Change in the structural and functional properties of goat milk protein due to pH and heat

Preparation and functional characteristics of protein from Ginkgo endophytic Pseudomonas R6 and Ginkgo seed

Ginkgo seed protein (GSP) has excellent processing characteristics and antioxidant properties. In this study, Gingko endophytic protein (GEP) was synthesized by Ginkgo endophytic Pseudomonas R6. SDS-PAGE analysis indicated that the molecular weights of GSP and GEP were mainly distributed at 17 KDa and 48 KDa, respectively. FTIR showed that GEP and GSP exhibited characteristic absorption in the amide I, II, and III bands, and absorption in amide A and B indicated the presence of hydrogen bonding. HPLC analysis showed that both proteins had 17 amino acids, but their relative abundance was different, with GSP having the highest Ser content (74.713 mg/g) and GEP having the highest Val content (35.905 mg/g). Stomata were observed on the surface of both proteins by SEM, and there were lamellar and some spherical structures on GEP, while the opposite was observed on GSP. GEP had superior solubility, OHC, FC and EC, while GSP showed good WHC. Both proteins exhibited antioxidant activities, with GSP exhibiting stronger hydroxyl radical scavenging ability than GEP, with IC50 of 0.46 mg/mL and 1.54 mg/mL, respectively. This work demonstrates the antioxidant potential of GEP as an alternative to GSP in the food industry.

The Impact of Goat Milk Pretreatment with Pulsed Electric Fields on Cheese Quality

To reduce the microbial load in goat's milk, which is less thermally stable than cow's milk, an alternative processing method was used in this study. This involved treating the milk with pulsed electric fields (PEFs) (at 10 kV·cm-1, with 50 µs pulses for 3 Hz) and then heat-treating it at 63 °C for 6.0 s, as well as using heat treatment alone at 75 °C for 3.4 s. Cheeses were made using both types of milk treatment, and samples were collected after 5, 15, and 25 days of ripening for DNA extraction and purification, followed by high-throughput sequencing on the MiSeq Illumina sequencing platform. Analysis of the bacterial populations in the two types of cheese using various diversity indices revealed no significant differences in species richness and abundance, although there was a trend for the PEF-treated cheese to have a less diverse set of species with an uneven distribution of relative abundance. However, when examining the composition of the microbial communities in the two types of cheese using Weighted UniFrac analysis and Analysis of Similarities, there were significant differences in the presence and abundance of various species, which could have implications for the development of starter cultures. Concerning physicochemical properties (pH, aw, moisture content, total acidity and L, and a and b color parameters), the results also reveal that, generally, no significant differences were found, except for the color parameter, where cheeses treated with PEF demonstrated more whiteness (L) and yellowness (b) during ripening. Sensory scores for typicity (caprylic, goaty, and acetic) increased over time, but between treatments, only small differences were perceived by panellists in cheese with 5 days of ripening. Concerning texture firmness and cohesiveness, the PEF+HT samples presented lower values than the HT samples, even over storage time. In general, concerning quality parameters, similar behavior was observed between the treatments during the ripening period.

Possibility of Using Different Calcium Compounds for the Manufacture of Fresh Acid Rennet Cheese from Goat's Milk

Calcium can be added to cheese milk to influence the coagulation process and to increase cheese yield. Calcium compounds used in the dairy industry show substantial differences in their practical application. Therefore, this study aimed to evaluate the potential use of 0, 5, 10, 15, and 20 mg Ca 100 g-1 of milk in the form of calcium gluconate, lactate, and carbonate as alternatives to calcium chloride in manufacturing fresh acid rennet cheese from high-pasteurized (90 °C, 15 s) goat's milk. The pH value of the cheese was reduced most strongly by the addition of increasing doses of calcium lactate (r = -0.9521). Each cheese sample showed increased fat content with the addition of calcium. Only calcium chloride did not reduce protein retention from goat's milk to cheese. The addition of 20 mg Ca 100 g-1 of milk in the form of gluconate increased cheese yield by 4.04%, and lactate reduced cheese yield by 2.3%. Adding each calcium compound to goat's milk significantly increased Ca and P levels in the cheese (p ≤ 0.05). The highest Ca levels were found in cheese with the addition of 20 mg Ca 100 g-1 of milk in the form of lactate. In all groups, similar contents of Mn, Mo, and Se were found. Calcium addition significantly affected cheese hardness, while higher calcium concentrations increased hardness. Carbonate caused the greatest increase in the cohesiveness of cheese. The addition of calcium compounds increased the adhesiveness and springiness of cheese compared to controls. The cheese with calcium chloride had the highest overall acceptability compared to the other cheese samples. The addition of calcium carbonate resulted in a lower score for appearance and consistency, and influenced a slightly perceptible graininess, sandiness, and stickiness in its consistency, as well as provided a slightly perceptible chalky taste.

Exploring the health benefits and functional properties of goat milk proteins

Goat milk proteins are unique in their nutritional and functional properties and have become increasingly popular in recent years. A variety of methods have been studied for extracting and isolating these proteins, with coprecipitation being a particularly effective approach. Compared to cow milk proteins, goat milk proteins contain higher levels of certain amino acids such as tryptophan and cysteine, while maintaining similar nutritional properties. Additionally, they have superior functional properties, including better emulsifying and foaming properties, which make them an attractive option for developing new food products. Research has shown that goat milk proteins have several health benefits, including immunomodulatory effects, allergy management, anti-inflammatory, and antioxidant effects, as well as antimicrobial and anticancer properties. They have the potential to be used as a treatment for autoimmune diseases, allergies, and other immune system disorders due to their ability to modulate the production of cytokines and other immune system components. Furthermore, their antimicrobial properties can help prevent the growth of harmful bacteria and reduce the risk of infection. Future research will focus on the potential of goat milk proteins as a functional food ingredient, their effects on gut health and microbiota, and their therapeutic potential for various health conditions. This research may lead to the development of new functional foods that promote health and prevent disease, and potentially pave the way for the use of goat milk proteins as a therapeutic agent for various health conditions.

Structure and in vitro digestion characteristics of skim goat milk protein during processing: effects of fat separation

BACKGROUND

Although nonfat milk has been used worldwide in the industrial dairy process, little is known about the effects of fat separation during the manufacturing process on skim milk's structural and digestive properties. This study investigated the effects of the manufacturing process on the structure and in vitro digestion properties of skim goat milk, particularly emphasizing fat separation.

RESULTS

Changes in the surface charge and hydrophobicity of milk proteins caused by fat separation resulted in oxidation and aggregation in the subsequent homogenization, heat and spray-drying processing, which affected its digestibility. Compared with separation by dish separator (DS), skim milk after tubular centrifugal separation (CS) showed a higher initial and final digestibility. The CS samples also had a lower surface hydrophobicity level and higher free sulfhydryl content, ζ-potential, and average particle size (P < 0.05). Goat milk protein after CS was more readily oxidized and aggregated during the subsequent homogenization and heat treatment, as evidenced by the higher carbonyl content and particle size. Centrifugal separation also converted more β-sheets to α-helices, thus promoting the aggregation of oxidized skim milk protein.

CONCLUSION

The skim milk after CS and DS demonstrated different structural and digestive properties. Skim goat milk products after CS were more susceptible to oxidant-induced protein structural changes, resulting in higher protein digestibility. These findings provide insights into the mechanism involved in the control of gastric digestion of skim milk during manufacturing process. © 2023 Society of Chemical Industry.

Physicochemical and Functional Properties of Thermal-Induced Polymerized Goat Milk Whey Protein

Goat milk whey protein products are a hard-to-source commodity. Whey protein concentrate was directly prepared from fresh goat milk. The effects of the heating temperature (69-78 °C), time (15-30 min), and pH (7.5-7.9) on the physicochemical and functional properties of the goat milk whey protein were investigated. The results showed that the particle size of the samples significantly increased (p < 0.05) after heat treatment. The zeta potential of polymerized goat milk whey protein (PGWP) was lower than that of native goat milk whey protein. The content of the free sulfhydryl groups of PGWP decreased with increasing heating temperature and time, while an increase in surface hydrophobicity and apparent viscosity of PGWP were observed after heat treatment. Fourier Transform Infrared Spectroscopy analysis indicated that heat treatment and pH had considerable impacts on the secondary structure of goat milk whey protein. Transmission electron microscope images revealed that heat induced the formation of a large and uniform protein network. Additionally, the changes in the physicochemical and structural properties contributed to the improvement of the emulsifying and foaming properties of goat milk whey protein after heat treatment. The results may provide a theoretical basis for the applications of polymerized goat milk whey protein in related products.

Nutritional Profile, Processing and Potential Products: A Comparative Review of Goat Milk

Goat milk contains an abundance of different macro and micro-nutrients. Compared with other milk, goat milk is a viable option due to its low allergy levels and is preferred for infants with cow milk allergies. A wide variety of goat milk-based products, including yoghurt, ice cream, fermented milk, and cheese, are available on the market. They are produced using effective processing technology and are known to exhibit numerous health benefits after consumption. However, goat milk consumption is limited in many nations (compared with cow, buffalo, camel, and sheep milk) due to a lack of awareness of its nutritional composition and the significance of its different byproducts. This review provides a detailed explanation of the various macronutrients that may be present, with special attention paid to each component, its purpose, and the health benefits it offers. It also compares goat milk with milk from other species in terms of its superiority and nutritional content, as well as the types, production methods, health advantages, and other beneficial properties of the various goat milk products that are currently available on the market.

Effect of Calcium Compound Type and Dosage on the Properties of Acid Rennet Goat's Milk Gels

The aim of this study was to determine the effect of adding calcium compounds to processed goat's milk, and on the properties of acid rennet goat's milk gels, which are a middle product obtained in the manufacture of acid rennet cheese. The properties of the gels directly affect the quality of acid rennet cheeses. The analysis of raw goat's milk was carried out, then acid rennet gels were produced with the addition of six different calcium compounds (chloride, citrate, bisglycinate, gluconate, lactate, and carbonate). The dynamics of milk fermentation were performed by monitoring the pH value of milk during acidification. The pH, syneresis, color, and texture profile were determined in the formulated acid rennet gels. An organoleptic evaluation was also performed. The study demonstrated that, not only calcium chloride, but also calcium citrate, gluconate, lactate, bisglycinate, and calcium carbonate could be used in the production of goat's milk acid rennet gels, or the middle product in the manufacture of acid rennet curd cheese from goat's milk. Notably, the addition of citrate, bisglycinate, and calcium carbonate in doses of 20 mg Ca 100 g-1 most effectively reduced syneresis compared to the control sample by 4.76% (citrate), 7.85% (bisglycinate), and 10.28% (carbonate). The hardness of the control gels ranged from 2.35 N to 2.99 N. The addition of chloride, citrate, gluconate, lactate, and calcium carbonate to the milk improved the acid rennet gel's hardness. The addition of 20 mg Ca 100 g-1 as gluconate increased the hardness the most (3.61 N). When increasing the calcium dosage in the form of all compounds, there was a tendency to increase the gel's springiness. The addition of chloride, citrate, and bisglycinate to milk did not result in a darkening of the gel's color. The addition of calcium compounds mostly reduced the intensity of goatish taste and odor. Calcium gluconate, in particular, reduced the goatish taste the most, a taste which is not always acceptable by the consumers.

Detection of bovine milk adulteration in caprine milk with N-acetyl carbohydrate biomarkers by using 1H nuclear magnetic resonance spectroscopy

In a return to tradition, the popularity of caprine milk is on the rise. However, particularly in countries with developed dairy industries based on bovine milk, there is the risk of adulteration with bovine milk, which is a cheaper alternative. Thus, a rapid, robust, and simple method for the detection of bovine milk added to caprine milk is necessary, and ¹H nuclear magnetic resonance spectroscopy appears to provide a solution. A matrix of 115 pure and artificially adulterated pasteurized milk samples was prepared and used to discover biomarkers of bovine milk that are independent of chemical and biological variation caused by factors such as genetics, diet, or seasonality. Principal component analysis and orthogonal projections to latent structures discriminant analysis of pure bovine milk and pure caprine milk revealed spectral features that were assigned to the resonances of 4 molecules. Of these, the peaks corresponding to protons in the N-acetylglucosamine and N-acetylgalactosamine acetyl moieties showed significant applicability for our method. Receiver operating characteristic curve analysis was used to evaluate the performance of the peak integrals as biomarkers of adulteration. This approach was able to distinguish caprine milk adulterated with 5% of bovine milk with 84.78% accuracy and with 10% of bovine milk an excellent 95.65% accuracy. This study demonstrates that N-acetyl carbohydrates could be used as biomarkers for the detection of bovine milk in caprine milk and could help in protecting caprine milk authenticity.

Evaluation of concentration process of bovine, goat and buffalo whey proteins by ultrafiltration

In this research, the protein concentration, the permeate flux, and the predominant fouling mechanisms were investigated during ultrafiltration of different whey samples. The research was carried out at different values of transmembrane pressure and temperature using an experimental design, and a protein concentration of approximately 37 g L-1 was obtained for the bovine whey powder solution, at 60 kPa and 40 °C. The maximum flux observed was 8.9 and 7.9 kg m-2 h-1, respectively, for the bovine whey powder solution and bovine whey, at 50 kPa and 30 °C. Although goat and buffalo whey presented lower permeate flux, probably due to high solutes and calcium contents, protein concentrates of around 40 g L-1 were obtained using the ultrafiltration process. This demonstrates the potential of ultrafiltration to obtain non-bovine protein concentrates. The best fit, verified by Ho and Zydney model, suggests that the fouling for all analyzed whey occurs due to pore blocking and subsequent deposit on the membrane surface.

Polyphenol bioaccessibility and antioxidant properties of in vitro digested spray-dried thermally-treated skimmed goat milk enriched with pollen

The aim of research was to determine polyphenols bioaccessibility and antioxidant properties of thermally-treated skimmed goat milk enriched with sunflower bee-collected pollen through in vitro digestion. HPLC analysis confirmed that pollen-enriched milk contained flavonols as the main phenolic fraction (80.7-76.2%) followed by phenolic acids (14.2-17.4%). Among individual compounds quercetin-3-O-glucoside (155.1-197.2 μg/L) and p-coumaric acid (29.5-30.7 μg/L) were the main quantified flavonols and phenolic acids, respectively. After digestion of milk/pollen sample, total polyphenols recovery was 30.71% with higher phenolic acids recovery (40.1%) compared to flavonols (28.3%) indicating strong interactions between caprine milk casein micelles and pollen polyphenols. Applied antioxidant assays (phosphomolybdenum, ABTS•⁺scavenging activity and ferrous-ion-chelating capacity) have confirmed complexity of prepared product- it had high ability to quench ABTS•⁺ radicals and to form chelating complexes with Fe²⁺ ions. Digestion provoked 20% reduction in total antioxidant capacity compared to the initial sample. TTSG milk/pollen powder could be good functional ingredient.