Non-thermal techniques as an approach to modify the structure of milk proteins and improve their functionalities: a review of novel preparation.

BACKGROUND: Milk proteins (MPs) have been widely used in the food industry due to their excellent functionalities. However, MPs are thermal-unstable substances and their functional properties are easily affected by heat treatment. Emerging non-thermal approaches (i.e., high-pressure homogenization (HPH), ultrasound (US), pulsed electric field (PEF)) have been increasingly popular. A detailed understanding of these approaches' impacts on the structure and functionalities of MPs can provide theoretical guidance for further development to accelerate their industrialization. SCOPE AND APPROACH: This review assesses the mechanisms of HPH, US and PEF technologies on the structure and functionalities of MPs from molecular, mesoscopic and macroscopic levels, elucidates the modifications of MPs by these theologies combined with other methods, and further discusses their existing issues and the development in the food filed. KEY FINDINGS AND CONCLUSIONS: The structure of MPs changed after HPH, US and PEF treatment, affecting their functionalities. The changes in these properties of MPs are related to treated-parameters of used-technologies, the concentration of MPs, as well as molecular properties. Additionally, these technologies combined with other methods could obtain some outstanding functional properties for MPs. If properly managed, these theologies can be tailored for manufacturing superior functional MPs for various processing fields.

Oil body extraction from high-fat and high-protein soybeans by laccase cross-linked beet pectin: physicochemical and oxidation properties.

BACKGROUND: Soybean oil bodies (SOB) are droplets of natural emulsified oil. Soybean oil emulsifies well but it is easily oxidized during storage. Beet pectin is a complex anionic polysaccharide, which can be adsorbed on the surface of liposomes to improve their resistance to flocculation. Laccase can covalently cross-link ferulic acid in beet pectin, and its structure is irreversible, which can improve the stability of polysaccharides. RESULTS: At pH 2.5, laccase cross-linked beet pectin high-oil soybean oil body (HOSOB) and high-protein soybean oil body (HPSOB) emulsions showed obvious aggregation and severe stratification, and the oxidation of the emulsions was also high. The flocculation of emulsions decreased with an increase in the pH. The effect of pH on the flocculation of emulsion was confirmed by confocal laser electron microscopy. The ζ potential, emulsification, and rheological shear force increased with increasing pH whereas the particle size and surface hydrophobicity decreased with increasing pH. CONCLUSION: This experiment indicates that the physicochemical stability of the two composite emulsions was strongly affected under acidic conditions but stable under neutral and weakly alkaline conditions. Under the same acid-base conditions, the degree of oxidation of HPSOB composite emulsion changes substantially. The results of this study can provide a basis for the design of very stable emulsions to meet the demand for natural products. © 2023 Society of Chemical Industry.

Lactitol and ß-cyclodextrin alleviate the intensity of goaty flavor.

BACKGROUND: Goat milk has balanced nutritional composition, is conducive to digestion and absorption, and does not easily lead to allergic reactions. However, the special goaty flavor in milk has seriously affected consumer acceptance. It is imperative to alleviate the goaty flavor in a safe and efficient way. RESULTS: This study indicated that the supplementation of 6 g kg-1 ß-cyclodextrin or 8 g kg-1 lactitol in goat milk significantly alleviated goaty flavor and improved sensory characteristics. Furthermore, the supplementation of ß-cyclodextrin and lactitol had a synergistic effect in reducing the content of free fatty acids that cause goaty flavor. The content of caproic acid (C6 H12 O2 ), octanoic acid (C8 H6 O2 ), and decanoic acid (C10 H20 O2 ) decreased by 42.46%, 39.45%, and 46.41%, respectively, after a combined group was supplemented with 6 g kg-1 ß-cyclodextrin and 7 g kg-1 lactitol, which was significantly lower than in groups given ß-cyclodextrin or lactitol individually. CONCLUSION: This study provides a novel and effective approach to alleviate goaty flavor and promote the competitiveness of goat milk products. © 2022 Society of Chemical Industry.

MFGM components promote gut Bifidobacterium growth in infant and in vitro.

PURPOSE: Infant gut microbiota which plays an important role in long-term health is mainly shaped by early life nutrition. However, the effect of nutrients on infants gut microbiota is less researched. Here, we present a study aiming to investigate in vitro a modified formula that is supplemented with milk fat globule membrane (MFGM) that were missing in common formulas when compared with human milk and to assess the impact of feeding scheme on microbiota and metabolism. METHODS: A total of 44 infants including 16 from breast milk feeding, 13 from common formula feeding and 15 from modified formula feeding were analyzed, and A cross-sectional sampling of fecal and urine was done at 1 month-of-age. Stool microbiota composition was characterized using high-throughput DNA sequencing, and urinary metabolome was profiled by nuclear magnetic resonance (NMR). In vitro growth experiment of Bifidobacterium with key components from MFGM was performed and analyzed by both DNA and RNA. RESULTS: Stool samples from the infants who were breastfed had a higher relative abundance of Bifidobacterium and a lower relative abundance of Escherichia than the formula-fed infants. The stool microbiome shifts were associated with urine metabolites changes. Three substances including lactadherin, sialic acid and phospholipid, key components of MFGM were significantly positively correlated to Bifidobacterium of stool samples from infants, and stimulated the growth rate of Bifidobacterium significantly by provided energy in vitro growth experiment with RNA analysis. CONCLUSIONS: These findings suggest that the key components from MFGM could improve infants' health by modulating the gut microbiome, and possibly supporting the growth of Bifidobacterium. REGISTRATION: Clinicaltrials.gov NCT02658500 (registered on January 20, 2016).

Characterization of major volatile compounds in whey spirits produced by different distillation stages of fermented lactose-supplemented whey.

This research aimed to advance the understanding of acceptable sensory qualities of potable whey-based spirit from nonsupplemented, mid-supplemented, and high-supplemented whey samples by analyzing major volatile compounds during different stages of distillation (head, heart, and tail). The results demonstrated that commercial Saccharomyces cerevisiae strain in lactase-hydrolyzed whey showed rapid and complete sugar hydrolysis and efficient ethanol production in 24, 30, and 36 h on average, producing up to 29.5, 42.1, and 56.4 g/L of ethanol, respectively. The variations in titratable acidity, specific gravity, pH value, residual protein, sugar content, and alcohol yield were investigated during the fermentation. The total amount of volatile compound concentrations significantly decreased from the head (2,087-2,549 mg/L) to the tail whey spirits (890-1,407 mg/L). In the whey spirit, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-propanol, 1-propanol, acetaldehyde, and ethyl acetate were the most prevalent dominant compounds, accounting for the largest proportion of total volatile compounds. The volatile compounds detected were far below the acceptable legal limit. The results suggest that high sensory qualities of potable whey-based spirits can be produced by fermentation of lactose-supplemented whey with S. cerevisiae cells.

NaCl induces flocculation and lipid oxidation of soybean oil body emulsions recovered by neutral aqueous extraction.

BACKGROUND: Soybean oil bodies (SOB) are naturally pre-emulsified lipid droplets recovered directly from soybean seeds. Almost all food emulsions contain salts. However, it was not clear how the incorporation of salts affected the physicochemical stability of SOB. RESULTS: This study investigated the effect of NaCl (0-1.2%) on the physical and oxidative stability of SOB emulsions under neutral (pH 7) and acidic (pH 3) conditions. In the presence of NaCl, the SOB emulsion (pH 7) showed strong flocculation during storage due to electrostatic screening. The NaCl-induced flocculation of SOB was attenuated at pH 3, which may be due to the difference in conformation or interaction of the protein interfaces covering SOB at different pH values. The increase in ionic strength or acid conditioning treatment resulted in a remarkable increase in the stability of SOB emulsions against coalescence. The confocal laser scanning microscopy images also confirmed the NaCl-induced changes in the flocculation/coalescence properties of SOB. The oxidative behavior tests indicated that SOB emulsions containing NaCl were more susceptible to lipid oxidation but protein oxidation was inhibited due to electrostatic screening, which reduced pro-oxidant accessibility of unadsorbed proteins in the emulsion. This oxidative behavior was attenuated at pH 3. CONCLUSION: The incorporation of NaCl significantly reduced the physical and oxidative stability of the SOB emulsion, and acidic pH mitigated NaCl-induced flocculation and lipid oxidation of SOB. © 2021 Society of Chemical Industry.

Physical and oxidative stability of astaxanthin microcapsules prepared with liposomes.

BACKGROUND: Oil bodies (OBs) are a kind of natural and stable oil nucleate microcapsule in which the triglyceride matrix can be used as an appropriate carrier of hydrophobic molecules. Astaxanthin has high antioxidant properties but is extremely sensitive to oxidation, causing the loss of its bioactive properties. RESULTS: The purpose of this study was to clarify the effects of environmental factors (light, oxygen, temperature, and pH) on the physical and oxidative stability of astaxanthin microcapsules prepared with peanut oil bodies (POBs). After 14 days of storage, the retention rate of astaxanthin in peanut oil microcapsules (POMs) was significantly increased. The astaxanthin retention rate of POMs stored under light conditions was higher than under dark conditions. Similarly, the retention rate of astaxanthin in POMs was significantly increased during vacuum storage. The astaxanthin retention rate was also the highest when POMs were stored at 4 °C, whereas it was the lowest at pH 3.0. CONCLUSION: The experiment demonstrated that microcapsulation could improve the astaxanthin retention rate and storage stability, and recombinant OBs were potential ideal wall materials for astaxanthin embedding. © 2022 Society of Chemical Industry.

Investigation of the consequences of ultrasound on the physicochemical, emulsification, and gelatinization characteristics of citric acid-treated whey protein isolate.

The effect of ultrasound (US) pretreatment (0, 200, 400, 600, and 800 W) on the physicochemical, emulsification, and gelatinization characteristics of citric acid (CA)-treated whey protein isolate (WPI) was investigated. Size exclusion chromatography demonstrated that when compared with untreated WPI, US pretreatment promoted production of more molecular polymers in the CA-treated WPI. There was a reduction in particle size of CA-treated WPI with the increase of US power (0-800 W), whereas its free sulfhydryl content, surface hydrophobicity, and intrinsic fluorescence strength increased. Furthermore, compared with untreated WPI, emulsifying ability index and emulsifying stability index of CA-treated WPI were increased by 14.04% and 10.10%, respectively, at 800 W. Accordingly, US pretreatment promoted the gel formation of CA-treated WPI, and its gel hardness was increased by 28.0% with US power ranging from 0 to 800 W. Therefore, US and CA treatment can be considered as an effective way to improve the emulsifying and gelatinization characteristics of WPI.

Effect of cinnamon essential oil on gut microbiota in the mouse model of dextran sodium sulfate-induced colitis.

Increasing evidence has confirmed that the antimicrobial and anti-inflammatory effects of cinnamon essential oil (CEO) contribute to protection against inflammatory bowel disease (IBD). The dextran sodium sulfate (DSS)-induced colitis mouse model was established to investigate the correlation between the protective effects of CEO and the regulation of intestinal microflora. The symptoms of IBD were assessed by measuring the hemoglobin content, myeloperoxidase activity, histopathological observation, cytokines, and toll-like receptor (TLR4) expression. The alteration of the fecal microbiome composition was analyzed by 16S rRNA gene sequencing. The results indicated that the oral administration of CEO enriched with cinnamaldehyde effectively alleviated the development of DSS-induced colitis. In contrast to the inability of antibiotics to regulate flora imbalance, the mice fed with CEO had an improved diversity and richness of intestinal microbiota, and a modified community composition with a decrease in Helicobacter and Bacteroides and an increase in Bacteroidales_S24-7 family and short-chain fatty acids (SCFA)-producing bacteria (Alloprevotella and Lachnospiraceae_NK4A136_group). Moreover, the correlation analysis showed that TLR4 and tumor necrosis factor-α was positively correlated with Helicobacter, but inversely correlated with SCFA-producing bacteria. These findings indicated from a new perspective that the inhibitory effect of CEO on IBD was closely related to improving the intestinal flora imbalance.

Effect of pH on physicochemical properties of oil bodies from different oil crops.

The objective of this study was to determine the effects of pH on the physicochemical properties of soybean oil bodies (SBOBs), peanut oil bodies (PNOBs) and sunflower oil bodies (SFOBs). The mean particle diameter[4,3] (D[4,3]) of oil bodies (OBs) changed to a stationary trend with increased pH. The surface hydrophobicity (H0) of SBOBs, PNOBs and SFOBs significantly decreased with increasing pH 2-12. The emulsifying activity index of SBOBs, PNOBs and SFOBs decreased with increased pH from 2 to 10. The viscosity modulus (G″) value of SBOBs at pH 4 was significantly higher than at pH 7 and pH 9. The initial elastic modulus (G') and G″ values of PNOBs at pH 9 were significantly higher than at pH 4 and pH 7. The G″ values of SFOBs at pH 4 and pH 9 were significantly lower than at pH 7. The steroleosin protein bands of SBOBs significantly decreased at pH 12. The protein bands of PNOBs were reduced at pH 2-4 and pH 10-12, and protein bands decreased most obviously at pH 2. The enthalpy of denaturation (ΔH) values of the oil body (OB) protein at pH 9 were significantly higher than at pH 4 and pH 7. The results showed that the ζ-potential, D[4,3], emulsifying property and H0 of SBOBs, PNOBs and SFOBs were similar to the change of pH value. The three types of OBs have better stability away from the isoelectric point.

Antibacterial Activity and Mechanism of Action of Bovine Lactoferricin Derivatives with Symmetrical Amino Acid Sequences.

In recent years, the overuse of antibiotics has become very serious. Many pathogenic bacteria have become resistant to them, with serious potential health consequences. Thus, it is urgent that we develop new antibiotic drugs. Antimicrobial peptides (AMPs) are important endogenous antibacterial molecules that contribute to immunity. Most have spectral antibacterial properties and do not confer drug resistance. In this paper, an 11-residue peptide (LFcinB18⁻28) with a sequence of KCRRWQWRMKK was modified by amino acid substitution to form a symmetrical amino acid sequence. The antibacterial activities and mechanisms of action of engineered peptides including KW-WK (KWRRWQWRRWK), FP-PF (FPRRWQWRRPF), FW-WF (FWRRWQWRRWF), and KK-KK (KKRRWQWRRKK) were investigated. The four engineered peptides could more effectively inhibit bacteria than the original peptide, LFcinB18⁻28. This suggested that a symmetrical amino acid sequence might enhance the antibacterial activity of AMPs. However, only peptides KW-WK, FP-PF, and KK-KK were safe; FW-WF displayed hemolytic activity. The engineered peptides shared cationic and amphipathic characteristics that facilitated interactions with the anionic microbial membranes, leading to disruption of membrane integrity and permeabilizing microbial membranes, resulting in cell death. Therefore, a symmetrical amino acid sequence and related structural parameters offer an alternative approach to the design of AMPs. This will provide a scientific basis for the design and synthesis of new AMPs.

Surface Hydrophobicity and Functional Properties of Citric Acid Cross-Linked Whey Protein Isolate: The Impact of pH and Concentration of Citric Acid.

The effects of citric acid-mediated cross-linking under non-acidic conditions on the surface hydrophobicity, solubility, emulsifying, and foaming properties of whey protein isolate (WPI) were investigated. In this research, citric acid-mediated cross-linking could not only increase the surface hydrophobicity of whey proteins at pH 7.0 and 8.0, but it also improved its emulsifying and foaming properties. The emulsifying activity and foaming ability of WPI reached a maximum under the condition of 1% citric acid and pH 7.0. However, the solubility of WPI-CA gradually decreased with pH and the content of citric acid increased. Therefore, the cross-linking mediated by citric acid under non-acidic aqueous conditions, markedly altered the surface hydrophobicity and enhanced emulsifying and foaming properties of WPI.

Broad-Spectrum Antimicrobial Activity and Low Cytotoxicity against Human Cells of a Peptide Derived from Bovine αS1-Casein.

The primary objective of this study was to improve our understanding of the antimicrobial mechanism of protein-derived peptides and to provide evidence for protein-derived peptides as food bio-preservatives by examining the antimicrobial activities, low cytotoxicity, stabilities, and mechanism of Cp1 (LRLKKYKVPQL). In this study, the protein-derived peptide Cp1 was synthesized from bovine αS1-casein, and its potential use as a food biopreservative was indicated by the higher cell selectivity shown by 11-residue peptide towards bacterial cells than human RBCs. It also showed broad-spectrum antimicrobial activity, with minimum inhibitory concentrations (MICs) of 64⁻640 µM against both gram-positive and gram-negative bacteria. The peptide had low hemolytic activity (23.54%, 512 µM) as well as cytotoxicity. The results of fluorescence spectroscopy, flow cytometry, and electron microscopy experiments indicated that Cp1 exerted its activity by permeabilizing the microbial membrane and destroying cell membrane integrity. We found that Cp1 had broad-spectrum antimicrobial activity, low hemolytic activity, and cytotoxicity. The results also revealed that Cp1 could cause cell death by permeabilizing the cell membrane and disrupting membrane integrity. Overall, the findings presented in this study improve our understanding of the antimicrobial potency of Cp1 and provided evidence of the antimicrobial mechanisms of Cp1. The peptide Cp1 could have potential applications as a food biopreservative.

Effects of ultrasound treatment on physico-chemical, functional properties and antioxidant activity of whey protein isolate in the presence of calcium lactate.

BACKGROUND: The aim of this study was to investigate the effects of ultrasound applied at various powers (0, 200, 400, 600 or 800 W) and for different times (20 or 40 min) on the physico-chemical, functional properties and antioxidant activities of whey protein isolate (WPI) dispersions in the presence of 1.20 mmol L-1 calcium lactate. RESULTS: Surface hydrophobicity and free sulfhydryl group of the WPI dispersions containing 1.2 mmol L-1 calcium lactate were significantly enhanced after sonication. Furthermore, particle size of WPI dispersions containing 1.20 mmol L-1 calcium lactate was minimised after sonication. Scanning electron microscopy of sonicated WPI suspensions containing 1.20 mmol L-1 calcium lactate showed that WPI microstructure had significantly changed. After WPI dispersions were treated by sonication assisted with calcium lactate, its gel strength enhanced and solubility decreased. Gel strength of sonicated WPI dispersions (600 W, 40 min) was the maximum among all the WPI treatments. Emulsification activity of sonicated WPI dispersions reduced while its emulsion stability increased. The DPPH radical scavenging activity and ferrous reducing power of sonicated WPI dispersions mostly increased. CONCLUSION: Ultrasound treatments induced structural changes in WPI molecules, leading to different microstructure and improved gel strength of WPI in the presence of calcium lactate. © 2017 Society of Chemical Industry.

[Study on biological characteristics and stability of the linear derivative Bac2a from bactenecin].

The objective of the study is to analyze the biological characteristics and stability of the linear derivative Bac2a from bactenecin, compared with the control peptide melittin. The secondary structure, antibacterial activity, hemolytic activity, cell toxicity and stability of the Bac2a were determined by circular dichroism spectroscopy, broth micro-dilution method and MTT assay. The results showed that Bac2a was a nonregular curl in aqueous solution, however, it was an α-helix structure in the hydrophobic environment. The minimal inhibitory concentration (MIC) of Bac2a ranged from 2 to 32 µmol/L, so the bacteriostatic activity of Bac2a was strong. The hemolytic rate was only 14.81% when the concentration of Bac2a was 64 µmol/L, which showed that the hemolytic rate of Bac2a was low. The therapy index of Bac2a was 3.26, and the cytotoxicity was relatively low, thus the cell selectivity was relatively high. In addition, with the heating treatment of 100℃ for 1 h, Bac2a still possessed rather a high antibacterial activity and showed a good heating stability. In a word, Bac2a has good application prospects in food, medicine and other fields, and is expected as a substitute for traditional antibiotics.

Seven sour substances enhancing characteristics and stability of whey protein isolate emulsion and its heat-induced emulsion gel under the non-acid condition.

Protein emulsion gels, as potential novel application ingredients in the food industry, are very unstable in their formation. However, the incorporation of sour substances (phosphoric acid, lactic acid, acetic acid, malic acid, glutamic acid, tartaric acid and citric acid) would potentially contribute to the stable formation of whey protein isolate (WPI) emulsion as well as its gel. Thus, in this work, physical stability of seven acid-treated WPI emulsions, and microstructures, rheological properties, water distribution of its emulsion gels were characterized and compared. Initially, the absolute zeta-potential, interfacial protein adsorption, and emulsifying characteristics of acid-induced WPI emulsions were higher in contrast to acid-untreated WPI emulsions. Moreover, acid-induced WPI emulsions were thermally induced (95 ℃, 30 min) to form its emulsion gel networks via disulfide bonds as the main force (acid-untreated WPI emulsions were unable to form gels). High-resolution microscopic observation revealed that acid-induced WPI in emulsion gel network showed the morphology of aggregates. Dynamic oscillatory rheology results indicated that acid-induced emulsion gel exhibited highly elastic behavior and its viscoelasticity was associated with the generation of protein gel networks and aggregates. In addition, PCA and heatmap results further illustrated that malic acid-induced WPI emulsion gels had the best water holding capacity and gel characteristics. Therefore, this study could provide an effective way for the foodstuffs industry to open up new texture and healthy emulsion gels as fat replaces and loading systems of bioactive substances.

Exploring the role of γ-Oryzanol on stabilization mechanism of Pickering emulsion gels loaded by α-Lactalbumin or ß-Lactoglobulin via multiscale approaches.

The research explored the role of γ-oryzanol (γs) on stabilization behavior of Pickering emulsion gels (PEGs) loaded by α-lactalbumin (α-LA) or ß-lactoglobulin (ß-LG), being analyzed by experimental and computer methods (molecular dynamic simulation, MD). Primarily, the average particle size of ß-LG-γS was expressed 100.07% decrease over that of α-LA-γS. In addition, γs decreased the dynamic interfacial tension of two proteins with the order of ß-LG < α-LA. Meanwhile, quartz crystal microbalance with dissipation proved that ß-LG-γS exhibited higher adsorption mass and denser rigid interface layer than α-LA-γS. Moreover, the hydrophobic group of γS had electrostatic repulsion with polar water molecules in the aqueous phase, which spread to the oil phase. ß-LG-γS had lower RMSD/Rg value and narrower fluctuation compared with α-LA-γS. This work strength the exploration of interfacial stabilization mechanism of whey protein-based PEGs, which enriched its theoretical research for industrial-scale production as the replacement of trans fat and cholesterol.

Impact of manufacturing processes on glycerolipid and polar lipid composition and ultrastructure in infant formula.

The introduction of exogenous lipids in the production of infant formula induces significant alterations in milk lipid composition, content, and membrane structure, thus affecting the lipid digestion, absorption, and utilization. This study meticulously tracks these changes throughout the manufacturing process. Pasteurization has a significant effect on phosphatidylcholine and sphingomyelin in the outer membrane, decreasing their relative contents to total polar lipids from 12.52% and 17.34% to 7.72% and 12.59%, respectively. Subsequent processes, including bactericidal-concentration and spray-drying, demonstrate the thermal stability of sphingomyelin and ceramides, while glycerolipids with arachidonic acid/docosahexaenoic acid and glycerophospholipids, particularly phosphatidylethanolamine, diminish significantly. Polar lipids addition and freeze-drying technology significantly enhance the polar lipid content and improve microscopic morphology of infant formula. These findings reveal the diverse effects of technological processes on glycerolipid and polar lipid compositions, concentration, and ultrastructure in infant formulas, thus offering crucial insights for optimizing lipid content and structure within infant formula.

Positive Regulation of Acetate in Adipocyte Differentiation and Lipid Deposition in Obese Mice.

Acetate is associated with adipocyte differentiation and lipid deposition. To further develop this scientific point, obese mice on a high-fat diet were given an intragastric administration of acetate for 8 weeks and mouse adipose mesenchymal stem cells (mAMSCs) were treated with acetate for 24 h. The results showed that the body weight, food intake, Lee's index, adipose tissue coefficient, liver index, blood lipid levels, insulin resistance, pro-inflammatory factors levels and fatty lesions in liver and adipose tissue in obese mice treated with acetate increased markedly, while anti-inflammatory factors levels and liver function decreased significantly (p < 0.05). The mRNA expression levels of PPAR-γ, C/EBP-α, SREBP, AFABP, FAS, ACC-1, SCD-1, LPL, LEPR, GPR41 and GPR43 genes in adipose tissue and mAMSCs were significantly increased, while the mRNA expression levels of HSL, CPT-1, CPT-2, AMPK, AdipoR1 and AdipoR2 genes were significantly reduced (p < 0.05). Except for AMPK-α signaling pathway proteins, the phosphorylation levels of p38 MAPK, ERK1/2, JNK and mTOR were significantly increased (p < 0.05) and these changes were dose-dependent. The findings indicated that acetate played a positive role in regulating adipocyte differentiation and lipid deposition by activating MAPKs and mTOR signaling pathways (the expression up-regulation of genes such as PPAR-γ, C/EBP-α and SREBP-1, etc.) and inhibiting the AMPK signaling pathway (the expression down-regulation of genes such as HSL, CPT-1 and AMPK-α, etc.).

Physicochemical stability and in vitro digestibility of goat milk affected by freeze-thaw cycles.

Freezing and thawing are widely used in dairy processing to ensure the continuous supply of raw milk. In virtue of this, the influences of freeze-thaw cycles on physicochemical stability and in vitro digestibility of goat milk were evaluated. Experimental results showed that repeated freeze-thaw cycles led to the increase of acidity and medium-short chain free fatty acids of goat milk, and the significant decrease of fat and apparent viscosity. Furthermore, the degree of protein oxidation was enhanced, and the secondary structure changed to random coil. The particle size distribution and microstructure all showed the aggregation of goat milk droplets, resulting in the decrease of physical stability. Nevertheless, repeated freeze-thaw cycles could enhance the simulated in vitro digestibility and antioxidant capacity of digested products. These results are helpful to evaluate the quality characteristics of raw goat milk and provide theoretical reference for the industrial production of goat milk products.