Microbial Inactivation Kinetics in Soymilk during Continuous Flow High-Pressure Throttling

ABSTRACT:  The thermal resistance of  Clostridium sporogenes  PA 3679 ATCC 7955 was determined in soymilk (pH 7) and 0.1% peptone water (pH 7) by the capillary tube method. In the continuous flow high-pressure throttling, the temperature of soymilk increased due to instantaneous pressure release and the additional heat was supplied by a heat exchanger to achieve the set temperature. The soymilk was immediately cooled after a short preset hold time to below 40 °C. A significant increase in the heat resistance was observed in  C. sporogenes  spores when heated in soymilk in comparison to 0.1% peptone water. The  D ₁₂₁-value for spores in soymilk was approximately 3-folds higher than peptone water. The  z- value was also much higher in soymilk as compared to that in 0.1% peptone water. Continuous flow high-pressure throttling (HPT) from 207 or 276 MPa to atmospheric pressure reduced the microbial populations in inoculated soymilk up to 6 log cycles when the holding times were 10.4, 15.6, and 20.8 s and the process temperatures were 85, 121, 133, and 145 °C, respectively. The sporicidal effect increased as the operating pressure, time, and temperature were increased. More injured spores were found at 207 MPa than at 276 MPa, indicating that lower pressure caused cell injury whereas high pressure caused cell death.     

Phytase Activity from Lactobacillus spp. in Calcium-Fortified Soymilk

Abstract: The presence of phytate in calcium-fortified soymilk may interfere with mineral absorption. Certain lactic acid bacteria (LAB) produce the enzyme phytase that degrades phytates and therefore may potentially improve mineral bioavailability and absorption. This study investigates the phytase activity and phytate degradation potential of 7 strains of LAB including: Lactobacillus acidophilus ATCC4962, ATCC33200, ATCC4356, ATCC4161, L. casei ASCC290, L. plantarum ASCC276, and L. fermentum VRI-003. Activity of these bacteria was examined both in screening media and in calcium-fortified soymilk supplemented with potassium phytate. Most strains produced phytase under both conditions with L. acidophilus ATCC4161 showing the highest activity. Phytase activity in fortified soymilk fermented with L. acidophilus ATCC4962 and L. acidophilus ATCC4161 increased by 85% and 91%, respectively, between 12 h and 24 h of fermentation. All strains expressed peak phytase activity at approximately pH 5. However, no phytate degradation could be observed.     

A Novel Functional Soy‐based Food Fermented by Lactic Acid Bacteria: Effect of Heat Treatment

ABSTRACT: The development of a novel fermented soymilk product using selected lactic acid bacteria was performed. The immunomodulatory properties of strains able to grow in soymilk were evaluated in a murine model using inbred BALB/c mice. Lactobacillus acidophilus CRL 43 and CRL 1064 and Lactobacillus paracasei CRL 75 and CRL 208 were all able to significantly increase the phagocytic index (41 ± 4) compared with the control group (16 ± 3) when given individually. These strains were then used in the elaboration of multicultured fermented soymilks that were able to stimulate an innate immune response (peritoneal macrophage activation). However, these novel fermented products sometimes caused undesired secondary effects such as microbial translocation and animal weight loss. When the same fermented products were subjected to heat treatment, they were still able to stimulate the innate immune response without causing secondary effects. These results clearly show that it is not always necessary for lactic acid bacteria to be alive to exert a beneficial physiological effect. This study could thus be used as a model in the design and future evaluation of novel fermented vegetable products.     

热处理对鲜豆奶中胰蛋白酶抑制子活性的影响

分别以95℃、120℃、140℃三种温度处理鲜豆奶,研究热处理对胰蛋白酶抑制子活性的影响。测定结果表明要达到胰蛋白酶抑制子90％的失活率,95℃时需要35min;120℃时需要7min;而140℃时只需要60s左右。胰蛋白酶抑制子的热致死时间曲线表明,加热温度增加30℃,钝化胰蛋白酶抑制子90％的热处理时间可缩短10倍。     

发酵酸豆乳脱腥工艺的研究

用大豆豆乳制作发酵酸豆乳的研究，在国内已经进行了大量的工作，生产工艺的问题已基本解决，但在实际的生产应用中较少。主要存在的问题是：豆乳的脱腥效果较差，严重影响了发酵酸豆乳的口感与风味，使消费者不易接受。本实验以大豆为基本原料，探讨了影响发酵酸豆乳脱腥的各种因素：大豆浸泡条件、大豆热处理条件、菌种的种类与接种量、豆乳浓度、产酸量、添加物如牛奶、糖等。结论表明：大豆采用微波热处理，经过0．1％总浓度的食盐与碳酸钾10h的浸泡，100％，20分钟的热处理，添加60％的牛奶或6．5％的全脂奶粉，制作的发酵酸豆乳脱腥效果最好。     

Effect of Grinding Temperature on Hydroperoxide and Off-flavor Contents during Soymilk Manufacturing Process

ABSTRACT: Hydroperoxides and n -hexanal of soymilk made at different temperatures in the soybean grinding process were investigated. Both hydroperoxides and n -hexanal showed maximum amounts at 30°C, 37.78 μmol/g, and 1.94 mg/g, respectively. However, at 3°C and 80°C, amounts of hydroperoxides were about half of that at 30°C. N -hexanal showed high correlation with hydroperoxides except for at 80°C. It suggests that controlling the grinding temperature is effective to reduce hydroperoxidation and off-flavor content. Protein solubility an important index of soymilk, was decreased as the temperature increased. Grinding soybeans at low temperature is considered an economical method to produce soymilk having less off-flavor and high protein.     

Spray Dried Soymilk Used in Reduced Fat Pork Sausage Patties

Spray-dried soymilks (SDSM) prepared from standard and lipoxygenase-null soybeans were incorporated into reduced fat pork sausage (PS). Comparisons of fat content, tenderness and consumer acceptance of SDSM PS with cooked regular (～30% fat), lean (～13% fat) and car-rageenan (0.4%) formulations were made. SDSM mixtures had 50-60% less fat and 41% lower caloric content than regular PS. Protein content and cooking yield were higher in SDSM PS than in regular PS. Texture of lean PS was improved by addition of SDSM, without alteration of flavor. No differences in PS flavor were noted between SDSMs or among formulations.     

豆浆在凝固过程中的动态流变特性研究

为了研究豆腐的凝固工序,实现豆腐的规格化和标准化生产,本研究对豆浆在凝固过程中的动态流变特性进行了研究,并进行了动力学分析。在凝固温度分别为75℃、80℃、85℃时进行动态时间扫描,得出豆浆的凝固过程由两段一级反应组成且符合连续一级反应模型;第一段反应速率远远大于第二段反应速率;根据弹性模量和黏性模量计算所得活化能分别为19.19×101 k J/mol和8.67×101 k J/mol;当温度小于70℃时,豆浆不能形成豆腐凝胶;当温度在75℃时,弹性模量G'和黏性模量G"相交,豆浆的凝胶温度为75℃。通过动态温度扫描得出豆浆的凝固过程可分为三个阶段:诱导阶段(65~70℃),弹性模量G'和黏性模量G"缓慢增大,豆浆体系中有絮状沉淀生成;加速阶段(70~92℃),弹性模量G'和黏性模量G"急剧增大;稳定阶段(温度大于92℃),弹性模量G'和黏性模量G"趋于稳定,凝胶反应结束,豆腐凝胶形成。     

延长鲜豆浆(豆乳)保质期的研究

豆浆(豆乳)保鲜一直是大豆业界的技术难题。为了保证豆浆(豆乳)良好的风味和常温下贮存的安全性，文中探讨了几种不同性能的食品防腐剂和巴氏杀菌工艺对延长豆浆(豆乳)保质期的可能性。试验证明，有少数防腐剂对豆浆(豆乳)具有较好的抑菌作用，可以适当延长产品的保质期，其中保鲜剂E可使巴氏杀菌的鲜豆浆(豆乳)产品在≤25℃条件下，保质期达到3d，37℃下保存1d。     

Frozen Wild Blueberry-Tofu-Soymilk Desserts

Both wild (lowbush) blueberries (Vaccinium angustifolium Ait.) and soybeans (Glycine max L.) possess a variety of antioxidants, and both foods appear to have multiple health benefits. Our objectives were to identify whether wild blueberry juice concentrate was more acceptable than puree in frozen desserts with a soy milk‐tofu base; to determine whether fat‐free products were as acceptable as those with 10% added fat; and to compare several levels of blueberry juice concentrate. Four frozen dessert formulations were prepared in duplicate from soy milk, silken tofu, sucrose, stabilizer, BJC or puree, soybean oil or polydextrose, sweetened dried blueberries, salt, and lemon juice. Samples were assayed for total anthocyanins, antioxidant activity using the DPPH method, color, overrun, and solids. Fifty‐five persons evaluated the samples using a 9‐point hedonic scale for color, flavor, texture, and overall acceptability. Samples containing blueberry juice concentrate were darker and less blue. Anthocyanin levels were highest in the puree sample and the fat‐free product with 7.8% blueberry juice concentrate. However, antioxidant activity was highest (28 Trolox equivalents per gram) in the samples made with soybean oil and 7.4% blueberry juice concentrate. The puree formulation received higher hedonic scores than did the low‐fat blueberry juice concentrate formulations. The puree formulation received overall acceptability scores of like very much or like extremely by 45% of the consumers. These findings may aid processors in defining potential formulations that combine 2 healthful food ingredients.