乳清多肽的制备及乳清多肽酒的研制

采用蛋白酶水解乳清粉,并对乳清多肽进行酵母菌发酵,并对发酵所得乳清酒进行风味调配。乳清粉最佳的水解条件为:[E/S]=1%、T=60℃、pH=9.0、时间=120min,水解度为DH=21.22%。乳清多肽酒的最优发酵条件:接种量为5%、起始pH为7.5、温度为22℃、发酵60h,酒度可达到3.9。多肽乳清酒的最佳基本调配是:酸量(苹果酸:柠檬酸=1:1)为0.1%、蔗糖为7%、环状糊精为0.6%。     

乳清多肽酒的开发

采用蛋白酶水解乳清粉,并对乳清多肽进行酵母菌发酵,对发酵所得乳清酒进行风味调配。乳清粉最佳的水解条件为:[E/S]=1%、T=60℃、pH=9.0、时间=120min,水解度为DH=21.22%。乳清多肽酒的最优发酵条件:接种量为5%、起始pH为7.5、温度为22℃、发酵60h,酒度可达到3.9。多肽乳清酒的最佳基本调配是:酸量(苹果酸∶柠檬酸=1∶1)为0.1%、蔗糖为7%、环状糊精为0.6%。     

乳清多肽的制备及乳清多肽酒的研制

采用蛋白酶水解乳清粉，对乳清多肽进行酵母菌发酵，并对发酵所得乳清酒进行风味调配。乳清粉最佳的水解条件为：酶浓度与底物浓度之比为1％、温度60℃、pH9．0、时间120min，水解度21．22％。乳清多肽酒的最优发酵条件：接种量5％、起始pH7．5、温度22℃、发酵60h，酒精度可达到3．9％。多肽乳清酒的最佳基本调配是总酸（苹果酸：柠檬酸=1：1）为0．1％、蔗糖为7％、环状糊精为0．6％。     

乳清酒饮料发酵工艺的研究

研究了乳清酒饮料的发酵工艺,结果表明,酒精发酵最佳条件为接种量4%,初始pH7.9,温度20℃,时间50h。乳清多肽酒精饮料的配方为β-环状糊精量0.3%,酸量0.15%,复合甜味剂量9%。     

酶法生产乳清多肽饮料

采用碱性蛋白酶水解乳清多肽,制备具有较好热稳定性的可溶性多肽混合物,然后以其为母液,生产乳清多肽饮料。获得最优水解工艺的最适pH为9.0、最适温度为35℃,乳清中水解度高达25.4%。所研制的乳清多肽饮料无苦味,且具有良好的稳定性。     

乳清发酵液的研究及应用

以乳清为原料经特殊菌种长时发酵后,对其发酵产物进行生物酶解.较佳酶解条件为:蛋白酶添加量18 000 U/g,水解温度45℃,水解pH4.5,蛋白底物质量分数为2%,此条件下发酵液的风味最好.应用在pro1.0alpis饮料中能显著增强发酵感.     

乳清蛋白肽苦味修饰及其发酵饮料的研究

通过胰蛋白酶和中性蛋白酶的水解比较实验,以及风味蛋白酶的复合水解实验,研究了乳清蛋白肽的酶解及其产生苦味的修饰方法,并以此进行了发酵饮料的制备.结果表明,最佳水解酶组合为胰蛋白酶和风味蛋白酶,水解条件分别为:胰蛋白酶[E/S]=1%,pH=8.0,温度45℃,时间45 min;风味蛋白酶[E/S]=2%,pH=7.0,时间2 h,温度50℃;而中性蛋白酶与风味蛋白酶组合则不理想,乳清蛋白水解液苦味浓,风味蛋白酶消除苦味效果也不明显;乳清发酵的水解液与发酵液按蛋白质量分数的最佳配比为1:1,能有效解决色泽与风味问题,使饮料保留乳制品特有的乳白色.     

乳清多肽饮料的开发

用碱性蛋白酶水解乳清多肽，制备热稳定的可溶性多肽混合物，然后以其为母液，生产乳清多肽饮料。碱性蛋白酶水解的最适pH为9.0，最适温度为35℃，乳清中水解度高达25．4％。所研制的乳清多肽饮料无苦味，且具有良好的稳定性。     

微生物发酵法制备乳清抗氧化肽的研究

通过筛选得到发酵法生产乳清抗氧化肽的最适乳酸菌菌株,同时以氧自由基清除率为指标研究了接种量、菌种比、发酵温度、初始pH值和时间对液态发酵法生产乳清多肽的影响,并采用正交试验确定了最佳发酵工艺条件.结果表明,接种量5%,菌种比1:1,发酵温度37℃,初始pH值6.4,时间16 h,此时测得乳清水解产物O2-清除率为39.45%,肽质量浓度为2.62 g/L.     

发酵法制备乳清抗氧化活性肽的研究

采用乳酸菌发酵法制备乳清抗氧化活性肽。从发酵菌株的筛选到发酵条件的优化以及多肽抗氧化活性比较方面做系统的研究。采用液态发酵法,以水解度和O2·-清除率为指标,筛选组建二元混菌体系;通过正交试验优化二元混菌体系的发酵工艺条件,以确定最佳发酵时间。试验结果表明,最佳发酵条件:初始pH6.4,发酵温度37℃,接种量5%,在此条件下测得乳清水解产物O2·-清除率为39.45%,最佳发酵时间14h。乳清多肽抗氧化活性的比较结果显示,随着活性肽浓度的升高,其总抗氧化能力、·OH清除率、O2·-清除率、总还原能力都有明显提高,表明乳清多肽具有抗氧化性。     

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.     

Production of a high gel strength whey protein concentrate from cheese whey

In order to develop a process for the production of a whey protein concentrate (WPC) with high gel strength and water-holding capacity from cheese whey, we analyzed 10 commercially available WPC with different functional properties. Protein composition and modification were analyzed using electrophoresis, HPLC, and mass spectrometry. The analyses of the WPC revealed that the factors closely associated with gel strength and water-holding capacity were solubility and composition of the protein and the ionic environment. To maintain whey protein solubility, it is necessary to minimize heat exposure of the whey during pretreatment and processing. The presence of the caseinomacropeptide (CMP) in the WPC was found to be detrimental to gel strength and water-holding capacity. All of the commercial WPC that produced high-strength gels exhibited ionic compositions that were consistent with acidic processing to remove divalent cations with subsequent neutralization with sodium hydroxide. We have shown that ultrafiltration/diafiltration of cheese whey, adjusted to pH 2.5, through a membrane with a nominal molecular weight cut-off of 30,000 at 15 degrees C substantially reduced the level of CMP, lactose, and minerals in the whey with retention of the whey proteins. The resulting WPC formed from this process was suitable for the inclusion of sodium polyphosphate to produce superior functional properties in terms of gelation and water-holding capacity.     

Characterization of major volatile compounds in whey spirits produced by different distillation stages of fermented lactose-supplemented whey

This research aimed to advance the understanding of acceptable sensory qualities of potable whey-based spirit from nonsupplemented, mid-supplemented, and high-supplemented whey samples by analyzing major volatile compounds during different stages of distillation (head, heart, and tail). The results demonstrated that commercial Saccharomyces cerevisiae strain in lactase-hydrolyzed whey showed rapid and complete sugar hydrolysis and efficient ethanol production in 24, 30, and 36 h on average, producing up to 29.5, 42.1, and 56.4 g/L of ethanol, respectively. The variations in titratable acidity, specific gravity, pH value, residual protein, sugar content, and alcohol yield were investigated during the fermentation. The total amount of volatile compound concentrations significantly decreased from the head (2,087–2,549 mg/L) to the tail whey spirits (890–1,407 mg/L). In the whey spirit, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-1-propanol, 1-propanol, acetaldehyde, and ethyl acetate were the most prevalent dominant compounds, accounting for the largest proportion of total volatile compounds. The volatile compounds detected were far below the acceptable legal limit. The results suggest that high sensory qualities of potable whey-based spirits can be produced by fermentation of lactose-supplemented whey with S. cerevisiae cells.     

Astringency of bovine milk whey protein

Whey protein solutions at pH 3.5 elicited an astringent taste sensation. The astringency of whey protein isolate (WPI), the process whey protein (PWP) that was prepared by heating WPI at pH 7.0, and the process whey protein prepared at pH 3.5 (aPWP) were adjusted to pH 3.5 and evaluated by 2 sensory analyses (the threshold method and the scalar scoring method) and an instrumental analysis (taste sensor method). The taste-stimulating effects of bovine and porcine gelatin were also evaluated. The threshold value of astringency of WPI, PWP, and aPWP was 1.5, 1.0, and 0.7 mg/mL, respectively, whereas the gelatins did not give definite astringency. It was confirmed by the scalar scoring method that the astringency of these proteins increased with the increase in protein concentration, and these proteins elicited strong astringency at 10 mg/mL under acidic conditions. On the other hand, the astringency was not elicited at pH 3.5 by 2 types of gelatin. A taste sensor gave specific values for whey proteins at pH 3.5, which corresponded well to those obtained by the sensory analysis. Elicitation of astringency induced by whey protein under acidic conditions would be caused by aggregation and precipitation of protein molecules in the mouth.     

Efficient encapsulation of fish oil: Capitalizing on the unique inherent characteristics of whey cream and hydrolyzed whey protein

The effects of protein concentration and of blending a phospholipid-rich whey coproduct, Procream (Salibra 700 Procream, Glanbia Nutritionals), with intact or hydrolyzed whey protein concentrate, on fish oil microencapsulation efficiency and oxidative stability were assessed. Trypsin and protease M, from Aspergillus oryzae, were used to produce 2 unique hydrolysates. All microcapsules had excellent encapsulation efficiencies (>92%) and good physical properties, regardless of protein content and Procream inclusion. Intact α-lactalbumin and β-lactoglobulin and their peptides were involved in stabilizing oil droplets. Disulfide interchange resulted in formation of protein aggregates, which were more pronounced in samples containing Procream. Although all microcapsules had relatively good oxidative stability, most had better stability at 2 versus 0.5% protein. Protease M hydrolysate + Procream microcapsules had the highest stability, regardless of protein content. Results demonstrated that Procream, at a reduced protein inclusion level, can partially replace more expensive whey protein ingredients in microencapsulation, when blended with a select hydrolysate.     

MVR技术在大豆乳清废水处理中的应用研究

研究了MVR技术在大豆乳清废水处理中的应用。通过单因素试验及对大豆乳清废水的分析,基于保证乳清蛋白活性的目的得到MVR处理大豆乳清废水最佳工艺条件为:压缩机频率100 Hz,加热温度65℃。在最佳条件下回收1 t大豆乳清废水用电13 k W·h。     

酸浆标准化生产工艺的研究

利用从豆腐酸浆老汤中筛选到的五株产酸菌,以大豆黄浆水为培养基,以酸浆的p H为考察指标,探讨了单菌发酵、双菌发酵、发酵温度、菌种接种量及菌种的混合比例对酸浆p H的影响。在单因素实验的基础上设计了正交实验,以确定酸浆纯种发酵的最佳生产工艺参数。结果表明:酸浆纯种发酵的最佳工艺参数为:双菌混合发酵,混合比例为1∶9(1号菌∶3号菌),接种量5%,发酵时间24h,发酵温度42℃。对正交实验的结果进行验证得到酸浆的p H为3.56。