Efficiency of removal of whey protein from sweet whey using polymeric microfiltration membranes

Our objective was to measure whey protein removal percentage from separated sweet whey using spiral-wound (SW) polymeric microfiltration (MF) membranes using a 3-stage, 3× process at 50°C and to compare the performance of polymeric membranes with ceramic membranes. Pasteurized, separated Cheddar cheese whey (1,080 kg) was microfiltered using a polymeric 0.3-μm polyvinylidene (PVDF) fluoride SW membrane and a 3×, 3-stage MF process. Cheese making and whey processing were replicated 3 times. There was no detectable level of lactoferrin and no intact α- or β-casein detected in the MF permeate from the 0.3-μm SW PVDF membranes used in this study. We found BSA and IgG in both the retentate and permeate. The β-lactoglobulin (β-LG) and α-lactalbumin (α-LA) partitioned between retentate and permeate, but β-LG passage through the membrane was retarded more than α-LA because the ratio of β-LG to α-LA was higher in the MF retentate than either in the sweet whey feed or the MF permeate. About 69% of the crude protein present in the pasteurized separated sweet whey was removed using a 3×, 3-stage, 0.3-μm SW PVDF MF process at 50°C compared with 0.1-μm ceramic graded permeability MF that removed about 85% of crude protein from sweet whey. The polymeric SW membranes used in this study achieve approximately 20% lower yield of whey protein isolate (WPI) and a 50% higher yield of whey protein phospholipid concentrate (WPPC) under the same MF processing conditions as ceramic MF membranes used in the comparison study. Total gross revenue from the sale of WPI plus WPPC produced with polymeric versus ceramic membranes is influenced by both the absolute market price for each product and the ratio of market price of these 2 products. The combination of the market price of WPPC versus WPI and the influence of difference in yield of WPPC and WPI produced with polymeric versus ceramic membranes yielded a price ratio of WPPC versus WPI of 0.556 as the cross over point that determined which membrane type achieves higher total gross revenue return from production of these 2 products from separated sweet whey. A complete economic engineering study comparison of the WPI and WPPC manufacturing costs for polymeric versus ceramic MF membranes is needed to determine the effect of membrane material selection on long-term processing costs, which will affect net revenue and profit when the same quantity of sweet whey is processed under various market price conditions.     

ADSA Foundation Scholar Award: defining dairy flavors

Production and consumption of dairy foods continue to increase annually. Further, new ingredient applications for dairy foods continue to expand. With continued production and consumption, there is also increased competition. Increased competition exists regionally, nationally, and globally. Processors as well as product developers must find ways to maximize existing markets and expand into new markets. A consistent high quality product is necessary to maintain competitiveness. Although microbial safety and stability are key ways to define quality, flavor is one method of defining quality that is often assumed or overlooked. The aggressive and competitive nature of today's market demands more precise and powerful tools for defining flavor and flavor quality. Traditional as well as more recent methods for evaluating dairy flavor are reviewed. The application of defining sensory flavors to fundamental research on flavor chemistry, product understanding, and effective marketing is addressed.     

Consumer perception of astringency in clear acidic whey protein beverages

Acidic whey protein beverages are a growing component of the functional food and beverage market. These beverages are also astringent, but astringency is an expected and desirable attribute of many beverages (red wine, tea, coffee) and may not necessarily be a negative attribute of acidic whey protein beverages. The goal of this study was to define the consumer perception of astringency in clear acidic whey protein beverages. Six focus groups (n=49) were held to gain understanding of consumer knowledge of astringency. Consumers were presented with beverages and asked to map them based on astringent mouthfeel and liking. Orthonasal thresholds for whey protein isolate (WPI) in water and flavored model beverages were determined using a 7-series ascending forced choice method. Mouthfeel/basic taste thresholds were determined for WPI in water. Acceptance tests on model beverages were conducted using consumers (n=120) with and without wearing nose clips. Consumers in focus groups were able to identify astringency in beverages. Astringency intensity was not directly related to dislike. The orthonasal threshold for WPI in water was lower (P < 0.05) than the mouthfeel/basic taste threshold of WPI in water. Consumer acceptance of beverages containing WPI was lower (P < 0.05) when consumers were not wearing nose clips compared to acceptance scores of beverages when consumers were wearing nose clips. These results suggest that flavors contributed by WPI in acidic beverages are more objectionable than the astringent mouthfeel and that both flavor and astringency should be the focus of ongoing studies to improve the palatability of these products.     

Influence of growth in a food medium on the detection of Escherichia coli O157:H7 by polymerase chain reaction

The effects of storage time and growth in broth culture and in a food medium on the efficiency of Escherichia coli O157: H7 DNA extraction and on the sensitivity of polymerase chain reaction (PCR) detection of E. coli O157:H7 were investigated. Detection limits were evaluated with dilution series PCR targeting the slt-II gene. The relationship between cell density and DNA yield was generally log-linear for pure cultures of E coli O157:H7. When the bacteria were suspended in skim milk at a density of 10(6) CFU/ml. held at 4 degrees C, and sampled at 24-h intervals, cell density, total DNA yield, and PCR detection limits remained stable throughout the 96-h storage period. However, when E coli O157:H7 was grown in skim milk to a final cell density of 10(6) CFU/ml, PCR amplification efficiency was drastically reduced, although overall DNA yields from these samples were consistent with those for the samples in which E. coli O157:H7 growth was static over 96 h of storage at 4 degrees C. This result is most likely due to poor DNA purity, which was consistently observed when DNA was extracted from food matrices in which the pathogen was grown rather than stored. The results of this investigation underscore the likelihood that multiple components may drastically affect DNA extraction and PCR amplification efficiency in the detection of pathogens in the food matrix. It is clear that before nucleic acid amplification technologies are widely applied to food systems, it would be prudent to test their efficacy in multiple food matrices and under conditions in which the bacterial population is both static and actively growing.     

Distancing after group success and failure: Basking in reflected glory and cutting off reflected failure.

Two image-maintenance processes by which people manipulate their association with others were tested: the tendency to bask in reflected glory as a means of increasing one's association with successful others and the tendency to cut off reflected failure as a means of decreasing one's association with unsuccessful others. 102 undergraduates were initially involved in a group task and were then assigned to 1 of 3 group-performance feedback conditions: failure, no information, or success. Self-report and behavioral (taking and wearing of team badges) dependent measures of distancing showed that Ss in the failure group manifested less association with their group than did Ss in the no-information feedback and success groups; there was a tendency on behavioral but not self-report measures for Ss in the success group to manifest more association with their group than for Ss in the no-information feedback group. Therefore, more support was found for the cutting-off-reflected-failure process than for the basking-in-reflected-glory process as an image-maintenance tactic. Because Ss truly identified with their group's relative sense of failure or success, it is suggested that it was this identification process that appeared to have driven Ss' distancing behaviors in relation to their groups. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.