Effect of cooling rate on the structure and mechanical properties of milk fat and lard

Multiscale assessment of the effect of a stearic-palmitic sucrose ester on the crystallization of anhydrous milk fat

Anhydrous milk fat (AMF) is a flavorful, but particularly complex fat containing a wide variety of fatty acids (FAs) and triglycerides (TGs), resulting in an extended melting range of -40 °C to 40 °C. The functionality of this fat can be steered by the addition of sucrose esters (SEs). In this study, the crystallization behavior of AMF in the presence of a stearic-palmitic SE was assessed. Samples were cooled at 1 °C/min (slow cooling) or 20 °C/min (fast cooling) to 0 °C, 20 °C or 25 °C and kept isothermal for one hour. At each of these temperatures, AMF was found to crystallize via different polymorphic pathways and chain length structures, as studied by wide- and small-angle X-ray scattering. The addition of the SE (0.5 wt%) accelerated nucleation and allowed crystallization to start at higher temperatures. Polymorphic transitions were accelerated, but not changed. For fast-cooled samples, ultra-small-angle X-ray scattering provided insights into the mesoscale behavior of the crystal nanoplatelets (CNPs). It was observed that CNPs formed at 20 °C were smaller than those at 25 °C. The addition of the SE did not change the size nor the shape of CNPs. Polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM) gave insight into the microstructure of the networks. Addition of the SE resulted in more fine and dense fat crystal networks at 0 °C and 20 °C. At 25 °C, large separate floc structures were encountered, with and without the addition of the SE.

How triacylglycerol thermal history impacts film removal by surfactant solution

HYPOTHESIS

The physical and mechanical properties of triacylglycerols (TAGs), or 'fats', depend on their composition and thermal history which, in turn, impact crystal structure and morphology. We examine whether thermal history can be mechanistically related to film removal by a surfactant solution.

EXPERIMENTS

Model TAG mixtures, comprising triolein:tripalmitin:tristearin 0.5:0.3:0.2, were subjected to a range of cooling profiles from the melt (0.5-80°C/min, Newtonian and annealed), and the resulting solid films characterised by microscopy, X-ray diffraction, infrared spectroscopy, and contact angle measurements. Film removal from a model glass substrate by an aqueous surfactant solution of sodium dodecylsulphate and dodecyldimethylamine oxide at room temperature fixed at 25°C was examined under quiescent flow conditions.

FINDINGS

Quantitative relations are established between TAG cooling profile, crystal structure and morphology, surface energy γSFE, and removal (or 'cleaning'). In general, films cooled slowly from the melt yield heterogeneous morphologies with predominantly β1' phase, higher polar γSFE, and faster removal timescales. By contrast, rapid cooling results in homogeneous films, rich in β2' phase, low polar γSFE, and long removal times. Our results elucidate the non-trivial impact of TAG thermal history, connecting the multiscale semi-crystalline structure to surface energy, and eventually to film delamination by micellar solutions.

Effect of temperature on the rheological, textural, and sensory properties of butters from New Zealand market

Texture and sensory studies at various temperatures are important in evaluating and improving the functionality of butter. While literature is scarce, we evaluated and compared the effect of temperature (5-25°C) on the texture, rheological and sensory properties of commercial butter samples (salted, unsalted, cultured, and spreadable) from the New Zealand market. In addition, the instrumental analyses were compared with the sensory evaluation, to understand the possibility of using instrumental analysis to evaluate consumer liking for different butters. Butter type, temperature, and their type-temperature interaction exhibited significant differences for all instrumental textural parameters. As expected, higher temperature produced softer butter that was more spreadable, liquid-like, less adhesive, less cohesive, had lower storage modulus (G') and lower loss modulus (G″) with the melting of milk fat crystals; however, the rate of change varied for the different butter samples. We have established meltability as the parameter for evaluating butter selection for different applications. The spreadable butter sample exhibited the lowest hardness and G', and highest spreadability (p < .05) at all temperatures, owing to its low solid fat content and the abundance of low-melting triglycerides. The cultured butter sample had the highest melting point, owing to compositional differences. The instrumental and sensory texture analyses were highly correlated, indicating the comparative effectiveness of both approaches for studying the effects of different temperatures on butter textural properties. Overall, our findings provide detailed reference to the dairy industry for butter manufacture, considering variation in fatty acid composition, texture analysis, rheology, and sensory analysis, over the range of storage/usage temperatures.

In situ single-droplet analysis of emulsified fat using confocal Raman microscopy: insights into crystal network formation within spatial resolution

Fat crystallization is one of the predominant factors influencing the structure and properties of fat-containing emulsions. In the present study, the role of emulsifiers on fat crystallization dynamics within droplet multiphase systems was evaluated via single-droplet analysis, taking advantage of the non-destructive properties of confocal Raman microscopy. Palm oil droplets dispersed in water were used as a model system, due to palm oil's well-known crystallization properties. Emulsion droplets of the same size were generated using two different emulsifiers (Whey Protein Isolate and Tween 60), at various concentrations. Fast and slow cooling treatments were applied to affect fat crystallisation and network formation as well as droplet morphology, and crystallization dynamics. Raman imaging analysis demonstrated that the chemical structure and concentration of the emulsifier significantly influenced both crystal nucleation within the droplets, as well as the spatial distribution and morphology of the fat crystal network. Additionally, analysis of the spectra of the crystallized phase provided essential information regarding the impact of the emulsifiers on the microstructure, degree of structural order, and structural arrangements of the fat crystal networks. Furthermore, by performing single droplet analysis during cooling it was possible to observe shape distortions in Tween 60 stabilized droplets, as a consequence of the formation of a three-dimensional network of fat crystals that strongly interacted with the interface. On the other hand, the droplets retained their shape when whey proteins were absorbed at the interface. Confocal Raman microscopy, in combination with polarized light microscopy, is, therefore, a well-suited tool for in situ, single-droplet analysis of emulsified oil systems, providing essential information about emulsified fat crystallization dynamics, contributing to better understanding and designing products with enhanced structure and function.

Effect of moderate hydrostatic pressure on crystallization of palm kernel stearin-sunflower oil model systems

Lipid crystallization under moderate hydrostatic pressure treatments (200 MPa, 20 °C, 1-24 h) was studied in palm kernel stearin (PS 100%) and its blends with sunflower oil (PS 80, 90 % w/w). Hyperbarically-crystallized samples exhibited significantly higher firmness, elastic modulus and critical stress values as compared to those of the samples crystallized at atmospheric pressure. These data indicate that moderate hydrostatic pressure favored the formation of a higher amount of small palm kernel stearin crystals as compared to those formed at atmospheric pressure. Pressurization did not affect fat polymorphism, but was able to enhance nucleation instead of crystal growth. This work clearly demonstrated the efficacy of moderate hydrostatic pressure in steering lipid crystallization, opening interesting possible applications of high-pressure processing technology in the fat manufacturing sector.

Thermophysical properties of blends composed of Amazonian fats and soybean oil

Thermophysical properties of blends composed of soybean oil and fats obtained from fruits and seeds from Brazilian Amazonian region (Murumuru, Tucuma, and Bacuri) were investigated, looking for more sustainable alternatives to the mostly used industrial fats, for applications in product formulation. Fatty acid (FA) and triacylglycerol composition, nutritional indexes, solid fat content (SFC), compatibility, consistency, melting, and crystallization profiles were determined. Soybean oil increased blends' unsaturated FA profile, leading to lower SFC, but higher nutritional quality. Fats' melting profiles were significantly altered with soybean oil addition: temperatures decreased with the increase in oil content. Iso-solids diagrams showed that lipids were compatible, which is a technological advantage. SFC and consistency profiles suggested that tucuma and murumuru fats could be used as hardstocks for lipid products, and bacuri fat could be applied in products such as margarine and spreads. Blends could improve fats' spreadability and other technological properties, which is promising for applications in products formulation.

Ice crystallization and structural changes in cheese during freezing and frozen storage: implications for functional properties

Temperature-mediated preservation techniques offer a simple, scalable, effective, and fairly efficient method of long-term storage of food products. In order to ensure the uninterrupted availability of cheese across the globe, a critical understanding of its techno-functional properties as affected by freezing and frozen storage is essential. Detailed studies of temperature-mediated molecular dynamics are available for relatively simpler and homogeneous systems like pure water, proteins, and carbohydrates. However, for heterogeneous systems like cheese, inter-component interactions at sub-zero temperatures have not been extensively covered. Ice crystallization during freezing causes dehydration of caseins and the formation of concentration gradients within the cheese matrix, causing undesirable changes in texture-functional attributes, but findings vary due to experimental conditions. A suitable combination of sample size, freezing rate, aging, and tempering can extend the shelf life of high- and low-moisture Mozzarella cheese. However, limited studies on other cheeses suggest that effects and suitability differ by cheese type, in most cases adversely affecting texture and functional attributes. This review presents an overview of the understanding of the effects of refrigeration, freezing techniques, and frozen storage on structural components of cheese, most prominently Mozzarella cheese, and the corresponding impact on microstructure and functionality. Also included are the mechanism of ice formation and relevant mathematical models for estimation of the thermophysical properties of cheese to assist in designing optimized schemes for their frozen storage. The review also highlights the lack of unanimity in critical understanding concerning the effect of freezing on the long-term storage of Mozzarella cheese with respect to its functionality.

Thermomechanical Properties of High Oleic Palm Oil Assessed Using Differential Scanning Calorimetry, Texture Analysis, Microscopy, and Shear Rheology

Standard Palm Oil (SPO) is widely used as a food ingredient partially due to its unique thermophysical properties. However, the American Heart Association recommends a saturated fat consumption of <5% of the caloric intake per day. The OxG Palm hybrid yields oil known as "palm oil with a higher content of oleic acid" (HOPO), with <35% SFA and >50% oleic acid. Characterizing novel high oleic oils is the starting point to find processes that can functionalize them such as oleogelation. This study compared the thermophysical properties of HOPO to SPO using Differential Scanning Calorimetry, shear rheology, polarized light microscopy, and texture analysis to characterize the differences between these oils. HOPO had a lower onset crystallization temperature (Δ7 °C) and its rheological behavior followed similar trends to SPO; however, large viscosity offsets were observed and were correlated to differences in crystallization temperatures. The maximum peak force of SPO was an order of magnitude higher than that of HOPO. Overall similar trends between the oils were observed, but differences in firmness, crystal morphology, and viscosity were not linearly correlated with the offset in crystallization temperature. This study quantified differences between these oils that will better enable industry to use HOPO in specific applications.

Polymorphism of a Highly Asymmetrical Triacylglycerol in Milk Fat: 1-Butyryl 2-Stearoyl 3-Palmitoyl-glycerol

Milk fat has more than 200 triacylglycerols (TAGs), which play a pivotal role in its crystallization behavior. Asymmetrical TAGs containing short butyryl chains contribute to a significant portion of milk fat TAGs. This work aims to elucidate the crystallization behavior of asymmetrical milk fat TAGs by employing the pure compound of 1-butyryl 2-stearoyl 3-palmitoyl-glycerol (BuSP). The structural evolution of BuSP after being cooled down to 20 °C from the melt is evaluated by small- and wide-angle X-ray scattering (SAXS and WAXS) and differential scanning calorimetry (DSC). The temporal structural observation shows that BuSP crystallizes into the α-form with short and long spacings of 4.10 and 56.9 Å, respectively, during the first hour of isothermal hold at 20 °C. The polymorphic transformation of the α to β' phase occurred after 4 h of isothermal hold, and the β'- to α-form fraction ratio was about 70:30 at the end of the isothermal experiment (18 h). Pure β'-form X-ray patterns are obtained from the BuSP powder with short spacings of 4.33, 4.14, and 3.80 Å, while the long spacing of 51.2 Å depicts a three-chain-length lamellar structure with a tilt angle of 32°. Corresponding DSC measurements display that BuSP crystallizes from the melt at 29.1 °C, whereas the melting of α- and β'-forms was recorded at 30.3 and 47.8 °C, respectively. In the absence of the β-form, the β'-polymorph is the most stable observed form in BuSP. This work exemplarily explains the crystallization behavior of asymmetrical milk fat TAGs and thus provides new insights into their role in overall milk fat crystallization.

Effect of Solid Fat Content in Fat Droplets on Creamy Mouthfeel of Acid Milk Gels

Previous studies have shown that emulsions with higher solid fat content (SFC) are related to a higher in-mouth coalescence level and fat-related perception. However, the effect of SFC in fat droplets on the fat-related attributes of emulsion-filled gels has not been fully elucidated. In this study, the effect of SFC on the creamy mouthfeel of acid milk gel was investigated. Five kinds of blended milk fats with SFC values ranging from 10.61% to 85.87% were prepared. All crystals in the blended milk fats were needle-like, but the onset melting temperature varied widely. Blended milk fats were then mixed with skim milk to prepare acid milk gels (EG10−EG85, fat content 3.0%). After simulated oral processing, the particle size distribution and confocal images of the gel bolus showed that the degree of droplet coalescence in descending order was EG40 > EG20 > EG60 > EG10 ≥ EG85. There was no significant difference in apparent viscosity measured at a shear rate of 50/s between bolus gels, but the friction coefficients measured at 20 mm/s by a tribological method were negatively correlated with the coalescence result. Furthermore, quantitative descriptive analysis and temporal dominance of sensations analysis showed that SFC significantly affected the ratings of melting, mouth coating, smoothness and overall creaminess, as well as the perceived sequence and the duration of melting, smoothness and mouth coating of acid milk gels. Overall, our study highlights the role of intermediate SFC in fat droplets on the creamy mouthfeel of acid milk gels, which may contribute to the development of low-fat foods with desirable sensory perception.

Encapsulation of Lactobacillus acidophilus in solid lipid microparticles via cryomilling

We herein delved into the microencapsulation of Lactobacillus acidophilus (LA) into solid lipid microparticles (SLMs) via the cryomilling technique. For this aim, a frozen lipid mixture containing LA was pulverized at different times (7, 14, 21, 28, and 35 min) using a cryogenic mixer mill to produce probiotic-loaded SLMs. The impacts of different cryomilling durations on the SLMs properties (morphology, particle size, water activity, polymorphism, crystallinity, and thermal behavior) and the viability of LA were evaluated. Microencapsulation improved the viability of LA in simulated gastrointestinal fluids, heat stress, and different concentrations of salt and sucrose. SLMs also were suitable to be incorporated into foods. However, once the cryomilling time was prolonged, the viability of encapsulated LA declined, and particle size grew. The cryomilling technique showed great potential as an alternative approach for encapsulation due to the lack of solvent, short processing time, and simplicity.

Quantifying cooperative flow of fat crystal dispersions

We quantify the cooperative flow behaviour of fat crystal dispersions (FCDs) upon varying crystallization conditions. The latter enabled altering the multiscale microstructure of the FCDs, from the nanometer-sized platelets, and the dispersed fractal aggregates, up to the strength of the mesoscopic weak-link network. To the goal of characterizing strongly-confined flow in these optically-opaque materials, we acquire high-resolution rheo-magnetic-resonance-imaging (rheo-MRI) velocimetry measurements using an in-house developed 500 μm gap Couette cell (CC). We introduce a numerical fitting method based on the fluidity model, which yields the cooperativity length, ξ, in the narrow-gap CC. FCDs with aggregates sizes smaller than the confinement size by an order of magnitude were found to exhibit cooperativity effects. The respective ξ values diverged at the yield stress, in agreement with the Kinetic Elasto-Plastic (KEP) theory. In contrast, the FCD with aggregates sizes in the order of the gap size did not exhibit any cooperativity effect: we attribute this result to the correspondingly decreased mobility of the aggregates. We foresee that our optimized rheo-MRI measurement and fitting analysis approach will propel further similar studies of flow of other multi-scale and optically-opaque materials.

A Review on the Commonly Used Methods for Analysis of Physical Properties of Food Materials

The chemical composition of any food material can be analyzed well by employing various analytical techniques. The physical properties of food are no less important than chemical composition as results obtained from authentic measurement data are able to provide detailed information about the food. Several techniques have been used for years for this purpose but most of them are destructive in nature. The aim of this present study is to identify the emerging techniques that have been used by different researchers for the analysis of the physical characteristics of food. It is highly recommended to practice novel methods as these are non-destructive, extremely sophisticated, and provide results closer to true quantitative values. The physical properties are classified into different groups based on their characteristics. The concise view of conventional techniques mostly used to analyze food material are documented in this work.

Effects of different tempering temperatures on the properties of industrial sheet margarine

Tempering conditions have significant effects on the microstructure, physicochemical properties and application functionalities of ISM.

Effect of cocoa bean origin and conching time on the physicochemical and microstructural properties of Indonesian dark chocolate

Abstract Indonesian cocoa is cheaper and considered second grade compared with most other cocoa. However, the domestic chocolate industry is not well-developed due to significantly low consumption. To cope with these issues, product innovation through technical process improvement is required to stimulate the domestic chocolate industry. This study aimed to investigate the effect of cocoa bean origin and conching time on the physicochemical (water content, texture, color, crude fat content, and melting enthalpy) and microstructural properties of chocolate. The experiment was conducted under a completely randomized factorial design consisting of two factors: cocoa bean origin (100% fermented cocoa beans from Jember, 100% fermented cocoa beans from Southeast Sulawesi, 50% fermented cocoa beans from Jember + 50% non-fermented cocoa beans from Southeast Sulawesi, and 50% fermented cocoa beans from Southeast Sulawesi + 50% non-fermented cocoa beans from Southeast Sulawesi) and conching time (4, 6 and 8 h). The results showed that cocoa bean origin significantly affected the hardness, gumminess and color of chocolate, including the redness and yellowness level, whereas conching time affected water content, hardness, cohesiveness, elasticity, and crude fat content. Differential scanning calorimetry (DSC) analysis showed that the treatment with 100% fermented cocoa beans from Jember presented higher values of Tonset, ΔHmelt and area compared with those of the treatment with 100% fermented cocoa beans from Southeast Sulawesi, which presented higher values of Tpeak and Tend. Scanning Electron Microscopy (SEM) analysis showed a distribution of solid and dense particles with crystal interaction with chocolate structures.

Effects of Domain Size on Viscosity of α-Gel (α-Form Hydrated Crystal) Prepared from Eco-friendly Cationic Surfactant

We determine the effects of the α-gel (α-form hydrated crystal) domain size on the viscosity of water-diluted α-gels consisting of the N-[3-(dimethylamino)propyl]docosanamide (APA-22) L-lactic acid salt, 1-octadecanol (C₁₈OH), and water. A decrease in the C₁₈OH mole content results in increased domain size and viscosity of the water-diluted α-gel system. Additionally, when a sample is prepared by slow cooling and/or at low stirring speed, the domain size and viscosity of the water-diluted α-gel system increase. A similar increase in the domain size and viscosity of the α-gel system is observed for annealed samples. The observed change in the α-gel domain size is explained by the crystal growth theory.

Characterisation of thermal and structural behaviour of lipid blends composed of fish oil and milkfat

The blend of fish oil with a high percentage of long chain poly-unsaturated fatty acids, and milkfat with a high percentage of saturated fatty acids, could potentially demonstrate desirable characteristics from both components, such as increased omega-3 fatty acids and melting point, as well as improved crystallization and oxidative stability. In this study, the effect of various milkfat concentrations on thermal properties and crystalline structure of these blends were analysed to understand parameters determining the overall characteristics of the blend. Blends with different ratios of fish oil: milkfat (9:1, 7:3, 5:5, 3:7, 1:9), as well as pure fish oil and pure milkfat, were investigated at different cooling conditions. The crystallization behaviour in all samples shifted to lower temperature ranges, by increasing the cooling rate from 1 to 32 °C/min. However, the changes in cooling rate did not have significant effect on the melting profile of the samples. Whereas changes in milkfat ratio affect both the crystallization and melting behaviour. New crystallization peaks were observed on DSC spectra between the range of -4 to -13 °C in the blends. Moreover, new melting peaks appeared in two ranges of -1 to -8 °C and 8-9 °C, in the blends. The crystallization and melting behaviour of the blends were similar to those of milkfat when >30% milkfat was used. This was further confirmed via XRD where milkfat demonstrated the dominant polymorphic behaviour. Regarding shape of the crystals, fractal dimension analysis showed a similarity between clusters in blends containing 50% milkfat or higher. Increasing the ratio of milkfat led to an increase in fractal dimension which indicates higher mass-spatial distribution of the crystal networks in the blends. The data showed that adding 30% or more milkfat to pure fish oil resulted in blends demonstrating similar characteristics to milkfat, including thermal, structural, and oxidative stability. This shows the potential of blending a high percentage of docosahexaenoic acid in milk fat to improve their overall stability.

Fat crystallization of blends of palm oil and anhydrous milk fat: A comparison between static and dynamic-crystallization

The application of dynamic-crystallization (a combination of shear with rapid cooling) often plays an important role in the production of industrial fat-based products such as shortenings/margarines but has been rarely reported. In this study, three blends of palm oil (PO) with anhydrous milk fat (AMF) (0, 25 and 50% AMF, w/w) were rapidly crystallized under static (using freezer) and dynamic conditions (using a benchtop scraped surface heat exchanger). Various techniques including differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized light microscopy (PLM), rheology and texture analysis were applied to investigate physicochemical properties of fat blends as well as their crystal morphology upon the long-term storage (4 weeks) at 5 °C and 15 °C. The results revealed that high cooling rate of dynamic-crystallization not only affected melting behavior of fat blends but also prevented the polymorphic transformation from β' to β crystals. Besides, the application of shear during fat crystallization helped to improve significantly the gel strength of produced shortenings. Although post-crystallization of low melting triacylglycerols (TAGs) occurred for all produced shortenings during storage at 5 °C which was accompanying with a firmness increase, it was more considerable for samples owning higher AMF content. Moreover, this phenomenon promoted the sintering as well as Ostwald ripening between fat crystals of dynamic-crystallized fat blends resulting in the formation of unwanted large aggregates (or granular crystals) with the size ranging from 100 to 500 μm.

Effect of processing conditions as high-intensity ultrasound, agitation, and cooling temperature on the physical properties of a low saturated fat

The objective of this work was to evaluate the effect that agitation rate, crystallization temperature, and sonication have on the physical properties of a soybean-based fat with low levels of saturated fatty acids crystallized in a scraped surface heat exchanger (SSHE). The sample was crystallized at two temperatures (20 and 25 °C) and agitation rates (344/208 rpm in the barrels/pin worker-high agitation HA and 185/71 rpm barrels/pin worker-low agitation LA), and a constant flow of 11 L/hr. High-intensity ultrasound (HIU - 12.7 mm-diameter tip, 50% amplitude, 5 s pulses) was coupled to a water jacketed flow-cell and placed at three different positions within the SSHE. The combination of all those parameters affected samples' physical properties. Higher oil binding capacity (OBC) and elasticity (G') were obtained at 20 °C compared to 25 °C (77% vs. 63.78% for OBC and 30.4 kPa vs. 6 kPa for G', respectively) due to the smaller crystals formed at 20 °C. Fewer or no differences were observed due to agitation alone, but LA conditions allowed for more secondary nucleation to form due to sonication and resulted in a higher improvement on the properties of the fat. PRACTICAL APPLICATION: Fat crystallization in a scrapped surface heat exchanger (SSHE) combined with a high-intensity ultrasound (HIU) gives a realistic idea of how the HIU would work in an industrial line under continuous flow, shaved shear, and different supercooling. Results from this research will provide industry with tools on how and where to incorporate HIU in their processing line. Moreover, will give information on how to combined crystallization conditions and sonocrystallization in order to obtain improved physical properties.

Effect of vacuum cooling on stability of macro-porous sausage during refrigerated storage-Vacuum-cooled sausage has a longer shelf life

In this study, two types of cooling methods (vacuum cooling and air cooling) were used to cool cooked macro-porous sausage. Alterations in the microbiological conditions, pH, instrumental color (L*, a*, and b*), total volatile nitrogenous bases (TVB-N), lipid oxidation (TBARS), water activity (aW), moisture content, and texture indicators were evaluated to determine sausages' quality changes during storage under refrigeration for up to 10 days. In general, the shelf life of sausages chilled by vacuum cooling (8 days) was similar to that of sausages cooled by air cooling (9 days). For pH, no significant difference (p > .05) was obtained between two cooling methods. However, vacuum-cooled sausages have lower L* value (p < .05), lower moisture content, and water activity compared with the air-cooled sausages. However, sausages cooled by vacuum cooling showed a sharp increase in TBARS and TVB-N values but maintained texture characteristics for a longer time compared with air-cooled sausages. Although the results indicated that the quality of sausages treated by those two methods remarkably decreased after 7 days, characteristics of sausages cooled by vacuum cooling are better within accepted standards compared with air-cooled sausages. In conclusion, vacuum cooling can be a feasible cooling method with great potential to be used in cooked macro-porous sausages to maintain the quality and may provide reference experiences for the food with similar structure.

Effect of Fractionation and Chemical Characteristics on the Crystallization Behavior of Milk Fat

The experiments reported in this study provided a more comprehensive insight into the effect of chemical composition on the crystallization behavior of milk fat (MF). MF was fractionated between 20 and 40 °C into nine fractions with different melting points and was first subjected to the heating step (L20, L30, L40, and S40) followed by the cooling phase (SS40, SL40, SS30, SL30, and LL40). Furthermore, the species of fatty acids (FAs) and triglycerides (TAGs) of the MF fractions were identified. The thermodynamics, crystallization behavior, and polymorphs were determined using differential scanning calorimetry, pulsed nuclear magnetic resonance, and X-ray diffraction, respectively. The results indicated that L40 yielded the highest percentage (∼35% of the total MF) of all the fractions. Enthalpies of the melting and crystallization processes of solid fat content in this study were related to the different FA and TAG compositions of MF and its fractions. High melting fractions (HMFs) were enriched with long-chain saturated fatty acids and tri-saturated (S3) TAGs, and low melting fractions (LMFs) were enriched with short-chain unsaturated FAs and tri-unsaturated (U3) TAGs. Moreover, the various nucleation mechanisms of MF fractions were identified according to the Avrami equation. The polymorphic transformation from a β' form of double chain length structures to a β form of triple chain length occurred in the native MF and HMFs, whereas the LMFs displayed almost no crystals. PRACTICAL APPLICATION: This study represented the first time that nine fractions were obtained using MF fractionation via a heating step, followed by a cooling phase. Furthermore, the chemical composition of MF fractions was investigated. The results obtained from this study might be of specific value in understanding the functional properties of fat-based dairy food in both storage conditions and real-time applications.

Ultrasound-mediated interfacial protein adsorption and fat crystallization in cholesterol-reduced lard emulsion

Lard with a substantially reduced cholesterol content through aqueous enzyme extraction is an attractive source of lipid in healthy and nutritious emulsion food product development. The objective of this study was to elucidate the crystallization behavior (4-20 °C) of emulsions prepared from low-cholesterol lard in relation to protein emulsifier (2 and 4% whey protein isolate, WPI) and ultrasound (475 w, 5 min) treatments. The physicochemical properties and fat crystallization pattern of the emulsions were investigated. Emulsions with 4% WPI were superior to those with 2% WPI on interfacial adsorption and crystal size reduction. Ultrasonic treatment of prepared emulsions further decreased fat crystal size, promoted small and uniform crystal distribution, and slightly destabilized emulsions. Protein concentration and ultrasonic treatment had no obvious effect on crystal transition from β' to the more stable β-form based on X-ray diffraction. The melting properties determined by differential scanning calorimetry indicated that emulsified lard had a lower onset melting temperature than bulk lard, and with ultrasound treatment, the melting enthalpy increased remarkably. The ultrasound-induced change in fat crystalline structure and emulsion meta-stability may be valuable to the manufacture of healthy, emulsion-incorporated food products.

Interesterified blend-based and physical blend-based special fats: storage stability under fluctuating temperatures

BACKGROUND

Temperatures that special fat faces in a real environment fluctuate, thus, understanding the property changes of special fats under fluctuating temperatures will be helpful in guiding how to keep its high quality in the production and application process. Therefore, a comparative study was carried out on the storage stability of physical blend-based and interesterified blend-based special fats (PBSFs and IBSFs) and their oxidative stability, crystallization and physical properties were studied under fluctuating temperatures.

RESULTS

The peroxide values of IBSFs and PBSFs were less than 10.0 mmol kg^-1 after 4 weeks of storage, and IBSFs had better oxidative stability. There was little change in the solid fat content, and the hardness decreased when IBSFs and PBSFs were stored for 4 weeks. X-ray diffraction results indicated that PBSFs had only β-crystal, but IBSFs had β- and β'-crystal after storage. Moreover, in IBSFs, the transformation from β'- to β-form in PS:RO-IBSF was more obvious than that in PS:SO-IBSF (PS, palm stearin; SO, soybean oil; RO, rapeseed oil) after 4 weeks of storage, and the good integrity of crystalline network in fast-frozen special fats during fluctuating temperature storage followed the order: IBSF > PBSF, PS:RO-PBSF > PS:SO-PBSF.

CONCLUSION

The results suggest IBSF can better maintain its quality during fluctuating temperature storage than PBSF. © 2019 Society of Chemical Industry.

Storage stability studies on interesterified blend-based fast-frozen special fats for oxidative stability, crystallization characteristics and physical properties

The storage stability of two kinds of interesterified blend-based fast-frozen special fats (PS:SO-IBSF, PS:RO-IBSF) with varied triacylglycerols (TAGs) compositions under different temperatures for 4 weeks was investigated. Rancimat and peroxide values experiments indicated that both IBSFs display good oxidation stability throughout a 4-week storage. As for the physical properties of both IBSFs, the solid fat content and hardness decreased with the increase of storage temperature, and IBSFs still exhibited a viscoelastic solid-like behavior. X-ray diffraction results showed that crystal transformation from β'- to β-form was more serious when stored at 25 °C. The more content of ECN 50-type TAGs in PS:RO-IBSF is helpful to reduce its crystal transformation from β'-to β-form compared to PS:SO-IBSF. On the other hand, storage at 4 °C was beneficial for both IBSFs to keep their crystal network integrity, and the PS:RO-IBSF maintained better quality under the same storage conditions.

Physical Properties of Monoglycerides Oleogels Modified by Concentration, Cooling Rate, and High-Intensity Ultrasound

The aim of this study was to investigate the effects of monoglycerides (MG) concentration (3, 4.5, and 6 wt%), cooling rate (0.1 and 10 °C/min), and high-intensity ultrasound (HIU) application on physical properties of oleogels from MG and high oleic sunflower oil. Microstructure, melting profile, elasticity (G'), and solid fat content (SFC) were measured immediately after preparation of samples (t = 0) and after 24 hr of storage at 25 °C. Samples' textural properties (hardness, adhesiveness, and cohesiveness) and oil binding capacity (OBC) were evaluated after 24 hr at 25 °C. In general, samples became less elastic over time. Slow cooling rate resulted in lower G' after 24 hr compared to the ones obtained using 10 °C/min. Network OBC was improved by increasing MG concentration and cooling rate, and by applying HIU. After storage, oleogel melting enthalpy increased with MG concentration. In general, this behavior was not correlated with an increase in SFC. An improvement in the network structure was generally reached with the increase in cooling rate, according to texture and rheology results, for both sonicated and nonsonicated conditions. At the highest MG concentration, HIU application was more efficient at increasing OBC and hardness of the network at 0.1 °C/min. Microscopy images showed that the oleogels microstructure was changed as a consequence of HIU application and cooling rate, evidencing smaller crystals both in sonicated and faster cooled samples. Obtained results demonstrate that cooling rate, MG concentration, and HIU can be used satisfactorily to tailor physical properties of MG oleogels. PRACTICAL APPLICATION: Oleogels have been studied in the last years as semisolid fat replacers in food products. Cooling rate is an important processing parameter in the oleogel preparation because it affects their final physical properties, while high-intensity ultrasound (HIU) is a relatively novel technique to tailor lipid properties. This study is focused on the application of a slow/fast cooling rate in combination with/without HIU treatment at different monoglycerides and high oleic sunflower oil mixtures as a successful strategy to obtain oleogels with different physical properties and with potential applications in the food industry, such as fat substitutes in bakery.

Carbohydrates as Fat Replacers

The overconsumption of dietary fat contributes to various chronic diseases, which encourages attempts to develop and consume low-fat foods. Simple fat reduction causes quality losses that impede the acceptance of foods. Fat replacers are utilized to minimize the quality deterioration after fat reduction or removal to achieve low-calorie, low-fat claims. In this review, the forms of fats and their functions in contributing to food textural and sensory qualities are discussed in various food systems. The connections between fat reduction and quality loss are described in order to clarify the rationales of fat replacement. Carbohydrate fat replacers usually have low calorie density and provide gelling, thickening, stabilizing, and other texture-modifying properties. In this review, carbohydrates, including starches, maltodextrins, polydextrose, gums, and fibers, are discussed with regard to their interactions with other components in foods as well as their performances as fat replacers in various systems.

Physicochemical characterization of organogels prepared from menhaden oil or structured lipid with phytosterol blend or sucrose stearate/ascorbyl palmitate blend

Phytosterol blend and sucrose stearate/ascorbyl palmitate blend organogelators and different oil phases formed organogels with different physicochemical properties.

Crystallization of Femtoliter Surface Droplet Arrays Revealed by Synchrotron Small-Angle X-ray Scattering

The crystallization of oil droplets is critical in the processing and storage of lipid-based food and pharmaceutical products. Arrays of femtoliter droplets on a surface offer a unique opportunity to study surfactant-free colloidlike systems. In this work, the crystal growth process in these confined droplets was followed by cooling a model lipid (trimyristin) from a liquid state utilizing synchrotron small-angle X-ray scattering (SAXS). The measurements by SAXS demonstrated a reduced crystallization rate and a greater degree of supercooling required to trigger lipid crystallization in droplets compared to those of bulk lipids. These results suggest that surface droplets crystallize in a stochastic manner. Interestingly, the crystallization rate is slower for larger femtoliter droplets, which may be explained by the onset of crystallization from the three-phase contact line. The larger surface nanodroplets exhibit a smaller ratio of droplet volume to the length of three-phase contact line and hence a slower crystallization rate.