In this study, whipped cream with blends of micellar casein (MCN) and whey protein (WPI) in different ratios were prepared to investigate the role of protein interfacial behavior in determining foam properties at multiple scales, using theoretical modeling, and microscopic and macroscopic analysis. Fluid force microscopy has been used for the first time as a more realistic and direct means of analyzing interfaces properties in multiphase systems. The adsorption kinetics showed that the interfacial permeability constant of WPI (4.24 × 10-4 s-1) was significantly higher than that of the MCN (2.97 × 10-4 s-1), and the WPI interfacial layer had a higher modulus of elasticity (71.38 mN/m) than that of the MCN (47.89 mN/m). This model was validated via the mechanical analysis of the fat globules in real emulsions. The WPI-stabilized fat globule was found to have a higher Young's modulus (219.67 Pa), which contributes to the integrity of its fat globule morphology. As the ratio of MCN was increased in the sample, however, both the interfacial modulus and Young's modulus decreased. Moreover, the rate of partial coalescence was found to increase, a phenomenon that decreased the stability of the emulsion and increased the rate of aeration. The mechanical analysis also revealed a higher level of adhesion between MCN-stabilized fat globule (25.16 nN), which increased fat globule aggregation and emulsion viscosity, while improving thixotropic recovery. The synergistic effect of the blended MCN and WPI provided the highest overrun, at 194.53 %. These studies elucidate the role of the interfacial behavior of proteins in determining the quality of whipped cream and provide ideas for the application of proteins in multiphase systems.

The physicochemical properties of anhydrous milk fats (AMF) often change according to different regions and seasons, inevitably affecting dry fractionation. This study analyzed the differences in the fraction yields and physicochemical characteristics of four AMFs from different sources. The results showed that single-stage dry fractionation conducted at 25 °C easily separated AMFs into liquid fractions (L25) and solid fractions (S25) via pressure filtration, both producing satisfactory yields. Moreover, all L25s exhibited few crystals with good fluidity at 25 °C, while S25s presented as semi-solids supported by β crystal networks with a certain hardness and plasticity. However, four AMFs displayed fractionation efficiency variation, while the thermal differences among them showed no obvious correlation with those among their fractions. Generally, more trisaturated triglycerides with 48 to 54 carbon atoms in the AMF increased the S25 yield and decreased the slip melting points (SMP) of both fractions.

This work elucidates the mechanism involved in the effect of varying sterilization intensities on RDC thickening via comparative analysis of the changes in the composition and structure of RDC interfacial protein after storage at 4 °C and at 25 °C. The results showed that pasteurized RDCs (75 °C for 16 s, 90 °C for 5 min) and high-temperature sterilized RDCs (105 °C for 3 min, 115 °C for 7 min and 121 °C for 7 min) did not thicken during storage at 25 °C, and had lower viscosities and higher Ca2+ concentrations than those stored at 4 °C. Whey protein (WP) aggregates were found to have been adsorbed at the interface of high-temperature treated RDCs stored at 4 °C, leading to the aggregation of fat globules and, consequently, reversible thickening. However, high-temperature sterilized RDCs underwent into irreversible thickening at 10 d, 7 d and 3 d. This phenomenon was attributed to the large amount of heat-induced whey protein and κ-casein complex that was absorbed on the oil-water interface, with Ca2+ bonded to form bridging flocculation, which altered the secondary structure of the interfacial protein to one with increased β-sheet content and decreased random coil content.

Polyglycerol esters (PGEs) are used as emulsifiers in recombined dairy cream (RDC) to improve product quality. In this study, the effects of four PGEs with different polymerization degrees and esterification on the particle size, viscosity, zeta potential, and microrheology of RDC emulsions were investigated, and the whipping time, overrun, serum loss, and firmness of the RDC emulsions were recorded. The results show that the addition of the PGEs reduced the particle size (from 2.75 μm to 1.48–1.73 μm) and increased the viscosity (from 41.92 cP to 73.50–100 cP) and stability (from 0.354 to 0.105–0.128), which were related to the change in interfacial properties and the weakening of Brownian motion, but there were differences in the effect on the whipping behavior of the RDCs. Although the addition of 0.9% triglyceride monolaurate gave the emulsion the best stability, the RDC had a longer whipping time (318 s) and a lower overrun (116.6%). Comparatively, the 0.7–0.9% concentrations of PGE55 and tripolycerol monostearate (TMS) provided RDC with good stability and aeration characteristics, allowing inflation within 100 s and expansion rates of up to 218.24% and 186.88%, respectively. In addition, the higher degree of polymerization of polyglyceryl-10 monstearate (PMS) did not work well at any concentration. These results contribute to understanding the mechanism of action of PGEs and improving the quality of RDC.

This study aimed to investigate the crystal network of bulk milk fat fractions and the partial coalescence, and the rheological properties of their oil-in-water (O/W) emulsions. Different milk fat fraction model systems were compared for their physicochemical properties, crystallization kinetics, and fat crystal networks across a range of temperatures. The extent of partial coalescence and rheological properties of the O/W emulsion prepared by different milk fat fractions were further analyzed. The results demonstrated that the ratio between saturated fatty acids (SFA) and unsaturated fatty acids and triacylglycerides (TAG) influenced the melting thermal behaviors, solid fat contents (SFC), and crystal networks of various milk fat fractions, which in turn influenced the partial coalescence and rheological characteristics of their O/W emulsions. Moreover, an excellent fit of the trend line confirmed that hardness increased exponentially with SFC. Trisaturated TAG in fractions with high melting points (HMF) such as milk fat fraction MF45, whose clarification temperature was 45°C, enriched long-chain SFA (saturated:unsaturated fatty acid = 2.2:1). We found that MF45 achieved higher SFC and hardness in the range of 0 to 40°C and, ultimately, formed a well-defined microstructural network with thick, rod-like crystals. Further, TAG in fractions with low melting points (LMF) such as MF10, whose clarification temperature was 10°C, were enriched with short-chain and unsaturated fatty acids (saturated:unsaturated fatty acid = 1.5:1), and a disordered crystal network in MF10, composed of randomly arranged, translucent platelets, was detected. Although fat globules of HMF and LMF were stabilized against coalescence, this could be attributed to a variety of mechanisms involving SFC, liquid fat, protective film around the fat globule, and minor lipids. According to the rheological profiles, all O/W emulsions exhibited weak viscoelastic "gel-like" structures [storage modulus (G') > loss modulus (G")] over most of the measured range. The G' values and apparent viscosity of HMF were greater than those of other fractions, indicating that the large and rigid crystals strengthen the networks more effectively.

This study aimed to find new strategies for enhancing the stability and texture properties of aerated emulsion by combining different animal fats with different ratios. Beef tallow (BT)/ lard (LA) were mixed at different ratios to prepare oil-in-water (O/W) emulsions, with and without aeration. The compatibility, crystallization behavior, stability, and rheology in both O/W and aerated emulsion systems prepared with BT/LA binary blends were further investigated. Larger and inhomogeneous β' and β crystal mixtures appeared as the BT ratio increased. Monotectic or eutectic interaction was displayed according to different BT/LA ratios, solid fat content (SFC) and temperatures. O/W emulsion prepared with BT/LA binary showed higher apparent viscosity with larger fat globules distributed as the BT ratio increased. BT had higher SFC at any given temperature and the fat globule aggregation extent was higher. Partial coalescence occurred as the LA ratio increased when SFC < 35 %. Higher foam firmness of the aerated emulsion was achieved by BT/LA binary with higher BT ratios. As a result, combining BT and LA with different ratios achieved higher emulsion stability and foam properties. This study provides a novel insight into the application of different animal fats and the improvement of high-quality whippable products.

The effects of variations in the heat treatment process of milk on its quality and flavor are inevitable. This study investigated the effect of direct steam injection and instantaneous ultra-high-temperature (DSI-IUHT, 143 °C, 1–2 s) sterilization on the physicochemical properties, whey protein denaturation (WPD) rate, and volatile compounds (VCs) of milk. The experiment compared raw milk as a control with high-temperature short-time (HTST, 75 °C 15 s and 85 °C 15 s) pasteurization and indirect ultra-high-temperature (IND-UHT, 143 °C, 3–4 s) sterilization. The results showed no significant differences (p > 0.05) in physical stability between milk samples with different heat treatments. The DSI-IUHT and IND-UHT milks presented smaller particle sizes (p < 0.05) and more concentrated distributions than the HTST milk. The apparent viscosity of the DSI-IUHT milk was significantly higher than the other samples (p < 0.05) and is consistent with the microrheological results. The WPD of DSI-IUHT milk was 27.52% lower than that of IND-UHT milk. Solid-phase microextraction (SPME) and solvent-assisted flavor evaporation (SAFE) were combined with the WPD rates to analyze the VCs, which were positively correlated with ketones, acids, and esters and negatively associated with alcohols, heterocycles, sulfur, and aldehydes. The DSI-IUHT samples exhibited a higher similarity to raw and HTST milk than the IND-UHT samples. In summary, DSI-IUHT was more successful in preserving the milk’s quality due to its milder sterilization conditions compared to IND-UHT. This study provides excellent reference data for the application of DSI-IUHT treatment in milk processing.

Oil addition is challenging during high-moisture extrusion due to the negative fiber formation effects. A previous study found that oil-in-water (O/W) emulsions could significantly increase the oil content in high-moisture extrudates, but the molecular mechanism remained unclear. This study aimed to determine O/W emulsion influence on protein physicochemical properties in SPI extrudates during high-moisture extrusion. O/W emulsions were mixed with soy protein isolates (SPI) to prepare extrudates with oil/water ratios of 0/65, 4/61, and 8/57 (w/w). SDS-PAGE and ATR-FTIR analysis showed that higher oil/water ratios enhanced protein aggregation and promoted alteration from β-sheet to random coil in SPI extrudates, which could be correlated to the reduction of protein solubility. The color was altered to lighter and yellow, and hardness, chewiness, and fiber degree decreased with increased oil/water ratios in SPI extrudates. In addition, in vitro digestion analyses showed that higher oil content contributed to improved protein digestibility.

Up to 0.9% (w/w) triglycerol monostearate (TGMS) was added as a stabiliser to recombined dairy cream (RDC), containing 36% anhydrous milk fat (AMF). The physical properties, such as droplet size, surface protein mass, zeta-potential, rheological characteristics, creaming stability, and whipping qualities, were compared based on the TGMS concentration. TGMS addition significantly improved the stability and whipping properties of RDC compared with cream stabilised with milk protein alone. Higher TGMS level substantially increased the viscosity and zeta-potential, narrowed droplet size distribution, and decreased average droplet size. Increasing the TGMS concentration during the whipping process resulted in a shorter whipping time, increased overrun, reduced serum loss, and softer cream texture. Furthermore, the adsorbed protein mass on the interface decreased from 1.14 +/- 0.01% to 0.60 +/- 0.04% in the presence of TGMS concentrations of 0.5% and higher, indicating the effective displacement of almost half of these proteins. (C) 2019 Elsevier Ltd. All rights reserved.

The current study aimed to compare the effectiveness of two extraction techniques, namely simultaneous distillation–extraction (SDE) and solid-phase microextraction (SPME), in evaluating key aroma compounds in butters. Volatile compounds’ contributions to butter flavors were evaluated employing both odor active values (OAVs) and gas chromatography olfactometry (GC-O). The results showed that the species of volatile compounds detected by the two techniques were almost the same, whereas their volatile profiles were obviously different. Using SDE method, methyl ketones took up the largest proportion of the volatile compounds, followed by fatty acids. Using SPME method, the most abundant compounds were the fatty acids, followed by lactones. More methyl ketones were detected in the SDE extract owing to lipid degradation as a consequence of the high temperature during extraction. Lactones were considered to be the key aroma compounds, especially δ-decalactone, which was identified by both OAVs and GC-O.

The effect of three casein products, micellar casein concentrate (MCC), calcium caseinate (CaC), and sodium caseinate (NaC), on the stability and whipping properties of recombined dairy cream (RDC) was investigated. The cream was prepared with a variety of casein concentrations at different levels (0.5, 1.5, and 2.5%, w/w). In each cream system, an increase in the concentration provided better stability for RDC due to smaller particle size and higher viscosity (except for 2.5% CaC). However, the trend did not apply to different cream systems. MCC creams exhibited superior stability at higher concentrations (1.5% and 2.5%), which could probably be attributed to the larger steric repulsions. The NaC cream could not be whipped into a stable aerated foam, while the excellent whipping properties of MCC and CaC creams resulted in well-whipped products. The results suggested that MCC was more suitable for RDC preparation.

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.

The correlation between thermodynamic and whipping properties of milk fat when used in recombined dairy cream (RDC) was investigated; thermodynamic behaviour of milk fat and the microstructure of RDC were analysed. Differential scanning calorimetry curves of anhydrous milk fats (AMFs) showed two peaks (7 degrees C and 15 degrees C), implying a difference in the crystallisation mechanisms. RDCs whipped at 7 degrees C demonstrated significantly higher cream overrun, firmness, and shorter optimum whipping time in comparison with these attributes at 15 degrees C. Additionally, RDC whipped at 7 degrees C generated bigger milk fat globules and was characterised by less flocculation and fewer broken air bubbles. Comparative analysis of the whipping properties at 7 degrees C and 4 degrees C revealed no significant differences. The results suggest that 7 degrees C is a more suitable temperature than 15 degrees C at which to whip RDC, and an ideal alternative temperature to that of 4 degrees C, for lower energy consumption. (C) 2019 Published by Elsevier Ltd.

This study aimed to evaluate the effects of different concentration methods (nanofiltration and evaporation) and heat treatments on the gel properties of milk protein concentrate (MPC). The MPC gels were produced using glucono-δ-lactone (GDL) as an acidifier with different preheat treatments (30 min at 80°C and 5 min at 92°C). We then evaluated the effect of preheat treatments on MPC gel properties, including storage modulus (G′), loss tangent (tan δ), firmness, whey separation, and microstructure. The results indicated that without preheating, evaporation (EP)-MPC had higher G′ and firmness, and lower tan δ and whey separation than nanofiltration (NF)-MPC. These results suggest that EP-MPC produced a better acid-induced gel than NF-MPC when no preheat treatments were performed. After preheating, however, except for a very small difference in the final G′ (EP-MPC was higher), the 2 MPC did not differ significantly in firmness, final tan δ, or whey separation. Additionally, compared with the gel of unheated MPC, both preheat-treated gels (NF-MPC and EP-MPC) achieved increased G′ and firmness and decreased tan δ and whey separation. The preheat-treated MPC also displayed a more flexible-stranded network. These findings demonstrate that, given a suitable heating treatment, NF-MPC compares favorably with EP-MPC in achieving desired gel properties.

This study sought to evaluate the role of intrinsic (hydrophobicity, zeta potential, and surface polysaccharides) and extrinsic (pH, temperature, ionic strength, and the treatment on the steel surface) factors in determining the adhesive ability of thermophilic bacilli. Hydrophobicity of the bacilli cells demonstrated the strongest linear correlation with their adhesion ability, producing an R-2 value of 0.83. All of the strains achieved their highest adhesion ability at their optimum growth temperature (47 and 55 degrees C) and at a neutral pH level. An ionic strength of sodium chloride solution at 3.54 g L-1 led to highest attachment of the bacilli, when compared with lower or higher ionic strengths. Additionally, treating the steel surface with domestic detergents was determined to be the most effective approach to inhibit the attachment of the bacilli; this appears to be a promising approach to improve the formula of production line cleaning detergents in milk powder factories. (C) 2018 Elsevier Ltd. All rights reserved.

It is useful to carefully observe the evolution of foam structures to elucidate the factors affecting cream during whipping. In this study, confocal laser scanning microscopy and a double dyeing technology were used to investigate the microstructural evolution of a rigid foam structure in whipped cream. The location of fat and proteins were determined according to the signals they produce at different characteristic wavelengths. Protein membranes on the surface of air bubbles were clearly observed. A simple yet comprehensive characterization of the whipping process was established according to the micrographs and supported by relevant theories. The formation of a rigid foam structure depends on foaming of the protein in the plasma phase and partial coalescence of fat globules. The formation of protein foam in the cream, creation of net structure, and system breakage and collapse phenomena occurring throughout the whole whipping evolution process was depicted and distinguished visually by different colors.

Milk protein concentrates (MPCs) serve as novel functional ingredients in the food industry and, in addition, are highly nutritional. The aim of this study is to evaluate the effects of two different concentration methods, namely nanofiltration and evaporation, on MPC gel properties. In this research, the MPC gels were produced using glucono-delta-lactone (GDL) as the acidifier, at different temperatures (25, 30, 35, 40, and 45 degrees C) and CaCl2 (between 5 and 30 mmol/L). The dependence properties of the MPC gels were observed, including storage modulus (G '), loss tangent (tan delta), firmness and microstructure. Measured at the same level of temperature and CaCl2, EP-MPC produced higher firmness and G ' value compared to NF-MPC. Also, EP-MPC exhibited a more homogeneous, branched microstructure of gel network than NF-MPC. These results indicated that EP-MPC has superior gel properties compared to NF-MPC, which contribute comprehensive information to improve decisions regarding concentrations in the production of MPC gels. Practical applications This study investigated the effects of concentration methods (nanofiltration and evaporation) and pretreatment parameters (gelation temperature and CaCl2 concentrations) on the gel properties of MPCs in terms of rheological behavior and texture characteristics. The results have manifested that the differences between the two kinds of MPCs produced from evaporation and nanofiltration depend on the levels of gelation temperature and CaCl2 concentrations, giving opportunity for the different MPCs to achieve similar gel properties. Manufacturers could benefit from this research in reasonably deciding concentration way in the production of MPC gels for different applications.

The effect of melting point on the physical properties of anhydrous milk fat were investigated. The results showed that high melting fractions (HMF) (S30,S35) were enriched in long-chain fatty acids, whereas low melting fractions (LMF)(S5,S10,S15) were enriched in short-chain and unsaturated fatty acids. From S5 to S35, enthalpy value was gradually increased on both crystallization and melting condition, so as SFC on different temperature. The mixture and chemical interesterification allowed obtaining fats with various degrees of plasticity, increasing the possibilities for the commercial use of different fraction of AMF.

This study evaluated the effect of transglutaminase (TGase) treatment on the textural properties of acid-induced milk protein concentrate (MPC) gel and yoghurt fortified with modified MPC. The effects of reaction duration, pH, temperature, and enzyme concentration on the strength and water-holding capacity (WHC) of MPC (72% protein) gel were analysed. The gelling mechanism of modified MPC was explored and the modified MPC was incorporated into production of stirred-style yoghurt. Optimal MPC gel properties were achieved after TGase treatment at pH 7.25 and 35 degrees C for 1 h using 2.5 U g(-1) TGase. The TGase-induced reaction occurred quickly in the first 0.5 h and led to the formation of large particles with fairly uniform size (from 100 to 1000 nm). All the kappa-casein and 61.7% of the beta-casein participated in the reaction. Modified MPC greatly enhanced the gel quality of the yoghurt in terms of gel strength, viscosity, WHC and serum-binding capacity. (c) 2017 Elsevier Ltd. All rights reserved.

Recombined low-fat dairy cream (RLFDC) primarily comprises anhydrous milk fat and milk protein. The primary advantage of RLFDC is that its ingredients can be easily stored and transported, whereas its most notable disadvantage is poor stability. The effects of glycerol monostearate (GMS) or sorbitan monooleate ethoxylate (Tween 80) on the physical properties and stability of RLFDC (20% fat and 2% protein) were investigated in this study. Physical properties were evaluated according to droplet size, surface protein concentration, ζ-potential, and apparent viscosity; stability was assessed according to creaming rate. Results showed that GMS and Tween 80 could significantly increase the creaming stability of RLFDC compared with a control sample. The creaming stability of RLFDC with GMS highly depended on ζ-potential and apparent viscosity, which contributed to electrostatic repulsion and intermolecular resistance. The effect of Tween 80 on the creaming stability of RLFDC was independent of the physical properties.