A microfiltration process to maximize removal of serum proteins from skim milk before cheese making

Microfiltration (MF) is a membrane process that can separate casein micelles from milk serum proteins (SP), mainly beta-lactoglobulin and alpha-lactalbumin. Our objective was to develop a multistage MF process to remove a high percentage of SP from skim milk while producing a low concentration factor retentate from microfiltration (RMF) with concentrations of soluble minerals, nonprotein nitrogen (NPN), and lactose similar to the original skim milk. The RMF could be blended with cream to standardize milk for traditional Cheddar cheese making. Permeate from ultrafiltration (PUF) obtained from the ultrafiltration (UF) of permeate from MF (PMF) of skim milk was successfully used as a diafiltrant to remove SP from skim milk before cheese making, while maintaining the concentration of lactose, NPN, and nonmicellar calcium. About 95% of the SP originally in skim milk was removed by combining one 3 x MF stage and two 3 x PUF diafiltration stages. The final 3 x RMF can be diluted with PUF to the desired concentration of casein for traditional cheese making. The PMF from the skim milk was concentrated in a UF system to yield an SP concentrate with protein content similar to a whey protein concentrate, but without residuals from cheese making (i.e., rennet, culture, color, and lactic acid) that can produce undesirable functional and sensory characteristics in whey products. Additional processing steps to this 3-stage MF process for SP removal are discussed to produce an MF skim retentate for a continuous cottage cheese manufacturing process.     

Pilot-scale ceramic membrane filtration of skim milk for the production of a protein base ingredient for use in infant milk formula

The protein composition of bovine skim milk was modified using pilot scale membrane filtration to produce a whey protein-dominant ingredient with a casein profile closer to human milk. Bovine skim milk was processed at low (8.9 °C) or high (50 °C) temperature using ceramic microfiltration (MF) membranes (0.1 μm mean pore diameter). The resulting permeate stream was concentrated using polyethersulfone ultrafiltration (UF) membranes (10 kDa cut-off). The protein profile of MF and UF retentate streams were determined using reversed phase-high performance liquid chromatography and polyacrylamide gel electrophoresis. Permeate from the cold MF process (8.9 °C) had a casein:whey protein ratio of ∼35:65 with no α_S- or κ-casein present, compared with a casein:whey protein ratio of ∼10:90 at 50 °C. This study has demonstrated the application of cold membrane filtration (8.9 °C) at pilot scale to produce a dairy ingredient with a protein profile closer to that of human milk.     

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.     

Effect of partial whey protein depletion during membrane filtration on thermal stability of milk concentrates

Membrane filtration technologies are widespread unit operations in the dairy industry, often employed to obtain ingredients with tailored processing functionalities. The objective of this work was to better understand the effect of partial removal of whey proteins by microfiltration (MF) on the heat stability of the fresh concentrates. The micellar casein concentrates were compared with control concentrates obtained using ultrafiltration (UF). Pasteurized milk was microfiltered (80 kDa polysulfone membrane) or ultrafiltered (30 kDa cellulose membrane) without diafiltration (i.e., no addition of water) to 2× and 4× concentration, based on volume reduction. The final concentrates showed no differences in pH, casein micelle size, or mineral concentration in the serum phase. The micellar casein retentates (obtained by MF) showed a 20 and 40% decrease in whey protein concentration compared with the corresponding UF milk protein concentrates for 2× and 4× concentration, respectively. The heat coagulation time decreased with increasing protein concentration, regardless of the treatment; however, MF retentates showed a higher thermal stability than the corresponding UF controls. The average diameter for casein micelles increased after heating in UF but not MF concentrates. The turbidity (measured by light scattering) increased after heating, but to a higher extent for UF retentates than for MF retentates at the same protein concentration. It was concluded that the reduced amount of whey protein in the MF retentates caused a significant increase in the heat stability compared with the corresponding UF retentates. This difference was not due to ionic composition differences or pH, but to the type and amount of complexes formed in the serum phase.     

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.     

Vatless manufacturing of low-moisture part-skim mozzarella cheese from highly concentrated skim milk microfiltration retentates

Low-moisture, part-skim (LMPS) Mozzarella cheeses were made from concentration factor (CF) 6, 7, 8, and 9, pH 6.0 skim milk microfiltration (MF) retentates using a vatless cheese-making process. The compositional and proteolytic effects of cheese made from 4 CF retentates were evaluated as well as their functional properties (meltability and stretchability). Pasteurized skim milk was microfiltered using a 0.1-microm ceramic membrane at 50 degrees C to a retentate CF of 6, 7, 8, and 9. An appropriate amount of cream was added to achieve a constant casein:fat ratio in the 4 cheesemilks. The ratio of rennet to casein was also kept constant in the 4 cheesemilks. The compositional characteristics of the cheeses made from MF retentates did not vary with retentate CF and were within the legal range for LMPS Mozzarella cheese. The observed reduction in whey drained was greater than 90% in the cheese making from the 4 CF retentates studied. The development of proteolytic and functional characteristics was slower in the MF cheeses than in the commercial samples that were used for comparison due to the absence of starter culture, the lower level of rennet used, and the inhibition of cheese proteolysis due to the inhibitory effect of residual whey proteins retained in the MF retentates, particularly high molecular weight fractions.     

Impact of low concentration factor microfiltration on milk component recovery and Cheddar cheese yield

The effect of microfiltration (MF) on the composition of Cheddar cheese, fat, crude protein (CP), calcium, total solids recovery, and Cheddar cheese yield efficiency (i.e., composition adjusted yield divided by theoretical yield) was determined. Raw skim milk was microfiltered twofold using a 0.1-microm ceramic membrane at 50 degrees C. Four vats of cheese were made in one day using milk at lx, 1.26x, 1.51x, and 1.82x concentration factor (CF). An appropriate amount of cream was added to achieve a constant casein (CN)-to-fat ratio across treatments. Cheese manufacture was repeated on four different days using a randomized complete block design. The composition of the cheese was affected by MF. Moisture content of the cheese decreased with increasing MF CF. Standardization of milk to a constant CN-to-fat ratio did not eliminate the effect of MF on cheese moisture content. Fat recovery in cheese was not changed by MF. Separation of cream prior to MF, followed by the recombination of skim or MF retentate with cream resulted in lower fat recovery in cheese for control and all treatments and higher fat loss in whey when compared to previous yield experiments, when control Cheddar cheese was made from unseparated milk. Crude protein, calcium, and total solids recovery in cheese increased with increasing MF CF, due to partial removal of these components prior to cheese making. Calcium and calcium as a percentage of protein increased in the cheese, suggesting an increase in calcium retention in the cheese with increasing CF. While the actual and composition adjusted cheese yields increased with increasing MF CF, as expected, there was no effect of MF CF on cheese yield efficiency.     

Improving the quality of some Egyptian fermented dairy products made from dried milk

A trial has been made to improve the quality of Zabadi and Kariesh cheese made from dried milk using whey protein concentrates. Fortification of recombined milk used for Zabadi making or reconstituted milk for Kariesh cheese manufacture with whey protein concentrates at levels of 2.5, 5.0, 7.5 and 10.0% enhanced the organoleptic and compositional qualities of both products. This treatment reduced wheying off and stimulated the formation of acetaldehyde and total volatile acidity and bacterial growth during storage of Zabadi at refrigeration temperature for one week.     

希腊式酸羊奶的研制

以新鲜羊奶为主要原料,添加羊乳清粉,研究了希腊式酸羊奶的工艺条件。 通过单因素试验和正交试验,以感官评分及酸度 为评价指标,确定希腊式酸羊奶的最佳发酵工艺条件。 结果表明,希腊式酸羊奶的最佳发酵工艺条件为羊乳清粉添加量1.0%,接种 量6%,发酵温度42 ℃,发酵时间8 h。 在此最佳条件下,感官评分达到87分,酸度为97 °T。 希腊式酸羊奶质地均匀,口感细腻浓郁,酸甜 适中,发酵乳香味明显,羊膻味不明显,其理化及微生物指标均符合相关国家标准。     

Compositional and physical properties of yogurts manufactured from milk and whey cheese concentrated by ultrafiltration

Yogurts made with 80% milk retentate (MR) [Volume Reduction Factor (VRF) = 1.5] and 20% cheese whey retentate (WR; VRF = 8.0) (yogurt 1) and yogurts made with 100% MR through ultrafiltration have been evaluated as to flow, texture profile analysis (TPA) and syneresis index. As with MR and WR, their physico‐chemical composition was also determined. The yogurt to which WR had been added showed; less apparent viscosity and greater tixotrophya; less firmness and adhesiveness and greater cohesiveness; higher syneresis index, less protein and mineral content, and greater lipid content in comparison with the yogurt made only with MR.     

Microfiltration of buttermilk and washed cream buttermilk for concentration of milk fat globule membrane components

Buttermilk, the by-product from butter manufacture, has gained much attention lately because of the application potential of its milk fat globule membrane (MFGM) components as health ingredients. Microfiltration (MF) has been studied for buttermilk fractionation because of its ability to separate particles from dissolved solutes. However, the presence in this by-product of skim milk solids, especially casein micelles, restricts concentration of MFGM. The use of cream washed with skim milk ultrafiltrate to produce buttermilk with lower casein content was studied as well as fractionation of this buttermilk by MF. Results have shown that washing the cream prior to churning yields buttermilk with 74% less protein than normal cream buttermilk. Analysis of the protein profile of washed cream buttermilk revealed that caseins and whey proteins were the main classes of proteins removed. The MF of washed cream buttermilk resulted in permeation fluxes 2-fold higher than with normal cream buttermilk. The second separation of the cream induced high losses of phospholipids in the skim phase. However, retention of remaining phospholipids in washed cream buttermilk by the MF membrane was higher resulting in a phospholipids concentration factor 66% higher than that of normal cream buttermilk. The results presented in this study highlight the impact of casein micelles on the separation of MFGM components as well as their effect on permeation flux during MF.     

Physical properties of yogurt fortified with various commercial whey protein concentrates

The effects of whey protein concentrates on physical and rheological properties of yogurt were studied. Five commercial whey protein concentrates (340 g kg^?1 protein nominal) were used to fortify milk to 45 g protein kg^?1. Fermentation was performed with two different starters (ropy and non‐ropy). Resulting yogurts were compared with a control yogurt enriched with skim milk powder. The water‐holding capacity of the yogurt fortified with skim milk powder was 500 g kg^?1 and ranged from 600 to 638 g kg^?1 when fortified with whey protein concentrates. Significant rheological differences have been noticed between the yogurts fortified with different whey protein concentrates, independent of the starter used. Three whey protein concentrates generated yogurts with a behavior similar to the control. The two others produced yogurt with lower firmness (15 g compared with 17 g), lower Brookfield viscosity (6 Pa s compared with 9 Pa s), lower yield stress (2 Pa compared with 4 Pa), lower complex viscosity (13 Pa s compared with 26 Pa s), and lower apparent viscosity (0.4 Pa s compared with 1 Pa s) than the control, respectively. The yogurts with the lowest firmness and viscosity were produced with concentrates which contained the highest amount of non‐protein nitrogen fraction (160 g kg^?1 versus 126 g kg^?1 of the total nitrogen), and the highest amount of denaturation of the whey protein (262 versus 200 g kg^?1 of the total nitrogen). Copyright © 2004 Society of Chemical Industry     

Effects of Polymerized Whey Proteins on Consistency and Water-holding Properties of Goat's Milk Yogurt

ABSTRACT The effects of polymerized whey proteins (PWP) on functional properties of goat's milk yogurt were investigated. PWP were prepared by heating whey protein isolate (WPI) dispersion (8.0% protein, pH 7.0) at 90 °C for 30 min. Three reconstituted goat milk (RGM) (12% total solids [TS] as control; RGM with 2.4% unheated WPI; and RGM with 2.4% PWP) and 1 RGM with 16.7% TS were prepared and inoculated with 0.04% yogurt starter culture. Inoculated milk was incubated at 43 °C for 5 h, cooled to 4 °C in an ice‐water bath, and then placed at refrigerator (4 °C) overnight before testing. Incorporation of PWP significantly (P < 0.001) increased the viscosity (by 80%) and decreased the syneresis (by 25%) of the yogurt samples, whereas addition of unheated WPI did not significantly affect the viscosity and syneresis compared with the control. There were no changes in pH, TS, ash, fat, protein, and lactose contents among yogurt samples except the solids fortified control. Yogurt with 16.7% TS had the lowest syneresis but did not improve in viscosity. Transmission electron microscopy micrographs demonstrated that the microstructure of the goat's milk yogurt gel with PWP was denser than the control. Results of this study indicate that polymerized whey proteins may be a novel protein‐based thickening agent for improving the functional properties of goat's milk yogurt and other similar products.     

Changes on expected taste perception of probiotic and conventional yogurts made from goat milk after rapidly repeated exposure

Goat milk yogurt is an excellent source of fatty acids, protein, and minerals; however, it is not well accepted by many consumers, due to its typical flavor derived from caprylic, capric, and caproic acids present in this milk and dairy products. Recently, the repeated-exposure test has been used to increase the consumption of particular foods. This methodology has been used to increase children’s willingness to eat food in some settings and has also been used to reduce sodium in soup. Based on these considerations, the aim of this study was to investigate whether repeated exposures may increase acceptance of both goat milk yogurt and probiotic goat milk yogurt. In a pre-exposure session, a total of 45 panelists (28 females and 17 males) from southeastern Brazil, who were not used to consuming dairy goat milk, evaluated the expected taste perception and the perceived liking after tasting 3 yogurt preparations. Then, consumers were randomly divided into 3 groups and participated in rapidly repeated exposure sessions performed within 6 d. Each panelist consumed only the yogurt that he or she would be exposed to. The day after the exposure sessions, all panelists returned to participate in the postexposure session and were asked to evaluate acceptance, familiarity, and the “goaty taste” characteristic of each yogurt. Regarding the expected liking before tasting, results showed higher expectations for cow milk yogurt compared with goat milk yogurt, which proved that consumers were not familiar with the goat milk yogurt. Likewise, only cow milk yogurt presented high acceptance and familiarity rates, confirming that these panelists were used to consuming cow milk products. With respect to the rapidly repeated exposure, 6 d were enough to significantly increase the consumers’ familiarity with goat milk yogurt and probiotic goat milk yogurt. However, this method was not suitable to significantly increase the acceptance of such products. Nonetheless, a correlation existed between the exposure sessions and the increase in acceptance of the exposure groups. Thus, hypothetically, the increasing of exposure sessions could be a strategy to increase goat milk product acceptance.     

Effect of HTST Pasteurization of Milk, Cheese Whey and Cheese Whey UF Retentate upon the Composition, Physicochemical and Functional Properties of Whey Protein Concentrates

The effect of high temperature-short time (HTST) pasteurization of milk, Cheddar cheese whey and cheddar cheese whey ultrafiltration (UF) retentate upon the composition, physicochemical and functional properties of whey protein concentrates (WPC) was investigated. HTST pasteurization (72°C-15 sec) of milk, whey and UF retentate caused no significant differences in chemical composition of resulting WPCs. HTST pasteurization of milk and whey had no significant effect upon WPC solubility, whereas, heating UF retentate caused significant loss of WPC solubility. HTST pasteurization of milk caused a significant lowering (P<0.10) of maximum foam expansion of WPC dispersions, but HTST pasteurization of whey and UF retentate had no significant effect upon this latter parameter.     

Autochthonous adjunct culture of Limosilactobacillus mucosae CNPC007 improved the techno-functional,physicochemical, and sensory properties of goat milk Greek-style yogurt

We evaluated the performance of Limosilactobacillus mucosae CNPC007 as an autochthonous adjunct culture in the production of goat milk Greek-style yogurt. The techno-functional, physicochemical, and sensory characteristics of the control yogurt (containing only starter culture, CY) and the probiotic yogurt (with the probiotic strain added, PY) were assessed during 28 d of refrigerated storage. Furthermore, we determined the survival of the strain throughout the gastrointestinal tract under simulated conditions. The PY yogurt had a lower extent of proteolysis index and a higher depth of proteolysis index. These results indicate that the proteolytic enzymes of L. mucosae may have a possible action in PY. The PY formulation exhibited viscosity almost 1.5 times as high as CY over the refrigeration period, probably due to higher production of exopolysaccharides by the probiotic strain, which directly interferes with the microstructure, texture, and viscosity of the product. The PY formulation received higher scores for color, flavor, and global acceptance at 1 d of storage and higher texture scores at 28 d. The counts of L. mucosae remained high (>7 log cfu/g and >8.5 log cfu/g) throughout mouth-ileum digestion and storage, respectively, in PY. The autochthonous adjunct culture of L. mucosae CNPC007 can be used for production of a novel potentially probiotic goat yogurt without negatively affecting the general characteristics of the product quality, adding value associated with maintaining its functional potential.     

Effect of heat and transglutaminase on solubility of goat milk protein‐based films

The effect of heat, transglutaminase and combination of heat and transglutaminase treatments on the solubility of films prepared from goat milk casein, goat milk whey proteins and whole goat milk proteins was investigated. Goat milk casein films were less soluble when treated with transglutaminase and combination of heat with transglutaminase compare with heat‐treated caseins alone. Heat treatment was more effective at decreasing the solubility of whey protein films. SDS‐PAGE patterns demonstrated that goat milk caseins were better cross‐linked by transglutaminase, whereas whey proteins were better cross‐linked by heat. The extent of cross‐linking was further enhanced when a combination of heat and transglutaminase was used.     

Major proteins of the goat milk fat globule membrane

Fat is present in milk as droplets of triglycerides surrounded by a complex membrane derived from the mammary epithelial cell called milk fat globule membrane (MFGM). Although numerous studies have been published on human or bovine MFGM proteins, to date few studies exist on MFGM proteins from goat milk. The objective of this study was thus to investigate the protein composition of the goat MFGM. Milk fat globule membrane proteins from goat milk were separated by 6% and 10% sodium dodecyl sulfate-PAGE and were Coomassie or periodic acid-Schiff stained. Most of MFGM proteins [mucin-1, fatty acid synthase, xanthine oxidase, butyrophilin, lactadherin (MFG EGF-8, MFG-E8), and adipophilin] already described in cow milk were identified in goat milk using peptide mass fingerprinting. In addition, lectin staining provided a preliminary characterization of carbohydrate structures occurring on MFGM proteins from goat milk depending on α_S1-casein genotype and lactation stage. We provide here first evidence of the presence of O-glycans on fatty acid synthase and xanthine oxidase from goat milk. A prominent difference between the cow and the goat species was demonstrated for lactadherin. Indeed, whereas 2 polypeptide chains were easily identified by peptide mass fingerprinting matrix-assisted laser desorption/ionization-time of flight analysis within bovine MFGM proteins, lactadherin from goat milk consisted of a single polypeptide chain. Another striking observation was the presence of caseins associated with MFGM preparations from goat milk, whereas virtually no caseins were found in MFGM extracts from bovine milk. Taken together, these observations strongly support the existence of a singular secretion mode previously hypothesized in the goat.     

Physiochemical Properties,Microstructure, and Probiotic Survivability of Nonfat Goats’ Milk Yogurt Using Heat‐Treated Whey Protein Concentrate as Fat Replacer

There is a market demand for nonfat fermented goats’ milk products. A nonfat goats’ milk yogurt containing probiotics (Lactobacillus acidophilus, and Bifidobacterium spp.) was developed using heat‐treated whey protein concentrate (HWPC) as a fat replacer and pectin as a thickening agent. Yogurts containing untreated whey protein concentrate (WPC) and pectin, and the one with only pectin were also prepared. Skim cows’ milk yogurt with pectin was also made as a control. The yogurts were analyzed for chemical composition, water holding capacity (syneresis), microstructure, changes in pH and viscosity, mold, yeast and coliform counts, and probiotic survivability during storage at 4 °C for 10 wk. The results showed that the nonfat goats’ milk yogurt made with 1.2% HWPC (WPC solution heated at 85 °C for 30 min at pH 8.5) and 0.35% pectin had significantly higher viscosity (P < 0.01) than any of the other yogurts and lower syneresis than the goats’ yogurt with only pectin (P < 0.01). Viscosity and pH of all the yogurt samples did not change much throughout storage. Bifidobacterium spp. remained stable and was above 10⁶CFU g^‐1 during the 10‐wk storage. However, the population of Lactobacillus acidophilus dropped to below 10⁶CFU g^‐1 after 2 wk of storage. Microstructure analysis of the nonfat goats’ milk yogurt by scanning electron microscopy revealed that HWPC interacted with casein micelles to form a relatively compact network in the yogurt gel. The results indicated that HWPC could be used as a fat replacer for improving the consistency of nonfat goats’ milk yogurt and other similar products.     

Effects of cyclodextrins on the flavor of goat milk and its yogurt

Goat milk fat includes several branched chain fatty acids (BCFAs), like 4-methyloctanoic acid, which when free, are responsible for goaty flavor. This flavor limits the market opportunities for goat milk. Prior research showed that cyclodextrins (CDs) can reduce goaty flavor, presumably by binding free fatty acids. This research extends that observation. In odor ranking trials in citrate buffer at pH 4.8, β-CD concentrations between 0% and 0.35% were increasingly effective in reducing odor intensity due to 4-methyloctanoic acid, but only when present in high molar excess. α-CD was also effective, but γ-CD was not. In lipase-treated goat milk only β-CD was effective but at much lower molar excess, a difference potentially explained by several factors. One was that BCFAs bind to CDs in marked preference to their straight chain isomers. Displacement experiments with phenolphthalein disproved that hypothesis. The ability of β-CD to reduce goaty flavor intensity extended to yogurt. An analytical panel showed that flavor of goat yogurt was reduced by addition of β-CD, but only if added before heating and fermentation. A hedonic trial showed that consumers preferred unsweetened and sweet/vanilla-flavored goat yogurt more when β-CD was included, P = 0.004 and 0.016, respectively. Males liked all yogurts more than females (P < 0.01), but there was a treatment × gender interaction (P = 0.016) for sweet/vanilla yogurt: sweet/vanilla masked the goaty flavor for males but not females. This results parallels previously demonstrated gender effects for sheepmeat flavor caused by BCFAs. PRACTICAL APPLICATION: β-Cyclodextrin masks goaty flavor in yogurt, and with its GRAS status means it could be used in commercial goat yogurts and similar products so the real or perceived nutritional advantages of goat milk are not lost to goaty flavor.