. The scanning electron microscopy (SEM) analysis exhibited that control sample showed wide voids and more intercellular spaces, while samples prepared with CU-601, CU-201, and CUL displayed compact structure, which was also evidenced by controlled expansion and improved hardness of the cookies. Low field nuclear magnetic resonance (LF-NMR) analysis showed that T21 relaxation time and amplitude were found to be shorter for CU-601 and CU-201 treatments, signifying the high amount of tightly bound water compared to control. The findings endorse the feasibility of adding CU-601, and CU-201 as an efficient hydrocolloid for the improved structural and functional properties of cookies.

Effect of Different Processing Methods on Quality, Structure, Oxidative Properties and Water Distribution Properties of Fish Meat-Based Snacks

Snack foods are consumed around to globe due to their high nutrition, taste and versatility; however, the effects of various processing methods on quality, structure and oxidative properties are scare in the literature. This study aims to evaluate the effect of various processing methods (frying, baking and microwave cooking) on quality, structure, pasting, water distribution and protein oxidative properties of fish meat-based snacks. The results showed that the frying method induced a significantly (p < 0.05) higher expansion than baking and microwave methods. Texture in terms of hardness was attributed to the rapid loss of water from muscle fiber, which resulted in compact structure and the increased hardness in microwave cooking, whereas in frying, due to excessive expansion, the hardness decreased. The pasting properties were significantly higher in baking, indicating the sufficient swelling of starch granules, while low in microwave suggest the rapid heating, which degraded the starch molecules and disruption of hydrogen bonds as well as glycosidic linkage and weakening of granules integrity. The water movement assessed by Low Field Nuclear Magnetic Resonance (LF-NMR) showed that frying had less tight and immobilized water, whereas microwave and baking had high amounts of tight and immobilized water, attributing to the proper starch-protein interaction within matrix, which was also evidenced by scanning electron microscopy (SEM) analysis. The protein oxidation was significantly (p < 0.05) higher in frying compared to baking and microwave cooking. The findings suggest the endorsement of baking and microwave cooking for a quality, safe and healthy snacks.

Early-Age Hydration Reaction and Strength Formation Mechanism of Solid Waste Silica Fume Modified Concrete

Solid waste silica fume was used to replace fly ash by different ratios to study the early-age hydration reaction and strength formation mechanism of concrete. The change pattern of moisture content in different phases and micro morphological characteristics of concrete at early age were analyzed by low field nuclear magnetic resonance (LF-NMR) and scanning electron microscope (SEM). The results showed that the compressive strength of concrete was enhanced optimally when the replacement ratio of solid waste silica fume was 50%. The results of LF-NMR analysis showed that the water content of modified concrete increased with the increase of solid waste silica fume content. The compressive strength of concrete grew faster within the curing age of 7 d, which means the hydration process of concrete was also faster. The micro morphological characteristics obtained by SEM revealed that the concrete was densest internally when 50% fly ash was replaced by the solid waste silica fume, which was better than the other contents.

Effect of pre-frying on distribution of protons and physicochemical qualities of mackerel

BACKGROUND

In this work, low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging were used to investigate the changes in protons (from water and oil) distribution of mackerel during the frying process. The relationship between proton migration and some physicochemical indexes was established by partial least squares regression (PLSR). The changing mechanism of the quality characteristics and physicochemical properties of fish meat under different frying conditions was analysed by LF-NMR combined with PLSR, which provided theoretical support for the development of canned mackerel food.

RESULTS

LF-NMR results showed that three kinds of T₂ protons assigned to protein-water interaction (T₂₁ ), multilayer bound water (T₂₂ ), oil and free water (T₂₃ ), respectively. As the frying temperature increased, protons from the T₂₂ peak significantly decreased, while protons from the T₂₃ peak remarkably increased. The microstructure of fried mackerel was destroyed; cooking loss, oil content, a* value, b* value, hardness and chewiness increased; and the protein content and L* value decreased. Furthermore, PLSR analysis revealed that significant correlation was observed between the cooking loss, TPA parameter (chewiness), colour parameter (L*) and LF-NMR parameters.

CONCLUSION

Different frying temperatures and times had a strong effect on the physicochemical properties of mackerel. Good prediction models could be established by proton migration using the LF-NMR technique and PLSR for fried mackerel. Quality control of fried fish could be realized by monitoring the change in LF-NMR data. © 2021 Society of Chemical Industry.

Loss of immobilized water and intense protein aggregation responsible for quality deterioration of ready to eat firm tofu

The influence of high-temperature treatment (100-120°C, 15 min) on the texture, color, and water-holding capacity of tofu gels was investigated. As the temperature increasing, the hardness and chewiness as well as the values of redness a and yellowness b increased gradually, while the water content and the lightness L value reduced progressively, and these variations were more pronounced at 115 or 120°C. Low field nuclear magnetic resonance showed that the loss of T₂₂ water led to the decrease of the water content. Scanning electron microscope revealed that the micropore in gels decreased after heating, and almost entirely disappeared at 120°C. Further analysis by SDS-PAGE indicated the soy protein aggregation formed via disulfide linkage was observed in the thermal treated tofu gels, and nondisulfide linkage might also be occurred as temperature reached 110°C or higher. The quality deterioration may be attributed to immobilized water loss combined with the protein aggregation.

Rapid screening for hazelnut oil and high-oleic sunflower oil in extra virgin olive oil using low-field nuclear magnetic resonance relaxometry and machine learning

BACKGROUND

As extra virgin olive oil (EVOO) has high commercial value, it is routinely adulterated with other oils. The present study investigated the feasibility of rapidly identifying adulterated EVOO using low-field nuclear magnetic resonance (LF-NMR) relaxometry and machine learning approaches (decision tree, K-nearest neighbor, linear discriminant analysis, support vector machines and convolutional neural network (CNN)).

RESULTS

LF-NMR spectroscopy effectively distinguished pure EVOO from that which was adulterated with hazelnut oil (HO) and high-oleic sunflower oil (HOSO). The applied CNN algorithm had an accuracy of 89.29%, a precision of 81.25% and a recall of 81.25%, and enabled the rapid (2 min) discrimination of pure EVOO that was adulterated with HO and HOSO in the volumetric ratio range of 10-100%.

CONCLUSIONS

LF-NMR coupled with the CNN algorithm is a viable candidate for rapid EVOO authentication. © 2020 Society of Chemical Industry.

Simultaneous, Rapid and Nondestructive Determination of Moisture, Fat Content and Storage Time in Leisure Dried Tofu Using LF-NMR

Leisure dried tofu is a kind of small packaged food which is popular with consumers in China. However, during the storage of leisure dried tofu, moisture and fat may be lost and deteriorate. For their own benefit, bad business operators might forge or mark the production date and shelf life. Therefore, it is necessary to explore a method to determine simultaneously the moisture, fat content, and storage time of leisure dried tofu. Samples were measured for obtaining transverse relaxation data by using low-field nuclear magnetic resonance (LF-NMR) spectrometer. The experimental data were analyzed and modeled by methods including partial least squares (PLS) or back-propagation artificial neural network (BP-ANN). The results show that the models can be used to predict the moisture, fat content, and storage time rapidly, nondestructively, accurately, and simultaneously. Furthermore, in order to explore the changes of nutrients in leisure dried tofu with the storage time, the storage dynamics of moisture and fat was considered by a using corresponding calibration model.

Quality Differences between Fresh and Dried Buckwheat Noodles Associated with Water Status and Inner Structure

Buckwheat noodles are mainly sold in the form of fresh and dried noodles in China. Among the noodles with varied proportions of extruded buckwheat flour (20% to 80%), the cooking or textural qualities of fresh and dried buckwheat noodles (FBN and DBN, respectively) were significantly different, and FBN showed a lower cooking loss and breakage ratio and were more elastic than DBN. FBN-20% showed the highest sensory score, followed by DBN-50%. The mechanisms causing the quality differences were investigated using water mobility and the internal structures of the noodles were investigated with low-field nuclear magnetic resonance and scanning electron microscopy, respectively. Compared with FBN, DBN showed a denser internal structure, which explained its higher hardness. The water within FBN and DBN was mainly in the form of softly bound water and tightly bound water, respectively. FBN with highly mobile softly bound water (longer T 22) and a more uniform internal structure had a lower breakage ratio, whereas the trends of water relation with texture properties were different for FBN and DBN. The drying process and added extruded buckwheat flour together contributed to the varied cooking and textural properties.

Beneficial effects of Jerusalem artichoke powder and olive oil as animal fat replacers and natural healthy compound sources in Harbin dry sausages

This study aimed to improve the nutritional quality of Harbin dry sausages using natural plant-based Jerusalem artichoke powder (JAP) and olive oil as animal fat replacers. Low-fat Harbin dry sausages were manufactured with 2 different formulations containing JAP and olive oil as pork fat replacers. The texture, rheological properties, microstructure, water holding capacity, muscle protein structure, physicochemical indices, microbiological characteristics, and sensory evaluation of the sausages were analyzed. The result showed that Harbin dry sausages with JAP and olive oil were healthier than control sausages based on the lower fat content and improved fatty acid composition. Scanning electron microscopy showed gel network formation in sausages with a high JAP content. Low-field nuclear magnetic resonance illustrated that the water-holding capacity of the modified sausages was improved, suggesting that the replacers enhanced protein gel formation by changes in C-H stretching and bending vibrations, a reduction in α-helixes, and increases in β-sheets and random coils accompanying the exposure of reactive groups and microenvironment of the tertiary structure. Dynamic rheological and texture tests indicated that the replacers improved the elasticity of sausages. The reduction of fat and addition of replacers significantly enhanced lipid oxidative resistance. Overall, JAP and olive oil improved the fatty acid composition, gel structure, lipid oxidative resistance, and sensory quality of the sausages. These results may contribute to the development of healthy meat products to further reduce animal fat.

[Correlation between water state and texture during moistening of Paeoniae Radix Alba by LF-NMR/MRI]

The changes of active ingredients content, moisture status and texture characteristics during the moistening of Paeoniae Radix Alba were studied by low-field NMR and imaging(LF-NMR/MRI) and texture analyzer, so as to analyze the correlation between LF-NMR parameters, texture characteristics and active ingredient content of Paeoniae Radix Alba during the moistening at diffe-rent times. The results showed that MRI technology could directly, vividly and accurately characterize the degree of moistening and the process of water migration, and the degree of moistening was consistent with the judgment results of traditional experience. The characteristics of moisture migration and moisture phase state in the moistening process of Paeoniae Radix Alba were that the total water content increased and existed in the form of free water, with an increased moisture mobility. In the case of dampening, the total water content did not increase, but the more watery part of the medicinal material was distributed to the less watery part, with a reduced fluidity. Finally, the medicinal materials were moistened, which can be mutually verified with the MRI results. The free water content and the total water content of Paeoniae Radix Alba had extremely negative correlations with hardness, surface toughness, internal toughness, Paeoniflorin and albiflorin contents(P&lt;0.01). It showed that the use of LF-NMR/MRI and texture analyzer could better characterize the moistening process. It provides data characterization for the scientific connotation of &quot;less soaking and more moisturizing, and the drug is completely saturated with water&quot;, and the traditional experience of &quot;observing the water head&quot;. The feasible and objective evaluation method was helpful to optimize the softening process parameters, scientifically standardize the operating specifications, define the scienti-fic connotation of traditional Chinese medicine softening, and promote the inheritance and innovation of traditional Chinese medicine processing.

Investigation on Spontaneous Shape Change of 4D Printed Starch-Based Purees from Purple Sweet Potatoes As Induced by Microwave Dehydration

The time evolution of three-dimensional (3D) printed food structures as affected by their composition and postprinting stimulus is an area of research that has recently received increasing attention. In this study, the spontaneous shape change of 3D printed purple sweet potato purees of different formulations as triggered by microwave dehydration was investigated. The rheological properties, water distribution behavior, and dielectric properties of the purees were first studied. Addition of salt reduced the viscosity, storage modulus, loss modulus, and yield stress but increased the relaxation time of the purees. Addition of fructose syrup resulted in opposite results. Addition of both salt and syrup decreased the dielectric constant but increased the dielectric loss of the purees. Increased microwave power and salt content increased the rates of dehydration and deformation but decreased the maximum deformation degree of the printed samples. The syrup also decreased the maximum deformation degree. A desirable deformation pattern could also be achieved by manipulating the infill parameters. Transformation of two-dimensional planar flowers and butterflies into 3D configurations as a result of varying the aforementioned parameters is illustrated. The proposed technique to induce spontaneous shape change of a 3D printed starch-based product should lay a foundation for further application of four-dimensional food printing.

The effect of fatty acid composition on the oil absorption behavior and surface morphology of fried potato sticks via LF-NMR, MRI, and SEM

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Oils’ fatty acid composition affects the oil absorption behavior of fried food.

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Oil content and distribution of samples are analyzed by LF-NMR and MRI.

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Oil content is positively correlated to peak height in the range of 20 ms–1000 ms.

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Viscosity of oils is positively correlated to total oil content of fried samples.

The oil absorption behavior of food during deep-frying greatly affects the quality of the final fried food. However, the research on oil absorption lacks comprehensive analysis and understanding. In this paper, the oil content, moisture content, oil distribution, and microstructure changes of fried potato sticks were explored via traditional method as well as advanced instruments, including low field nuclear magnetic resonance, magnetic resonance imaging, and scanning electron microscopy, and the differences and their corresponding relevance were analyzed and discussed. Results showed that the fatty acid composition of oils is highly related to their viscosity and surface tension, influencing the oil uptake of final products. Oil content was positively correlated with the peak height in the range of 20 ms–1000 ms (r² = 0.99348 at 140 ℃, r² = 0.99060 at 180 ℃). Oil distribution and microscopic morphology of the fried strips were affected by oil type and temperature.

Curing Behaviors of Alkynyl-Terminated Copolyether with Glycidyl Azide Polymer in Energetic Plasticizers

Alkynyl-terminated polyethylene oxide−tetrahydrofuran (ATPET) and glycidyl azide polymer (GAP) could be linked through click-chemistry between the alkynyl and azide, and the product may serve a binder for solid propellants. The effects of the energetic plasticizers A3 [1:1 mixture of bis-(2,2-dinitropropy) acetal (BDNPA) and bis-(2,2-dinitropropyl) formal(BDNPN)] and Bu-NENA [N-butyl-N-(2nitroxyethyl) nitramine] on the curing reaction between ATPET and GAP have been studied. A diffusion-ordered nuclear magnetic resonance spectroscopy (DOSY-NMR) approach has been used to monitor the change in the diffusion coefficient of cross-linked polytriazole polyethylene oxide−tetrahydrofuran (PTPET). The change in the diffusion coefficient of PTPET with A3 plasticizer is significantly higher than that of PTPET with Bu-NENA. Viscosity analysis further highlighted the difference between A3 and Bu-NENA in the curing process—the curing curve of PTPET (A3) with time can be divided into two stages, with an inflection point being observed on the fourth day. For PTPET (Bu-NENA), in contrast, only one stage is seen. The above methods, together with gel permeation chromatography (GPC) analysis, revealed distinct effects of A3 and Bu-NENA on the curing process of PTPET. X-ray Photoelectron Spectroscopy (XPS) analysis showed that Bu-NENA has little effect on the valence oxidation of copper in the catalyst. Thermogravimetric (TG) analysis indicated that Bu-NENA helps to improve the thermal stability of the catalyst. After analysis of several possible factors by means of XPS, modeling with Material Studio and TG, the formation of molecular cages between Bu-NENA and copper is considered to be the reason for the above differences. In this article, GAP (Mn = 4000 g/mol) was used to replace GAP (Mn = 427 g/mol) to successfully synthesize the PTPET elastomer with Bu-NENA plasticizer. Mechanical data measured for the PTPET (Bu-NENA) sample included ε = 34.26 ± 2.98%, and σ = 0.198 ± 0.015 MPa.

A low-field nuclear magnetic resonance DNA-hydrogel nanoprobe for bisphenol A determination in drinking water

A low-field nuclear magnetic resonance (LF-NMR) DNA-hydrogel (LNDH) nanoprobe was designed for bisphenol A (BPA) determination. It consists of Fe₃O₄ superparamagnetic iron oxide nanoparticles (SPIONs) and a DNA-hydrogel technology. Fe₃O₄ SPIONs were encapsulated in the DNA-hydrogel to form an aggregated state. After adding BPA, the gel system transformed into a sol gel due to the target-aptamer specific binding. The coated gathered particles dispersed and thus, the relaxation time T₂ declined. The LNDH nanoprobe was developed to realize a simple, sensitive, and effective BPA determination method without repeated magnetic separation steps. Under the optimal experimental conditions, the determination range of the LNDH biosensor was 10^-2~10² ng mL^-1 and the limit of determination was 0.07 ng mL^-1. The LNDH nanoprobe was applied to two kinds of water samples (tap water and bottled water). The recovery ranged from 87.85 to approximately 97.87%. This strategy offered a new method to detect BPA by LF-NMR. It is also expected to be applicable in related fields of food safety determination, environmental monitoring, and clinical diagnosis. Graphical abstract Schematic presentation of LNDH biosensor. Acrydite-modified ssDNA was copolymerized with acrylamide to form linear conjugates PS-A/B, adding aptamer and SPIONs to form DNA-hydrogel. When aptamer captured the target, the hydrogel was destroyed to disperse the coated SPIONs. T₂ relaxation time declined.

High pressure-assisted vacuum-freeze drying: A novel, efficient way to accelerate moisture migration in shrimp processing

High pressure processing (HPP), as nonthermal processing technology, has the potential to increase the drying rate due to its improvement of heat and mass exchange in different processes. In this study, the moisture migration in shrimps during HPP-vacuum-freeze drying (HPP-VFD) processes has been monitored by using low-field nuclear magnetic resonance and magnetic resonance image (MRI) in comparison with hot air-drying and VFD. Based on the T₂ relaxation spectra, three water fractions corresponding to bound water (hydrogen-bonded water), immobile water (water trapped by organization structure or cell member), and free water were observed. For group B, with increasing drying time (4 to 22 hr), the transverse relaxation times of T₂₁ , T₂₂ , and T₂₃ were significantly decreased (76.79%, 57.78%, and 40.9%) (P < 0.05). The content of immobile water (A₂₂ ) and free water (A₂₃ ) decreased (81.55% and 89.07%), whereas the bound water (A₂₁ ) increased (7.26%). In comparison with group B, the T₂₁ , T₂₂ , and T₂₃ of group C showed greater decrease (83.12%, 87.12%, and 89.57% for group C) so that HPP pretreatment could shorten the relaxation time. MRI analysis further proved that HPP-VFD drying has improved drying efficiency, and moisture migration was from the exterior to the interior part with increasing drying time. SEM analysis demonstrated that no significant damage of muscle fibers with narrower gaps was observed for groups B and C. Overall, HPP, as a pretreatment technology, could accelerate the moisture migration and improve the drying efficiency of VFD process for shrimp. PRACTICAL APPLICATION: High pressure processing (HPP) is now well known as a nonthermal processing technology and becoming increasingly acknowledged. However, there is limited information about its application in shrimp-drying process and the moisture dynamic of shrimp subjected to high pressure processing-assisted vacuum-freeze drying. This study could provide valuable information regarding the moisture status and migration in HPP-VFD shrimp monitored by LF-NMR and MRI methods. The results showed that HPP processing at 550 MPa for 10 min can be used as an interesting method for drying pretreatment, increasing its drying rate and consequently reducing its process time, and it demonstrated that the methods used in this study had good correlation coefficient with physicochemical properties of shrimp, which may be real-time and nondestructive monitoring methods for shrimp-drying process.

On-line monitoring of the sol-gel transition temperature of thermosensitive chitosan/β-glycerophosphate hydrogels by low field NMR

A temperature controlled low field nuclear magnetic resonance (LF-NMR) T₂ relaxometry technique based on the mobility changes of water trapped in hydrogels, was successfully used for on-line determination of the sol-gel transition temperature for chitosan/β-glycerophosphate (CS/GP) hydrogels in real time. The LF-NMR results indicated that the gelation temperature decreased gradually with increasing GP concentration, and the results were supported by both thermogravimetric differential scanning calorimetry (DSC) and rheological findings; however, LF-NMR allows non-destructive monitoring of samples during continuous heating. Moreover, as the mobility of water molecules varies greatly during the sol-gel phase transition, the LF-NMR measurement was more sensitive and accurate (RSD ≤ 0.1 %, n = 5) compared with DSC (RSD: 1.2 %-3.7 %, n = 5) and rheology (RSD: 1.1 %-2.3 %, n = 5).

Assessment of Water Mobility in Surf Clam and Soy Protein System during Gelation Using LF-NMR Technique

Water mobility and distribution of a dual-protein system of surf clam myofibrillar protein (MP) and soy protein (SP) was investigated by the nondestructive low field nuclear magnetic resonance (LF-NMR) technique. Four proton populations were found in the contour plots of T₂ relaxation times for the SP-MP system. The first component, (T₂₁), was assigned to the highly integrated water located in protein macromolecules with a relaxation time of approximately 1.15 ms. The second signal, T₂₂, with a relaxation time of 2.20 to 38.00 ms was regarded as the inter-myofibrillar water trapped in organized protein structures. The third component, T₂₃, with a relaxation time of around 100 ms was ascribed to the extra-myofibrillar water. With an increase in temperature, T₂₄ appeared which was assigned to the free water within the extra-myofibrillar space. The gelation behavior occurred at 70, 62, and 52 °C as the proportion of SP/MP was 4:6, 2:8, and 0:10, respectively. The principal component analysis (PCA) and heatmap of LF-NMR data analysis showed potential for distinguishing the different dual-protein systems formed at various temperatures. The analysis of storage modulus G′, loss modulus G″, and tanδ confirmed the change trend of the LF-NMR results. The measurements of cooking loss, water holding capability, and gel strength further revealed that the SP and MP were likely to form a gel network with an increase of additional clam protein. The hydrophobicity analysis showed, for the systems with the SP/MP proportions of 4:6, 2:8, and 0:10, more hydrophobic groups were exposed when the temperature was over 50 °C. Scanning electron microscopy showed that the number of the micropores increased with an addition of MP in the dual-protein system of SP/MP. All the results demonstrated that LF-NMR has great potential for characterizing the gelation process of a dual-protein system.

Optimization of Total Polar Compounds Quantification in Frying Oils by Low-field Nuclear Magnetic Resonance

To improve the accuracy of total polar compounds (TPC) quantification in frying oils by low-field nuclear magnetic resonance (LF-NMR), an optimized statistical method was proposed. The method uses a specially designed sequence to detect the NMR signal in frying oils, and establishes the TPC prediction model by partial least squares (PLS) regression on relaxation properties extracted from the NMR signal. Compared with inversion recovery (IR) and Carr-Purcell-Meiboom-Gill (CPMG) sequences, the designed sequence provides more relaxation information. The experimental result shows that the proposed method is more accurate than reported methods that are based on longitudinal and transverse relaxation times in the TPC quantification of frying oils.

Nitroso-hemoglobin Increased the Color Stability and Inhibited the Pathogenic Bacteria in a Minced Beef Model: A Combined Low-field NMR Study

This study mainly investigated the improvement effect of nitroso-hemoglobin (NO-Hb) and four lactic acid bacteria (LAB) (Streptococcus thermophiles, Lactobacillus bulgaricus, Lactobacillus casei, and Montessori enterococcus) on the color and microbiological qualities of raw beef. Three strains of Escherichia coli, Staphylococcus, Salmonella, and Pseudomonas were used as pathogenic bacteria. The results showed that both NO-Hb and LAB could enhance the color stability and scavenged the spoilage bacteria in a minced beef model. But the improvement effect of NO-Hb was more significant than LAB. This suggested that NO-Hb, as a novel ingredient, could be used as a promising substitute for nitrite in meat products to improve the color and safety of meat products. In addition, low field (LF)-NMR method has been established to be practicable to identify changes in the relaxation times of water and fat caused by different type of bacteria and the storage periods. The number of relaxation components in minced beef was affected by bacteria and increase of the storage period.

Characterizing the sludge moisture distribution during anaerobic digestion process through various approaches

Exploring moisture distribution plays an important role in improving sludge dewatering. However, the moisture content usually varies based on the measurements, and a comparison of various measurement methods for the same sample during the anaerobic digestion (AD) process is lacking. In this study, the moisture distributions of two types of sludge samples with different digestion times during the AD process are characterized by four methods (i.e., thermal drying, thermal gravimetric analyzer (TGA), thermogravimetry differential scanning calorimetry (TG/DSC), low field ¹H nuclear magnetic resonance (LF-NMR)). The advantages and disadvantages of each test method are evaluated and discussed. It is found that, compared with the other three methods, LF-NMR has the advantages of high recovery rate and coincidence degree between total moisture content (TMC) and moisture content measurements. In addition, the moisture content in various occurrence states is compared. Experimental results show that the content of free moisture increases, while that of bound moisture decreases during the AD process, suggesting that bound moisture is converted into free moisture, which improves the sludge dewaterability. However, these findings can provide an important reference for characterizing the sludge moisture distribution and identifying the effect of the AD process on sludge dewatering.

Vesicle formation by ultrashort alkyl-phosphonic acids and serine in aqueous solutions

Vesicles possess unique biofilm structures and offer biomimetic advantages for drug and gene delivery. Herein, we report the spontaneous vesicle formation from ultrashort alkyl-phosphonic acids in the presence of amino acids. The aggregation characteristics and self-assembly structures of vesicles in aqueous solution were investigated by using dynamic light scattering, zeta potential, and cryo-transmission electron microscopy. We combined low-field nuclear magnetic resonance and Fourier transform infrared spectroscopy to study the H-proton-induced multilamellar vesicle formation. When we increased the molar fraction of serine, stable and closed spherical vesicles were formed at relatively low critical micelle concentrations. This transition of the self-assembled structure indicates that vesicle formation occurs when the chain length and the magnitude of the surface charge cause a fluctuation in the volume of the vesicle. Density functional theory reveals the critical role of the mixed alkyl-phosphonic acid/amino acid-enhanced electrostatic attraction between the head groups and hydrogen bonds associated with the aggregated states.

Comparison of dynamic water distribution and microstructure formation of shiitake mushrooms during hot air and far infrared radiation drying by low-field nuclear magnetic resonance and scanning electron microscopy

BACKGROUND

An abundance of shiitake mushrooms is consumed in dried form around the world. In the present study, changes in water state, water distribution and microstructure of shiitake mushrooms during hot-air drying (HAD) and far-infrared radiation drying (FIRD) processes were investigated using low-field nuclear magnetic resonance and scanning electron microscopy. Quality attributes of the dried products were compared in terms of drying property, appearance, rehydration behavior, texture and storage stability.

RESULTS

Compared with HAD, the rate of water diffusion and evaporation of the shiitake mushrooms dried by FIRD was higher, thus resulting in a shorter drying time (630 min), a lower water content (0.07 g g^-1 wet basis) and a higher glass transition temperature (7.88 °C) for dried products. Moreover, a homogenous and porous microstructure with less shrinkage and case hardening was demonstrated by the FIRD samples, indicating a superior texture, including a larger pileus diameter (3.4 cm), a higher rehydration ratio (7.31), a lower hardness (37.93 N) and a higher crispness (1.41 mm) for FIRD shiitake mushrooms.

CONCLUSION

High-quality shiitake mushrooms with a desirable texture could be produced by FIRD by enhancing the diffusion of internal water and alleviating the case hardening during a relatively short drying process. © 2018 Society of Chemical Industry.

Structure-property of crosslinked chitosan/silica composite films modified by genipin and glutaraldehyde under alkaline conditions

In this study, genipin and glutaraldehyde in varied concentrations were utilized in chitosan crosslinking under alkaline condition. A UV/Vis analysis was used to investigate the molecular structure of genipin and glutaraldehyde in an aqueous alkaline solution. The results showed the formation of glutaraldehyde dimer and polymerized genipin. The FTIR-ATR, SEM, DSC, XRD, mechanical properties, crosslinking degree and swelling ratio of chitosan based films crosslinked by genipin and glutaraldehyde were determined. The results indicated that the hydrogen bonds formed between genipin and chitosan enabled the films crosslinked by genipin (1 and 5 mmol/L) to have a higher degree of crosslinking, but a lower swelling ratio than glutaraldehyde (1 and 5 mmol/L). Genipin enabled the chitosan-based film to possess better mechanical properties and crystallinity than glutaraldehyde. The polymerization of genipin had a substantial effect on the network structure and swelling behavior of chitosan-based films crosslinked by genipin.

UV-B mediates isoflavone accumulation and oxidative-antioxidant system responses in germinating soybean

This study investigated the relationships among UV-B radiation dose, isoflavone monomers and the oxidative-antioxidant system in germinating soybean. Results showed that the isoflavone monomers content showed a good fit to the quadratic model with UV-B radiation dose, except for aglycones. UV-B decreased phenylalanine content and up-regulated the key enzymes activities in isoflavone biosynthesis. H2O2, electrolyte leakage, malondialdehyde, T22 and M22 were increased, while T23 and M23 decreased. Microscopic analysis showed excess UV-B radiation resulted in the reduced cell volume, irregular cell shape, and increased cell space. The antioxidant enzymes activities were enhanced by UV-B. These results demonstrated that UV-B could trigger the formation of H2O2, resulting in the oxidative stress. Thus, the antioxidant system, including the enzymatic (enhanced the antioxidant enzymes activities) and nonenzymatic (accumulated isoflavones) were activated to minimize oxidative damage. This study provides theoretical basis for enhancing isoflavone monomer accumulation in plant-source foods by UV-B.

Rapid Assessment of Deep Frying Oil Quality as Well as Water and Fat Contents in French Fries by Low-Field Nuclear Magnetic Resonance

Most of the health hazards in fried foods are related to unqualified frying oil and excessive oil content. In this study, the feasibility of using low-field nuclear magnetic resonance techniques (LF-NMR) for analysis of the water and oil contents in French fries, as well as simultaneous evaluation of frying oil quality during deep frying, was investigated. Three proton populations were identified and successfully assigned to water and oil relaxation signals. Significant correlation between the T₂ relaxation parameters ( A_water and RC_oil) and the water and oil content was acquired. MRI could visualize the changes of signal intensity and spatial distribution, as well as the internal structural changes during frying. Using the correlation model built by multiple regression analysis, the total polar compounds content of the frying oil could be successfully predicted by LF-NMR relaxation characteristics, which indicates that LF-NMR was an effective method to monitor the quality of frying oil.

Effect of fermentation on water mobility and distribution in fermented cornmeal using LF-NMR and its correlation with substrate

Cordyceps militaris (C. militaris) was utilized to ferment cornmeal by solid state fermentation. The main objective of this study was to investigate effect of fermentation on the dynamic state of water and microstructure distribution of water within cornmeal with Low-field nuclear magnetic resonance, as well as the effect on composition and microstructure properties. The spin-spin relaxation time (T₂) showed significant changes in solid-state fermented cornmeal. Principal component analysis further revealed that the variations within different fermentation stage could be discriminated by the T₂ parameters. Bulk water (T₂₂) was the main form of water present and lost in substrates. The weights of different indicators, as assessed by multiple regression analysis, demonstrated that there was a strong correlation between starch and T₂ relaxation. Scanning electron microscopy demonstrated that fermentation can cause the appearance of micropores. The longer relaxation time of T₂₂ during logarithmic period can be interpreted as a loosening of the structure at the starch hydrolysis, introducing more water into the structure. Thus, the differences in composition and structure of the substrate at different fermentation time produce different T₂ values.

Evaluation of a Nondestructive NMR and MRI Method for Monitoring the Drying Process of Gastrodia elata Blume

Gastrodia elata Blume (G. elata) is a prominent traditional herb and its dry tuber is officially listed in the Chinese Pharmacopoeia. To ensure the quality of dried G. elata, the establishment of a nondestructive and convenient method to monitor the drying process is necessary. In this study, a nondestructive low-field nuclear magnetic resonance (LF-NMR) and magnetic resonance imaging (MRI) method was introduced to monitor the drying process of G. elata. Three water states (bound, immobilized, and free) in G. elata samples were investigated through multiexponential fitting and inversion of the NMR data. The variation and distribution of the three water states during drying were monitored by LF-NMR, and the spatial distribution of water and internal structural changes were analyzed by MRI. Linear analysis of the moisture content, L* (lightness), b* (yellowness), and NMR parameters showed good correlations among them. Furthermore, partial least squares regression (PLSR) model analysis, which takes into account all NMR parameters, also showed good correlations among these parameters. All results showed that LF-NMR was feasible and convenient for monitoring moisture content. Therefore, LF-NMR and MRI could be used to monitor the moisture content nondestructively in the drying process of Chinese traditional herbs.

Characterization and Mechanisms of Novel Emulsions and Nanoemulsion Gels Stabilized by Edible Cyclodextrin-Based Metal-Organic Frameworks and Glycyrrhizic Acid

In this study, a novel emulsion stabilized by nano-cyclodextrin-based metal-organic frameworks and glycyrrhizic acid (CD-MOF/GA) was successfully fabricated, exhibiting long-term storage stability. The characterization and mechanisms for the emulsion formation with CD-MOF/GA were studied. The phase change of the emulsions from sol to gel could be controlled using different oil fractions and mass ratios of CD-MOF and GA. The rheological results showed that the emulsions were transformed from liquid emulsions to emulsion gels when the oil fractions were higher than 0.3 and the mass ratio of CD-MOF and GA was 1:3. The low-field nuclear magnetic resonance results revealed that the T₂₂ relaxation time of emulsions decreased from 403.702 to 231.013 ms when the oil fractions increased from 0.1 to 0.6, indicating that movable water was converted to constructal water. The emulsions showed good stability, even in high-alkaline pH and high-temperature conditions.

Changes in secondary structure of myofibrillar protein and its relationship with water dynamic changes during storage of battered and deep-fried pork slices

Fourier transform infrared spectroscopy was used to analyze the changes of secondary structure of myofibrillar proteins in short-term storage of battered and deep-fried pork slices. These changes were combined with low-field NMR analysis results to analyze the correlation between secondary structure and dynamic changes of water content. The results showed that the number of α-helix and β-sheet decreased by 22.90 and 16.54% respectively, and the orderly structure changed to the disorder structure. The correlation results show that NMR spin-spin relaxation time (T₂₁) has a high negative correlation with α-helix, β-sheet, and has a high positive correlation with irregular curl and β-turn. The population of immobile water (P₂₂) has a very high positive correlation with α-helix, β-sheet, and has a relatively high negative correlation with irregular curl and β-turn. The immobilized water plays an important role in maintaining the secondary structure.

Physiochemical properties and tastes of gels from Japanese Spanish mackerel (Scomberomorus niphonius) surimi by different washing processes

The study investigated the properties of gels from Japanese Spanish mackerel (Scomberomorus niphonius) (JSM) surimi received conventional washing (CW) or alkaline-saline washing (AW) and un-washing (UW). AW gel exhibited the highest breaking force and deformation as well as water-holding capacity, but CW gel only had higher breaking force than UW gel. Low-field NMR analysis showed that peak P₂₂ in AW gel was shifted to higher relaxation time and the areas of peak P₂₁ and P₂₂ in AW gel were higher than those in UW and CW gels. Compared with UW gel, network structure of AW gel was more continuous with many tiny voids, but CW gel microstructure showed partially uneven area with large voids. SDS-PAGE showed that band intensity of myosin heavy chain attenuated more in AW gel than in UW and CW gels in nonreducing electrophoresis and it recovered more pronounced in reducing electrophoresis. Solubility attributed to hydrophobic interaction, hydrogen and disulfide bonds increased in CW and AW gels. AW gel gave stronger bitterness and aftertaste A while CW gel showed heavier sourness, astringency, and aftertaste B than UW gel. Results suggest that AW improved physiochemical properties of gel and preserved a closer taste pattern to UW gel. It is recommended for JSM surimi producing. PRACTICAL APPLICATIONS: Surimi food has great potential due to its convenience, elasticity, and nutritional value. Japanese Spanish mackerel (JSM), a popular fish species in China, is widely used for producing surimi food, such as fish ball, dumpling, and sausage. Washing is a practical way to improve its gel properties. This study investigated the gel strength, water status, protein pattern, molecular interactions, microstructure, color, and taste of gels from JSM surimi received conventional washing or alkaline-saline washing and un-washing. Some practical information of effects of washing on gel properties was obtained. These results provide supports to the gel properties improvement by appropriate washing for JSM.

Combined Used of Rheology and LF-NMR for the Characterization of PVP-Alginates Gels Containing Liposomes

PURPOSE

This paper is based on the characterization of the rheological and Low Field NMR (LF-NMR) properties of an interpenetrated hydrogel made up by poly(N-vinyl-2-pyrrolidone) and sodium alginate. The final aim is to use the hydrogel as a delivery matrix for liposomes, widely used tools in the drug delivery field.

METHODS

Rheology, LF-NMR, TEM, cryo-TEM, confocal laser scanning microscopy and release test were employed to characterize the interpenetrated hydrogel. Different theoretical approaches such as Flory, Chui, Scherer and Schurz theories were used to interpret the experimental results.

RESULTS

We found that the crosslinking mechanisms of the two polymers produced an anti-synergistic effect on the final mechanical properties of the interpenetrated hydrogel. Instead of creating a continuous network, alginate formed isolated, cross-linked, clusters embedded in a continuous network of poly(N-vinyl-2-pyrrolidone). Additionally, gel structure significantly influenced liposome delivery.

CONCLUSIONS

The rheological and LF-NMR characterization were confirmed and supported by the independent techniques TEM, cryo-TEM and release tests Thus, our findings reiterate the potentiality of both rheology and LF-NMR for the characterisation of soft materials such as interpenetrated polymeric networks.

Low frequency ultrasound pretreatment of carrot slices: Effect on the moisture migration and quality attributes by intermediate-wave infrared radiation drying

The effect of low frequency ultrasound (LFU) pretreatment prior to intermediate-wave infrared radiation (IW-IR) drying on water migration and quality attributes of carrot slices was investigated in this study. Results showed that the vacuole water of LFU pretreated carrot samples decreased, while the cytoplasm and intercellular space water increased by low-field nuclear magnetic resonance analysis. In addition, LFU pretreatment caused the disruption of cell structures and formation of micro-channels, resulting in significant (p<0.05) decrease of drying time required. The IW-IR dried carrot slices with LFU pretreatment showed higher β-carotene content and rehydration ratio in comparison with control samples. The color parameters of ultrasound pretreated dried carrot slices after dehydration were closer to the raw carrot samples. The results of electronic nose showed that the aromatic and volatile organic compounds of dried carrot increased by sonicated pretreatment, while the nitrogen oxides decreased, indicating that LFU can improve the flavor of dried carrot slices.

Water dynamics of Ser-His-Glu-Cys-Asn powder and effects of moisture absorption on its chemical properties

BACKGROUND

This study has elucidated moisture dynamics in the soybean peptide, Ser-His-Glu-Cys-Asn (SHECN) powder by using dynamic vapor sorption (DVS) and nuclear magnetic resonance (NMR). We also tried to investigate the effects of moisture absorption on the biological activity and chemical properties of SHECN with some effective methods such as mid-infrared (MIR) spectroscopy and gas chromatography-mass spectrometry (GC-MS).

RESULTS

DVS results showed that the moisture absorption of SHECN could reach a maximum of 33%, and the SHECN powder after synthesis actually existed in a trihydrate state of SHECN.3H2 O. Low-field NMR revealed that three water proportions including strong combined water, binding water and bulk water were involved in SHECN moisture absorption and absored water dominantly existed in the form of combined water. Magnetic resonance imaging (MRI) and MIR spectroscopy results indicated that moisture absorption could change the morphology and structure of SHECN. After moisture absorption at 50% and 75% relative humidity, 19 volatiles were identified by GC-MS analysis. Additionally, this study showed that a part of reductive groups in SHECN was oxidized and its antioxidant ability declined significantly (P < 0.05) after moisture absorption.

CONCLUSION

Water absorbed into SHECN powder can significantly change its microstructure and cause its activity to decrease. We must prevent SHECN from absorbing moisture during storage because the water can accelerate the oxidation of samples and promote microbial reactions. © 2016 Society of Chemical Industry.

Application of near infrared reflectance (NIR) spectroscopy to identify potential PSE meat

BACKGROUND

Pale, soft and exudative (PSE) meat is a quality problem that causes a large economic loss to the pork industry. In the present work, near infrared (NIR) quantification and identification methods were used to investigate the feasibility of differentiating potential PSE meat from normal meat.

RESULTS

NIR quantification models were developed to estimate meat pH and colour attributes (L*, a*, b*). Promising results were reported for prediction of muscle pH (R(2) CV  = 70.10%, RPDCV = 1.83) and L* (R(2) CV  = 77.18%, RPDCV = 1.91), but it is still hard to promote to practical application at this level. The Factorisation Method applied to NIR spectra could differentiate potential PSE meat from normal meat at 3 h post-mortem. Correlation analysis showed significant relationship between NIR data and LF-NMR T2 components that were indicative of water distribution and mobility in muscle. PSE meat had unconventionally faster energy metabolism than normal meat, which caused greater water mobility.

CONCLUSION

NIR spectra coupled with the Factorisation Method could be a promising technology to identify potential PSE meat. The difference in the intensity of H2 O absorbance peaks between PSE and normal meat might be the basis of this identification method. © 2015 Society of Chemical Industry.