Preparation and functional properties of protein coprecipitate from sheep milk

The optimum conditions for the production of coprecipitate from sheep milk were studied. The best percentage of calcium chloride added to milk was 0.2%, which resulted in a recovery of 97.5% of milk proteins. At low pH (4.5–5), the recovery of protein was low, but it increased at higher pH values (5.5–6.5); recovery was greatest at pH 6.5. The optimum heating temperature to obtain coprecipitate from sheep milk was 85–95°C. The functional properties of the sheep milk coprecipitate were studied. At pH values higher than 6, there were no differences between the solubility of sheep milk coprecipitate and sheep milk sodium caseinate, but the solubility of coprecipitate at pH values lower than 5 was relatively higher than those of the caseinate. At pH ≥6, the emulsion activity index (EAI) for emulsions of sheep milk coprecipitate and caseinate increased as pH increased; at all pH values, the EAI of the coprecipitate was higher than that of the caseinate. Sheep milk coprecipitate showed higher foaming ability and stability than sheep milk sodium caseinate.     

Different effects of the methods of administering lactoferrin,IGF-1 and IgG from bovine colostrum to rabbits based on the cytokine communication network

Lactoferrin, IGF-1 and IgG are three well-known bioactive proteins found in bovine colostrum. We studied the effects of these three active ingredients on the levels of eight cytokines in serum and on the cellular communication networks in vivo by oral administration, intraperitoneal injection and intravenous injection. The results suggested that bioactive ingredients, especially biomacromolecules, can induce different effects, even opposite effects, on the immune system depending on the route of administration. These effects are related to both the functions of the bioactive ingredient in vivo and to its specific receptor binding in the gastrointestinal mucosa that activates different signalling pathways.     

A review on polyphenols: Classification,beneficial effects and their application in dairy products

Recently, the number of studies regarding the physiological activities of food‐derived bioactives and food components with functional properties has greatly increased. Many studies have emphasised the beneficial effects of polyphenols regarding their antioxidant, antiproliferative and anti‐inflammatory properties. This study highlights their application in dairy products, notes in which form they are applied and discusses the effects on the physicochemical and sensory characteristics of products, although some dairy matrices remain unexploited. It was noted that the inclusion of polyphenols improves not only the antioxidant properties but also, in some cases, the sensory attributes. This review also includes the synthesis, classification and beneficial effects of polyphenols.     

Interaction of dietary polyphenols with bovine milk proteins: molecular structure-affinity relationship and influencing bioactivity aspects

Scope : Dietary flavonoids and stilbenes are important polyphenols in foods, such as, e.g. fruits, vegetables, nuts, and tea as they are of great interest for their bioactivities, which are related to the anti‐oxidative property. Methods and results : The relationship between the structural properties of dietary polyphenols and their affinities for milk proteins (MP) was investigated. Methylation and methoxylation of flavonoids decreased (or hardly affected) the affinities for MP. Hydroxylation on the rings A and B of flavones and flavonols enhanced the interaction slightly. The hydroxylation on the ring A of flavanones significantly improved the affinities. Glycosylation of flavonoids weakened the affinities by 1–2 orders of magnitude. The hydrogenation of the C2?C3 double bond of flavonoids decreased the binding affinities by 7.24–75.86‐fold. Galloylation of catechins significantly improved the binding affinities by about 100–1000‐fold. Glycosylation of resveratrol decreased its affinity for MP. Esterification of gallic acid increased its binding affinity. MP significantly weakened the DPPH radical scavenging activity of polyphenols. The decreasing DPPH scavenging percentages of polyphenols increased with increasing affinities of MP–polyphenol complexes. Conclusion : The binding affinities with MP were strongly influenced by the structural differences of dietary polyphenols. The MP–polyphenol interaction weakened with the DPPH free radical scavenging potential of polyphenols.     

乳脂肪球膜功能特性的研究进展

乳脂肪以脂肪球的形式存在,乳脂肪球膜是包裹在乳脂肪球周围的三层生物薄膜,具有很高的营养价值。随着食品科学研究的深入和分离技术的发展,乳脂肪球膜中的活性成分及其功能作用正在逐渐被揭示。乳脂肪球膜是含有蛋白质、磷脂、鞘脂、神经节苷脂、胆碱、唾液酸和胆固醇的混合物,这些成分是具有重要功能的食品成分,应用于配方食品生产。本文综述了乳脂肪球膜中常见的蛋白质、脂质及其生物活性,综述了近年来乳脂肪球膜及其成分在改善肠道健康、改善大脑发育、改善肥胖及相关并发症、改善老年人虚弱、抗癌、抗氧化和缓解疲劳等方面的体内研究和临床研究进展,并讨论了其可能的作用机制,以期为乳脂肪球膜配料的研发及其在配方食品中的应用提供借鉴和参考。     

The influence of enzymatic cross‐linking of proteins on the Maillard reaction in milk

The influence of transglutaminase (TGase) on the Maillard reaction was investigated in skimmed milk samples during heat treatment. TGase‐treated and control samples were heated at 80, 120 and 140 °C for 1, 5, 15, 30, 40 and 60 min. Compared with the TGase‐treated samples heated at 80 and 120 °C, the sample heated at 140 °C showed a larger decrease in furosine concentration. It was also found that TGase did not affect the formation of hydroxymethylfurfural and lactulose at 120 °C, whereas their concentrations increased in the presence of TGase at 140 °C. It was concluded that blockage of lysine residues via enzymatic cross‐linking of milk proteins had a limited effect on the Maillard reaction.     

The effect of milk protein on the bioavailability of cocoa polyphenols

ABSTRACT:  In order to determine whether milk proteins interact with cocoa polyphenols to modulate the uptake and concentration of polyphenols in plasma, 24 middle-aged men and women consumed 2 g of chocolate polyphenols, plus sugar and cocoa butter in 200 mL water, on 2 occasions. On 1 occasion, the chocolate mix contained 2.45 g of milk proteins. Blood samples were taken fasting and at regular intervals for 8 h. Catechin and epicatechins levels were measured in these samples and no differences were seen in average concentrations between the 2 treatments. Milk protein caused a slight increase in concentration at the early time points and a decrease at the later time points. In conclusion, milk powder did not influence the average concentration of polyphenols. While it slightly accelerated absorption, this is of no physiological significance.     

Effects of different types and concentrations of thickeners on yoghurt protein bioaccessibility by an in vitro dynamic gastrointestinal digestive model

This study analysed the protein bioaccessibility of yoghurt containing different concentrations of pectin, acid-resistant carboxymethylcellulose (CMC), guar gum and xanthan gum before and during in vitro gastrointestinal digestion, respectively. Soluble protein contents and protein digestion rates of yoghurt with 0.2% (m/v) guar gum, CMC and xanthan gum were significantly higher and faster, whereas other thickeners had slower rates than control yoghurt during gastric digestion phase. In addition, the contents of small peptides and amino acids were higher in yoghurt with 0.2% (m/v) thickeners than those with 1.0% (m/v) thickeners during simulated intestinal digestion in most of the samples.     

Does the addition of caseinophosphopeptides or milk improve zinc in vitro bioavailability in fruit beverages?

The influence of caseinophosphopeptides (CPPs) added to fruit beverage versus milk based fruit beverage upon zinc retention, transport, and uptake, as well as the influence of Fe supplementation, were studied using a combined simulated gastrointestinal digestion/Caco-2 cell system.Zinc retention, transport, and uptake of milk based fruit beverage was 4- to 5-fold greater than that of fruit beverages with or without CPPs – no statistically significant differences being observed in relation to the presence or absence of CPPs. Possibly, a slow release of CPPs throughout the digestive tract, as can be expected to take place during the digestion of casein, has a more beneficial effect than the addition of preformed CPPs upon Zn availability.A significantly negative Fe × Zn interaction in relation to Zn retention and uptake was observed in fruit beverages. This should be taken into account in the formulation of such beverages, where the supplementing of both of these mineral elements is common practice.     

Effect of hydrocolloid type and concentration on flow behaviour and sensory properties of milk beverages model systems

Formulation of low-calorie flavoured milk beverages involves the use of hydrocolloids to obtain an acceptable mouthfeel. Sodium alginate and κ-carrageenan are the most commonly used. In this paper, the rheological behaviour of model solutions containing either of these two hydrocolloids, with or without the addition of sucrose, in water or milk, has been studied. All solutions fitted well to the Ostwald de Waele model. The analyses of variance showed that in κ-carrageenan solutions, the effect of the medium–hydrocolloid interaction on both flow index (n) and apparent viscosity at 1 s⁻¹ (η₁) was significant. Milk-based solutions were more pseudoplastic and more viscous than the aqueous solutions, due to the well known κ-carrageenan–casein molecular interaction. In alginate solutions, the medium–hydrocolloid interaction was also significant but the differences in both n and η₁ values were of less entity. Sensory viscosity differences of more viscous chocolate milk model systems were well explained by apparent viscosity values at low shear rate (10 s⁻¹), while for less viscous samples apparent viscosity at higher shear rate (300 s⁻¹) values were appropriate. At similar viscosity, κ-carrageenan systems showed better flavour-releasing properties than alginate.     

The quality of set‐style yoghurt responsible to partial lactose hydrolysis followed by protein cross‐linking of the skimmed milk

Skimmed milk used for set‐style yoghurt production was treated with lactase at 0.1 g/kg for 30 min to give partial lactose hydrolysis and then treated with horseradish peroxidase and glucose oxidase at 200 and 6 kU/kg protein to result in protein cross‐linking. Two treatments conferred higher apparent viscosity on the milk, but led to the yoghurt prepared from it with insignificantly different chemical compositions to the counterparts (P > 0.05). The prepared yoghurt also showed decreased syneresis (about 17.7%), higher apparent viscosity and viscoelastic modulus, firmer texture and finer microstructure. This ternary enzyme system is a potential approach to improving the quality of set‐style yoghurt.     

Interactions between milk proteins and polyphenols: Binding mechanisms,related changes,and the future trends in the dairy industry

The biological activity and techno-functional properties of phenolic compounds have gained great importance due to the epidemiologically-proved health benefits. Use of polyphenols as fortification agents for functional food production and nanotechnological approaches using natural vehicles for polyphenol delivery have been recently discussed. In this respect, milk proteins and dairy products represent unique characteristics for polyphenol studies. The conflicting results on the functionality of polyphenols interacting with milk proteins either in model systems or in complex dairy matrices reveal the need for future studies.     

Study of the effect of different iron salts used to fortify infant formulas on the bioavailability of trace elements using ICP-OES

Five different iron salts—sulphate, lactate, diphosphate, encapsulated sulphate, and EDTA-Fe(III)—were used to fortify an infant formula to study possible differences in iron bioavailability. The effect of iron fortification at two levels (0.5 mg Fe 100 kcal⁻¹ and 1.5 mg Fe 100 kcal⁻¹) on the bioavailability of other important trace elements such as copper and zinc were also evaluated. An in vitro method based on element dialysability (i.e., the fraction available by absorption) to simulate newborn digestion was applied to study iron, copper and zinc bioavailability. Enzyme treatment was carried out in two stages involving pepsin at pH 5.0 followed by pancreatin at pH 7.0. The incubation times were short to mimic the transit of meal in an infant's gastrointestinal tract. Iron, copper and zinc were determined using inductively coupled plasma atomic emission spectrometry using an axially configured device. The percentages of Fe, Cu and Zn dialysable at both iron fortification levels are discussed. From these results, EDTA-Fe (III) appears to be the most adequate salt for iron fortification of infant formulas.     

Impact of fortification with iron salts and vitamin A on the physicochemical properties of laboratory‐pasteurised toned milk and bioaccessibility of the added nutrients

The sensory and physicochemical attributes of pasteurised milk fortified with soluble ferric pyrophosphate (FPP) (25 mg/L iron) and vitamin A (2500 IU) were comparable to unfortified control samples. The heat coagulation time (HCT) of fortified milks was comparable to the control and exhibited a type A curve with HCT–pH maxima at the acidic side of the natural pH. The distribution pattern of iron in different milk fractions was similar in control and fortified milk samples. The bioaccessibility of iron, estimated through in vitro digestibility of milk fortified with vitamin A and iron, was found to be slightly higher than that of milk fortified with iron alone.     

Evaluation of physicochemical,microbiological and sensorial characteristics of fermented milk beverages with buttermilk addition

This study evaluated three fermented milk beverages to which had been added sugar strawberry puree post‐fermentation. The base was composed of 70% of milk, with whey and buttermilk in the concentrations of 30% and 0%, 15% and 15%, and 0% and 30%, respectively. The starter culture developed well with all formulations reaching pH 4.7–4.9 in 180 min of fermentation. Lactic acid bacteria in the products were above 8 log cfu/mL throughout the study. The beverages presented similar pH, acidity and viscosity. Buttermilk and whey can be interesting ingredients to be added into fermented milk beverages, because the consumers liked all the products equally, which had an average acceptance score exceeding ‘liked moderately’.     

Texture and other changes during storage in model high-protein nutrition bars formulated with modified milk protein concentrates

Extruded or toasted milk protein concentrate with approximately 80 g protein per 100 g were incorporated into model high-protein nutrition bars formulated at 30 g protein per 100 g. The model high-protein nutrition bars also contained other constituents, including glycerol, palm kernel stearin, sugar alcohol syrup, and high-fructose corn syrup, to mimic commercial high-protein nutrition bars. The bars were stored at room temperature (∼22 °C), 32 °C, or 42 °C for up to 42 days. Texture, water activity, and color were measured periodically over the storage period. High-protein nutrition bars formulated with unmodified milk protein concentrate served as the control and maintained similar texture to those high-protein bars formulated with toasted milk protein concentrate. High-protein nutrition bars prepared with milk protein concentrate extruded at 65 °C were significantly softer than the control. Significant differences in hardness and fracturability between high-protein nutrition bars formulated with milk protein concentrate extruded at 120 °C and the control were intermittent over the storage period. Water activity of the high-protein nutrition bars increased slightly during storage, but remained less than 0.65, which assured shelf stability. Surface color change was minimal at 22 °C storage, but increased at 32 °C and 42 °C.