酪蛋白水解物对发酵乳中乳酸菌增殖作用的研究

嗜酸乳杆菌（Lactobacillus acidophilus）是乳酸菌家族中极为重要的益生菌之一，已广泛地被人们所接受，因此，研究利用该菌于发酵酸乳制品中具有重要意义。本文采用嗜酸乳杆菌（Lactobacillus acidophilus）和嗜热链球菌（Streptococcus thermophilus）共发酵技术，较系统地研究了酸奶发酵的最佳条件，确定了酪蛋白水解物对嘈酸乳杆菌增殖有明显的促进作用并可提高其生存能力。实验结果表明，嗜酸乳杆菌：嗜热链球菌=2：1，37℃培养时，酸奶凝乳时间最短，产品质地最好。同时，水解度为25．0％酪蛋白酶解物对嗜酸乳杆菌增殖有明显的促进作用，添加2g／L，37℃培养，2h后即可凝乳，所得产品质地细腻，酸度达到80DT，终产品中嗜酸乳杆菌活菌数达到10^9cfu／mL。     

超氧化物歧化酶益生菌发酵酸奶的研究

本文研究了在不同的益生菌发酵剂配比条件下酸奶的品质和口感.双歧杆菌:嗜酸乳杆菌:保加利亚乳杆菌:嗜热链球菌比例为(10∶4∶2∶2)用于酸奶的混合发酵生产,可以使双歧杆菌活菌数达到1.5×108cfu/ml、嗜酸乳杆菌活菌数达到3.1×108 cfu/ml;采用添加低聚木糖等益生元,可以促进双歧杆菌的活菌数目提高;发酵后在LABS酸奶中添加SOD,可保持其在酸奶中较高的酶活力.SOD-LABS益生菌酸奶在4℃保存21d,SOD酶活性能保持75%以上.     

对酸奶中益生菌应用种类和含量的分析

从益生菌的使用状况出发,为研发新的益生菌酸奶产品提供依据。采用GNPD数据库分析国内市场上新品益生菌酸奶的益生菌添加种类,并通过选择性培养方式检测在售的几款益生菌酸奶产品中益生菌的含量。通过GNPD搜索到的61份新品益生菌酸奶中,添加嗜酸乳杆菌和双歧杆菌的分别占总量的52.5%和67.2%,且嗜酸乳杆菌和双歧杆菌组合添加的比例达到45.9%。对几款益生菌酸奶产品中益生菌含量进行检测,益生菌活菌含量在货架期内为106~108CFU/g。旨在加强对国内市场上现有益生菌酸奶产品的分析,本实验为国内首次对益生菌酸奶产品中益生菌菌种的应用状况进行分析,为益生菌酸奶的研发提供参考。     

益生菌素对嗜酸乳杆菌LA-5生长的影响

脱脂乳(110 g/L)中分别添加3种益生菌素(菊粉、麦芽低聚糖和低聚异麦芽糖)增殖发酵嗜酸乳杆菌LA-5,研究这3种益生菌素对LA-5菌株生长的影响,如活菌数、酸乳黏度、双乙酰含量、酸度、pH等的变化等指标.研究结果表明:低聚异麦芽糖对LA-5生长促进作用最佳,12h左右CFU值达到最高,为2.37×108 CFU/mL,其酸乳产品双乙酰含量＜0.2 mg/L,无不愉快气味;其酸度在16h时达到58.87.T,为添加3种益生菌素中最高.     

西红柿益生菌酸乳的研制

利用鲜牛乳和番茄汁为原料,通过添加嗜酸乳杆菌发酵来制备西红柿益生菌酸乳;通过测定活菌数和感官评定确定了番茄汁最适的添加量,测定了嗜酸乳杆菌的发酵特性,发酵结束后在4℃下贮存,在此过程中测定了嗜酸乳杆菌的存活状态及贮存过程中酸度和pH的变化,分析了番茄汁对嗜酸乳杆菌发酵的影响.实验结果表明,蔗糖添加量为8%,嗜酸乳杆菌发酵剂的接种量为45,发酵温度为37℃,发酵时间为9h,可以得到呈浅红色,状态均匀,酸甜适口的西红柿益生菌酸乳,40C下贮存10d后嗜酸乳杆菌活菌数仍达107cfu/mL以上.     

嗜酸乳杆菌KLDS 1.0901对酸奶发酵特性及抗氧化活性的影响

研究嗜酸乳杆菌KLDS 1.0901在发酵酸奶过程中对酸奶特性及抗氧化活性的影响,开发出一种抗氧化活性强的酸奶发酵剂。通过选取嗜热链球菌S1、德式乳杆菌保加利亚亚种KLDS 1.0207发酵酸奶以及向其中加入嗜酸乳杆菌KLDS 1.0901共同发酵制备酸奶,评价其产酸性能、活菌数含量,并分析所发酵酸奶的质构特性、乙醛和双乙酰产量,进行感官评价,最后对制备酸奶的体外抗氧化活性进行探索和研究,进而比较研究嗜酸乳杆菌KLDS 1.0901对发酵酸奶的发酵性能和抗氧化能力。结果表明:用嗜热链球菌S1、德式乳杆菌保加利亚亚种KLDS 1.0207及嗜酸乳杆菌KLDS 1.0901共同发酵的酸奶产酸速度快,5 h基本凝乳,与未添加嗜酸乳杆菌KLDS 1.0901发酵的酸奶相比,其中乳酸菌的活菌数为3.55×10~8CFU/g、风味物质乙醛的含量为22.8μg/mL、双乙酰含量为7.5μg/mL,以及感官评分为86分,仅次于3号汉森发酵剂。与3号汉森发酵剂相比,添加KLDS 1.0901的2号发酵剂在清除自由基的体外抗氧化能力方面与其相近。     

大豆肽对发酵酸奶乳酸菌生长及活力的影响

将两种水解度不同的大豆肽A、B添加至酸奶发酵中,作为乳酸菌发酵的促进剂,研究其对乳酸菌生长及产酸活力及其对乳酸菌活力保持的促进作用.实验采用单一嗜酸乳杆菌菌种,采用了两大类发酵A和B),通过乳酸菌37℃恒温静态培养,测定乳酸菌培养液各种指标(pH值、吸光度、滴定酸度、美兰还原褪色时间以及活菌计数).结果显示,两种大豆肽对乳酸菌生长、产酸均有较显著促进作用,且在酸奶发酵中添加大豆肽浓度为5g/L时,大豆肽对乳酸菌作用效果最佳.两种肽相比,大豆肽B对乳酸菌生长、产酸作用更为显著.     

添加魔芋低聚糖对益生菌增殖和酸奶品质的影响

研究了魔芋低聚糖对酸奶中益生菌增殖和感官品质的影响。在酸奶发酵过程中添加不同比例的魔芋低聚糖,在其0,7,14 d采用平板涂布法检测酸奶中益生菌的生长情况,同时对该酸奶的感官进行评价。结果表明:在酸奶发酵过程中添加魔芋低聚糖,对酸奶中双歧杆菌、乳杆菌以及嗜热链球菌有显著的增殖作用,且魔芋低聚糖添加量为3%时酸奶中益生菌增殖作用最好,感官品质也较好。在酸奶发酵过程中添加魔芋低聚糖还可使益生菌活菌数在贮存过程中保持较高的水平。结论:酸奶发酵过程中添加魔芋低聚糖可促进酸奶中益生菌的增殖、改善酸奶的感官品质,并使益生菌活菌数在贮存过程中保持较高的水平。     

活性酸乳中每种益生菌总数的同时计数法

益生菌酸奶的营养作用和保健功能决定于成品中必须含有一定数量级的活性益生菌数.本实验通过研究分析活性酸奶中嗜热链球菌、保加利亚乳杆菌、嗜酸乳杆菌、双歧杆菌、鼠李糖乳杆菌(LGG菌)、干酪乳杆菌等乳酸菌在BBL.平板培养基上的菌落特征及菌体形态,提出了一种可同时准确计数每种益生菌总数的新方法,该方法可直观地观察到各种益生菌的生长活度,免除了传统方法计数不同益生菌总数要用不同培养基的繁琐,为快速鉴定益生菌酸奶品质好坏和保健功能活性高低提供了检测依据.     

6种益生菌及其添加方式对发酵米酒品质的影响

目的:探究不同益生菌及其添加方式对米酒制作效果的影响。方法:以糯米为原料,通过外源添加鼠李糖乳杆菌BV-77、发酵乳杆菌TSF-331、唾液乳杆菌AP-32、约氏乳杆菌MH-68、嗜酸乳杆菌TYCA-06、干酪乳杆菌CS-773酿制益生菌米酒,对比只添加糖化酶、同时添加糖化酶和酵母以及添加方式(益生菌麸曲和益生菌菌粉)对米酒酒精度、还原糖、总酸和感官质量的影响。结果:酵母对益生菌米酒的发酵有促进作用,可显著提高米酒酒精度和还原糖含量。利用发酵乳杆菌菌粉同时添加用量为200 U/g的糖化酶和0.04%的酵母,在30℃发酵3 d的米酒发酵效果最佳,酒精度和还原糖含量达到最高,分别为7.20%vol和270.00 mg/mL,总酸含量达到最低,为8.40 mL/L,酿造出的米酒口感较为浓郁。结论:发酵乳杆菌是6种益生菌中最适宜酿造米酒的益生菌。     

Effect of milk base and starter culture on acidification,texture, and probiotic cell counts in fermented milk processing

In the present work, the compared effect of milk base and starter culture on acidification, texture, growth, and stability of probiotic bacteria in fermented milk processing, was studied. Two strains of probiotic bacteria were used, Lactobacillus acidophilus LA5 and L. rhamnosus LR35, with two starter cultures. One starter culture consisted only of Streptococcus thermophilus ST7 (single starter culture); the other was a yogurt mixed culture with S. thermophilus ST7 and L. bulgaricus LB12 (mixed starter culture). For the milk base preparation, four commercial dairy ingredients were tested (two milk protein concentrates and two casein hydrolysates). The resulting fermented milks were compared to those obtained with control milk (without enrichment) and milk added with skim milk powder. The performance of the two probiotic strains were opposite. L. acidophilus LA5 grew well on milk but showed a poor stability during storage. L. rhamnosus LR35 grew weakly on milk but was remarkably stable during storage. With the strains tested in this study, the use of the single starter culture and the addition of casein hydrolysate gave the best probiotic cell counts. The fermentation time was of about 11 h, and the probiotic level after five weeks of storage was greater than 106 cfu/ml for L. acidophilus LA5 and 10(7) cfu/ml for L. rhamnosus LR35. However, an optimization of the level of casein hydrolysate added to milk base has to be done, in order to improve texture and flavor when using this dairy ingredient.     

Growth of Probiotic and Traditional Yogurt Cultures in Milk Supplemented with Whey Protein Hydrolysate

ABSTRACT: Growth of some probiotic bacteria was significantly improved in milk supplemented with whey protein hydrolysate (WPH). However, WPH had no effect on the growth of Lactobacillus delbrueckii ssp. bulgaricus 18, L. delbrueckii ssp. bulgaricus 10442, and Streptococcus thermophilus 1. When the probiotic bacteria were grown in combination with different yogurt cultures in milk, WPH caused significant increases in growth of Bifidobacterium longum S9, L. acidophilus O16, and L. acidophilus L-1. However, by day 28 of refrigerated storage, the populations of the probiotic cultures that had been grown in samples supplemented with WPH were similar or below those in the control samples.     

乳清蛋白酶解物促嗜酸乳杆菌增殖作用研究

利用胃蛋白酶水解乳清蛋白,获得酶解产物的优化工艺条件是pH 值为2.2,水解温度为65℃,底物质量浓度为2g/100mL,酶与底物比为7%,其蛋白水解度为12.51%。乳清蛋白水解物与经过超滤和凝胶过滤后的分离物对嗜酸乳杆菌B 有较好的增殖作用,其中分子量1000D 以下的酶解产物增殖效果最为显著。质谱分析证实该段水解产物是分子量集中在213.2～956.9D 之间的寡肽和氨基酸复合物,可使嗜酸乳杆菌B 活细胞数量提高一个对数级。显然,应用廉价乳清蛋白水解产物作为培养基质可以提高嗜酸乳杆菌B 的细胞数量。     

胞壁蛋白酶（CEP）酶解对酪蛋白结构及功能特性的影响

通过纳米粒度分析、傅立叶红外光谱（FTIR）、乳化性、乳化稳定性、蛋白溶解性、抗氧化性及ACE抑制率的测定,分析探讨酪蛋白及其不同水解度（DH 2.4%、4.5%、7.1%、8.3%）的嗜酸乳杆菌胞壁蛋白酶（CEP）酶解产物的结构及功能特性。FTIR分析表明CEP酶解改变了酪蛋白各种构象所占的比例,酪蛋白二级结构发生了不同程度的变化;纳米粒度分析表明酪蛋白颗粒大小随水解的加深先减小后增大,其水解物颗粒在DH 4.5%时最小,乳化稳定性最大;酪蛋白的乳化性随水解的加深先增大后减小,DH 7.1%时增至最大,与其溶解性的变化趋势一致;此外酪蛋白的酶解物具有一定的ACE抑制活性及抗氧化性,且DPPH清除能力在一定范围内随水解度及浓度的增大而增大,当DH为8.3%,浓度为5mg/mL时,DPPH清除能力增大至35.00%。因此CEP酶解可有效改善酪蛋白的结构及功能特性,为乳源性功能多肽的开发提供理论依据。     

Incorporation of citrus fibers in fermented milk containing probiotic bacteria

The incorporation of Lactobacillus acidophilus CECT 903, Lactobacillus casei CECT 475 and Bifidobacterium bifidum CECT 870 together with lemon (LF) and orange (OF) fibers obtained from juice by-products were tested in (i) a model system: fiber enriched with de Man Rogosa Sharp (MRS) broth cultured with each probiotic bacteria and (ii) evaluation of populations of probiotic bacteria in fermented milks formulated with citrus fibers. Citrus fibers enhanced L. acidophilus CECT 903, and L. casei CECT 475 survival in MRS during refrigerated storage, whereas erratic results were obtained for B. bifidum CECT 870, OF enhanced its growth and LF had inhibitory effect. Populations of probiotic bacteria decreased with storage time in MRS broth. The presence of yogurt starter bacteria in probiotic fermented milks favored the growth and survival of L. acidophilus and B. bifidum. Citrus fiber presence in fermented milks also enhanced bacterial growth and survival of the tested probiotic bacteria. This study indicates that citrus fiber enriched fermented milk have good acceptability and are good vehicles for a variety of commercial probiotics but survival of B. bifidum will need to be improved.     

三种氨基酸添加下酶法修饰酪蛋白水解物的ACE抑制活性

采用碱性蛋白酶水解酪蛋白,制备水解度为12.4%、IC50为42.19μg/mL的酪蛋白水解物。在添加外源氨基酸的情况下对水解物进行类蛋白反应修饰,并响应面法研究氨基酸添加量、酶添加量、反应温度及3种氨基酸的影响。结果表明:氨基酸添加量、反应温度、氨基酸种类对修饰反应影响显著,而酶添加量的影响不大;分别添加苯丙氨酸、亮氨酸、缬氨酸制备3个酪蛋白水解物修饰产物,其IC50降低至21.03～25.13μg/mL,表明添加外源氨基酸可提高修饰产物的体外ACE抑制活性,但添加不同氨基酸的影响不显著。     

山羊乳酪蛋白酶解物制备及体外抗氧化活性研究

以自由基清除能力、金属离子螯合能力和抗脂质过氧化能力为指标,采用均匀试验研究山羊乳酪蛋白酶解物的制备及其体外抗氧化活性,并且比较自由基清除能力的方法。结果表明：山羊乳酪蛋白适宜的酶解工艺为在60g/kg的底物浓度下,中性蛋白酶和碱性蛋白酶的添加量分别为4000U/g和250U/g,45℃、pH7.5条件下酶解24h。山羊乳酪蛋白经酶解后其体外抗氧化活性显著增强。山羊乳酪蛋白酶解物 ·OH清除率的EC50值是其蛋白的3.59倍,ABTS＋ ·的清除能力是其蛋白的158.72倍,螯合Fe2＋的能力是其蛋白的5.44倍;在亚油酸体系中抗脂质过氧化能力强于TBHQ,与VE相当。清除 ·OH、DPPH自由基、O2－ ·和ABTS＋ ·的方法不能相互替代。     

Effect of milk supplementation and culture composition on acidification, textural properties and microbiological stability of fermented milks containing probiotic bacteria

In the present work, the combined effect of milk supplementation and culture composition on acidification, textural properties, and microbiological stability of fermented milks containing probiotic bacteria, was studied. Three powders (whey, casein hydrolysate, and milk proteins) were tested as supplementation. Two strains of probiotic bacteria, Lactobacillus acidophilus (LA5) and Lactobacillus rhamnosus (LC35), were used in pure culture, and in mixed culture with Streptococcus thermophilus (ST7). Acidifying activity was enhanced with mixed cultures, compared to pure cultures resulting in a shorter time to reach pH 4.5. Acidifying activity was greatly improved with casein hydrolysate, with a reduction of the fermentation time by about 55% by comparison with the other supplementations. The stability of probiotic bacteria was weakly affected by milk supplementation and culture composition. However, pure cultures were more stable than mixed cultures. The texture of the fermented products was not dependent on culture composition, but strongly dependent on milk supplementation. Sweet whey supplementation gave products with lower firmness and viscoelasticity than products supplemented with casein hydrolysate or milk proteins (decrease by 70%). It was observed that all products containing probiotic counts over 2.2×10⁷ CFU mL⁻¹ are suitable for the development of a lactic beverage containing probiotics.     

Limited hydrolysis of β‐casein by cell wall proteinase and its effect on hydrolysates's conformational and structural properties

Optimisation of enzymatic hydrolysis of β‐casein with cell envelope proteinase (CEP) from Lactobacillus acidophilus JQ‐1 to produce the angiotensin‐I‐converting enzyme (ACE) inhibitory peptides using response surface methodology (RSM). Under optimal conditions (enzyme‐to‐substrate ([E]/[S]) ratio (w/w) of 0.132 and pH of 8.00 at 38.8 °C), the ACE inhibitory activity of hydrolysates was 72.06% and the total peptides was 11.75 mg mL^?1. Scanning electron microscopy (SEM) micrographs indicated that the tightness of the β‐casein surface structure was gradually weakened and small holes appeared after enzymatic treatment, while Fourier transform infrared spectroscopy (FTIR) spectra indicated remarkable changes in the chemical composition and macromolecular conformation of β‐casein after enzymatic hydrolysis. Differential scanning calorimetry (DSC) analysis indicated that the corresponding hydrolysates had higher thermal stability. The enzymatic hydrolysis also led to an increase in the free sulfhydryl content of β‐casein hydrolysates compared with raw β‐casein, which led to the increase in the antioxidant activity of β‐casein hydrolysates.     

Physical properties and microstructure of yoghurts supplemented with milk protein hydrolysates

The physical properties and the microstructure of yoghurts containing probiotic bacteria, and supplemented with milk protein hydrolysates, were studied. Three casein hydrolysates and three whey protein hydrolysates were added to milk at a concentration ranging from 0.25 to 4 g L⁻¹. The milks were then fermented with either of two different cultures. The resulting yoghurts with added hydrolysates were compared to the control yoghurt without supplementation. For both cultures, addition of hydrolysates decreased the complex viscosity and graininess in yoghurts. The addition of hydrolysates also reduced fermentation time. Microstructural observations showed a more open and less branched structure in yoghurts when milk protein hydrolysates were incorporated. The difference in fermentation time between milks with different levels of added hydrolysates could partially explain the differences in microstructure and physical properties of the final yoghurts.