Analysis of Lunasin in Commercial and Pilot Plant Produced Soybean Products and an Improved Method of Lunasin Purification

Abstract: Lunasin is a bioactive peptide present in soybean. It is important to quantify lunasin concentration in soy products to assess its potential impact as functional food. The objectives of this study were to analyze lunasin in commercial soymilk products and implement an efficient method to isolate and purify it from defatted soybean flour. Defatted soybean flour was suspended in water, and the extract was loaded in a pre‐equilibrated diethylaminoethyl column and bound proteins eluted using a step gradient of salt. Most lunasin was eluted from the column at 0.2 to 0.4M NaCl as quantified by immunoassays and purified using ultracentrifugation and ultrafiltration techniques. Lunasin purity was ≥90% and a standard curve was used to quantify its concentration in soymilk products. Concentration of lunasin in soy products, including organic soymilk, soy protein shakes, and soy infant formulas, ranged from 1.78 to 9.26 mg lunasin/100 g product. The concentration per serving ranged from 1.59 ± 0.01 to 22.23 ± 0.74 mg lunasin with variability depending on brand and size per serving. Steam‐ground‐cooked soy had the highest concentration of lunasin (22.23 ± 0.74 mg/serving), similar to some commercial products. Ground‐cooked soymilk contained roughly half the concentration of lunasin (14.39 ± 1.4 mg/serving). Soy infant formulas that used soy protein isolate revealed lower concentrations of lunasin (P < 0.05). It was concluded that all soymilk products analyzed contained lunasin, and a more efficient method to isolate lunasin with higher purity was developed. Practical Application: Soy foods have shown to play a role in cardiovascular health prevention. The quantification of lunasin in commercially available soy products can add to the already existing health claim for soy foods and encourage consumers to include soy products in their diets.     

增稠剂和乳化剂对豆浆稳定性的影响

为增加豆浆的稳定性,采用测定豆浆稳定系数、表面张力及进行感官评分的方法筛选适合用于豆浆样品的增稠剂和乳化剂,确定了最适宜的豆浆增稠剂和乳化剂的种类及其用量。经过黄原胶、刺槐豆胶、卡拉胶、结冷胶和海藻酸钠的单因素实验,黄原胶和刺槐豆胶的复配实验及黄原胶、刺槐豆胶和乳化剂(单硬脂酸甘油酯和蔗糖脂肪酸酯)的正交实验得出以下结果:黄原胶和刺槐豆胶对增加豆浆稳定性有着较好的效果,当它们的质量浓度分别为0.2g/L时,其稳定系数分别为0.737、0.742。单硬脂酸甘油酯和蔗糖脂肪酸酯复配后HLB=8、质量浓度为2g/L时,豆浆样品的稳定性最好,表面张力为41.7mN/m。当黄原胶、刺槐豆胶、乳化剂质量浓度(单硬脂酸甘油酯质量∶蔗糖脂肪酸酯质量=7∶4)分别为0.14、0.14、2g/L时豆浆的稳定性最好,此时豆浆样品的稳定系数为0.879,表面张力为41.6mN/m,感官评分为96。     

紫背天葵色素对酸豆奶发酵进程的影响

大豆为主要原料,将紫背天葵提取色素添加到豆奶中,保加利亚乳杆菌和嗜热链球菌等比混合为发酵剂进行乳酸发酵制酸豆奶。通过单因素试验,探讨紫背天葵色素对酸豆奶发酵pH、乳酸菌数、酸豆奶品质及保藏性能的影响。结果表明,豆水质量比为1∶10的豆奶中添加6%紫背天葵色素提取液,6%蔗糖和2%葡萄糖,85℃杀菌30 min后冷却至43℃,接种3%乳酸菌发酵6 h,紫背天葵色素的添加有利于乳酸菌的生长繁殖,加速酸豆奶的发酵进程,缩短发酵时间,能改善产品的组织状态,提高产品的保藏性能。制得的酸豆奶色泽鲜红,组织细腻,凝固性好,滋味和气味优良,营养价值高。     

The Role of Composition and Content of Protein Particles in Soymilk on Tofu Curding by Glucono-δ-lactone or Calcium Sulfate

ABSTRACT: The effects of composition and content of protein particles on tofu curding were investigated by using soymilk prepared from mixtures of glycinin-rich and β-conglycinin-rich soybeans. The breaking stress of tofu curds increased with the increase of protein particle content in soymilk. The soymilk from glycinin-rich soybeans had a high protein particle content and formed harder tofu curds. There is a significant positive correlation between the content of protein particles and the breaking stress of tofu curds. It is suggested that the increase of the quantity of protein particles reinforces the combination among protein particles during the tofu curding, thus forming a stronger network of tofu curds.     

Fermentation and Properties of Calcium-fortified Soy Milk Yogurt

Calcium-fortified soy milk yogurt containing 190 mg calcium/100g was produced and evaluated for textural and microstructural properties. The soy milk base contained 10% full fat soy flour, 2.25% soy protein isolate, 2.75% high fructose corn syrup, 1.55% calcium lactogluconate, and 1.25% potassium citrate. The mixture was heated 5 min at 80°C, cooled to 42°C, and inoculated with yogurt cultures. Calcium-fortified soy milk required a higher rate of inoculation (5%) than non-fortified soy milk (2.5%) and had higher titratable acidity and more syneresis. Calciumfortified soy milk yogurts showed comparable gel strength with that of commercial regular yogurt. Gels from nonfortified soy milk yogurts were hard and brittle. Addition of calcium did not significantly affect microstructure of the yogurts.     

Incorporation of Soymilk Lipid into Soy Protein Coagulum by the Addition of Calcium Chloride

ABSTRACT: The effect of protein composition on the lipid incorporation into protein coagulum (tofu curd) was investigated using soymilk prepared from mixtures of glycinin-rich and β-conglycinin-rich soybeans. The lipid incorporation takes place with the addition of CaCl₂ so that a particulate fraction of the protein is aggregated. The incorporation occurred by less addition of CaCl₂ with increasing glycinin in soymilk. The protein particle content and the glycinin content of the particles increased along with increasing glycinin. The lipid incorporation took place at lower CaCl₂ concentration when the particulate glycinin content was high. The mechanism of the lipid incorporation into soybean curd is discussed from these results.     

全子叶豆乳悬浮稳定性的研究

针对全子叶豆乳的悬浮稳定性进行了研究。在全子叶豆乳的加工过程中 ,膳食纤维是影响豆乳稳定性的主要因素。采用高压均质两次 ( 2 .0× 10 7Pa ,4 .0× 10 6Pa)方法来提高产品的稳定性 ,主要从均质压力、均质次数、均质温度三方面来研究均质对豆乳稳定性的影响