超微粉碎技术在豆腐加工中的研究进展

在豆腐的制备过程中,豆浆的制取方式十分重要,直接影响豆腐的凝胶强度、弹性、内聚性和口感。超微粉碎技术作为一种新兴的制浆技术,不仅能减小豆浆的粒径、赋予产品细腻的口感、改善原料的加工性能,还能在一定程度上避免豆渣中所含营养成分的流失,在豆浆及豆腐的制备过程中使用越来约普遍。本文综述了干法超微粉碎制浆技术和超声波、胶体磨、高压均质、超高压均质等湿法超微粉碎制浆技术的研究与应用现状,比较了各种制浆技术的优、缺点,并对今后豆腐制浆技术的研究方向进行了展望,旨在为加快研究\     

碱性蛋白酶Alcalase凝固豆乳的物性特征

在Alcalase凝固豆乳过程中pH下降程度小于0.2,SDS-PAGE电泳表明,大豆蛋白质各亚基在凝固过程中均降解为8～14kDa的肽段,说明大豆蛋白的部分降解是Alcalase凝固豆乳的根本原因。对Alcalase与盐类凝固剂氯化镁和氯化钙凝固豆乳的主要流变学性质比较发现,Alcalase凝固豆乳的硬度比盐类凝固剂大,凝胶强度比盐类凝固剂低,粘附性比盐类凝固剂高10倍以上,使凝胶较粘,乳清不易排出。      

Preference Mapping of Soymilk with Different U.S. Consumers

This study determined and compared drivers of liking for unflavored soymilk with different U.S. consumer groups. A highly trained panel documented appearance, mouthfeel and flavor attributes of 26 commercial soymilks. Twelve representative soymilks were then selected for evaluation by consumers from 3 age/cultural categories (n = 75 each category; Caucasian/African American females aged 18 to 30 y; Asian females aged 18 to 30 y; Caucasian/African American females aged 40 to 64 y). Consumers evaluated overall liking and liking and intensity of specific attributes. Results were evaluated by analysis of variance, followed by internal and external preference mapping. Age had no effect on overall liking, while ethnicity did (Caucasian/African American compared with Asian; P < 0.05). Caucasians/African Americans differentiated soymilks more than Asians and assigned a wider range of liking scores than Asians (2.1 to 7.2 compared with 4.0 to 6.1). Three consumer clusters were identified. Sweet taste with vanilla/vanillin and sweet aromatic flavors and higher viscosity were preferred by most consumers and differences between consumer clusters were primarily in drivers of dislike. Drivers of dislike were not identified for Cluster 1 consumers while Clusters 2 and 3 consumers (n = 84, n = 80) disliked beany, green/grassy and meaty/brothy flavors and astringency. Cluster 3 (n = 80) consumers scored all soymilks higher in liking (P < 0.05) than Cluster 2 consumers, and were willing to overlook disliked attributes with the addition of sweet taste, whereas the Cluster 2 consumers were not. These findings can be utilized to produce soymilks with attributes that are well liked by target consumers and to tailor attributes for segments of the population that have not yet been accommodated.     

通电加热条件对豆浆中脂肪氧化酶活性的影响

采用通电加热和传统(油浴)加热两种方式处理豆浆样品,研究通电加热过程中电源电压、电源频率和保温时间对豆浆中脂肪氧化酶活性的影响。结果表明:采用的电源电压越高,通电加热处理后的豆浆中脂肪氧化酶活性越高;较高的电源频率对脂肪氧化酶的钝化具有显著的促进作用,但是当电源频率超过500 Hz后,电源频率的提高对脂肪氧化酶的活性影响较小;延长保温时间会促进脂肪氧化酶的钝化,通电加热过程中电场的存在会促进脂肪氧化酶的钝化。各因素对脂肪氧化酶活性的作用规律,可以对通电加热设备的设计与生产产生积极的指导作用。     

Changes of soy protein under ultra-high hydraulic pressure

High pressure (<500 MPa) was applied to soy milk and the protein changes were examined. Soy milk remained a liquid within the range of examined pressures, although its viscosity increased when the time of pressurization was less than 10 min. However, the soy milk changed from a liquid to a sol after treatment at 500 MPa for 30 min. the liquid soy milk showed improved emulsifying activity and stability but reduced emulsifying capacity. Sulfhydryl content of this soy milk was increased slightly after anaerobic pressurization. Harder tofu could be made from pressurized soy milk with CaC1₂ than could be made with unpressurized soy milk. Electrophoresis and isoelectrofocusing revealed that soy proteins were dissociated and some of them coagulated by high pressure. Fluorescence analysis also revealed that soy proteins were modified by high pressure to have larger hydrophobic regions. After pressure treatment, soy milk showed a higher affinity for beany flavour components and saponins which would lead to better use of soy milk in soy foods.     

Hydrothermal Cooking Affects Protein Efficiency Ratio and Zinc Bioavailability of Soymilk-Based Diets in Rats

Hydrothermally cooked (HTC) and conventionally processed soymilks were compared with respect to protein efficiency ratio (PER) and zinc bioavailability in Sprague-Dawley rats fed isocaloric, isonitrogenous diets. When dietary zinc was 50 mg/kg, PER (mean ± SD, n = 12) was greater for HTC (processed 20 sec) (2.69 ± 0.34) than for conventional soymilk (2.39 ± 0.17). When dietary zinc was 20 mg/kg, PER (n = 10) was less for HTC processed 40 sec (1.86 ± 0.17) than for conventional soymilk (2.08 ± 0.19). Processing (HTC vs conventional) did not affect zinc bioavailability by the slope ratio bioassay procedure. PER of HTC processed 20 sec was higher than that of reference casein and conventional soymilk when dietary zinc was near recommended levels; pancreatic hypertrophy was not observed.     

Effect of electroporation on viability and bioconversion of isoflavones in mannitol‐soymilk fermented by lactobacilli and bifidobacteria

BACKGROUND: The aim of this study was to evaluate the effect of electroporation (2.5–7.5 kV cm^?1 for 3.0–4.0 ms) on the growth of lactobacilli and bifidobacteria, membrane properties and bioconversion of isoflavones in mannitol‐soymilk. RESULTS: The viability of lactobacilli and bifidobacteria decreased immediately after electroporation. This was attributed to lipid peroxidation, which led to alterations in the membrane phospholipid bilayer, specifically at the polar head, interface and apolar tail regions. Such alterations also resulted in decreased membrane fluidity and increased membrane permeability upon electroporation (P < 0.05). However, the effect was reversible and treated cells showed better growth than the control upon fermentation for 24 h at 37 °C (P < 0.05). Additionally, electroporation increased the bioconversion of glucosides to bioactive aglycones in mannitol‐soymilk, which was attributed to increased intracellular and extracellular β‐glucosidase activities of cells upon treatment (P < 0.05). CONCLUSION: Application of electroporation on lactobacilli and bifidobacteria could be beneficial for the development of fermented soymilk with enhanced bioactivity. Considering the enhanced bioactive aglycones, this soymilk could be useful for the prevention of hormone‐dependent disorders. Copyright © 2012 Society of Chemical Industry     

Sensory properties of soy yoghurts prepared from yellow and black soymilk using Streptococcus infantarius 12 and Weisellia sp. 4

BACKGROUND: Soy yoghurts containing enhanced bioactive isoflavone aglycones were prepared from combinations of yellow (YS) and black soymilk (BS) (YS:BS = 100:0, 70:30, 50:50 and 0:100, v/v) by fermentation with Streptococcus infantarius 12 and Weisellia sp. 4 at 37 °C for 10 h. Sensory properties of the bioactive soy yoghurts were investigated. Furthermore, other characteristics including the contents of isoflavones, viable cell numbers, pH, colour and DPPH radical scavenging activity were investigated. RESULTS: One hundred percent YS yoghurt showed the highest scores of all sensory attributes while 100% BS yoghurt was the lowest for colour and smoothness. The overall acceptability scores were 5.9 and 5.2 for 100% YS and 100% BS yoghurts, respectively (9‐point scale). The L‐values of soy yoghurts decreased as the percentage BS increased, indicating darkening of soy yoghurts. The contents of bioactive isoflavone aglycones (daidzein and genistein) in soy yoghurts remarkably increased (>1300 mg kg^?1) by fermentation. Viable cell numbers and pH of soy yoghurts ranged from 8.4 × 10⁸ to 9.6 × 10⁸ CFU g^?1 and 4.43 to 4.54, respectively. DPPH radical scavenging activity significantly increased as the percentage BS increased (P < 0.05). CONCLUSION: One hundred percent YS yoghurt was better for overall sensory properties while 100% BS yogurt was more bioactive in terms of the isoflavone aglycone contents and DPPH radical scavenging activity compared to other yoghurts. Copyright © 2008 Society of Chemical Industry     

Rapid Measurement of Phytate in Soy Products by Mid-infrared Spectroscopy

ABSTRACT: The rapid measurement of phytate from soybean and its products, such as soy flour, defatted meal, soymilk, and tofu, was investigated using Fourier transfer infrared spectroscopy (FT-IR) with an attenuated total refraction accessory. The phytate, separated from protein by trichloroacetic acid (TCA), was precipitated completely by the addition of calcium, pH > 7.0, even in the presence of TCA. The precipitate was dissolved in citrate buffer (pH 6.0) and then used for infrared measurement. The absorbance at 1070 cm⁻¹ correlated well the phytate content of the each sample. The measurement of phytate can be done rapidly by FT-IR with an ATR accessory and gives reproducible values.