Nonfat Dry Milk Research Articles

Bootstrapping for Estimating the Conservative Kill Ratio of the Surrogate to the Pathogen for Use in Thermal Process Validation at the Industrial Scale

A surrogate is commonly used for process validations. The industry often uses the target log cycle reduction for the test (LCRTest) microorganism (surrogate) to be equal to the desired log cycle reduction for the target (LCRTarget) microorganism (pathogen). When the surrogate is too conservative with far greater resistance than the pathogen, the food may be overprocessed with quality and cost consequences. In aseptic processing, the Institute for Thermal Processing Specialists recommends using relative resistance (DTarget)/(DTest) to calculate LCRTest (product of LCRTarget and relative resistance). This method uses the mean values of DTarget and DTest and does not consider the estimating variability. We defined kill ratio (KR) as the inverse of relative resistance.The industry uses an extremely conservative KR of 1 in the validation of food processes for low-moisture foods, which ensures an adequate reduction of LCRTest, but can result in quality degradation. This study suggests an approach based on bootstrap sampling to determine conservative KR, leading to practical recommendations considering experimental and biological variability in food matrices. Previously collected thermal inactivation kinetics data of Salmonella spp. (target organism) and Enterococcus faecium (test organism) in Non-Fat Dried Milk (NFDM) and Whole Milk Powder (WMP) at 85, 90, and 95°C were used to calculate the mean KR. Bootstrapping was performed on mean inactivation rates to get a distribution of 1000 bootstrap KR values for each of the treatments. Based on minimum temperatures used in the industrial process and acceptable level of risk (e.g., 1, 5, or 10% of samples that would not achieve LCRTest), a conservative KR value can be estimated. Consistently, KR increased with temperature and KR for WMP was higher than NFDM. Food industries may use this framework based on the minimum processing temperature and acceptable level of risk for process validations to minimize quality degradation.

Development and validation of a targeted mass spectrometry method for the quantification of milk protein allergens in multiple complex food matrices using matrix-independent calibration

Quantitative detection of food allergens is crucial in assessing the risk of allergic responses in susceptible individuals and ensuring regulatory compliance. Targeted mass spectrometry methods provide an opportunity to analyze allergens from complex, processed food matrices. However, probable interferences of diverse food matrices mandates preparation of matrix-matched calibration curves, challenging adaptation of methods into multiple matrices. In this study, we have developed a novel matrix-independent calibration strategy employing exogenous carrier proteins as background and demonstrated its adaptability in quantification of milk from multiple food matrices at concentrations relevant for risk assessment applications. Peptides representing casein or whey fractions of milk were detectable from concentrations as low as 1 ppm nonfat dry milk (NFDM) in baked cookie matrix at 46–99% accuracy, 0.5 ppm total milk protein (TMP) in pasteurized beverages at 94–138% accuracy, and 1 ppm casein in chocolate at 35–51% accuracy. Quantitative estimations of milk from matrix-independent calibration curves in the background of egg white powder as exogenous carrier were comparable to those from a matrix-matched calibration curve, and the quantitative precision was within 30% CV across the inter-day replicates. The sensitivity, accuracy, and precision of this matrix-independent approach ensure robustness of the method for high throughput food allergen analysis as required in routine testing labs.

Цветовые характеристики мороженого при использовании концентратов и микропартикулятов сывороточных белков

Ice cream is one of the most popular desserts all over the world because it possesses excellent sensory characteristics and is highly nutritional. Whey proteins can increase the biological value of ice cream. They are often used in non-fat dry milk powder to reduce its cost. However, whey proteins and casein differ in color. Therefore, replacing milk solids of non-fat proteins with whey proteins hay affect the color profile of the final product. The study registered the color changes in ice cream with different ratios of non-fat dry milk powder, microparticles, and whey protein concentrates. The spectrophotometric method made it possible to assess the key color characteristics, i.e., yellowness, whiteness, and overall color difference. Larger quantities of protein concentrates darkened the final product from 96 to 91.5. A mix of microparticles and whey protein concentrates had no effect on the color profile while each component applied on its own proved significant, as did some other variables. After replacing dry milk proteins, the whiteness index dropped to 85 whereas the yellowness index reached 18. The overall color difference showed that the consumer is likely to notice the replacement of dry milk powder with whey protein concentrates. However, the differences between samples with different ratios were either undetectable or insignificant. The obtained results can be used in qualitative tests to detect the presence of whey proteins in the ice cream protein composition.

Evaluation of air impingement for dry-cleaning nonfat dry milk residues on a stainless-steel surface.

The use of air jet impingement to remove residues from surfaces in food manufacturing operations offers an alternative to the use of water and liquid cleaning agents. During this investigation, air impingement was used to remove nonfat dry milk (NFDM) residues from a stainless-steel surface. The influence of the water activity (aw ) of the residue, the time after the residue reached an equilibrium water activity, and the thickness of residue at the time of removal from the surface have been investigated. All three factors had a significant effect on the time for removal. An increase in the water activity, the time at equilibrium, the sample thickness, or a combination of all three resulted in an increase in the time required to remove the deposits. Visible changes in the structure of deposits were observed as NFDM samples equilibrated to water activities above 0.43. NFDM residues with water activities less than 0.33 were removed within 1s of using air impingement regardless of wall shear stress. When the water activities were greater than 0.50, the thickness of deposit was greater than 1mm, and the time after reaching an equilibrium water activity was over 7days, more than 5min of air impingement with wall shear stress over 9.48Pa was required to remove the residue. The results from these experiments indicated that air impingement has the potential to provide effective cleaning in manufacturing facilities for low-moisture foods. PRACTICAL APPLICATION: The introduction of water in low-moisture food environments is often undesirable due to the possibility of pathogenic microorganism growth. The normal cleaning operations in the food industry use water as a cleaning agent. This study evaluates the application of air impingement technology as a dry-cleaning method.

Preparation and Characterization of Boza Enriched with Nonfat Dry Milk and Its Impact on the Fermentation Process.

Boza is an indigenous, traditional, low-alcohol and highly viscous beverage prepared by fermenting cereals. Its thick and gel-like consistency make it suitable for consumption via spoon. Although boza is a nutritious beverage, its protein content is very low (<2%). A new type of boza was developed by incorporating nonfat dry milk (NFDM) to elevate the protein content of the beverage. Different NFDM amounts (10 to 40% w/v) were added to determine the best concentration and fermentation time based on the refractive index and pH values at room temperature (0-48 h). The best sample was further characterized by rheological analyses and Fourier transform infrared (FTIR) spectroscopy. The sample with 10% NFDM was the best, as fermentation was successfully performed, and further addition of NFDM increased the initial pH. The refractive index and pH decreased from 21.9 ± 0.1 to 11.8 ± 0.1 and 5.77± 0.50 to 4.09 ± 0.35 during fermentation, respectively. The samples exhibited shear-thinning, solid-like behavior, and a gel-like structure. FTIR analysis by independent modeling of class analogy (SIMCA) demonstrated that unfermented slurry and the fermented product could be effectively differentiated. With the addition of 10% NFDM, the increase in the protein content of the boza medium became significant.

Whey permeate powder is a suitable ingredient for ice cream

The objective of this research was to evaluate the suitability of whey permeate powder for ice cream. Three white mixes were formulated with equivalent total solids, fat, and carbohydrates, but different concentrations of lactose and added sugar. Vanilla ice creams contained either reduced lactose (RL, 3.8% lactose and 17% added sugar), standard lactose (SL, 5.8%; 15%), or high lactose (HL, 7.8%; 13%). Trained panelists evaluated 8 body and texture, and 6 flavor characteristics through 10 mo of storage. All ice creams maintained low mean scores (<4.0/15.0 cm) for crumbly, lacks freshness, nonfat dry milk flavor, and whey, and moderate mean scores (5.0–8.3/15.0 cm) for gummy, melt rate, melt viscosity, sweet, and vanilla flavor for 10 mo. In mo 1 and 10, consumers in Iowa (n = 94, n = 55) and in mo 4 and 6, consumers in Kansas (n = 44; n = 56) rated the acceptability of the ice creams. Overall acceptability, flavor, and texture acceptability for products did not significantly differ until mo 10, when HL mean scores decreased lower than SL ice cream mean scores. The lower scores are attributed to crumbly and sandy texture defects, noted by trained panelists, only for HL ice cream stored 10 mo. The research demonstrates that whey permeate powder can be used to produce ice creams of acceptable quality for up to 10 mo.

Production and functional evaluation of nonfat dry milk with whey proteins as fibrils

Commercial manufacturing of dairy products involves the addition of dairy ingredients (such as nonfat dry milk and milk protein concentrates), as well as nondairy additives (such as gums, stabilizers, emulsifiers, and texture modifiers) to get the best product appearance, maintain the product quality, and extend shelf life. Though these nondairy additives are not harmful, consumers do not prefer them in dairy food formulations. Therefore, the dairy industry is working on improving the inherent functionality of dairy ingredients using different processes. Recently, fibrillation emerged as a new technique to convert globular proteins such as whey proteins into fibrils, which provide enhanced viscosity, foaming, and emulsification capacity. Therefore, skim milk was subjected to microfiltration followed by ultrafiltration of microfiltration permeate to fractionate whey proteins. Then, whey proteins were selectively fibrillated and mixed back with other streams of microfiltration and ultrafiltration to get fibrillated skim milk. Fibrillated skim milk was spray-dried to get fibrillated nonfat dry milk (NDM). Visible whey protein fibrils were observed in reconstituted fibrillated NDM, which showed survival of fibrils in fibrillated NDM. Fibrillated NDM showed significantly higher viscosity than control NDM. Fibrillated NDM also showed higher emulsification capacity, foaming capacity, and stability than the control NDM but lower gel strength. Considering the improved functionality of fibrillated NDM, they can be used in product formulations such as ice cream mix, where the thickening of a solution, good emulsification, and foaming properties are required.

Partition of milk phospholipids during ice cream manufacturing

The distribution of phospholipids (PL) within the fat and serum phase of ice cream manufacturing was evaluated through partition coefficients (KPL) after mixing, pasteurization, freezing, and hardening. Ice creams containing about 40.41 ± 3.45 (± standard deviation; control formulation) and 112.29 ± 9.06 (enriched PL formulation) mg of PL per g of fat were formulated with nonfat dry milk and β-serum, respectively. Overall, the KPL were lower than 1, indicating that the PL were predominantly found in the fat phase, and only a small amount was left in the serum and sediment. Confocal micrographs visually confirmed this generalization. The addition of PL significantly increased the viscosity of the mixes between 4- and 9-fold, depending on the shear rate. Additionally, mixes containing high PL exhibited higher yield stress than those formulated with low PL (0.15 ± 0.09 and 0.016 ± 0.08 Pa, respectively). Ice creams with high PL delayed the onset of meltdown and exhibited a slower rate of a meltdown than low-PL ice creams (18.53 ± 0.57 and 14.83 ± 0.85 min, and 1.01 ± 0.05 and 0.71 ± 0.04% min-1, respectively). This study provides useful guidelines for manufacturing ice cream enriched in milk PL. Additionally, the use of β-serum, a byproduct stream, as a source of PL is illustrated. The development will require studying the sensorial description of the product as well as consumer acceptance.

Validation of the KangarooSci® Aerobic Count Plate for the Enumeration of Meosphilic Aerobic Bacteria in Selected Foods and on Stainless Steel Environmental Surfaces: AOAC Performance Tested MethodSM 062301.

The KangarooSci® Aerobic Count Plate is a sample-ready culture medium system, for direct counting of aerobic bacteria colonies after 48-72 h of incubation. The KangarooSci Aerobic Count Plate was evaluated for AOAC® Performance Tested Methods SM certification. The KangarooSci Aerobic Count Plate (ACP) was evaluated through matrix studies and product consistency/stability study and robustness testing. For the matrix study, nine food products (nonfat dry milk powder, fresh raw bovine milk, pasteurized liquid bovine milk, fresh raw ground beef, frozen uncooked chicken breast, cooked shredded pork, apple juice, ice cream, and fresh strawberries), and one environmental surface (stainless steel) were evaluated following the KangarooSci ACP product instructions and compared to the ISO 4833-1:2013-pat 1, Microbiology of food and animal feeding stuffs-Horizontal methods for the enumeration of microorganisms-Part 1: Colony count at 30 °C by the pour plate technique reference standard. The product consistency and stability testing evaluated three separate production lots of the KangarooSci ACP. The robustness testing examined three test parameters, volume of sample plated, incubation time, and incubation temperature using a factorial study design. Results from the matrix study demonstrated equivalent performance between the KangarooSci ACP and the ISO 4833-1:2013 reference standard. The product consistency and stability testing showed that the performance of the assay was equivalent over time up to 12 months and between production lots. Minor changes to the operational test conditions showed no significant impact on performance during the robustness testing. The KangarooSci ACP is an effective method for aerobic plate count for all matrixes evaluated. The KangarooSci Aerobic Count Plate allows for fast, reliable enumeration of aerobic bacteria. Utilizing the alternative method takes up less space in incubators, requiring no sample spreader, and requires less consumables compared to the reference method.

Enhancement of the quality attributes and health benefits synbiotic yoghurt from cow's milk

The present work delighted on extraction of galactomannan polysaccharide from guar gum beans and microbial galactomannan source. Effect of replacing non-fat dry milk that used to fortify cow's milk in yoghurt industry with the two extracted galactomannans and commercial galactomannan as food additives was studied. Control yoghurt treatment was made from 3.0% fat cow's milk that was fortified with 1.5% non-fat dry milk. Another 6 yoghurt treatmentwas fortified with 0.15, 0.25% of commercial, guar and microbial galactomannan respectively. All treatments were cultured with the probiotic starter (1.0% Streptococcus thermophilus + 1.0% Lactobacillus delbrueckii subsp. Bulgaricus + 1.0% Bifidobacteriumbifidum). The obtained results indicated that yoghurt supplementation with the three types of galactomannans increased the acidity, curd tension, total solids content, decreased pH values and syneresis of yoghurt treatments. Control yoghurt and commercial galactomannan yoghurt were not significantly different from the corresponding batches those made with either guar galactomannan and microbial galactomannan in fat, protein and ash content. Yoghurt treatments which supplemented with the three types of galactomannans have higher bifidobacteria counts and organoleptic scores than the control treatment yoghurt.

Short-term feeding of defatted bovine colostrum mitigates inflammation in the gut via changes in metabolites and microbiota in a chicken animal model

BackgroundNondrug supplement strategies to improve gut health have largely focused on the effects of individual compounds to improve one aspect of gut homeostasis. However, there is no comprehensive assessment of the reproducible effects of oral, short-term, low-level colostrum supplementation on gut inflammation status that are specific to the ileum. Herein, a chicken animal model highly responsive to even mild gut inflammatory stimuli was employed to compare the outcomes of feeding a standard diet (CON) to those of CON supplemented with a centrifuge-defatted bovine colostrum (BC) or a nonfat dried milk (NFDM) control on the efficiency of nutrient use, ileal morphology, gut nitro-oxidative inflammation status, metabolites, and the composition of the microbiota.ResultsA repeated design, iterative multiple regression model was developed to analyze how BC affected ileal digesta-associated anti-inflammatory metabolite abundance coincident with observed changes in the ileal microbiome, mitigation of epithelial inflammation, and ileal surface morphology. An improved whole body nutrient use efficiency in the BC group (v CON and NFDM) coincided with the observed increased ileum absorptive surface and reduced epithelial cell content of tyrosine-nitrated protein (NT, biomarker of nitro-oxidative inflammatory stress). Metabolome analysis revealed that anti-inflammatory metabolites were significantly greater in abundance in BC-fed animals. BC also had a beneficial BC impact on microbiota, particularly in promoting the presence of the bacterial types associated with eubiosis and the segmented filamentous bacteria, Candidatus Arthromitus.ConclusionThe data suggest that an anti-inflammatory environment in the ileum was more evident in BC than in the other feeding groups and associated with an increased content of statistically definable groups of anti-inflammatory metabolites that appear to functionally link the observed interactions between the host’s improved gut health with an observed increase in whole body nutrient use efficiency, beneficial changes in the microbiome and immunometabolism.

Comparison of micellar casein isolate and nonfat dry milk for use in the production of high-protein cultured milk products.

High protein levels in yogurt, as well as the presence of denatured whey proteins in the milk, lead to the development of firm gels that can make it difficult to formulate a fluid beverage. We wanted to prepare high-protein yogurts and explore the effects of using micellar casein isolate (MCI), which was significantly depleted in whey protein by microfiltration. Little is known about the use of whey protein-depleted milk protein powders for high-protein yogurt products. Microfiltration also depletes soluble ions, in addition to whey proteins, and so alterations to the ionic strength of rehydrated MCI dispersions were also explored, to understand their effects on a high-protein yogurt gel system. Yogurts were prepared at 8% protein (wt/wt) from MCI or nonfat dry milk (NDM). The NDM was dispersed in water, and MCI powders were dispersed in water (with either low levels of added lactose to allow fermentation to achieve the target pH, or a high level to match the lactose content of the NDM sample) or in ultrafiltered (UF) milk permeate to align its ionic strength with that of the NDM dispersion. Dispersions were then heated at 85°C for 30 min while stirring, cooled to 40°C in an ice bath, and fermented with yogurt cultures to a final pH of 4.3. The stiffness of set-style yogurt gels, as determined by the storage modulus, was lowest in whey protein-depleted milk (i.e., MCI) prepared with a high ionic strength (UF permeate). Confocal laser scanning microscopy and permeability measurements revealed no large differences in the gel microstructure of MCI samples prepared in various dispersants. Stirred yogurt made from MCI that was prepared with low ionic strength showed slow rates of elastic bond reformation after stirring, as well as slower increases in cluster particle size throughout the ambient storage period. Both the presence of denatured whey proteins and the ionic strength of milk dispersions significantly affected the properties of set and stirred-style yogurt gels. Results from this study showed that the ionic strength of the heated milk dispersion before fermentation had a large influence on the gelation pH and strength of acid milk gels, but only when prepared at high (8%) protein levels. Results also showed that depleting milk of whey proteins before fermentation led to the development of weak yogurt gels, which were slow to rebody and may be better suited for preparing cultured milk beverages where low viscosities are desirable.

Manufacture of process cheese products without emulsifying salts using acid curd and micellar casein concentrate.

Process cheese products (PCP) are dairy foods prepared by blending dairy ingredients (such as natural cheese, protein concentrates, butter, nonfat dry milk, whey powder, and permeate) with nondairy ingredients [such as sodium chloride, water, emulsifying salts (ES), color, and flavors] and then heating the mixture to obtain a homogeneous product with an extended shelf life. The ES, such as sodium citrate and disodium phosphate, are critical for the unique microstructure and functional properties of PCP because they improve the emulsification characteristics of casein by displacing the calcium phosphate complexes that are present in the insoluble calcium-paracaseinate-phosphate network in natural cheese. The objectives of this study were to determine the optimum protein content (3, 6, and 9% protein) in micellar casein concentrate (MCC) to produce acid curd and to manufacture PCP using a combination of acid curd cheese and MCC that would provide the desired improvement in the emulsification capacity of caseins without the use of ES. To produce acid curd, MCC was acidified using lactic acid to get a pH of 4.6. In the experimental formulation, the acid curd was blended with MCC to have a 2:1 ratio of protein from acid curd relative to MCC. The PCP was manufactured by blending all ingredients in a KitchenAid blender (Professional 5 Plus, KitchenAid) to produce a homogeneous paste. A 25-g sample of the paste was cooked in the rapid visco analyzer (RVA) for 3 min at 95°C at 1,000 rpm stirring speed during the first 2 min and 160 rpm for the last min. The cooked PCP was then transferred into molds and refrigerated until further analysis. This trial was repeated 3 times using different batches of acid curd. MCC with 9% protein resulted in acid curd with more adjusted yield. The end apparent viscosity (402.0-483.0 cP), hardness (354.0-384.0 g), melting temperature (48.0-51.0°C), and melting diameter (30.0-31.4 mm) of PCP made from different acid curds were slightly different from the characteristics of typical PCP produced with conventional ingredients and ES (576.6 cP end apparent viscosity, 119.0 g hardness, 59.8°C melting temperature, and 41.2 mm melting diameter) due to the differences in pH of final PCP (5.8 in ES PCP compared with 5.4 in no ES PCP). We concluded that acid curd can be produced from MCC with different protein content. Also, we found that PCP can be made with no ES when the formulation uses a 2:1 ratio of acid curd relative to MCC (on a protein basis).

Validation of the CompactDryTM "Nissui" TCR for Rapid Enumeration of Aerobic Bacteria in a Variety of Matrixes: AOAC Performance Tested MethodSM 082201.

CompactDry™ "Nissui" TCR are ready-to-use dry media sheets using a chromogenic medium for the enumeration of mesophilic aerobic bacteria in foods in as little as 24 h. The CompactDry "Nissui" TCR method was validated to achieve AOAC Performance Tested MethodsSM certification. The performance of the CompactDry "Nissui" TCR was compared to that of USDA/FSIS MLG 3.02, FDA BAM Chapter 3, and SMEDP Chapter 6 for 11 matrixes. All 11 matrixes were tested by CompactDry incubation at 35 ± 1°C for 24 ± 2 and 48 ± 3 h. The three dairy matrixes were also evaluated by CompactDry incubation at 32 ± 1°C for 24 ± 2 and 48 ± 3 h and additionally at 72 ± 3 h for nonfat dry milk. After log10 transformation of the data, the standard deviation of repeatability (sr) was similar between CompactDry "Nissui" TCR and the respective reference methods, and method equivalence based on the 90% confidence interval of the difference of means being within (-0.5, 0.5) was demonstrated for all matrixes, incubation temperatures, and incubation times in the method developer and independent laboratory studies. The method was shown to be robust, and data are presented supporting product consistency and 18-month shelf life. The CompactDry "Nissui" TCR method was validated for the determination of mesophilic aerobic bacteria in a variety of matrixes with incubation at 35 ± 1°C for 24 ± 2 and 48 ± 3 h and for dairy matrixes also at 32 ± 1°C for 24 ± 2, 48 ± 3, and 72 ± 3 h. The CompactDry "Nissui" TCR method is equivalent to the USDA/FSIS MLG 3.02, FDA BAM Chapter 3, and SMEDP Chapter 6 reference methods and is suitable for Performance Tested MethodsSM certification for the matrixes tested.

Interlaboratory Evaluation of Enterococcus faecium NRRL B-2354 as a Salmonella Surrogate for Validating Thermal Treatment of Multiple Low-Moisture Foods

This multi-institutional study assessed the efficacy of Enterococcus faecium NRRL B-2354 as a nonpathogenic Salmonella surrogate for thermal processing of nonfat dry milk powder, peanut butter, almond meal, wheat flour, ground black pepper, and date paste. Each product was analyzed by two laboratories (five independent laboratories total), with the lead laboratory inoculating (E. faecium or a five-strain Salmonella enterica serovar cocktail of Agona, Reading, Tennessee, Mbandaka, and Montevideo) and equilibrating the product to the target water activity before shipping. Both laboratories subjected samples to three isothermal treatments (between 65 and 100°C). A log-linear and Bigelow model was fit to survivor data via one-step regression. On the basis of D80°C values estimated from the combined model, E. faecium was more thermally resistant (P < 0.05) than Salmonella in nonfat dry milk powder (DEf-80°C, 100.2 ± 5.8 min; DSal-80°C, 28.9 ± 1.0 min), peanut butter (DEf-80°C, 133.5 ± 3.1 min; DSal-80°C, 57.6 ± 1.5 min), almond meal (DEf-80°C, 34.2 ± 0.4 min; DSal-80°C, 26.1 ± 0.2 min), ground black pepper (DEf-80°C, 3.2 ± 0.8 min; DSal-80°C, 1.5 ± 0.1 min), and date paste (DEf-80°C, 1.5 ± 0.0 min; DSal-80°C, 0.5 ± 0.0 min). Although the combined laboratory D80°C for E. faecium was lower (P < 0.05) than for Salmonella in wheat flour (DEf-80°C, 9.4 ± 0.1 min; DSal-80°C, 10.1 ± 0.2 min), the difference was ∼7%. The zT values for Salmonella in all products and for E. faecium in milk powder, almond meal, and date paste were not different (P > 0.05) between laboratories. Therefore, this study demonstrated the impact of standardized methodologies on repeatability of microbial inactivation results. Overall, E. faecium NRRL B-2354 was more thermally resistant than Salmonella, which provides support for utilizing E. faecium as a surrogate for validating thermal processing of multiple low-moisture products. However, product composition should always be considered before making that decision.

Opportunity Cost: An Economic Concept That May Improve the Functioning of Federal Milk Marketing Orders and the U.S. Dairy Industry

AbstractIn the United States, over 70% of milk production is priced under Federal Milk Marketing Orders (FMMOs). A primary purpose of FMMOs is to facilitate orderly allocation of milk as a limited, perishable resource among alternative uses. Fundamental to FMMOs are the regulatory prices applicable to milk used in cheese and whey (Class III), and nonfat dry milk and butter (Class IV). This work examines a novel milk pricing method based on the concept of opportunity cost for milk used in cheese and whey. This novel method may improve the functioning of FMMOs and the U.S. dairy industry.

Amino Acid Fingerprinting of Authentic Nonfat Dry Milk and Skim Milk Powder and Effects of Spiking with Selected Potential Adulterants.

A collaborative study was undertaken in which five international laboratories participated to determine amino acid fingerprints in 39 authentic nonfat dry milk (NFDM)/skim milk powder (SMP) samples. A rapid method of amino acid analysis involving microwave-assisted hydrolysis followed by ultra-high performance liquid chromatography-ultraviolet detection (UHPLC-UV) was used for quantitation of amino acids and to calculate their distribution. The performance of this rapid method of analysis was evaluated and was used to determine the amino acid fingerprint of authentic milk powders. The distribution of different amino acids and their predictable upper and lower tolerance limits in authentic NFDM/SMP samples were established as a reference. Amino acid fingerprints of NFDM/SMP were compared with selected proteins and nitrogen rich compounds (proteins from pea, soy, rice, wheat, whey, and fish gelatin) which can be potential economically motivated adulterants (EMA). The amino acid fingerprints of NFDM/SMP were found to be affected by spiking with pea, soy, rice, whey, fish gelatin and arginine among the investigated adulterants but not by wheat protein and melamine. The study results establish an amino acid fingerprint of authentic NFDM/SMP and demonstrate the utility of this method as a tool in verifying the authenticity of milk powders and detecting their adulteration.

Microcalorimetric Investigations of Reversible Staphylococcal Enterotoxin Unfolding.

Staphylococcal food poisoning (SFP) is a common food-borne illness often associated with contamination during food handling. The genes for Staphylococcal enterotoxin (SE) isoforms SEA and SEB are frequently detected in human nasal Staphylococcus aureus isolates and these toxins are commonly associated with SFP. Past studies described the resistance of preformed SE proteins to heat inactivation and their reactivation upon cooling in foods. Full thermodynamic analyses for these processes have not been reported, however. The thermal stabilities of SEA, SEB, and SEH and reversibility of unfolding in simple buffers were investigated at pH 4.5 and pH 6.8 using differential scanning calorimetry (DSC). SEA and SEB unfolding was irreversible at pH 6.8 and at least partially reversible at pH 4.5 while SEH unfolding was irreversible at pH 4.5 and reversible at pH 6.8. Additional studies showed maximum refolding for SEB at pH 3.5–4.0 and diminished refolding at pH 4.5 with increasing ionic strength. SE-stimulated secretion of interferon-gamma by human peripheral blood mononuclear cells was used to assess residual SE biological activity following heat treatments using conditions matching those used for DSC studies. The biological activities of SEB and SEH exhibited greater resistance to heat inactivation than that of SEA. The residual activities of heat-treated SEB and SEH were measurable but diminished further in the presence of reconstituted nonfat dry milk adjusted to pH 4.5 or pH 6.8. To different extents, the pH and ionic strengths typical for foods influenced the thermal stabilities of SEA, SEB, and SEH and their potentials to renature spontaneously after heat treatments.

Effect of Storage of Skim Milk Powder, Nonfat Dry Milk and Milk Protein Concentrate on Functional Properties

The physicochemical changes during the storage of high protein powders, such as skim milk powder (SMP), nonfat dry milk (NDM), and milk protein concentrates (MPC), can result in a variation in the functional properties of the powders. The objective of this study was to evaluate the effects of the storage of various milk powders (SMP, NDM, MPC40, and MPC70) on their functional properties. Three different lots of the powders were collected from US manufacturers and were analyzed for functional properties after 3, 9, and 15 months of storage at 25 °C. Additionally, this study also evaluated the effects of seasonal variation on the functionality of SMP and NDM. Functional properties, such as solubility, emulsification ability index (EAI), foaming, and surface hydrophobicity index (SHI), were evaluated at each storage time point. The solubility of MPC70 and the foam overrun of SMP, MPC40, and MPC70 decreased significantly (p &lt; 0.05) with an increase in the storage time. The emulsification properties of MPC70 were significantly higher than other powders. Except for foam drainage, there was no effect of the season on the SMP and NDM functional properties. The storage of milk powders has an impact on some functional properties, and a proper selection of powders based on end-use is recommended.

Evaluation of Potential for Butyl and Heptyl Para-Hydroxybenzoate Enhancement of Thermal Inactivation of Cronobacter sakazakii during Rehydration of Powdered Infant Formula and Nonfat Dry Milk

In previous studies, parabens in model systems enhanced the thermal inactivation of foodborne pathogens, including Cronobacter sakazakii, Salmonella enterica serotype Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes. However, few studies have been conducted to evaluate this phenomenon in actual food systems. In the present study, the potential enhancement of thermal inactivation of C. sakazakii by butyl para-hydroxybenzoate (BPB) was evaluated in powdered infant formula (PIF) and nonfat dry milk (NFDM) in dry and rehydrated forms. When PIF was rehydrated with water at designated temperatures (65 to 80°C) in baby bottles, BPB did not enhance thermal inactivation. When rehydrated NFDM and lactose solutions with BPB were inoculated and heated at 58°C, BPB enhancement of thermal inactivation of C. sakazakii was negatively associated with the concentration of NFDM solutions in a dose-dependent manner, whereas thermal inactivation was enhanced in the presence of lactose regardless of its concentration, suggesting an interaction between proteins and BPB. Fluorescence testing further indicated an interaction between BPB and the proteins in PIF and NFDM. In inoculated dry NFDM with and without BPB stored at 24 and 55°C for 14 days, BPB did not substantially enhance bacterial inactivation. This study suggests that BPB is not likely to enhance mild thermal bacterial inactivation treatments in foods that have appreciable amounts of protein.