胡萝卜汁双歧杆菌酸乳发酵培养基优化研究

本文以从健康人体中选育出2株发酵活力高、耐氧性和抗逆性强的优良发酵菌株两歧双歧杆菌Bbm和长双歧杆菌Blm作为试验菌株,研究了胡萝卜汁和蔗糖在牛乳中的添加量对双歧杆菌在牛乳中发酵的凝乳时间、凝乳时活菌数及pH值、产品感官风味的影响,确定了发酵培养基中胡萝卜汁和蔗糖的最适添加量分别为20%～30%和5%～6%,完成了以胡萝卜汁乳作为双歧杆菌最佳载体的初步探索,为功能性益生菌乳制品的研制和开发提供了必要条件.     

双歧杆菌纯种发酵胡萝卜汁牛乳工艺研究

以健康人体中选育出的发酵活力高、耐氧性和抗逆性强的优良发酵菌株--长双歧杆菌(Blm)为试验菌株,研究了接种量、基质起始pH值、发酵温度、氧等因素对Blm在胡萝卜汁牛乳中发酵的凝乳时间、活菌含量、pH值和感官质量的影响;利用正交试验优化并确定了Blm发酵的最佳工艺条件在胡萝卜汁牛乳培养基(添加250 mL/L胡萝卜汁和50 g/L蔗糖的牛乳培养基)中,接种量5×107 cfu/mL,基质起始pH值7.0,发酵温度39℃,有氧发酵.产品凝乳时间在5 h内,双歧杆菌活菌数在1×109 cfu/mL以上,pH值5.0.制备的胡萝卜汁双歧杆菌酸乳呈橙黄色,组织状态致密,无乳清析出,且综合了双歧杆菌、胡萝卜、牛乳的功能特性,集风味、营养、保健功能于一体.     

双歧杆菌与乳酸菌混合发酵胡萝卜汁牛乳饮料的工艺研究

以从健康人体中选育出的发酵活力高、耐氧性和抗逆性强的优良发酵菌株长双歧杆菌(Blm)作为主要试验菌株,以乳酸菌保加利亚乳杆菌(L.b-DR)和嗜热链球菌(S.t-3)作为辅助菌株,研究了接种量及菌种配比、基质起始pH值、发酵温度、氧气等因素对双歧杆菌与乳酸菌混合发酵胡萝卜汁牛乳饮料时,对凝乳时间、活菌含量、pH值和产品感官风味的影响。利用正交试验优化并确定了Blm与乳酸菌混合发酵的最佳工艺条件,即在胡萝卜汁牛乳培养基(25%胡萝卜汁和5%蔗糖)中,总接种量3%(3×107cfu/mL),其菌种配比为Lb-DR∶St-3∶Blm=1∶1∶1,基质起始pH值7.0,发酵温度39℃,有氧条件发酵。产品凝乳时间在3.33 h,pH值为4.5左右,总活菌数可达1×109cfu/mL以上,橙黄色,组织状态致密细腻,无乳清析出。对该产品的工艺条件探究,为开发其它功能性益生菌乳制品提供了新的思路和方法。     

胡萝卜汁双歧杆菌发酵饮料的研制

在添加 5 %脱脂牛乳和 4%～ 5 %蔗糖的胡萝卜汁中接种 5× 1 0 6 /mL的长双歧杆菌 (Bifi dobacteriumlongum) ,发酵 1 0～ 1 4h后或终点pH达到 4 2左右时 ,可获得总菌数在 1 0 9/mL数量级、色泽鲜艳、口感良好、风味上佳的双歧杆菌胡萝卜汁发酵饮料制品。产品低温贮运的保质期为1周左右。     

双歧杆菌发酵胡萝卜汁饮料的研制

采用已耐氧驯化的两歧双歧杆菌与普通乳酸菌共同发酵胡萝卜汁制得发酵饮料。通过正交试验确定的最优发酵条件为:发酵温度39℃,发酵时间9h,胡萝卜汁浓度27％,乳糖添加量1％,双歧杆菌接种量7％,乳酸菌接种量1％。用此条件所得产品中双歧杆菌和乳酸菌活菌数分别达6.5×10~7cfu/mL和1.7×10~8cfu/mL。该产品是色、香、味俱佳的天然营养保健制品。     

双歧杆菌发酵黑米酸乳的研究

以双歧杆菌为主要发酵剂，黑米为主要基质进行了双歧黑米酸乳生产技术参数的研究。以黑米浆７０％添加３０％的牛乳、６％蔗糖，４％的混合发酵剂和０．２５％的ＳＳＬ－１复合剂，发酵３￣４小时，４℃后发酵４￣５小时可获得酸甜适口，口味纯正的双歧黑米酸乳。     

乳酸发酵胡萝卜汁的研制

以胡萝卜汁为基质,对若干乳酸发酵菌株进行发酵性能及生长曲线的研究,确定了以嗜酸乳杆菌为主要发酵菌种.并使之与耐氧驯化的青春双歧杆菌混合培养,表现出良好的共发酵特性.在胡萝卜汁中加入食盐1%,蔗糖2%,豆浆7%,接种量1%,种间比(La∶Ba)1∶1,在37℃下发酵24h,活菌总数可达1.2×109个/ml.以此培养液为发酵剂,对胡萝卜汁进行发酵,即可制得色泽纯正、风味优良、质地细腻的乳酸发酵胡萝卜汁.最佳发酵参数为接种量2%,砂糖4%,食盐0.3%,37℃,16h.     

胡萝卜汁双歧杆菌酸奶的研制

采用已耐氧驯化的两歧双歧杆菌,与普通乳酸菌共同发酵含胡萝卜汁的牛奶制品。试验选定了胡萝卜汁的最佳添加量,并确定生产工艺为：双歧杆菌与乳酸菌以5：3比例添加到含25％胡萝卜汁的牛乳中,于39℃发酵4．5h。制品中双歧杆菌活菌含量达107个／ml以上,风味与普通酸奶类似,营养保健价值远高于普通酸奶。     

双歧杆菌发酵黑米酸乳的研究

以双歧杆菌为主要发酵剂，黑米为主要基质进行了双歧黑米酸乳生产技术参数的研究。以黑米浆70％添加30％的牛乳、6％蔗糖、4％的混合发酵剂和0.25％的SSL-1复合稳定剂，发酵3～4小时,4℃后发酵4～5小时可获得酸甜适口、口味纯正的双歧黑米酸乳。     

双歧杆菌在大豆酸乳中的应用研究

对双歧杆菌菌种发酵大豆酸乳的可行性进行了研究,并对开发大豆酸乳的生产工艺及各种主要影响因素作了进一步探讨。实验结果证明：只要做好菌种的驯化工作和选择合适的工艺技术参数,利用两歧双歧杆菌发酵大豆酸乳是完全可行的。     

Viability and activity of bifidobacteria in yoghurt containing fructooligosaccharide during refrigerated storage

The viability of yoghurt bacteria and two commercial strains of bifidobacteria was assessed in either yoghurt containing chicory fructooligosaccharide (FOS) or without any prebiotic, during 28 days storage at 4 °C. All the products showed a decrease in the viable count of yoghurt bacteria and bifidobacteria during storage. Numbers of Lactobacillus delbrueckii ssp. bulgaricus decreased faster than those for Streptococcus thermophilus. The viability of bifidobacteria in yoghurt was affected by the strain type and the presence of FOS. Bifidobacterium animalis exhibited better stability in the yoghurt than B. longum. The recommended level of 1 million cells was exceeded for B. animalis throughout storage. The highest viable number of bifidobacteria (3.59–2.25 × 10⁷ CFU g^?1) was obtained in the product containing B. animalis and FOS. Viability of B. longum in yoghurt containing FOS remained above 10⁶ CFU g^?1 for up to 21 days, whereas this level was maintained for only 7 days for that organism in yoghurt without any prebiotic.     

Effects of storage temperature and water activity on the survival of bifidobacteria in powder form

Effects of water activity and storage temperature on survival of bifidobacteria in powder form were investigated and kinetic analyses were performed to reveal characteristics of the stability. A significant positive correlation was observed between water activity and natural logarithm of the inactivation rate constant of bifidobacteria powder, indicating that higher water activity induced lower stability of bifidobacteria in powder form. Also, higher temperature condition induced lower survival rate, which was supported by that the stability was followed the Arrhenius theory. These findings constructed a prediction model for bifidobacteria survival in powder form.     

Microstructure, rheology and storage stability of low-fat yoghurt structured by carrot cell wall particles

Plant cell wall particles derived from fruits and vegetables are natural fibre materials with a low calorie content that can be used as a healthy alternative to gum stabilisers and starches for structuring low-fat yoghurt. In this study we investigated the effect of cell wall particle (CWP) addition on the gelation kinetics, viscoelastic properties, microstructure, texture and whey loss of the set yoghurt gels as a function of CWP concentration, particle size and storage time. Three particle sizes of dried carrot CWP (d_0.5 = 34, 71 and 80 ??m) were produced from an industrial carrot pomace. Rehydrated CWP was added to skim milk prior to acidification. The results showed that the addition of carrot CWP accelerated the rate of pH reduction and induced earlier gelation. The gel viscoelastic properties were enhanced with increased CWP concentration. This was accompanied with progressive reduction in the whey loss. The smallest cell wall particles (d_0.5 = 34 ??m) gave better gel strength and lower whey loss compared to the larger CWP particles, possibly due to higher contact between the CWP and casein particles thus contributing to the stronger gel network. The CLSM images of yoghurt gels containing CWP showed that carrot CWP occupied the void space within casein particle network. The enhanced gel strength and reduced whey loss achieved by the addition of CWP were maintained throughout the 28 day storage period. The reduction of fermentation processing by almost 1 h, yet still achieving good gel properties for the yoghurt type product could be a significant benefit from a manufacturing point of review.     

胡萝卜复合汁乳酸发酵饮料贮存稳定性的研究

将发酵后的胡萝卜复合汁乳酸饮料分别存放在室温和冷藏2种条件下，定期测定饮料的糖度、酸度、风味及所含活菌数的变化情况。通过6次检测得知：随贮存时间延长，饮料糖度逐渐降低，室温贮存降低幅度大于冷藏；酸度逐渐升高，室温贮存升高幅度较大；双乙酰含量前期升高，后期基本稳定；活菌数渐减，但冷藏条件下饮料活菌数远高于室温贮存。     

Effect of synthetic antioxidants on storage stability of Khoa – a semi-solid concentrated milk product

Effect of synthetic antioxidants on storage stability of freshly prepared khoa was evaluated. Free fatty acids (FFA), peroxide value (POV) and iodine values (IV) were used to assess the development of rancidity during 30 days of storage of khoa at 25 and 45 °C. Butylated hydroxy anisole (BHA) and butylated hydroxy toluene (BHT) were added to freshly prepared khoa to extend the storage life. After 30 days of storage at 45 °C, freshly prepared khoa containing 200 ppm of BHA and BHT showed lower values of FFA (0.066%, 0.058%) and POVs (23.0, 21.0 meq/kg) than the control samples (FFA 0.320%, POV 127 meq/kg). Iodine values of khoa sample containing 200 ppm of BHA and BHT were 67 and 69 after 30 days storage at 45 °C. However, iodine value of a khoa sample without antioxidant (control) after 30 days of storage at 45 °C was 30. Similarly, khoa samples treated with 100 ppm of BHA, along with 100 ppm of BHT, showed FFA value (19.0%), POV (0.049 meq/kg) and iodine value (72) after storage for 30 days at 45 °C. These results illustrate that synthetic antioxidants inhibited the development of rancidity during storage of khoa. Therefore, storage life of khoa can easily be extended for 30 days by the addition of BHA and BHT.     

喷雾干燥对双歧杆菌存活影响的研究

为了研究喷雾干燥后双歧杆菌的存活情况，选择了三种B．longtma和两种B．infantis菌与分别含有明胶、树胶和可溶性淀粉的载体一起喷雾干燥。结果发现，喷雾干燥后双歧杆菌的存活因其种类不同而不同，同时很大程度上也取决于所用载体。比较不同的载体浓度对存活的影响，发现双歧杆菌在与10％的明胶、树胶或可溶性淀粉喷雾干燥后其存活率最高。经50℃干燥后双歧杆菌表现最大存活，温度升高则失活升高。然而温度升高引起的失活程度因所用载体不同而不同，采用可溶性淀粉失活程度最大，采用脱脂乳则最小。     

Acid production by bifidobacteria and yoghurt bacteria during fermentation and storage of milk

Three species of bifidobacteria, namelyBifidobacterium bifidum, Bifidobacterium longumandBifidobacterium adolescentiswere used in pure culture and in combination with yoghurt bacteria (B3 and SBI cultures) for the production of fermented milks. The number of bacteria during fermentation and the level of acid produced during fermentation and storage were assessed using Rogosa's modified selective agar and high performance liquid chromatography (HPLC). It was found that during fermentation all bifidobacteria exhibited growth uncoupled from acid production. Two of the species examined produced only low levels of acids when grown individually and onlyB. adolescentisproduced appreciable amounts. In mixed cultures, the level of acid was a reflection of the combination of yoghurt culture and species ofBifidobacterium, and this, observation suggests that there is a degree of influence between the cultures. During storage, the acid concentration remained quite stable in most samples. The prevention of post-production acidification that normally occurs during storage of yoghurt can be attributed to the presence of bifidobacteria, and it could be that acetic acid has a marginally inhibitory effect on theLactobacillusandStreptococcusspp.     

Evaluation of culture media for selective enumeration of probiotic strains of lactobacilli and bifidobacteria in combination with yoghurt or cheese starters

A series of culture media were evaluated for selective enumeration of 10 commercial probiotic cultures. The media M17 and MRS 5.2 were most suitable to enumerate the yoghurt starters Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus, respectively. For the enumeration of probiotic Lb. acidophilus cultures, the MRS-clindamycin medium was found to be most optimal. Selective recovery results of the tested Bifidobacterium sp. were not uniform but indicated strain-to-strain variations depending on whether NPLN or MRS-LP were used. For the enumeration of probiotic cultures of Lb. rhamnosus and Lb. paracasei, LC medium (for yoghurt products) and MRS-AC medium (for cheese products) are recommended. In conclusion, our data indicate that the choice of culture medium and methodology for selective enumeration of commercial probiotic strains in combination with starters depends strongly on the product matrix, the target group and the taxonomic diversity of the bacterial background flora in the product.     

Effect of storage environment on carrot root rots and biochemical changes during storage

 The optimum temperature and relative humidity for the development of carrot root rot during storage were found to be 20°C and 60%, respectively, and rot development increased as these environmental factors increased in magnitude. Temperature and relative humidity both enhance the biodeterioration of the carrot root through an increase in the diameter the rotted area of infected roots. The rot during storage was found to be caused by Rhizopus oryzae, Trichoderma harzianum, Botryodiplodia theobromae, Aspergillus niger and Aspergillus flavus. The fungi enter through wounds and natural openings. The amounts of total soluble sugar in rotted carrot root were substantially decreased 2 – 4 days after infection and paper chromatography showed the presence of glucose, maltose, sucrose, lactose and galactose in healthy carrot roots, while only lactose and galactose were present in infected roots. The ascorbic acid, total nitrogen, crude protein, crude fibre, fat and mineral contens in infected carrot roots reduced as the storage period was prolonged. Received: 16 October 1996     

双歧活性菠萝酸豆乳加工工艺的研究

研究了以大豆、鲜牛奶为主要原料,配以蔗糖、异麦芽低聚糖、葡萄糖、蜂蜜及菠萝果浆等,通过两歧双歧杆菌和嗜热链球菌发酵制备新双歧活性酸豆乳的加工工艺,并探讨了基料的配制及主辅发酵剂接种比例对产品质量的影响。