Upgrading plant amino acids through cattle to improve the nutritional value for humans: effects of different production systems.

Efficiency in animal protein production can be defined in different ways, for example the amount of human-digestible essential amino acids (HDEAA) in the feed ration relative to the amount of HDEAA in the animal products. Cattle production systems are characterised by great diversity and a wide variety of feeds and feed ration compositions, due to ruminants' ability to digest fibrous materials inedible to humans such as roughage and by-products from the food and biofuel industries. This study examined the upgrading of protein quality through cattle by determining the quantity of HDEAA in feeds and animal products and comparing different milk and beef production systems. Four different systems for milk and beef production were designed, a reference production system for milk and beef representing typical Swedish production systems today and three alternative improved systems: (i) intensive cattle production based on maize silage, (ii) intensive systems based on food industry by-products for dairy cows and high-quality forage for beef cattle, and (iii) extensive systems based on forage with only small amounts of concentrate. In all four production systems, the quantity of HDEAA in the products (milk and meat) generally exceeded the quantity of HDEAA in the feeds. The intensive production models for beef calves generally resulted in output of the same magnitude as input for most HDEAA. However, in beef production based on calves from dairy cows, the intensive rearing systems resulted in lower output than input of HDEAA. For the extensive models, the amounts of HDEAA in meat were of the same magnitude as the amounts in the feeds. The extensive models with beef calves from suckler cows resulted in higher output in meat than input in feeds for all HDEAA. It was concluded that feeding cattle plants for production of milk and meat, instead of using the plants directly as human food, generally results in an upgrading of both the quantity and quality of protein, especially when extensive, forage-based production models are used. The results imply that the key to efficiency is the utilisation of human-inedible protein by cattle and justifies their contribution to food production, especially in regions where grasslands and/or forage production has comparative benefits over plant food production. By fine-tuning estimation of the efficiency of conversion from human-edible protein to HDEAA, comparisons of different sources of protein production may be more complete and the magnitude of amino acid upgrading in plants through cattle more obvious.

Systematic microRNAome profiling reveals the roles of microRNAs in milk protein metabolism and quality: insights on low-quality forage utilization.

In this study, we investigated the molecular regulatory mechanisms of milk protein production in dairy cows by studying the miRNAomes of five key metabolic tissues involved in protein synthesis and metabolism from dairy cows fed high- and low-quality diets. In total, 340, 338, 337, 330, and 328 miRNAs were expressed in the rumen, duodenum, jejunum, liver, and mammary gland tissues, respectively. Some miRNAs were highly correlated with feed and nitrogen efficiency, with target genes involved in transportation and phosphorylation of amino acid (AA). Additionally, low-quality forage diets (corn stover and rice straw) influenced the expression of feed and nitrogen efficiency-associated miRNAs such as miR-99b in rumen, miR-2336 in duodenum, miR-652 in jejunum, miR-1 in liver, and miR-181a in mammary gland. Ruminal miR-21-3p and liver miR-2285f were predicted to regulate AA transportation by targeting ATP1A2 and SLC7A8, respectively. Furthermore, bovine-specific miRNAs regulated the proliferation and morphology of rumen epithelium, as well as the metabolism of liver lipids and branched-chain AAs, revealing bovine-specific mechanisms. Our results suggest that miRNAs expressed in these five tissues play roles in regulating transportation of AA for downstream milk production, which is an important mechanism that may be associated with low milk protein under low-quality forage feed.

Nutritive and Bioactive Proteins in Breastmilk.

Protein ingested with breast milk provides indispensable amino acids which are necessary for new protein synthesis for growth and replacement of losses via urine, feces, and the skin. Protein gain in the body of an infant is highest during the first months when protein concentrations in breast milk are higher than during later stages of lactation. Low-birth-weight infants have higher protein needs than term infants and need protein supplements during feeding with breastmilk. Based on our better understanding of protein evolution in breastmilk during the stages of lactation, new infant formulas with lower protein concentration but better protein quality have been created, successfully tested, and are now available in many countries. Besides providing indispensable amino acids, bioactive protein in breast milk can be broadly classified into 4 major functions, that is, providing protection from microbial insults and immune protection, aiding in digestive functions, gut development, and being carriers for other nutrients. Individual proteins and their proposed bioactivities are summarized in this paper in brief. Indeed, some proteins like lactoferrin and sIgA have been extensively studied for their biological functions, whereas others may require more data in support to further validate their proposed functions.

Invited review: The effect of native and nonnative enzymes on the flavor of dried dairy ingredients.

Dried dairy ingredients are used in a wide array of foods from soups to bars to beverages. The popularity of dried dairy ingredients, including but not limited to sweet whey powder, whey proteins and milk powders, is increasing. Dried dairy ingredient flavor can carry through into the finished product and influence consumer liking; thus, it is imperative to produce a consistent product with bland flavor. Many different chemical compounds, both desirable and undesirable, contribute to the overall flavor of dried dairy ingredients, making the flavor very complex. Enzymatic reactions play a major role in flavor. Milk contains several native (indigenous) enzymes, such as lactoperoxidase, catalase, xanthine oxidase, proteinases, and lipases, which may affect flavor. In addition, other enzymes are often added to milk or milk products for various functions such as milk clotting (chymosin), bleaching of whey products (fungal peroxidases, catalase to deactivate hydrogen peroxide), flavor (lipases in certain cheeses), or produced during the cheesemaking process from starter culture or nonstarter bacteria. These enzymes and their possible contributions will be discussed in this review. Understanding the sources of flavor is crucial to produce bland, flavorless ingredients.

Effect of bleaching whey on sensory and functional properties of 80% whey protein concentrate.

Whey is a highly functional food that has found widespread use in a variety of food and beverage applications. A large amount of the whey proteins produced in the United States is derived from annatto-colored Cheddar cheese. Color from annatto is undesirable in whey and must be bleached. The objective of this study was to compare 2 commercially approved bleaching agents, benzoyl peroxide (BP) and hydrogen peroxide (HP), and their effects on the flavor and functionality of 80% whey protein concentrate (WPC80). Colored and uncolored liquid wheys were bleached with BP or HP, and then ultrafiltered, diafiltered, and spray-dried; WPC80 from unbleached colored and uncolored Cheddar whey were manufactured as controls. All treatments were manufactured in triplicate. The WPC80 were then assessed by sensory, instrumental, functionality, color, and proximate analysis techniques. The HP-bleached WPC80 were higher in lipid oxidation compounds (specifically hexanal, heptanal, octanal, nonanal, decanal, dimethyl disulfide, and 1-octen-3-one) and had higher fatty and cardboard flavors compared with the other unbleached and BP-bleached WPC80. The WPC80 bleached with BP had lower norbixin concentrations compared with WPC80 bleached with HP. The WPC powders differed in Hunter color values (L, a, b), with bleached powders being more white, less red, and less yellow than unbleached powders. Bleaching with BP under the conditions used in this study resulted in larger reductions in yellowness of the powders made from whey with annatto color than did bleaching with HP. Functionality testing demonstrated that whey bleached with HP treatments had more soluble protein after 10 min of heating at 90°C at pH 4.6 and pH 7 than the no-bleach and BP treatments, regardless of additional color. Overall, HP bleaching caused more lipid oxidation products and subsequent off-flavors compared with BP bleaching. However, heat stability of WPC80 was enhanced by HP bleaching compared with control or BP-bleached WPC80.

The use of lactoperoxidase for the bleaching of fluid whey.

Lactoperoxidase (LP) is the second most abundant enzyme in bovine milk and has been used in conjunction with hydrogen peroxide (H2O2) and thiocyanate (SCN⁻) to work as an antimicrobial in raw milk where pasteurization is not feasible. Thiocyanate is naturally present and the lactoperoxidase system purportedly can be used to bleach dairy products, such as whey, with the addition of very little H2O2 to the system. This study had 3 objectives: 1) to quantify the amount of H2O2 necessary for bleaching of fluid whey using the LP system, 2) to monitor LP activity from raw milk through manufacture of liquid whey, and 3) to compare the flavor of whey protein concentrate 80% (WPC80) bleached by the LP system to that bleached by traditional H2O2 bleaching. Cheddar cheese whey with annatto (15 mL of annatto/454 kg of milk, annatto with 3% wt/vol norbixin content) was manufactured using a standard Cheddar cheesemaking procedure. Various levels of H2O2 (5-100 mg/kg) were added to fluid whey to determine the optimum concentration of H2O2 for LP activity, which was measured using an established colorimetric method. In subsequent experiments, fat-separated whey was bleached for 1h with 250 mg of H2O2/kg (traditional) or 20 mg of H2O2/kg (LP system). The WPC80 was manufactured from whey bleached with 250 mg of H2O2/kg or 20mg of H2O2/kg. All samples were subjected to color analysis (Hunter color values and norbixin extraction) and proximate analysis (fat, protein, and moisture). Sensory and instrumental volatile analyses were conducted on WPC80. Optimal LP bleaching in fluid whey occurred with the addition of 20mg of H2O2/kg. Bleaching of fluid whey at either 35 or 50°C for 1 h with LP resulted in > 99% norbixin destruction compared with 32 or 47% destruction from bleaching with 250 mg of H2O2/kg, at 35 or 50°C for 1 h, respectively. Higher aroma intensity and increased lipid oxidation compounds were documented in WPC80 from bleached whey compared with WPC80 from unbleached whey. Monitoring of LP activity throughout cheese and whey manufacture showed that LP activity sharply decreased after 30 min of bleaching (17.01 ± 1.4 to < 1 U/mL), suggesting that sufficient bleaching takes place in a very short amount of time. Lactoperoxidase averaged 13.01 ± 0.7 U/mL in unpasteurized, fat-separated liquid whey and 138.6 ± 11.9 U/mL in concentrated retentate (11% solids). Lactoperoxidase may be a viable alternative for chemical whey bleaching.

Physical properties, molecular structures, and protein quality of texturized whey protein isolate: effect of extrusion moisture content.

To explore the complex relationship between processing conditions and functional and nutritional properties of food products containing whey protein isolate (WPI), we investigated the effect of extrusion texturization at various temperatures (50, 75, and 100 °C) and varying moisture levels of the feed (20, 30, 40, and 50%) on changes in the composition, molecular structure, and protein quality of the extrudates. Bradford assay methods were used to determine protein solubility of the extruded WPI as a function of changing level of moisture. Protein compositional changes as a function of extrusion conditions were quantitatively characterized and analyzed by sodium dodecyl sulfate-PAGE and reversed-phase-HPLC techniques. We showed that at a given temperature, increasing the extrusion moisture content resulted in a slight increase in the overall protein water solubility (at 50 and 75 °C), averaging approximately 5% per 10% increase in moisture content. A reduction in ß-lactoglobulin content was observed at 50 °C with increasing moisture content, indicative of the sensitive nature of ß-lactoglobulin to extrusion treatment, whereas the amount of α-lactalbumin remained unchanged at all moisture contents used at a set temperature. The protein quality of the extruded WPI, determined chemically by available sulfhydryl and primary and secondary amines, remained relatively unchanged as a function of moisture level. Circular dichroism and intrinsic tryptophan fluorescence spectroscopic studies revealed considerable structural changes, both at the secondary structural level and the tertiary contacts as a function of increasing temperature, and higher moisture levels can slightly preserve secondary structures but not the tertiary contacts of the protein molecules. Atomic force microscopy provided direct visualization of the fine difference of the protein particles caused by changing extrusion moisture contents, which is in close agreement with the results obtained using other techniques in this work.

Cow's milk in treatment of moderate and severe undernutrition in low-income countries.

Cow's milk products have a central role in treatment of under nutrition, and the introduction of products with a high milk content (F-100 and ready to use therapeutic foods) has resulted in marked improvements in weight gain and reduction in mortality. Milk also has a specific effect on linear growth. Milk protein has a high quality score (PDCAAS) and contains many peptides and other bioactive factors, which might have special effects on recovery from under nutrition. Milk is an important source of minerals supporting growth (type II nutrients), such as potassium, magnesium, phosphorus and zinc, and the high lactose content also seems to support growth due to a prebiotic effect and improved absorption of minerals. The risk that the use of cow's milk products suppresses breastfeeding should be prevented by supporting mothers in breastfeeding. There is consensus that children with severe under nutrition should be treated with products with high milk content, but because of the high cost of milk there is a need to perform more studies to determine the minimal amount of milk protein needed to make a clinically relevant difference in treating the 36 million children with moderate wasting. Such studies should not only focus on weight gain but also on linear growth, body composition, physical activity and cognitive development.

The use of whey or skimmed milk powder in fortified blended foods for vulnerable groups.

Fortified blended foods (FBF), especially corn soy blend, are used as food aid for millions of people worldwide, especially malnourished individuals and vulnerable groups. There are only a few studies evaluating the effect of FBF on health outcomes, and the potential negative effect of antinutrients has not been examined. Different lines of evidence suggest that dairy proteins have beneficial effects on vulnerable groups. Here we review the evidence on the effects of adding whey or skimmed milk powder to FBF used for malnourished infants and young children or people living with HIV or AIDS. Adding whey or skimmed milk powder to FBF improves the protein quality, allowing a reduction in total amount of protein, which could have potential metabolic advantages. It also allows for a reduced content of soy and cereal and thereby a reduction of potential antinutrients. It is possible that adding milk could improve weight gain, linear growth, and recovery from malnutrition, but this needs to be confirmed. Bioactive factors in whey might have beneficial effects on the immune system and muscle synthesis, but evidence from vulnerable groups is lacking. Milk proteins will improve flavor, which is important for acceptability in vulnerable groups. The most important disadvantage is a considerable increase in price. Adding 10-15% milk powder would double the price, which means that such a product should be used only in well-defined vulnerable groups with special needs. The potential beneficial effects of adding milk protein and lack of evidence in vulnerable groups call for randomized intervention studies.

Determination of protein in milk powder using 2-sulfophenylazo-rhodanine as a probe by the enhanced resonance Rayleigh light-scattering technique.

In this paper, the interaction between 2-sulfophenylazo-rhodanine and protein was investigated by Rayleigh light-scattering technique. Based on this, a novel method for the determination of protein was developed. The effects of different conditions, such as acidity and media, were investigated thoroughly, and the optimum conditions were confirmed. Bis(2-ethylhexyl)sulfosuccinate (AOT) microemulsion, which is introduced into the protein determination, markedly increased the sensitivity of the system by changing the microenvironment. In pH 2.80 Britton-Robinson buffer solution in the presence of AOT microemulsion, the detection limits of bovine serum albumin, human serum albumin, ovalbumin, and gamma-globulin are 5.4, 4.5, 9.8, and 10.1 ng/mL, respectively. The method developed in this paper has been applied to the determination of protein in milk powder with satisfactory results.

Minimizing variations in functionality of whey protein concentrates from different sources.

Enhancement in processing technology has improved the nutritional and functional properties of whey protein concentrates by increasing the content and quality of the protein, leading to their increased use in different food products. The extent of heat treatment affects the quality of the whey protein concentrate, and wide variation in product quality exists due to the various means of manufacture and from the whey product history from farm to factory. The study was carried out with 6 commercial whey protein concentrates with 80% protein (WPC80) to determine variations in physical properties, particle size and density, and functional properties--solubility, gel strength, foam volume, and stability. Significant differences were observed among all the products for every property compared. Particulate size was the most important determinant of functional characteristics. Larger particulate WPC80 had significantly higher fat content and were less soluble with poor foam stability; but narrowing the particle size distribution through sieving, minimized variations. We determined that sieving all products within the particle size distribution range of 100 to 150 microns minimized variation in physical composition, making functionality uniform. WPC80 from different manufacturers can be made to perform uniformly within a narrow functionality range by reducing the particle size distribution through sieving.

Whey components: millennia of evolution create functionalities for mammalian nutrition: what we know and what we may be overlooking.

Nutrition is undergoing a revolution owing to the recognition that some foods contain trophic, health-promoting factors distinct from essential nutrients. In this revolution, whey is increasingly being viewed as more than a source of proteins with a particularly nutritious composition of essential amino acids. Milk evolved under continuous Darwinian selection pressure to nourish mammalian neonates. Evolutionary pressure appears to have led to the elaboration of a complex food that contains proteins, peptides, complex lipids, and oligosaccharides that act as growth factors, toxin-binding factors, antimicrobial peptides, prebiotics, and immune regulatory factors within the mammalian intestine. Importantly, these trophic macromolecules are not essential, although the health benefits that their biological activities within the intestine provide likely contributed to neonatal survival. Human and bovine milks contain many homologous components, and bovine whey may prove to be a source for molecules capable of providing biological activities to humans when consumed as food ingredients. To approach this potential, food and nutrition research must move beyond the description of food ingredients as delivering only essential nutrients and develop a mechanistic understanding of the interactions between dietary components and the metabolic and physiological properties of the intestine.

Thrice-daily milking throughout lactation maintains epithelial integrity and thereby improves milk protein quality.

Cows managed for extended lactations of 16 months duration were milked on a half-udder basis twice or thrice daily, commencing in lactation week 9. Mammary epithelial integrity (assessed by milk sodium : potassium ratio) was greater in the half-udder which was milked thrice daily. This difference was evident throughout the lactation but became greater after week 41. Milk protein composition was assessed during late lactation (52+/-3 weeks). Casein number (casein as a proportion of total protein) was significantly higher in half-udders milked thrice daily, as were the relative amounts of alpha- and beta-caseins, whilst those of kappa- and- caseins were reduced. Two days of inverted milking frequency (i.e. thrice-milked udder halves now milked twice, and vice versa) only partly reversed these differences. We concluded that thrice-daily milking will help to prevent or ameliorate the usual decline in milk processing quality associated with late lactation. Part of this effect is due simply to reduced exposure to proteolytic enzymes as a result of decreased storage time in the udder, but part is due to a better maintenance of epithelial tight junction integrity as lactation advances, which restricts leakage of proteolytic enzymes from serum into milk.

Vegetable proteins: are they nutritionally equivalent to animal protein.

On the basis of the rate of animal growth, proteins have been traditionally classed as high quality, such as egg and milk protein, or low quality such as gluten. In general, vegetable proteins are of low quality but soy protein is an exception. The paper by Capristo et al. in this issue of the journal has shown that enteral formulations consisting of soy protein are as effective nutritionally as enteral formulations containing milk protein.

Evaluation of milk chocolate product as a substitute for whey in pig starter diets.

Four experiments were conducted to study the effects of substituting milk chocolate product MCP) for dried whey (DW) on growth performance of starter pigs. In Exp. 1 (4 wk) and 2 (5 wk), 440 pigs (age, 25 d) were assigned to one of four diets: 1) 0% DW + 0% MCP, 2) 20% DW + 0% MCP, 3) 10% DW + 10% MCP, or 4) 0% DW + 20% MCP. Linear reductions (P < .06) in ADG, ADFI, and gain/feed (G/ F) were detected as MCP increased. Replacement of DW with 10% MCP had little effect on ADG or ADFI in Exp. 1, but it reduced them in Exp. 2. In Exp. 3(5 wk), 192 pigs (age, 20 d) were fed one of four complex diets: 1) 15% DW + 0% MCP, 2) 10% DW + 5% MCP, 3) 5% DW + 10% MCP, or 4) 0% DW + 15% MCP. As MCP increased, ADG and ADFI decreased linearly (P < .01), but growth performance was similar between pigs fed the 0 and 5% MCP diets. Experiment 4 was a 14-d preference trial in which the four diets from Exp. 3 and 270 pigs (age, 24 d) were used to make three comparisons: a) diet 1 vs diet 2, b) diet 1 vs diet 3, and c) diet 1 vs diet 4. Pigs consumed between 65 and 77% of their total feed intake as MCP-containing diets (P < .01). In summary, MCP could replace DW at a dietary level of 5% without reducing pig performance, but MCP at dietary levels of 10% or more reduced pig performance. Pigs strongly preferred MCP over DW.

Influence of protein standardization by ultrafiltration on the viscosity, color, and sensory properties of skim and 1% milk.

Permeate and retentate (concentration factor ca. 2x) from UF of skim milk were combined, and cream was added to produce skim milk (0.1% fat) and 1% milk with a range of true protein contents (1.0 to 4.8%) within each fat level. A panel that had been trained for descriptive sensory analysis evaluated the appearance, aroma, flavor, and textural attributes of milks. Relative viscosity and Hunter color values for whiteness (L value), greenness to redness (a value), and blueness to yellowness (b value) increased when either protein or fat was increased. The rate of change of L, a, and b values as protein content changed was greater for skim milk than for 1% milk and was greater as protein contents decreased. Sensory scores for several descriptors of appearance, texture, and flavor had a stronger positive correlation with objective measurements of whiteness than with objective measurements of viscosity. Thus, the judgment of panelists about milk texture and flavor in milks that differed in protein content was influenced more by appearance than by viscosity. As the protein content of skim and 1% milk was increased from 2.9 to 4.8% true protein, the sensory properties of the milks were made more like those of higher fat milk, particularly those of skim milk, mainly because of whiter appearance. Panelists perceived changes in the sensory characteristics of both skim and 1% fat milk when the true protein content was increased by 0.9%, the smallest increase that was studied in the experiment.

Recombinant human milk proteins - an opportunity and a challenge.

Several human milk proteins have physiologic functions in infants. These proteins are involved in defense against infectious agents and in the optimization of nutrient uptake from milk. Therefore, interest in producing recombinant human milk proteins to use in infant formula has been growing. Microorganisms and transgenic animals can now be used for the production of bioactive proteins. However, the benefits of each protein must be evaluated in cells, animal models, and infants before claims can be made that adding them to formula improves the health or nutrition of infants. Once benefits are shown, proper manufacturing conditions must be developed for introducing the protein or proteins into formula. Processing conditions must be evaluated to ensure that biologic activity is maintained. Dry blending, aseptic processing, sterile filtration, and other techniques will likely be necessary for introducing proteins that require specific tertiary structure for activity. The importance of posttranslational modifications must also be considered: some proteins may require proper glycosylation or phosphorylation for physiologic activity.

Performance and nutrient digestibility in weanling pigs as influenced by yeast culture additions to starter diets containing dried whey or one of two fiber sources.

Three experiments were conducted using crossbred weanling pigs (7.2 to 8.6 kg; 25 to 29 d of age) to determine the effect on performance and nutrient digestibility of .75% yeast culture (YC) additions to starter diets containing whey or one of two fiber sources. An 18% CP corn-soybean meal basal diet was used in all experiments. In Exp. 1 (n = 192), the addition of YC did not affect ADG, ADFI, or gain: feed ratios (G:F) of pigs fed diets without or with 15% dried whey in two 5-wk trials. In Exp. 2 (n = 174), ADG and ADFI were not affected by YC addition to diets containing no added fiber, 8% soybean hulls (SH), or 8% peanut hulls (PH) in two 5-wk trials. The addition of SH or PH did not affect ADG or ADFI; however, a YC x SH interaction (P < .05) and a YC x PH interaction (P < .10) for G:F indicated that the addition of SH or PH to the diet in the absence of YC reduced G:F, but in the presence of YC, G:F were maintained. In a 3-wk grower phase of one trial in Exp. 2 (n = 54), SH and PH additions decreased ADG (P < .005), whereas YC additions improved ADG (P < .01), particularly for pigs fed diets that also contained SH (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)