Storage of parbaked bread affects shelf life of fully baked end product: A 1H NMR study

Starch retrogradation in starch-based foods: Mechanisms, influencing factors, and mitigation strategies

Starch-based foods are the most common foods in the daily diets. However, starch-based foods are prone to starch retrogradation, resulting in texture hardening, taste deterioration and nutrient loss. This paper reviewed the mechanisms and the influencing factors of starch retrogradation in starch-based foods, and the strategies to mitigate it. The core mechanisms and influencing factors of starch retrogradation are analyzed in depth, and various methods to alleviate it are summarized. Starch retrogradation is mainly caused by recrystallization of amylose and amylopectin, accompanied by moisture migration and rearrangement of starch molecules. The amylose to amylopectin ratio, moisture content, protein and lipids are intrinsic factors. At the same time, processing methods and storage temperatures are extrinsic conditions that significantly affect the rate and extent of starch retrogradation. Effective measures to alleviate starch retrogradation include the addition of food ingredients and exogenous substances, the optimization of processing methods and storage conditions, as well as the application of edible coatings. This review aims to summarize the latest progress in delaying aging of starch-based foods, enhance the understanding of starch retrogradation mechanisms, and promote the development of starch-based foods with longer shelf lives, thereby providing scientific basis and technical support for the food industry.

Fermentation properties and functional stability of dough starter Jiaozi and Laomian after frozen storage

Purpose

This study aims to investigate the effects of frozen storage on the stability of traditional dough starters in China.

Methods

The microbial community structure and abundance of related metabolic genes in different fermented sourdough prepared by Jiaozi (JZ) and Laomian (LM) starters before and after frozen storage at -20°C for half a year were analyzed using the shotgun metagenomic sequencing method, and differences in characteristics of texture in steamed bread were also compared by formal methods.

Results

The fermentation ability (FA) and metabolic activities of yeast in the JZH sourdough (started by JZ which was stored at -20°C for half a year) were better than those of LMH sourdough (started by LM which was stored at -20°C for half a year). The dominant genera of Acetobacter were found to be increased in the JZH0 sourdough (started by JZH and fermented for 0 h) and those of Lactobacillus were found to be decreased. Lactobacillus (98.72%), Pediococcus (0.37%), Saccharomyces (0.27%), and Acetobacter (0.01%), were dominant in sourdough LMH0 (started by LMH and fermented for 0 h). The abundances of "oxidative phosphorylation-related enzymes" and the "biosynthesis of glutamate"-related enzymes and genes related to "biosynthesis of glutamate" and "unsaturated fatty acid" were higher in JZH0 than in the JZ0 sourdough (started by JZ without being frozen and fermented for 0 h). The good FA of yeast, the acid production capacity of bacteria in the sourdough, and the quality of the JZH steamed bread (made by the JZH starter) indicated the better freezing tolerance of the microorganisms in JZ than in LM.

Conclusion

The conclusion of this study suggests the better application potential of the JZ as the fermentation starter in actual production.

An Impact Assessment of Par-Baking and Storage on the Quality of Wheat, Whole Wheat, and Whole Rye Breads

Par-baking technology increases the production efficiency of bread. However, the degree of par-baking can vary significantly amongst product types and intended sales markets, leading to substantial differences in the quality attributes of the finished product. The objective of this study was to explore the impact of the degree of par-baking on the technological quality of wheat, whole wheat, and whole rye bread (95, 75, and 50% of full baking time). More specifically, this study focused on the starch pasting behavior of different flour formulations, the crumb core temperature during par-baking, and the influence of the degree of par-baking on the bread characteristics of (composite) wheat bread as a function of storage time. The quality attributes of par-baked bread (0 and 4 days after par-baking) and fully baked bread (0 and 2 days after full baking) were assessed. A reduction in the degree of par-baking from 95 to 50% resulted over time in 19.4% less hardening and 8.6% more cohesiveness for the re-baked wheat breads. Nevertheless, it also negatively impacted springiness (-9.1%) and adhesion (+475%). It is concluded that using the core temperature to define the degree of par-baking is not sufficient for bread loaves intended to be consumed over time, but the results indicate that reducing the degree of par-baking can be beneficial for certain quality aspects of the breads.

Influences of Particle Size and Addition Level on the Rheological Properties and Water Mobility of Purple Sweet Potato Dough

This paper investigated the effects of different particle sizes and addition levels of purple sweet potato flour (PSPF) on the rheological properties and moisture states of wheat dough. There was deterioration in the pasting and mixing properties of the dough, due to the addition of PSPF (0~20% substitution), which was reduced by decreasing the particle size of the PSPF (260~59 μm). Dynamic rheology results showed that PSPF enhanced the elasticity of the dough, providing it solid-like processability. PSPF promoted the binding of gluten proteins and starch in the dough, resulting in a denser microstructure. Differential scanning calorimetry and low-field nuclear magnetic resonance showed that PSPF converted immobilized water and freezable water to bound water and non-freezable water in the dough, making the dough more stable, and that the reduction in PSPF particle size facilitated these processes. Our results provide evidence for the great application potential of purple sweet potatoes for use in flour-based products.

The use of time domain 1 H NMR to study proton dynamics in starch-rich foods: A review

Starch is a major contributor to the carbohydrate portion of our diet. When it is present with water, it undergoes several transformations during heating and/or cooling making it an essential structure-forming component in starch-rich food systems (e.g., bread and cake). Time domain proton nuclear magnetic resonance (TD ¹ H NMR) is a useful technique to study starch-water interactions by evaluation of molecular mobility and water distribution. The data obtained correspond to changes in starch structure and the state of water during or resulting from processing. When this technique was first applied to starch(-rich) foods, significant challenges were encountered during data interpretation of complex food systems (e.g., cake or biscuit) due to the presence of multiple constituents (proteins, carbohydrates, lipids, etc.). This article discusses the principles of TD ¹ H NMR and the tools applied that improved characterization and interpretation of TD NMR data. More in particular, the major differences in proton distribution of various dough and cooked/baked food systems are examined. The application of variable-temperature TD ¹ H NMR is also discussed as it demonstrates exceptional ability to elucidate the molecular dynamics of starch transitions (e.g., gelatinization, gelation) in dough/batter systems during heating/cooling. In conclusion, TD NMR is considered a valuable tool to understand the behavior of starch and water that relate to the characteristics and/or quality of starchy food products. Such insights are crucial for food product optimization and development in response to the needs of the food industry.

Application progress of intelligent flavor sensing system in the production process of fermented foods based on the flavor properties

Fermented foods are sensitive to the production conditions because of microbial and enzymatic activities, which requires intelligent flavor sensing system (IFSS) to monitor and optimize the production process based on the flavor properties. As the simulation system of human olfaction and gustation, IFSS has been widely used in the field of food with the characteristics of nondestructive, pollution-free, and real-time detection. This paper reviews the application of IFSS in the control of fermentation, ripening, and shelf life, and the potential in the identification of quality differences and flavor-producing microbes in fermented foods. The survey found that electronic nose (tongue) is suitable to monitor fermentation process and identify food authenticity in real time based on the changes of flavor profile. Gas chromatography-ion mobility spectrometry and nuclear magnetic resonance technology can be used to analyze the flavor metabolism of fermented foods at various production stages and explore the correlation between flavor substances and microorganisms.

Water loss and status in sponge cake: Impact of Eucheuma as a flour replacement

The impact of Eucheuma on water loss and status in sponge cakes was measured and analyzed in this study. Eucheuma was used to replace 0%, 10%, and 20% of wheat flour to make sponge cakes, coded as the control, EP10, and EP20, respectively. The initial water content of batters showed no significant differences (around 57.0%, dry basis), whereas the final EP10 and EP20 products had higher water content. Three stages were found during baking in control sample and these three stages were fitted by linear, linear, and exponential models with root mean squared error (RMSE) of 0.016, 0.018, and 0.133, respectively. Eucheuma addition decreased the water loss rate and changed the water loss stages, which were fitted by linear, linear, and linear models in EP20 sample (RMSE = 0.027, 0.047, and 0.108, respectively). The crust formation and crumb structure analysis showed that the formation of cracks and the disappearance of pore structures hindered the water evaporation. The low-field proton nuclear magnetic resonance and magnetic resonance imaging results showed that the water status in the final EP20 products was not as tightly as that in the control samples. A proposed schematic diagram was developed based on the qualitative analysis of the transfer mechanisms to explain the total effect of Eucheuma on the water loss rate and status. These results aid our understanding of the water loss process of sponge cakes and promote the potential application of Eucheuma in bakery products. PRACTICAL APPLICATION: Eucheuma as a flour replacement can improve the contents of dietary fiber and minerals like potassium of sponge cake. The impact of Eucheuma on water loss and status in sponge cake was measured and analyzed in this study. The results can promote the potential application of Eucheuma in bakery products and predict the quality attributes of baking products.

The effect of additives combination on rheological properties of dough and quality of bread with Agaricus bisporus powder

The bread with Agaricus bisporus powder has the defects of poor texture and taste, so it is necessary to optimize the appropriate additives in order to improve its quality. The purpose of this study was to evaluate improvement of the combination of vital wheat gluten, sucrose fatty acid esters and cellulase on the improved Agaricus bisporus powder bread (IABPB), with wheat bread (WB) and bread with Agaricus bisporus powder (ABPB) as control. The results of rheological properties indicated the dough samples improved with three improvers had higher solid-like behaviour than the control sample. The results of nutritional quality analysis showed that the protein and dietary fiber content of IABPB was higher than those of WB and ABPB, but the fat content was relatively low. In addition, the additives combination could effectively improve the baking quality of ABPB. Compared with ABPB without additives, the specific volume increased by 21.22%, the brightness of bread crumb increased by 8.75%, but the crumb hardness decreased by 32.57%. Furthermore, the study on texture property and water migration during the storage showed that the addition of three improvers could delay the aging of bread. Therefore, it was feasible to use additives combination as a special quality improver for ABPB, which could effectively improve its quality.

Effects of the size distribution of wheat starch on noodles with and without gluten

To understand the effects of A- and B-type wheat starch on noodle quality, two noodle models with (Model 1) and without (Model 2) gluten were constructed with five different ratios of A- to B-granules (100A-0B, 75A-25B, 50A-50B, 25A-75B, and 0A-100B). With increasing proportions of B-granules, the noodle structures of Models 1 and 2 became increasingly dense. The cooking loss, water absorption, proportion of free water, chewiness, cohesiveness and resilience decreased from 35.64 to 15.49%, 240.92 to 228.58%, 88.89 to 85.98%, 21.93 to 13.24 N, 0.77 to 0.56, and 0.61 to 0.36, respectively, with the increased proportion of B-granules in Model 2, while those parameters normally presented "V" or inverted "V" trends in Model 1. Compared to their counterparts in Model 2, gluten networks with 25-50% B-granules had an outstanding ability to increase the percentage of tightly bound water, hardness, chewiness and springiness by 4.50%, 24.07 N, 25.05 N, and 0.17 at most and reduce the proportion of free water and water absorption by 5.56 and 73.70% at most, respectively. The results indicated that the effect of the gluten network on noodle qualities may partially depend on its structure, which is shaped by the granule size distribution. Compared to the other characteristics of noodles, the springiness was influenced by a more complicated mechanism involving A- and B-granules in Model 2, while it was strongly affected by the gluten network under the given experimental conditions in Model 1.

Evaluation of specific volume, texture, thermal features, water mobility, and inhibitory effect of staling in wheat bread affected by maltitol

The influence of maltitol on the physicochemical properties of wheat flour dough and bread were evaluated in terms of texture, thermal features, water mobility, and retrogradation kinetics. The presence of maltitol could slow down the fermentation rate of dough. Breads with 6% of maltitol exhibited lower hardness and chewiness, with a significant decrease of 42% and 31%, respectively (p < 0.05). The use of maltitol could remarkably enhance the gelatinization temperature (p < 0.05) that was confirmed by DSC tool. Through the approach of LF-NMR, the addition of maltitol could increase the mobility of immobilized water, further retarded bread staling. The k values from chewiness and total signal amplitude in breads with 2% and 4% levels of maltitol were smaller than the control, which was proven through kinetics of retrogradation analysis, revealing an overall retarding effect of maltitol in prevention of bread staling.

Variable Temperature Nuclear Magnetic Resonance and Magnetic Resonance Imaging System as a Novel Technique for In Situ Monitoring of Food Phase Transition

A nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) system with a 45 mm variable temperature (VT) sample probe (VT-NMR-MRI) was developed as an innovative technique for in situ monitoring of food phase transition. The system was designed to allow for dual deployment in either a freezing (-37 °C) or high temperature (150 °C) environment. The major breakthrough of the developed VT-NMR-MRI system is that it is able to measure the water states simultaneously in situ during food processing. The performance of the VT-NMR-MRI system was evaluated by measuring the phase transition for salmon flesh and hen egg samples. The NMR relaxometry results demonstrated that the freezing point of salmon flesh was -8.08 °C, and the salmon flesh denaturation temperature was 42.16 °C. The protein denaturation of egg was 70.61 °C, and the protein denaturation occurred at 24.12 min. Meanwhile, the use of MRI in phase transition of food was also investigated to gain internal structural information. All these results showed that the VT-NMR-MRI system provided an effective means for in situ monitoring of phase transition in food processing.

Influence of Barley Sourdough and Vacuum Cooling on Shelf Life Quality of Partially Baked Bread

Driven by the bakery industry urge to satisfy consumer demand for fresh, diverse and high quality bakery products, we investigated the influence of barley sourdough and vacuum cooling on shelf life quality of partially baked bread stored in modified atmosphere packaging at ambient conditions. Barley sourdough was fermented with Lactobacillus reuteri (DSM 20016, F275). Partially baked bread with sourdough was microbiologically acceptable during 30 days of storage, while bread without sourdough had detectable mould on the 30th day. Stored bread samples were rebaked after 1, 8, 15, 22 and 30 days to determine moisture content, physical and sensorial properties. Moisture loss (5%) was detected on the 15th day, after which it remained stable until the end of investigated storage period. Nevertheless, textural quality of stored bread continuously declined due to crumb firming. Bread flavour did not change during mould-free storage time. The principal component analysis identified major differences in the flavour of sour and control bread, also in crumb firmness and moisture content of samples. This study indicates the positive role of barley sourdough fermented with L. reuteri in improving crumb texture for at least 15 days, and ensuring mould- and bacteria-free partially baked bread for 30 days. Vacuum cooling combined with sourdough improved bread shape, porosity, and reduced sour taste, crust colouring and crumbliness. Hence, it can successfully extend shelf life quality of partially baked bread in modified atmosphere packaging.

The Impact of Parbaking on the Crumb Firming Mechanism of Fully Baked Tin Wheat Bread

The impact of parbaking on the quality and shelf life of large tin bread baked from 270 g of wheat flour was investigated using a proton nuclear magnetic resonance method combined with techniques that measure at different length scales. With increasing partial baking time, the resilience of fresh partially baked crumb increased because of its more extended amylose and gluten networks. During subsequent storage, the crumb became more firm due to an increased extent of amylopectin retrogradation and moisture redistribution. Although only amylopectin retrogradation was reversed during final baking, a fresh fully baked (FB) bread with reversed crumb softness was obtained. Furthermore, the rate of crumb firming during final storage of FB bread was not higher than that of conventionally baked bread. This was attributed to the high crumb to crust ratio of large tin bread which caused the crumb moisture content to remain sufficiently high despite nonreversible moisture redistribution during intermediate storage.

Multi-scale NMR and MRI approaches to characterize starchy products

This review deals with the use of Nuclear Magnetic Resonance techniques to monitor the behavior of starch as well as the migration and distribution of water during the processing or storage of starchy matrices. The aim is to emphasize the potentials of NMR techniques for the quantitative characterization of water transfers in starch-water systems on different length scales. Relaxation and self-diffusion experiments using low-field NMR spectrometry provided important information on the relationship between water dynamics and the microscopic organization of starch granules at various temperatures and water contents. Some works dealt with the botanical origin of starch but also the impact of possible additives. Indeed, the investigation on model starch-based systems was recently expanded to more complex real systems, including dough, bread, cakes, spaghetti and lasagna. Two-dimensional (2D) cross correlation methods have also been developed to elucidate chemical and diffusional proton exchange phenomena, and to improve the interpretation of results obtained in 1D. Finally, magnetic resonance micro-imaging methods were developed to study or to quantify water intake into starch-based matrices.

Use of fermented glutinous rice as a natural enzyme cocktail for improving dough quality and bread staling

Jiu-niang (rice wine) could be used as a natural enzyme cocktail for the improvement of bread quality.

Kinetics of bread crumb hydration as related to porous microstructure

An in vitro approach enabled to investigate the relationship between bread crumb porous micro structure and kinetics of hydration.