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.     

The Effect of Feed Solids Concentration and Inlet Temperature on the Flavor of Spray Dried Whey Protein Concentrate

Previous research has demonstrated that unit operations in whey protein manufacture promote off‐flavor production in whey protein. The objective of this study was to determine the effects of feed solids concentration in liquid retentate and spray drier inlet temperature on the flavor of dried whey protein concentrate (WPC). Cheddar cheese whey was manufactured, fat‐separated, pasteurized, bleached (250 ppm hydrogen peroxide), and ultrafiltered (UF) to obtain WPC80 retentate (25% solids, wt/wt). The liquid retentate was then diluted with deionized water to the following solids concentrations: 25%, 18%, and 10%. Each of the treatments was then spray dried at the following temperatures: 180 °C, 200 °C, and 220 °C. The experiment was replicated 3 times. Flavor of the WPC80 was evaluated by sensory and instrumental analyses. Particle size and surface free fat were also analyzed. Both main effects (solids concentration and inlet temperature) and interactions were investigated. WPC80 spray dried at 10% feed solids concentration had increased surface free fat, increased intensities of overall aroma, cabbage and cardboard flavors and increased concentrations of pentanal, hexanal, heptanal, decanal, (E)2‐decenal, DMTS, DMDS, and 2,4‐decadienal (P < 0.05) compared to WPC80 spray dried at 25% feed solids. Product spray dried at lower inlet temperature also had increased surface free fat and increased intensity of cardboard flavor and increased concentrations of pentanal, (Z)4‐heptenal, nonanal, decanal, 2,4‐nonadienal, 2,4‐decadienal, and 2‐ and 3‐methyl butanal (P < 0.05) compared to product spray dried at higher inlet temperature. Particle size was higher for powders from increased feed solids concentration and increased inlet temperature (P < 0.05). An increase in feed solids concentration in the liquid retentate and inlet temperature within the parameters evaluated decreased off‐flavor intensity in the resulting WPC80.     

A Process for Increasing the Free Fat Content of Spray-dried Whole Milk Powder

Exposing spray‐dried whole milk powder to high shear and elevated temperature in a twin‐screw continuous mixer increased the free fat content. The effects of operating conditions (powder feed rate, processor screw speed, and process temperature) on lactose crystallinity, particle size distribution, color, and moisture content of spray‐dried whole milk powder were investigated using response surface methodology. Exposure to elevated temperatures and high shear: (a) increased the free fat to more than 80%, (b) crystallized the lactose, (c) reduced the average volume‐based particle size, and (d) broadened the particle size distribution. The raw whole milk powder with creamy‐white color turned into an oily paste with bright‐yellow color. Processing enhanced the functional properties of spray‐dried whole milk powder for milk chocolate manufacture.     

The functionality of milk powder and its relationship to chocolate mass processing, in particular the effect of milk powder manufacturing and composition on the physical properties of chocolate masses

Summary The functionality of twelve different milk powders that are used for chocolate mass processing was investigated. In two types of spray‐dried and one type of roller‐dried powder, the milk fat and milk fat fractions were integrated. Depending on the production process, the amount of free fat available in the milk powders varied greatly. A good correlation was found between the free fat content of the milk powder and the viscosity of the chocolate mass when comparable particle sizes were used. This study reports on the development of spray‐dried milk powders, which when used in chocolate processing produced low viscosities, comparable with those obtained by using roller‐dried milk powder. Calorimetric analysis showed that the shape of the milk powder particles has no influence on the calorimetric qualities of chocolate masses. Only when milk fat was added in a free form, was a higher ‘mixing effect’ in the crystallization peak of cocoa butter and milk fat observed.     

巧克力专用乳粉

研究了不同乳粉的颗粒大小和结构、游离脂肪含量对巧克力浆料粘度的关系。滚筒乳粉与喷雾乳粉之对比，滚筒干燥的全乳粉具有下列优点；游离脂肪含量高，可减少可脂的用量，赋与巧克力以更好的风味；可降低巧克力浆料的粘度。乳粉中羟甲基糠醛含量可增进巧克力风味、口感，提高喷雾乳粉中游离脂肪含量改进的工艺。     

The Impact of Iron on the Bleaching Efficacy of Hydrogen Peroxide in Liquid Whey Systems

Whey is a value‐added product that is utilized in many food and beverage applications for its nutritional and functional properties. Whey and whey products are generally utilized in dried ingredient applications. One of the primary sources of whey is from colored Cheddar cheese manufacture that contains the pigment annatto resulting in a characteristic yellow colored Cheddar cheese. The colorant is also present in the liquid cheese whey and must be bleached so that it can be used in ingredient applications without imparting a color. Hydrogen peroxide and benzoyl peroxide are 2 commercially approved chemical bleaching agents for liquid whey. Concerns regarding bleaching efficacy, off‐flavor development, and functionality changes have been previously reported for whey bleached with hydrogen peroxide and benzoyl peroxide. It is very important for the dairy industry to understand how bleaching can impact flavor and functionality of dried ingredients. Currently, the precise mechanisms of off‐flavor development and functionality changes are not entirely understood. Iron reactions in a bleached liquid whey system may play a key role. Reactions between iron and hydrogen peroxide have been widely studied since the reaction between these 2 relatively stable species can cause great destruction in biological and chemical systems. The actual mechanism of the reaction of iron with hydrogen peroxide has been a controversy in the chemistry and biological community. The precise mechanism for a given reaction can vary greatly based upon the concentration of reactants, temperature, pH, and addition of biological material. In this review, some hypotheses for the mechanisms of iron reactions that may occur in fluid whey that may impact bleaching efficacy, off‐flavor development, and changes in functionality are presented. Practical Application: Cheese whey is bleached to remove residual carotenoid cheese colorant. Concerns regarding bleaching efficacy, off‐flavor development, and functionality changes have been reported for whey proteins bleached with hydrogen peroxide and benzoyl peroxide. It is very important for the dairy industry to understand how whey bleaching can impact flavor and functionality of dried ingredients. Proposed mechanisms of off‐flavor development and functionality changes are discussed in this hypothesis paper.     

Influence of Antioxidant Addition and Processing Treatment on the Formation of Lipid Oxidation Compounds in Spray-dried Bovine Plasma Protein

The effects of antioxidant (tert‐butylhydroquinone, propyl gallate, butylated hydroxytoluene, and rosemary) addition, processing treatments, and storage time on the formation of lipid oxidation compounds in spray‐dried bovine plasma protein (BPP) were determined. Lipid oxidation is initiated by spray‐drying; formation of lipid oxidation compounds was highest in BPP processed using a gas‐fired spray‐drier. The most effective antioxidant in inhibiting the formation of hexanal and other lipid oxidation compounds was tert‐butylhydroquinone. Increased spray‐drier residence time and extended storage contributed to increases in lipid oxidation products. Use of effective antioxidants and selection of processing parameters to minimize lipid oxidation reactions can improve the flavor quality of spray‐dried BPP.     

The influence of additives and drying methods on quality attributes of fish protein powder made from saithe (Pollachius virens)

BACKGROUND: Fish protein powder (FPP) is used in the food industry for developing formulated food products. This study investigates the feasibility of increasing the value of saithe (Pollachius virens) by producing a functional FPP. Quality attributes of spray and freeze‐dried saithe surimi containing lyoprotectants were studied. A freeze‐dried saithe surimi without lyoprotectants was also prepared as a control sample. RESULTS: The amount of protein, moisture, fat and carbohydrate in the FPPs were 745–928, 39–58, 21–32 and 10–151 g kg^?1. Quality attributes of FPPs were influenced by the two drying methods and lyoprotectants. The highest level of lipid oxidation was found in the control and the second highest in the spray‐dried FPP. The spray‐dried fish protein had the lowest viscosity among all FPPs. Gel‐forming ability of samples with lyoprotectants was higher than that of the control. Water‐binding capacity, emulsion properties and solubility of the freeze‐dried fish protein containing lyoprotectants were significantly higher than spray‐dried and control samples. However, functional properties of spray‐dried FPP were higher than the control sample. CONCLUSION: It is feasible to develop value‐added FPP from saithe surimi using spray‐ and freeze‐drying processes, but freeze‐dried FPP containing lyoprotectant had superior functional properties and stability compared with spray‐dried sample. Both products might be used as functional protein ingredients in various food systems. Copyright © 2010 Society of Chemical Industry     

Influence of milk components on properties and consumer acceptance of milk chocolate

The objective of the study was to assess the effects of various milk components on chocolate quality, defined by measurable properties and decisively by consumer liking.The choice of milk products considered different types, technologies and suppliers. Samples produced under standardised conditions were analysed for particle size, flow properties, colour and by a trained sensory panel. Consumer testing determined overall liking. Results revealed that milk ingredients influence consumer liking of milk chocolate through the quality driving parameters of particle size/sandiness, viscosity/melting mouthfeel and milk flavour. Chocolates made from milk products that contain high amounts of free fat - e.g. skim milk powder plus anhydrous milk fat - scored better than those using bound fat - e.g. whole milk powder. Milk fat status had more influence than differences between spray and roller-dried powders. High free fat cream powders were most suitable for cream chocolates. All milk components need to be free from off-notes that require sensory checks. Fillers like lactose could replace some sucrose, and whey protein concentrate can partially replace skim milk powder.     

Effect of spray‐drying parameters on the solubility and the bulk density of camel milk powder: A response surface methodology approach

Response surface methodology coupled with a Box–Behnken experimental design was used to investigate the effect of the air inlet drying temperature, the feed rate, and the fat content on the solubility and the bulk density of spray‐dried camel and cow milk powders. The response surface methodology analysis highlighted that milk fat content and feed rate were the most effective parameters affecting the solubility and the bulk density of cow and camel milk powders. Importantly, there was no significant interaction between the studied drying parameters and camel milk powder solubility or bulk density. Overall, camel milk powder exhibited a comparable solubility to that of cow milk powder with a higher bulk density.     

Effect of Sucrose on Physical Properties of Spray‐Dried Whole Milk Powder

ABSTRACT: Spray‐dried whole milk powders were prepared from whole condensed milk with various sucrose concentrations (0%, 2.5%, 5%, 7.5%, and 10% w/w), and their glass transition temperature and some physical properties of importance in chocolate manufacture were evaluated. In milk powder samples, the glass transition temperature and free‐fat content decreased in a nonlinear manner with sucrose addition. Moreover, increasing sucrose concentration reduced the formation of dents on the particle surface. Addition of sucrose in whole condensed milk increased linearly the apparent particle density and in a nonlinear manner the particle size of spray‐dried milk powders. The particle size volume distribution of milk powders with the highest sucrose concentration differed from the log‐normal distribution of the other samples due to the formation of large agglomerates. Neither vacuole volume, nor the amorphous state of milk powders was affected by sucrose addition.     

Differences in particle characteristics and oxidized flavor as affected by heat-related processes of milk powder

Understanding the formation of oxidized flavor will be highly useful in the improvement of milk powder quality. Effects of preheating, concentration and spray-drying on the particle characteristics and the oxidized flavor stability of milk powder were investigated. The surface composition and free radicals were analyzed using x-ray photoelectron spectroscopy and electron spin resonance spectrometry, respectively. The concentrations of selected oxidized volatiles hexanal and 2-heptanone were determined using solid-phase microextraction gas chromatography-mass spectrometry. Levels of hexanal and 2-heptanone in fresh milk powder were higher than those in raw milk and heated milk, which drastically increased with increasing time of storage. Differences in the morphological observations, free fat, and surface composition of fresh milk powder were found among different heat-related processes. During storage, a radical (g value, a characteristic constant whose value serves to identify any given free radical, was 2.0054) was detected in milk powder. The specific population of the radical increased from 2.99 × 10⁷ at 3 mo to 1.23 × 10⁸ at 6 mo of storage. Addition of ascorbic acid in milk powder changed the type of radicals and reduced the oxidation off-flavor. According to the Pearson correlations, not the surface compositions but the morphological characteristics of milk powder particles should be considered in maintaining the stability of oxidized flavor in storage.     

Maillard Reaction Products as Encapsulants for Fish Oil Powders

The use of Maillard reaction products for encapsulation of fish oil was investigated. Fish oil was emulsified with heated aqueous mixtures comprising a protein source (Na caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrates (glucose, dried glucose syrup, oligosaccharide) and spray‐dried for the production of 50% oil powders. The extent of the Maillard reaction was monitored using L*, a*, b* values and absorbance at 465 nm. Encapsulation efficiency was gauged by measurement of solvent‐extractable fat and the oxidative stability of the fish oil powder, which was determined by assessment of headspace propanal after storage of powders at 35 °C for 4 wk. Increasing the heat treatment (60 °C to 100 °C for 30 to 90 min) of sodium caseinate‐glucose‐glucose syrup mixtures increased Maillard browning but did not change their encapsulation efficiency. The encapsulation efficiency of all heated sodium caseinate‐glucose‐glucose syrup mixtures was high, as indicated by the low solvent‐extractable fat in powder (<2% powder, w/w). However, increasing the severity of the heat treatment of the sodium caseinate‐glucose‐glucose syrup mixtures reduced the susceptibility of the fish oil powder to oxidation. The increased protection afforded to fish oil in powders by increasing the temperature‐time treatment of protein‐carbohydrate mixtures before emulsification and drying was observed irrespective of the protein (sodium caseinate, whey protein isolate, soy protein isolate, or skim milk powder) and carbohydrate (glucose, glucose/dried glucose syrup, or oligosaccharide/dried glucose syrup) sources used in the formulation. Maillard reaction products produced by heat treatment of aqueous protein‐carbohydrate mixtures were effective for protecting microencapsulated fish oil and other oils (evening primrose oil, milk fat) from oxidation.     

Sensory Threshold of Light-Oxidized Flavor Defects in Milk

Reduced fat (2%) milk in high‐density polyethylene (HDPE) containers was exposed to fluorescent light in a 6 °C walk‐in cooler. Samples were evaluated by 10 trained panelists and by 94 consumers to assess the presence and intensity of sensory differences from unexposed control samples using the semi‐ascending paired difference method. Trained panelists detected flavor defects following 15 to 30 min of light exposure; consumers detected defects between 54 min and 2 h. As approximately 50% of plastic containers remain in dairy cases for at least 8 h, these results suggest that the majority of milk on the market in light‐transmissible containers is vulnerable to development of detectable light‐oxidized flavor defects.     

Vitamin Fortification of Fluid Milk

Vitamin concentrates with vitamins A and D are used for fortification of fluid milk. Although many of the degradation components of vitamins A and D have an important role in flavor/fragrance applications, they may also be source(s) of off‐flavor(s) in vitamin fortified milk due to their heat, oxygen, and the light sensitivity. It is very important for the dairy industry to understand how vitamin concentrates can impact flavor and flavor stability of fluid milk. Currently, little research on vitamin degradation products can be found with respect to flavor contributions. In this review, the history, regulations, processing, and storage stability of vitamins in fluid milk are addressed along with some hypotheses for the role of vitamin A and D fortification on flavor and stability of fluid milk.