Formulation and Processing of a Heat Stable Calcium-fortified Soy Milk

Calcium-fortified soy milk (200 mg/100g) was formulated by adding water (85–90°C) full-fat soy flour (10%), sucrose (2.75%) and soy protein isolate (2.25%). Following homogenization, the blend was twice clarified and pasteurized at 65°C/30 min before refrigeration. Samples of the soy milk (45°C) were adjusted to pH 8 before adding calcium lactogluconate (1.55%) and varying amounts of sodium hexametaphosphate or potassium citrate. Samples with 1.25% potassium citrate the best heat stability. For successful calcium fortification, it is recommended to maintain a calcium-to-protein ratio < 38 mg/g and to use an appropriate sequestering agent at a molar ratio of 0.8/mole calcium.     

豆酸凝乳的研制

研究了以大豆为主要原料,利用嗜热乳酸链球菌和保加利亚乳杆菌混合发酵,制得无豆腥味且具有豆腐味及乳酸发酵特殊香味的大豆凝乳。     

Fatty Acids Profiles of Fresh Milk,Yogurt and Concentrated Yogurt from Peranakan Etawah Goat Milk

The objective of the study was to characterize the fatty acids profiles of goat milk and its fermented products i.e. yogurt and concentrated yogurt. Fresh milk from Peranakan Etawah goats was collected directly from local goat farmers, and processed into stirred-type fresh yogurt. The yogurt was then further processed into concentrated yogurt using Berge method. A total of 26 fatty acids were detected in milk, yogurt and concentrated yogurt, comprised of both saturated and unsaturated fatty acids. The oleic acid, stearic acid and palmitic acid were the major fatty acids found in fresh milk, yogurt and concentrated yogurt. There were changes in the profiles of individual fatty acids during processing of fresh goat milk into yogurt and concentrated yogurt.     

Effect of Tetrasodium Pyrophosphate on the Physicochemical Properties of Yogurt Gels

The effect of tetrasodium pyrophosphate (TSPP) on the properties of yogurt gels was investigated. Various concentrations (0.05 to 0.2%) of TSPP were added to preheated (85°C for 30 min) reconstituted skim milk, which was readjusted to pH 6.50. Milk was inoculated with 2% starter culture and incubated at 42°C until the pH reached 4.6. Acid-base buffering profiles of milk and total and soluble calcium levels were measured. Turbidity measurements were used to indicate changes in casein dispersion. Storage modulus (G′) and loss tangent (LT) values of yogurts were monitored during fermentation using dynamic oscillatory rheology. Large deformation properties of gels were also measured. Microstructural properties of yogurt were observed using fluorescence microscopy. The addition of TSPP resulted in the disappearance of the buffering peak during acid titration at pH ∼5.1 that is due to the solubilization of colloidal calcium phosphate (CCP), and a new peak was observed at lower pH values (pH 4.0-4.5). The buffering peak at pH 6.0 during base titration virtually disappeared with addition of TSPP and a new peak appeared at pH ∼4.8. The addition of TSPP reduced the soluble Ca content of milk and increased casein-bound Ca values. The addition of up to 0.125% TSPP resulted in a reduction in turbidity because of micelle dispersion but at 0.15%, turbidity increased and these samples exhibited a time-dependent increase in turbidity because of aggregation of casein particles. Gels made with 0.20% TSPP were very weak and had a very high gelation pH (6.35), probably due to complete dispersion of the micelle structure in this sample. The LT value of gels at pH 5.1 decreased with an increase in TSPP concentration, probably due to the loss of CCP with the addition of TSPP. The G′ values at pH 4.6 of gels made with ≤0.10% TSPP were not significantly different but the addition of ≥0.125% TSPP significantly decreased G′ values. The addition of 0.05 to 0.125% TSPP to milk resulted in a reduction in the yield stress values of yogurt compared with yogurt made without TSPP. Greater TSPP levels (>0.125%) markedly reduced the yield stress values of yogurt. Lowest whey separation levels were observed in yogurts made with 0.10% TSPP. High TSPP levels (>0.10%) greatly increased the apparent pore size of gels. Addition of very low levels of TSPP to milk for yogurt manufacture may be useful in reducing the whey separation defect, but at TSPP concentrations ≥0.125% very weak gels were formed.     

酸奶发酵机理及后酸化控制措施

介绍了酸奶发酵过程中 ,乳酸菌代谢乳糖的机理及发生的各种生理生化反应。酸奶在储藏过程中 ,会发生后酸化。基于以上机理 ,重点介绍了防止酸奶后酸化的措施     

Effect of Mixing During Fermentation in Yogurt Manufacturing

In traditional yogurt manufacturing, the yogurt is not agitated during fermentation. However, stirring could be beneficial, particularly for improving heat and mass transport across the fermentation tank. In this contribution, we studied the effect of low-speed agitation during fermentation on process time, acidity profile, and microbial dynamics during yogurt fermentation in 2 laboratory-scale fermenters (3 and 5 L) with different heat-transfer characteristics. Lactobacillus bulgaricus and Streptococcus thermophilus were used as fermenting bacteria. Curves of pH, lactic acid concentration, lactose concentration, and bacterial population profiles during fermentation are presented for static and low-agitation conditions during fermentation. At low-inoculum conditions, agitation reduced the processing time by shortening the lag phase. However, mixing did not modify the duration or the shape of the pH profiles during the exponential phase. In fermentors with poor heat-transfer characteristics, important differences in microbial dynamics were observed between the agitated and nonagitated fermentation experiments; that is, agitation significantly increased the observable specific growth rate and the final microbial count of L. bulgaricus.     

大豆非发酵型和发酵型酸豆乳的制备

将新鲜大豆经浸泡、去酶、提取,而后在60℃,pH 4.5的水中浸渍8 h,并在90 ℃热水中处理3 min,成功提取出色泽好、风味佳、蛋白质含量高,无豆腥味的豆浆.还分别对发酵型和非发酵型酸豆乳的生产工艺进行了研究,着重考察了加水量、稳定剂添加量、发酵条件的影响,最终确定了最佳工艺参数:在生产非发酵酸豆乳时,豆水比为1:20,并添加12%葡萄糖、0.3%稳定剂(CMC-Na+果胶:0.15%+0.15%)、0.2%柠檬酸钠、0.3%柠檬酸.在发酵型酸豆乳生产中选用嗜热链球菌(S.t)和保加利亚乳杆菌(L.b)1:1混合作为发酵剂经5级纯化,在40 ℃下发酵12 h.     

萌发大豆制备益生菌发酵豆乳流变特性的研究

以萌发大豆作为主要原料,经瑞士乳杆菌(Lactobacillus helveticus B02)、保加利亚乳杆菌(Lactobacillus bulgaricus AS1.1482)和嗜热链球菌(Streptococcus thermophilus IFFI 6038)组合发酵制成发酵豆乳,研究益生菌发酵豆乳的发酵特性及流变特性。结果表明,大豆经萌发后,游离氨基酸总量增加了近2倍;与未萌发大豆制成的发酵豆乳相比,萌发大豆发酵豆乳中乳酸菌菌落总数显著增加,产生更多的游离H离子及有机酸,且其剪切稀化作用减弱,表观黏度显著下降,更为接近发酵纯牛乳的流变特性。大豆萌发后制成发酵豆乳,可促进乳酸菌的生长及产酸,有助于改善发酵豆乳的流变特性。     

Survival of Yersinia enterocolitica During Fermentation and Storage of Yogurt

The fate of Yersinia enterocolitica was investigated during the manufacture and storage of yogurt produced using commercial starter cultures YC470 (rapid acid-producer), YC180 (slow acid-producer), both containing Streptococcus thermophilus and Lactobacillus bulgaricus , and a "home-use" culture that contained these bacteria as well as Lactobacillus acidophilus. Preparations were fermented at 44°C and stored at 4°C. During the first few hours of fermentation, Y. enterocolitica populations increased in all preparations. Y. enterocolitica populations were reduced to undetectable levels after 72 and 96h in YC470 and YC180 yogurt, respectively, but survived up to 144h in "home-use" yogurt. The home-use starter produced lactic acid in greater amounts and more rapidly (p<0.05) than YC470 or YC180 starters, but enabled longer survival. Y. enterocolitica survival was least (p<0.05) in yogurt produced using the YC470 starter culture.     

酸乳流变学特性的初步研究

采用德国产HAAKEROTOVISICORV12型黏度测定仪 ,对黏性和非黏性酸乳的流变学特性进行了测定 ,分析了影响酸乳流变特性的因素 ,结果表明 :在 2～ 3 5℃的范围内 ,黏性和非黏性酸乳都是触变性流体 ;在配料和工艺相同的条件下 ,由产黏菌株形成的酸乳在大多数情况下表观黏度比非产黏菌株酸乳大 ,但有时反而小 ,初步分析这是由其微观结构的不同造成的 ;配料中无脂乳固体 (SNF)和乳脂肪的含量对酸乳的表观黏度具有强烈的影响 ,在一定条件下 ,后者影响力稍大于前者     

Effects of partially replacing skimmed milk powder with dairy ingredients on rheology, sensory profiling, and microstructure of probiotic stirred-type yogurt during cold storage

This study aimed to evaluate the quality of stirred-type skim milk probiotic yogurt fortified by partially replacing skim milk powder (SMP) with whey protein concentrate (WPC) and sodium caseinate (Na-CN) during cold storage for 28 d compared with nonfortified yogurt. The rheological properties (as measured using dynamic oscillation) and sensory profiles of probiotic yogurts were greatly enhanced when SMP (i.e., 45%) was replaced with WPC and Na-CN. Higher values of mechanical parameters related to storage and loss modulus and consistent microstructure were found in the fortified yogurts. The acidification profile was not affected by supplementation of the solids in the milk base, and the viable counts of probiotic microbiota were high and satisfactory. These positive characteristics of probiotic yogurts were maintained until the end of the storage period. The microstructure of the fortified yogurt showed some differences compared with the nonfortified product, which were due to changes in chemical composition of the milk base in addition to the colloidal characteristics of the product.     

Lactoperoxidase Effects on Rheological Properties of Yogurt

A mixed culture ( Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus ) was inoculated into reconstituted skim milk and incubated. When 0.45 Unit/g or more of lactoperoxidase (LPO) was added, the yogurts had softer and smoother texture than untreated yogurt. The apparent viscosity of yogurt was also reduced by addition of LPO. The storage modulus (G') of the gel of LPO-treated yogurt decreased but the frequency-dependency remained unchanged. The amount of exopolysaccharide or degree of proteolysis in yogurt was not changed by addition of LPO.     

蛋白质强化对搅拌型酸奶品质特性的影响

为了研究蛋白质强化对搅拌型酸奶品质特性的影响,以脱脂奶粉(SMP)和乳清浓缩蛋白-80(WPC-80)作为蛋白源,研究了强化不同种类及不同含量(2.7%、3.1%、3.5%、3.9%)的蛋白质强化对搅拌型酸奶感官品质、黏度和持水性的影响。结果表明:用SMP和WPC-80强化原料乳的蛋白质均可提高搅拌型酸奶的感官品质、黏度和持水性;比较同种蛋白源、不同蛋白质强化水平制得的搅拌型酸奶,其组织状态变化明显,风味稍有变化,色泽保持不变;酸奶的黏度和持水性都随蛋白质水平的上升而显著提高。SMP强化蛋白质含量至2.7%时,酸奶的感官品质最好;WPC-80含量则在3.5%时,酸奶的感官品质最好。同一蛋白质水平、不同强化蛋白相比较,WPC-80强化酸奶比SMP有更好的感官品质和更高的持水性,而SMP强化则得到更高的黏度值;从感官评定的黏稠度得分和测得的黏度值对比得出,搅拌型酸奶的黏度并不是越高越好,最佳黏度值在537～712mPa.s之间。实验中搅拌型酸奶的最佳蛋白强化配方为WPC-80强化蛋白质含量3.5%。     

Chemical, Microbiological and Sensory Properties of Plain Nonfat Yogurt

Chemical and microbiological properties of plain nonfat yogurt were determined after 2, 6 and 12 days refrigerated storage. Sensory properties were determined after 6 days storage. Viable culture bacteria concentrations ranged from 140 to 8,000 × 10⁶/g and ratios of lactobacillus to streptococcus ranged from 0.18 to 15.4. Chemical criteria used to characterize products included: pH, titratable acidity, lactic and four other organic acids and lactose by HPLC, and 23 major volatile organic compounds by dynamic headspace analysis. Lactic acid concentrations ranged from 7.5 to 9.9 mg/g. Major flavor volatiles in all yogurts included: acetaldehyde, heptane, acetone, diacetyl, and benzothiazole. Untrained sensory panels showed differences for flavor, aroma and acceptability.     

Rheology of Stirred Yogurt as Affected by Added Milk Fat, Protein and Hydrocolloids

The rheological characterization of stirred yogurt with added milk fat, Na caseinate (or micellar casein) and gelatin (4 Bloom strengths), starch or a xanthan gum/LBG 50:50 mixture was carried out. Dynamic and shear values were measured at 8°C and syneresis at 4°C. Consistency (k* and k) and syneresis were more frequently influenced by the composition variables than the power law factors n* and n and the critical strain γ_c. The k* ranged from 15.8 to 576 Pa sn*, n* from 0.038 to 0.220, γ^c from 1.6 to 49.0 10^-3, k from 0.37 to 32.47 Pa sⁿ, n from 0.005 to 0.587, and syneresis from 0.0 to 49.2%.     

胃蛋白酶预处理对大豆酸奶发酵过程的影响

采用乳酸菌发酵经胃蛋白酶预水解后的豆浆,优化大豆酸奶的制作工艺参数.大豆经磨粉后制成6％的豆浆,在37℃下利用胃蛋白酶处理30 min,降解其中的蛋白质.随后添加玉米糖浆使糖浓度达到6％,接种豆浆量5％的乳酸菌种子,采用恒温发酵法,在38℃下,进行厌氧发酵并冷藏24h.用占大豆干粉量0.5％的酶预处理30 min后,制...     

Enhancement of Biological Properties of Soymilk by Fermentation

Soymilk has attracted much interest in the food industry because of its health- promoting properties. Fermentation with lactic acid bacteria is known to provide value addition to soymilk by reducing the beany flavor and content of indigestible oligosaccharides and by enhancing the bioavailability of isoflavones, resulting in a nutritious probiotic food product. In the present study, Soymilk fermentation was studied using Lactobacillus acidophilus strain isolated from ragi, and effect of soymilk supplementation on the fermentation characteristics was also investigated. Viable count of 1.99 × 10⁹ CFU/mL sample and 630.1 U/g of β-glucosidase activity were determined in soymilk after 12 h of fermentation. Soymilk supplementation with skimmed milk powder at 5% level gave best results with viable counts of 22.9 × 10⁹ CFU/ml sample or 212.9 × 10⁹ CFU/g solids; 764 U/g of β-glucosidase activity, 1.44% la titratable acidity and pH of 3.9. Daidzein and genistein profile in fermented soymilk showed that 45.8% and 57.5% of respective isoflavones existing as aglycone form, indicating enhancement of the biological property of soymilk through improvement of health-relevant bioactive forms.     

乳清蛋白木瓜蛋白酶酶解物对酸奶发酵及贮藏特性影响

采用3个水解度(6.63%、8.21%和9.21%)的乳清蛋白木瓜蛋白酶酶解液取代等量蛋白的奶粉用于酸奶发酵,探讨酶解液对酸奶发酵及贮藏特性的影响。结果表明,乳清蛋白木瓜蛋白酶酶解物能明显促进酸奶发酵,在一定水解度范围内,水解度越大,其促发酵能力越强;与对照相比,酶解物能增加酸奶在贮藏期的表观黏度,且在一定水解度范围内,水解度越大,其表观黏度越大;9.21%水解度的酶解液抑制了酸奶的后酸化,而水解度6.63%和8.21%的酶解液则对酸奶的后酸化有促进作用。     

Physicochemical and Organoleptic Properties of Yogurt with Cornelian Cherry Paste

Stirred-type fruit-flavored yogurt was made by adding cornelian cherry paste and sugar at different ratios. The effects of the paste and sugar addition on the physicochemical and organoleptic properties of yogurt were examined. The titratable acidity, pH, viscosity, whey separation, and organoleptic properties of experimental yogurts were determined at weekly intervals for 21 days. Statistically significant differences were found between the control and fruit-flavored yogurts in terms of viscosity and whey separation. The addition of the fruit paste and sugar to yogurt resulted in an increase in the whey separation, and a decrease in the viscosity. During the storage, the values of the titratable acidity, viscosity and whey separations of experimental yogurts increased, while pH of the yogurts decreased significantly (P < 0.01). Yogurt with 10 kg/100 kg fruit paste and 10 kg/100 kg sugar was more acceptable and high scored with respect to overall acceptability value by panelists; however the result was not significant statistically.     

硒多糖酸奶贮藏期间的理化特性研究

为研究硒多糖对酸奶4℃贮藏25d内理化特性的影响,将0.06%硒多糖添加到纯牛奶中通过乳酸菌发酵制得硒多糖酸奶,测定硒多糖酸奶和对照酸奶中持水力、酸度、乳酸菌及硒含量等指标。结果表明:低温贮藏5-25 d内,对照酸奶和硒多糖酸奶持水力比较稳定;当贮藏时间为第15 d时,硒多糖酸奶持水力显著高于对照酸奶(P<0.05)。酸度随着贮藏时间的延长而显著增加(P<0.05),硒多糖酸奶和对照酸奶之间酸度无明显差异性。乳酸菌数量于贮藏时间5-25d呈现明显下降趋势(P<0.05),硒多糖酸奶在贮藏时间1d、10d和15d时乳酸菌数量显著低于对照酸奶(P<0.05)。低温贮藏期间酸奶硒含量比较稳定,且硒多糖酸奶硒含量是对照酸奶的10倍左右。硒多糖能改善酸奶在贮藏期间的一些理化特性。