Kefir源植物乳杆菌MA2的牛乳发酵特性研究

该试验对Kefir源植物乳杆菌MA2的牛乳发酵特性进行了研究,结果显示,在4℃、21d的冷藏期间内,相比较于普通酸奶,添加了植物乳杆菌MA2的益生菌酸奶的后酸化程度显著降低;且MA2菌株提高了酸奶的黏度,降低了储存期间酸乳的乳清析出率;另外,感官评价结果显示,MA2菌株发酵的酸奶口感更加细腻、绵滑、黏稠、均匀,香气更加浓郁;基于前期试验证明MA2菌株还具有降胆固醇、调节肠道菌群的生理功能,因此其具有良好的乳制品益生菌发酵剂应用前景.     

植物乳杆菌MA2对大鼠血脂代谢的影响

评价西藏Kefir蹶植物乳杆菌MA2体内降胆固醇的功效.饲喂大鼠高胆固醇饲料的同时,灌胃Lactobacillus plantarum MA2活菌制剂(1011 cells/dper rat).实验结果显示,植物乳杆菌MA2显著降低了大鼠血清总胆固醇(TC)、低密度胆固醇(LDL-C)、甘油三酯(TG)的水平,但是对高密度胆固醇(HDL-C)的水平并没有显著影响.另外,该制剂还显著降低了肝胆固醇和甘油三酯的含量,却明显提高了粪便中胆固醇和甘油三酯的含量.研究证明了植物乳杆菌MA2具有降血脂的益生菌应用潜力.     

益生性植物乳杆菌对切达干酪挥发性风味形成的影响

将分离自西藏灵菇的益生性植物乳杆菌1-2通过在杀菌乳中添加活菌数8.0、9.0（lg（CFU/mL））和在排乳清后添加于凝乳块8.0（lg（CFU/g））的方式分别加入到切达干酪中,考察植物乳杆菌活菌数量、添加方式和成熟时间对干酪挥发性风味物质组成的影响。利用固相微萃取和气相色谱-质谱联用技术检测出对照组干酪的风味物质26种,益生菌干酪组风味物质30种,添加植物乳杆菌1-2可产生乙苯、十二烷、己醇和丙酮4种挥发性风味物质。成熟时间对干酪风味的影响最大,随成熟时间的延长,益生菌干酪组中苯含量显著增加,而对照组干酪在成熟12周时才检测到苯。益生菌添加量和添加方式对干酪挥发性风味的影响相似,丁酸受益生菌活菌数和添加方式的影响最大,益生菌干酪组成熟12周时,丁酸含量最高达对照组的3.96倍（P＜0.05）。在杀菌乳中添加益生菌活菌数8.0（lg（CFU/mL））组和9.0（lg（CFU/mL））组干酪中挥发性风味物质含量有显著差异,但在杀菌乳中添加高活菌数9.0（lg（CFU/mL））和在排乳清后添加低活菌数8.0（lg（CFU/g））于凝乳块中对干酪挥发性风味的形成具有相似的影响。本研究结果为改进益生菌干酪的加工工艺和风味品质提供了实验依据。     

植物乳杆菌MA2的生物学特性研究

对Kefir源植物乳杆菌MA2的生物学特性进行了研究,结果显示,MA2菌株在MRS培养基初始pH为6.60,接种量为4%,37℃厌氧条件下培养18 h,活菌数可达到1.2×109cfu/mL。乙酸和乳酸为发酵液中的优势有机酸,且厌氧条件下发酵液中的有机酸的含量较高,厌氧发酵液中检测出的6种脂肪酸中C18∶1的含量最高。降胆固醇试验证明,低聚葡萄糖(GOS)可以促进MA2的胆固醇移除能力,移除率可达到70%;菌体细胞脂肪酸的测定结果显示MA2菌株降胆固醇的机理主要是吸附、吸收同化机理。MA2菌株的牛乳发酵试验结果显示其具有良好的产黏特性,在乳清培养基中胞外多糖产量可达380 mg/L。结合其良好的耐酸、耐胆盐特性,植物乳杆菌MA2具有良好的益生菌应用潜力。     

采用实时荧光定量PCR法同时定性定量检测发酵乳中多种益生菌

为快速、准确地对益生菌发酵乳中的干酪乳杆菌及罗伊氏乳杆菌进行定性、定量检测,通过设计干酪乳杆菌及罗伊氏乳杆菌种属特异性引物,建立了双重实时荧光定量聚合酶链式反应(polymerase chain reaction,PCR)检测方法。结果表明,所建标准曲线方程线性关系良好,相关系数R²均达到0.99以上。对市售产品随机抽样检测发现:样品1、样品2未添加干酪乳杆菌及罗伊氏乳杆菌。样品3中检出干酪乳杆菌(1.39±0.25)×10⁹copies/mL,未检出罗伊氏乳杆菌。自制益生菌发酵乳检出干酪乳杆菌(3.7±0.35)×10⁹copies/mL、罗伊氏乳杆菌(4.8±0.26)×10⁹copies/mL,检测结果均与所知的益生菌种类及数量信息相符。结果表明,上述建立的实时荧光定量PCR方法能够同时对益生菌发酵乳中的干酪乳杆菌及罗伊氏乳杆菌进行快速、准确地定性、定量检测,克服了平板培养法和流式细胞术的局限,具有一定的优势和应用前景。     

九种益生菌之间的相互作用及协同共生机理

为了研究9种益生菌之间的相互作用及协同共生机理,采用牛津杯扩散法,对德氏乳杆菌保加利亚亚种、植物乳杆菌、嗜热链球菌、鼠李糖乳杆菌、嗜酸乳杆菌、乳双歧杆菌、两歧双歧杆菌、干酪乳杆菌、副干酪乳杆菌9种益生菌进行拮抗试验,再将菌种之间无拮抗作用的实验组,按1%接种量以1∶1的比例两两混合发酵,测其OD600nm值。约1/3的益生菌之间都存在拮抗作用,但嗜热链球菌与德氏乳杆菌保加利亚亚种、嗜酸乳杆菌、干酪乳杆菌,以及干酪乳杆菌与嗜酸乳杆菌存在协同共生作用,由于乳杆菌有较强分解蛋白质的能力,能产生多种氨基酸可刺激嗜热链球菌生长,嗜热链球菌因产酸速率快,可以快速代谢产生乳酸、甲酸、CO2等,从而促进乳杆菌的生长。该研究分析了9种常用益生菌之间的相互作用,为益生菌混合发酵、微生物制剂的开发提供理论依据。     

富硒平菇多糖对益生菌生长代谢的研究

以2%葡萄糖和2%菊粉分别作为对照,测定在无葡萄糖的MRS培养基中添加2%平菇多糖,0.5%和2%富硒平菇多糖对副干酪乳杆菌（Lactobacillus paracasei）和植物乳杆菌（Lactobacillus plantarum）发酵后活菌数、pH及代谢产物的影响。结果显示,发酵24 h后,平菇多糖和富硒平菇多糖都促进了副干酪乳杆菌和植物乳杆菌两种益生菌的增殖,其中0.5%富硒平菇多糖效果更好;2%富硒平菇多糖对发酵48 h副干酪乳杆菌的增殖效果优于菊粉,对植物乳杆菌的增殖效果与菊粉相当。平菇多糖和富硒平菇多糖促进了副干酪乳杆菌和植物乳杆菌代谢生成短链有机酸的含量,其中2%富硒平菇多糖的促进作用更强,两种益生菌发酵后的甲酸、乙酸、丙酸、丁酸含量分别比对照组（葡萄糖2%）提高了340%、32.5%、43.4%、51.4%和122.7%、186.5%、183.3%、412.5%。     

传统发酵牦牛乳中2株高产胞外多糖乳酸菌在模拟消化道中耐受力的研究

从传统发酵牦牛发酵乳中分离出的2株高产胞外多糖乳酸菌,为了研究其在模拟消化道中耐受力,对2株乳酸菌(植物乳杆菌、干酪乳杆菌)分别在人工胃液、人工肠液、人工胆汁和高盐4个模拟人工胃肠道消化环境中进行培养,测其耐受力以及对Caco﹣2细胞的黏附能力。结果表明:植物乳杆菌和干酪乳杆菌在人工胃液中作用3 h的存活率随pH值的增大而增加。在pH4.5时,植物乳杆菌的存活率达到53.63%,干酪乳杆菌的存活率达到50.83%;在人工肠液中作用4h,植物乳杆菌的存活率达到了59.58%,干酪乳杆菌的存活率达到了51.42%;在胆盐环境中培养24 h后的植物乳杆菌和干酪乳杆菌活菌数随牛胆盐质量浓度的增加而降低,活菌数均保持在108cfu/m L以上;在高盐环境中培养24 h后的活菌数随盐质量浓度的增加而降低,活菌数均在108 cfu/mL以上;并且2株乳酸菌的黏附能力也很强,植物乳杆菌可以达到16.83%、干酪乳杆菌可以达到14.86%。结论:植物乳杆菌和干酪乳杆菌均能通过胃进入肠道并保持活力,而且能在肠道很好地定植,为植物乳杆菌和干酪乳杆菌作为益生菌应用在食品中提供了理论基础。     

益生菌干酪乳杆菌Zhang和乳双歧杆菌V9发酵乳胞外多糖含量对流变学特性、质构和稳定性的影响

干酪乳杆菌Zhang和乳双歧杆菌V9是我国自主开发具有良好益生特性的益生菌,发酵乳是益生菌的最优载体之一。本研究以2株益生菌应用于发酵乳为研究对象,采用多频扩散波谱法研究发酵过程中的流变学特性,通过稠度、硬度、内聚性和黏度指数测定分析发酵乳的质构特性,并分析贮藏期间活菌数和稳定性,胞外多糖(EPS)含量。结果表明,干酪乳杆菌Zhang、乳双歧杆菌V9和二者复配的发酵乳中EPS含量从贮藏期起始的(546.3±31.5),(361.1±20.1),(515.2±17.5)mg/L至贮藏期末增至(1 165.4±37.8),(903.6±33.9),(1 103.8±45.6)mg/L,显著高于对照组(P0.05)。在发酵过程中,干酪乳杆菌Zhang组表现出较高弹性因子和低固液平衡值的流变学特性,显示形成紧密的凝胶结构。后熟后,干酪乳杆菌Zhang(包括单一和复配)发酵乳的稠度、硬度、内聚性和黏度指数显著较高,乳双歧杆菌V9发酵乳硬度和黏度指数显著较高,前者的黏度和持水性显著高于对照组,后者的黏度显著高于对照组(P0.05)。各组发酵乳贮藏期间的后酸化程度没有显著差异(P0.05),表明益生菌及其代谢产生的EPS对发酵乳流变学特性、质构特性及贮藏稳定性具有积极影响,且干酪乳杆菌Zhang作用较为突出。此外,干酪乳杆菌Zhang和乳双歧杆菌V9在贮藏期间活菌数在10~8CFU/mL以上,可有效保证益生菌发挥其促进健康的作用。综上,在发酵乳中添加益生菌干酪乳杆菌Zhang和/或乳双歧杆菌V9,不仅能够赋予发酵乳益生功效,而且能够改善质构特性和贮藏稳定性。本研究为实际生产、推广应用提供技术依据,同时为益生菌发酵乳的发酵及贮藏特性评价提供研究思路和方法。     

益生菌发酵豆乳对高脂血症小鼠降血脂及肝损伤缓解的作用

研究干酪乳杆菌、植物乳杆菌和双歧杆菌在体外降胆固醇能力及三种益生菌混合发酵豆乳对高脂饮食小鼠血脂及肝损伤的影响。采用邻苯二甲醛法评价益生菌体外降胆固醇能力。采用C57BL/6N小鼠,并将其随机分为7组,即对照组;高脂组;干酪乳杆菌发酵豆乳干预组;植物乳杆菌发酵豆乳干预组;双歧杆菌发酵豆乳干预组;三种益生菌混合发酵豆乳干预组;未发酵豆乳干预组。连续喂养7周后,测定血清和肝脏中相关血脂指标,并观察肝脏组织病理学变化。结果表明:干酪乳杆菌、植物乳杆菌和双歧杆菌在体外降胆固醇能力分别为43.14%、46.27%和40.53%。益生菌混合发酵豆乳显著降低小鼠腹部和肾周脂肪指数,血清总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDL),升高高密度脂蛋白(HDL)水平,降低肝脏TC、TG、丙氨酸转氨酶(ALT)和天冬氨酸转氨酶(AST)水平,并明显改善肝脏脂肪堆积。     

无糖花生香蕉开菲尔饮料生产工艺研究

利用Kefir 粒中分离的酵母菌和乳酸菌研究了无糖花生香蕉Kefir 的工艺,结果表明,无糖花生香蕉Kefir发酵工艺可以牛奶、香蕉浆和花生浆10:3:4 的比例发酵,乳酸菌和酵母菌(从Kefir 粒中分离)混合比例为1:2,接种量为5%,发酵温度为28℃,发酵时间为14h,蜂蜜和低聚果糖作为复合甜味剂代替蔗糖,混合比例为蜂蜜:低聚果糖=2:1(W/W),添加量为6%,所得产品风味、色泽和组织俱佳,乙醇含量达到1.329%。     

Correlation Between Process Cheese Meltability Determined by Sensory Analysis,Computer Vision Method and Olson and Price Test

The meltabilities of 14 process cheese samples were determined at 2 and 4 weeks after manufacture using sensory analysis, a computer vision method, and the Olson and Price test. Sensory analysis meltability correlated with both computer vision meltability (R² = 0.71, P < 0.001) and Olson and Price meltability (R² = 0.69, P < 0.001). There was a marked lack of correlation between the computer vision method and the Olson and Price test. This study showed that the Olson and Price test gave greater repeatability than the computer vision method. Results showed process cheese meltability decreased with increasing inorganic salt content and with lower moisture/fat ratios. There was very little evidence in this study to show that process cheese meltability changed between 2 and 4 weeks after manufacture.     

Kefir粒发酵过程中牛乳体系的品质变化

为明确开菲尔粒(Kefir grains)在发酵过程中对牛乳体系品质变化的影响。本文将Kefir粒作为发酵剂应用于牛乳体系中,研究接种量、发酵时间和发酵温度对牛乳酸度、主要风味成分和流变性质的影响。结果表明,接种量、发酵温度、发酵时间对Kefir粒发酵作用的影响复杂。分析酸度变化的规律可知,相同条件下,接种量越大,酸度越高;电子鼻测定发酵乳中主要风味物质的变化发现,发酵温度越高,Kefir粒中的乳酸菌和酵母生长越快,产生风味物质的时间越短,但是菌种过快生长会导致发酵乳风味变差;流变仪测定发酵乳黏弹性、流动常数的变化可知,Kefir发酵乳的复合黏度随角频率增大而减小,储能模量G'和损耗模量G″随温度上升而增大,G'始终大于G″,tanδ始终小于1,体系呈现弹性特征。综合考虑实验结果和成本,选用在30℃条件下,接种量为0.40%的Kefir粒发酵48 h得到的酸度为86 °T,最终产品性质较为稳定,感官品质较为优良,这对Kefir发酵乳的工业化生产具有一定的指导意义。     

开菲尔粒及其发酵液中菌相分析

为了研制开菲尔发酵剂，本试验测定了开菲尔粒及其发酵液中几种主要微生物的数量。两者结果均表明其中乳酸菌多于醋酸菌，醋酸菌多于酵母菌，而且乳酸菌类中大多数为兼性厌氧菌。     

类Cheddar豆乳干酪工艺参数的优化

研究了类Cheddar豆乳干酪的生产工艺并对其工艺参数进行了优化,对影响产品质量的主要因素进行了研究。通过正交试验,对发酵剂、豆乳、凝乳酶、CaCl2的最适添加量、凝乳时间和凝乳效果进行了研究和探讨。结果表明,添加豆乳20%、发酵剂3%、凝乳酶0.03%(活力为9 000 u/g)、CaCl20.06%时凝乳效果较好,在质构上与纯牛乳Cheddar干酪无明显差异。     

Influence of rate of inclusion of microalgae on the sensory characteristics and fatty acid composition of cheese and performance of dairy cows

Modification of milk and cheese fat to contain long-chain n-3 fatty acids (FA) by feeding microalgae (ALG) to dairy cows has the potential to improve human health, but the subsequent effect on the sensory attributes of dairy products is unclear. The objective was to determine the effect of feeding dairy cows different amounts of ALG that was rich in docosahexaenoic acid (DHA) on milk and cheese FA profile, cheese sensory attributes, and cow performance. Twenty Holstein dairy cows were randomly allocated to 1 of 4 dietary treatments in a 4 × 4 row and column design, with 4 periods of 28 d, with cheddar cheese production and animal performance measurements undertaken during the final 7 d of each period. Cows were fed a basal diet that was supplemented with ALG (Schizochytrium limancinum) at 4 rates: 0 (control, C), 50 (LA), 100 (MA), or 150 g (HA) of ALG per cow per day. We found that both milk and cheese fat content of DHA increased linearly with ALG feed rate and was 0.29 g/100 g FA higher in milk and cheese from cows fed HA compared with C. Supplementation with ALG linearly reduced the content of saturated FA and the ratio of n-6:n-3 FA in milk and cheese. Supplementation with ALG altered 20 out of the 32 sensory attributes, with a linear increase in cheese air holes, nutty flavor, and dry mouth aftertaste with ALG inclusion. Creaminess of cheese decreased with ALG inclusion rate and was positively correlated with saturated FA content. We also observed a quadratic effect on fruity odor, which was highest in cheese from cows fed HA and lowest in LA, and firmness and crumbliness texture, being highest in MA and lowest in HA. Supplementation with ALG had no effect on the dry matter intake, milk yield, or live weight change of the cows, with mean values of 23.1, 38.5, and 0.34 kg/d respectively, but milk fat content decreased linearly, and energy-corrected milk yield tended to decrease linearly with rate of ALG inclusion (mean values of 39.6, 38.4, 37.1, and 35.9 g/kg, and 41.3, 41.3, 40.5, and 39.4 kg/d for C, LA, MA, and HA, respectively). We conclude that feeding ALG to high-yielding dairy cows improved milk and cheese content of DHA and altered cheese taste but not cow performance, although milk fat content reduced as inclusion rate increased.     

Short communication: Effect of kefir grains on proteolysis of major milk proteins

The effect of kefir grains on the proteolysis of major milk proteins in milk kefir and in a culture of kefir grains in pasteurized cheese whey was followed by reverse phase-HPLC analysis. The reduction of κ-, α-, and β-caseins (CN), α-lactalbumin (α-LA), and β-lactoglobulin (β-LG) contents during 48 and 90 h of incubation of pasteurized milk (100 mL) and respective cheese whey with kefir grains (6 and 12 g) at 20°C was monitored. Significant proteolysis of α-LA and κ-, α-, and β-caseins was observed. The effect of kefir amount (6 and 12 g/100 mL) was significant for α-LA and α- and β-CN. α-Lactalbumin and β-CN were more easily hydrolyzed than α-CN. No significant reduction was observed with respect to β-LG concentration for 6 and 12 g of kefir in 100 mL of milk over 48 h, indicating that no significant proteolysis was carried out. Similar results were observed when the experiment was conducted over 90 h. Regarding the cheese whey kefir samples, similar behavior was observed for the proteolysis of α-LA and β-LG: α-LA was hydrolyzed between 60 and 90% after 12 h (for 6 and 12 g of kefir) and no significant β-LG proteolysis occurred. The proteolytic activity of lactic acid bacteria and yeasts in kefir community was evaluated. Kefir milk prepared under normal conditions contained peptides from proteolysis of α-LA and κ-, α-, and β-caseins. Hydrolysis is dependent on the kefir:milk ratio and incubation time. β-Lactoglobulin is not hydrolyzed even when higher hydrolysis time is used. Kefir grains are not appropriate as adjunct cultures to increase β-LG digestibility in whey-based or whey-containing foods.     

Kefir奶的制作工艺及标准

介绍了Kefir奶的营养成分和有益健康的功效，着重对Kefir粒的结构，特别是其中重要的微生物种类、数量、相互关系以及它们在开菲奶发酵过程中所起的作用做了较为细致的叙述。在很大程度上，开菲尔奶的最终质量与Kefir生产发酵剂中微生物的种类和组成有关，而Kefir粒培养条件的任何一点偏差都将引起生产发酵剂中微生物组成的改变，进而使发酵时间改变并导致发酵产物的特性发生变化，最终引起产品质量出现波动。阐述了影响Kefir奶发酵剂质量的多种因素，包括Kefir粒与牛乳的接种比例、发酵温度、发酵时间、过滤条件以及搅拌次数和冲洗处理等。最后，列举了3种Kefir奶生产的工艺流程，并参照1986年国际乳品联合会(IDF)制定的发酵乳饮料生产标准，对涉及到Kefir奶的有关原料乳、发酵剂、发酵参数、后期处理以及质量和法律等控制标准作了总结。     

THE EFFECTS OF pH AND TIME ON RHEOLOGICAL CHANGES DURING EARLY CHEESE MATURATION

Changes in rheological properties of cheese curd during the initial stages of ripening, with pH (5.45–6.05) and with time (2–14 days), were evaluated using a small strain oscillatory test and a newly designed large strain deformation test. The new test method developed for evaluation of grated cheese employed extrusion flow technique and was carried out using the Instron Universal Testing Machine. The values for the storage modulus (G') measured using the small strain test increased with an increase in the pH of cheese curds from 5.45 to 5.90. The results from the large strain test showed essentially similar trends. The samples of curd also showed an increased solid-like behaviour as the pH increased and appeared to become more elastic with time during the two-week period of analysis.