Why semicarbazide (SEM) is not an appropriate marker for the usage of nitrofurazone on agricultural animals

A comprehensive global database on semicarbazide (SEM) in foodstuffs and food ingredients is presented, with over 4000 data collected in foods such as seafood (crustaceans, fish powders), meat (beef, chicken powders), dairy products (e.g. raw milk, milk powders, whey, sweet buttermilk powder, caseinate, yoghurt, cheese), honey and other ingredients. The results provide evidence that the presence of SEM in certain dairy ingredients (whey, milk protein concentrates) is a by-product of chemical reactions taking place during the manufacturing process. Of the dairy ingredients tested (c. 2000 samples), 5.3% showed traces of SEM > 0.5 µg/kg. The highest incidence of SEM-positive samples in the dairy category were whey (powders, liquid) and milk protein concentrates (35% positive), with up to 13 µg/kg measured in a whey powder. Sweet buttermilk powder and caseinate followed, with 27% and 9.3% positives, respectively. SEM was not detected in raw milk, or in yoghurt or cheese. Of the crustacean products (shrimp and prawn powders) tested, 44% were positive for SEM, the highest value measured at 284 µg/kg. Fish powders revealed an unexpectedly high incidence of positive samples (25%); in this case, fraudulent addition of shellfish shells or carry-over during processing cannot be excluded. Overall, the data provide new insights into the occurrence of SEM (for dairy products and fish powders), substantially strengthening the arguments that SEM in certain food categories is not a conclusive marker of the use of the illegal antibiotic nitrofurazone.     

Concentration of furfuryl alcohol in fluid milk,dried dairy ingredients,and cultured dairy products

Maillard reactions occur in dairy products during heat treatment. Furfuryl alcohol (FA) may be found in dairy products as a result of Maillard reactions. The recent posting in California Proposition 65 indicates that FA may be carcinogenic, and for this reason it is crucial to accurately measure FA concentrations in dairy products. The objective of this study was to identify an extraction and quantitation method for FA from dairy products and to determine FA concentrations in milk, dairy powders, and cultured dairy products. Solvent-assisted flavor extraction, solid-phase microextraction, stir bar sorptive extraction with gas chromatography-mass spectrometry and triple quadrupole mass spectrometry were compared for recovery of FA. Internal standards for the quantitation of FA (2-methyl-3-heptanone, furfuryl-d₅ alcohol, 2,5-dimethylphenol, 5-methyl-2-furfuryl alcohol, and 5-methyl furfural) were also compared. Subsequently, fluid milk [high temperature, short time (HTST) and ultrapasteurized], whey protein isolates (3 mo–4 yr), whey protein concentrates (3 mo–4 yr), whole milk powders (1 yr), high and low heat skim milk powders (SMP; 0–8 yr), milk protein isolates (3 mo–3 yr), milk protein concentrates (3 mo–3 yr), Cheddar cheese (mild, medium, sharp, and extra sharp), mozzarella cheese (whole and part skim), cottage cheese (nonfat, low fat, and full fat), sour cream (nonfat, low fat, and full fat), traditional yogurt (nonfat, low fat, and full fat), and Greek-style yogurt (nonfat; n = 139 products total) were evaluated. Furfuryl alcohol was extracted from products by headspace solid-phase microextraction followed by gas chromatography-triple quadrupole mass spectrometry using a ZB-5ms column (30 m × 0.25 mm × 0.25 µm; Phenomenex Inc., Torrance, CA). Furfuryl-d₅ alcohol was used as an internal standard. Each food was extracted in triplicate. Ultrapasteurized milks had higher levels of FA than HTST milks (122.3 vs. 7.350 µg/kg). Furfuryl alcohol concentrations ranged from 0.634 to 26.55 µg/kg in whey protein isolates, 2.251 to 56.19 µg/kg in whey protein concentrates, 11.99 to 121.9 µg/kg in milk protein isolates, and 8.312 to 49.71 µg/kg in milk protein concentrates, and concentrations increased with powder storage. High heat SMP had higher concentrations of FA than low heat SMP (11.8 vs. 1.36 µg/kg) and concentrations increased with storage time. Concentrations of FA in Cheddar and mozzarella cheese ranged from 2.361 to 110.5 µg/kg and were higher than FA concentrations in cottage cheese or sour cream (0.049–1.017 µg/kg). These results suggest that FA is present at higher levels in dairy products that have been subjected to higher temperatures or have been stored longer. Sour cream and cottage cheese had lower levels of FA. Compared with other studies on food products with reported levels of FA, such as coffee (200–400 µg/g), dairy products have very low levels of FA.     

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.     

Maximizing the value of milk through separation technologies.

Milk is the source of a wide range of proteins that deliver nutrition to the most promising new food products today. Isolated milk proteins are natural, trusted food ingredients with excellent functionality. Separation technologies provide the basis for adding value to milk through the production of proteins that provide the food industry with ingredients to meet specific needs, not possible with milk itself or with other ingredients. The major milk proteins, casein and whey protein, can be isolated by manipulating their compositional and physical properties and then by using various separation technologies to recover the proteins. Additionally, they can be processed in various ways to create a wide range of ingredients with diverse functional characteristics. These ingredients include milk protein concentrate, milk protein isolate, casein, caseinate, whey protein concentrate, whey protein isolate, hydrolysates, and various milk fractions. Within each of these ingredient categories, there is further differentiation according to the functional and nutritional requirements of the finished food. Adding value to milk by expanding from consumer products to ingredients often requires different technologies, marketing structure and distribution channels. The worldwide market for both consumer products and ingredients from milk continues to grow. Technology often precedes market demand. Methods for the commercial production of individual milk components now exist, and in the future as clinical evidence develops, the opportunity for adding value to dairy products as functional foods with health benefits may be achieved. The research and development of today will be the basis of those value-added milk products for tomorrow.     

乳清产品在冰淇淋和冷冻乳制品甜食中的应用

<正> 乳清和乳清蛋白产品在过去的60多年中已经被成功应用于冰淇淋和其他冷冻乳制品甜食中。甜乳清、乳清浓缩蛋白(蛋白质含量34～89%)和乳清分离蛋白(蛋白质含量≥90%)是最常用的乳清产品。其他的乳清配料,如脱乳糖乳清和脱盐乳清也是常用的配料。成本优势和提升产品质量是使用乳清产品的主要出发点,     

Use of dairy proteins in lean poultry meat batters – a comparative study

The use of dry whole milk, skimmed milk, caseinate, regular and modified whey, at 2% level (w/w) and with 2% additional protein level was studied in a chicken breast meat system with 51% water addition. At the 2% (w/w) level, all dairy proteins significantly reduced cooking loss compared with the control, with caseinate showing the best results. When compared on an equal protein level (2% total protein), the best performing ingredients were the whole milk and modified whey. A similar observation was made in their effect on the products’ hardness and fracturability. A cost analysis revealed that modified whey provided the most economical ingredient even when used in quantities three times greater than that of as caseinate. Microscopy results showed the formation of larger fine‐protein‐matrix regions in the treatments that provided higher fracturability values.     

Innovative Uses of Milk Protein Concentrates in Product Development

Milk protein concentrates (MPCs) are complete dairy proteins (containing both caseins and whey proteins) that are available in protein concentrations ranging from 42% to 85%. As the protein content of MPCs increases, the lactose levels decrease. MPCs are produced by ultrafiltration or by blending different dairy ingredients. Although ultrafiltration is the preferred method for producing MPCs, they also can be produced by precipitating the proteins out of milk or by dry‐blending the milk proteins with other milk components. MPCs are used for their nutritional and functional properties. For example, MPC is high in protein content and averages approximately 365 kcal/100 g. Higher‐protein MPCs provide protein enhancement and a clean dairy flavor without adding significant amounts of lactose to food and beverage formulations. MPCs also contribute valuable minerals, such as calcium, magnesium, and phosphorus, to formulations, which may reduce the need for additional sources of these minerals. MPCs are multifunctional ingredients and provide benefits, such as water binding, gelling, foaming, emulsification, and heat stability. This article will review the development of MPCs and milk protein isolates including their composition, production, development, functional benefits, and ongoing research. The nutritional and functional attributes of MPCs are discussed in some detail in relation to their application as ingredients in major food categories.     

The Distribution of Fat in Dried Dairy Particles Determines Flavor Release and Flavor Stability

Dried dairy ingredients are utilized in various food and beverage applications for their nutritional, functional, and sensory properties. Dried dairy ingredients include milk powders of varying fat content and heat treatment and buttermilk powder, along with both milk and whey proteins of varying protein contents. The flavor of these ingredients is the most important characteristic that determines consumer acceptance of the ingredient applications. Lipid oxidation is the main mechanism for off‐flavor development in dried dairy ingredients. The effects of various unit operations on the flavor of dried dairy ingredients have been investigated. Recent research documented that increased surface free fat in spray dried WPC80 was associated with increased lipid oxidation and off‐flavors. Surface free fat in spray‐dried products is fat on the surface of the powder that is not emulsified. The most common emulsifiers present in dried dairy ingredients are proteins and phospholipids. Currently, only an association between surface free fat and lipid oxidation has been presented. The link between surface free fat in dried dairy ingredients and flavor and flavor stability has not been investigated. In this review, some hypotheses for the role of surface free fat on the flavor of dried dairy ingredients are presented along with proposed mechanisms.     

Delactosed permeate as a dairy processing co-product with major potential value: a review

Delactosed permeate (DLP) is the co-product generated during the separation of pre-crystallised lactose from milk and whey permeates. DLP production has grown with the increased production of high protein content ingredients such as whey protein concentrates and isolates. Although DLP is nutritionally rich, with approximately 0.5–1.5, 68–70, 9–10 and 8–9 g/100 g dry matter of protein, total sugars, total mineral and organic acids, respectively, it is still currently underutilised, mostly for animal feed or energy production. There are a number of novel, promising and sustainable DLP-derived food and non-food applications which are the subject of current research. Therefore, there exists the opportunity to exploit this dairy co-product in the development of new value-added ingredients. In this comprehensive review, DLP production, processing challenges and potential applications are discussed, along with identification and assessment of selected strategies for the valorisation of DLP.     

Functional and technological aspects of whey powder and whey protein products

Commercial whey powder, whey protein concentrates and whey protein isolates (WPIs) were evaluated for certain functional properties and for their application in full‐fat and nonfat yoghurts. The functional properties of whey products varied, and the highest functionality was recorded in samples with high protein levels. Whey powder had the lowest foaming performance and emulsifying capacity, while WPIs possessed the best functional properties of all the other samples. Curd tension (CT), viscosity and syneresis were improved in yoghurts made using fortified cow's milk or reconstituted skim milk with any whey products, while whey powder had no impact on CT.     

Size classification of precipitated calcium phosphate using hydrocyclone technology for the recovery of minerals from deproteinised acid whey

Acid whey is generated during the manufacture of acidified dairy products, such as soft cheeses, acid casein ingredients and strained yoghurts. Examples of these whey‐based by‐products include Cottage cheese acid whey and Greek yoghurt acid whey. Alkalisation of acid whey at elevated temperatures (60 °C) precipitates calcium phosphate, which can be recovered and used as an ingredient. The novel application of a liquid–solid hydrocyclone in the size classification of calcium phosphate from heated and neutralised acid whey was investigated in this study. Factors influencing hydrocyclone performance were tested, and the technology was integrated into a membrane filtration‐based process for the production of milk mineral powders.     

Plasmin levels in fresh milk whey and commercial whey protein products

Growth of psychrotrophic bacteria in nonfat dry milk at refrigeration temperatures was shown previously in our laboratory to cause a shift in plasmin (a native milk protease) from the casein to the whey fraction. The whey fraction from cheesemaking is commonly used to make whey protein concentrates and isolates, which then are used as functional ingredients in various food systems. Plasmin activity in whey protein products may cause breakdown of food proteins to have desirable or undesirable effects on food quality. This raised questions about the level of plasmin in commercial whey protein products and factors that affect this plasmin level. Therefore, the objectives of this study were to determine: 1) plasmin concentrations in sweet and acid whey protein products as influenced by Pseudomonas growth during storage of fresh milk, and 2) plasmin concentrations in commercial whey protein products. Whey type (sweet or acid) had a significantly (P < 0.05) greater effect on whey-associated plasmin activity than did Pseudomonas fluorescens M 3/6 growth. Acid whey protein products had significantly (P < 0.05) higher plasmin concentrations than sweet whey. Plasmin activities associated with acid and sweet whey protein products were both significantly (P < 0.0001) affected by the growth of Pseudomonas fluorescens M 3/6. The interaction effect between bacterial growth and whey type on plasmin activity was not significant (P = 0.2457). Plasmin activity in the reconstituted commercial whey protein concentrates (i.e., sweet and acid) varied considerably (16.3 to 330 micrograms/g of protein), but was significantly lower (2.1 to 4.4 micrograms/g of protein, P < 0.05) in whey isolates. These quantitative data were supported by plasmin activity visualized by casein SDS-PAGE.     

Influence of skimmed milk concentrate replacement by dry dairy products in a low fat set‐type yoghurt model system. I: Use of whey protein concentrates,milk protein concentrates and skimmed milk powder

Ten commercial samples of dry dairy products used for protein fortification in a low fat yoghurt model system at industrial scale were studied. The products employed were whey protein concentratres, milk protein concentrates, skimmed milk concentrates and skimmed milk powder which originated from different countries. The gross chemical composition of these dried products were determined, including polyacrylamide gel electrophoresis (SDS‐PAGE) and isoelectric focusing of the proteins, and minerals such as Na, Ca, K and Mg. Yoghurts were formulated using a skim milk concentrated as a milk base enriched with different dry dairy products up to a 43 g kg⁻¹ protein content. Replacement percentage of skim milk concentrated by dry dairy products in the mix was between 1.49 and 3.77%. Yoghurts enriched with milk protein concentrates did not show significantly different viscosity (35.12 Pa s) and syneresis index (591.4 g kg⁻¹) than the two control yoghurts obtained only from skimmed milk concentrates (35.6 Pa s and 565.7 g kg⁻¹) and skimmed milk powder (32.77 Pa s and 551.5 g kg⁻¹), respectively. Yoghurt fortified with the whey protein concentrates, however, was less firm (22.59 Pa s) and had less syneresis index (216 g kg⁻¹) than control yoghurts. Therefore, whey protein concentrates may be useful for drinking yoghurt production. © 1999 Society of Chemical Industry     

Assessing economic and demographic factors that influence United States dairy demand

Low-fat dairy products are key components of a healthy diet for all Americans. As the USDA increases its focus on nutrition and healthy eating, it is important to understand the underlying demands for dairy products, both the healthy and the less healthy ones. The consumption of fluid milk products has decreased over the last decade, whereas milk used for manufactured dairy products such as cheese, ice cream, yogurt, and butter, and for use as an ingredient in other food products, has risen. The objective of this study is to determine the effects of changes in demographic variables, retail prices, and total dairy expenditure on at-home consumption of dairy products, using purchase data from Nielsen 2007 Homescan (ACNielsen, New York, NY) data. To derive the demand elasticities for 16 products, a censored Almost Ideal Demand System model is used. Results reveal that demographic variables do have effects on the purchase of the 16 products, and own-price elasticities are 1 or greater for all 16 products for both uncompensated and compensated elasticities except 4: ice cream, refrigerated yogurt, processed cheese, and margarine. A substitution relationship exists among all fluid milk categories, natural and processed cheese, low-fat ice cream, and refrigerated yogurt, butter, and margarine.     

Invited review: Plasmin protease in milk: current knowledge and relevance to dairy industry

Plasmin is by far the predominant and most completely studied endogenous protease in bovine milk. Plasmin-induced proteolysis can have either beneficial or detrimental effects on the texture and flavor of dairy products, depending on the extent of hydrolysis and type of dairy product. In cheese, the breakdown of protein can help develop desirable flavors and texture during ripening, whereas in pasteurized milk and ultra-high-temperature milk, proteolysis causes undesirable gelation. Plasmin is part of a complex protease-protease inhibitor system in milk that consists of active and inactive forms of the enzyme, activators, and inhibitors. Considerable research has been done to isolate and characterize components of the plasmin system, determine how they interact, develop and compare quantitation methods, and determine how they are affected by cow characteristics, processing conditions, other milk components, storage conditions, and bacterial proteases. Considerable research has focused on enhancing or minimizing the activity of plasmin system components. The intent has been to control protease activity in casein and whey fractions, depending on the final food or ingredient application. Controlling the activity of plasmin has a great potential to improve dairy product quality and reduce their processing costs.     

Texturized Dairy Proteins

ABSTRACT: Dairy proteins are amenable to structural modifications induced by high temperature, shear, and moisture; in particular, whey proteins can change conformation to new unfolded states. The change in protein state is a basis for creating new foods. The dairy products, nonfat dried milk (NDM), whey protein concentrate (WPC), and whey protein isolate (WPI) were modified using a twin-screw extruder at melt temperatures of 50, 75, and 100 °C, and moistures ranging from 20 to 70 wt%. Viscoelasticity and solubility measurements showed that extrusion temperature was a more significant (P < 0.05) change factor than moisture content. The degree of texturization, or change in protein state, was characterized by solubility (R²= 0.98). The consistency of the extruded dairy protein ranged from rigid (2500 N) to soft (2.7 N). Extruding at or above 75 °C resulted in increased peak force for WPC (138 to 2500 N) and WPI (2.7 to 147.1 N). NDM was marginally texturized; the presence of lactose interfered with its texturization. WPI products extruded at 50 °C were not texturized; their solubility values ranged from 71.8% to 92.6%. A wide possibility exists for creating new foods with texturized dairy proteins due to the extensive range of states achievable. Dairy proteins can be used to boost the protein content in puffed snacks made from corn meal, but unmodified, they bind water and form doughy pastes with starch. To minimize the water binding property of dairy proteins, WPI, or WPC, or NDM were modified by extrusion processing. Extrusion temperature conditions were adjusted to 50, 75, or 100 °C, sufficient to change the structure of the dairy proteins, but not destroy them. Extrusion modified the structures of these dairy proteins for ease of use in starchy foods to boost nutrient levels. Practical Application: Dairy proteins can be used to boost the protein content in puffed snacks made from corn meal, but unmodified, they bind water and form doughy pastes with starch. To minimize the water binding property of dairy proteins, whey protein isolate, whey protein concentrate, or nonfat dried milk were modified by extrusion processing. Extrusion temperature conditions were adjusted to 50, 75, or 100 °C, sufficient to change the structure of the dairy proteins, but not destroy them. Extrusion modified the structures of these dairy proteins for ease of use in starchy foods to boost nutrient levels.     

Acid induced gelation behavior of skim milk concentrated by membrane filtration

This work reports a detailed study of the effect of ultrafiltration (UF) and diafiltration (DF) on the acid-induced gelation behavior of fresh milk retentates (2× and 4×). Concentrates were heated at 80°C for 15 min, and compared to unheated samples. The use of extensive DF caused a significantly greater amount of protein (both caseins and whey proteins) in the supernatant fraction, compared to UF retentates at the same concentration, both in unheated and heated samples. DF retentates showed higher pH of gelation, compared to the corresponding UF retentates. The development of tan δ is reported for the first time as a function of colloidal calcium release, and the protein gelation behavior discussed in light differences in composition of the soluble fraction. The results demonstrate how processing history can affect compositional changes and the gelation behavior of fresh milk retentates. Membrane filtration is a widespread unit operation in the dairy industry, employed either to prepare fresh concentrates for further processing, or ingredients with specific functional properties. This work describes in detail the effect of processing history during membrane filtration on the rheological properties of acid induced gels and will help in optimizing formulations and prepare the right ingredients for the right application. It will also be possible to determine new ways to define processing quality of the milk protein concentrates, as it relates to their ability to form texture in fermented dairy products.     

Effect of low lactose dairy powder addition on the properties of gluten-free batters and bread quality

Different low lactose dairy ingredients including sodium caseinate (SC), milk protein isolate (MPI), whey protein isolates (WPIS and WPIM) and whey protein concentrate (WPC) were tested in a gluten-free bread formulation and compared to controls with the addition of no dairy ingredient (C) and one dairy ingredient containing lactose, skim milk powder. Rheological characterisation (frequency sweep and creep-recovery) of the batters at 90% water level (WL) suggested that the addition of WPIS, WPIM and WPC significantly decreased G′ and G″ values. SC and MPI had the opposite effect with a significant increase in both these parameters being found (p < 0.05). The WL of the batters was adjusted in order to obtain the same consistency of the batter C at 90% WL. A Power Law model was used to predict the new WL based on single frequency measurements of G* for each sample. The baking analysis demonstrated that the correction of the WL did not show a strong impact in the quality of the breads. Nevertheless, whey proteins demonstrated the ability to increase significantly the specific volume of the breads and decrease the hardness over time (p < 0.05). SC had a negative impact on the specific volume, which led to an increase in crumb hardness (p < 0.05).