Synthesis and utilisation of folate by yoghurt starter cultures and probiotic bacteria

Thirty-two bacterial isolates from species commonly used in yoghurts and fermented milks were examined for their ability to synthesise or utilise folate during fermentation of skim milk. The organisms examined included the traditional yoghurt starter cultures, Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, and probiotic lactobacilli, bifidobacteria, and Enterococcus faecium. Folate was synthesised by S. thermophilus, bifidobacteria, and E. faecium. S. thermophilus was the dominant producer, elevating folate levels in skim milk from 11.5 ng g⁻¹ to between 40 and 50 ng g⁻¹. Generally, lactobacilli depleted the available folate in the skim milk. Fermentations with mixed cultures showed that folate production and utilisation by the cultures was additive. Fermentations using a combination of Bifidobacterium animalis and S. thermophilus resulted in a six-fold increase in folate concentration. Although increased folate levels in yoghurts and fermented milks are possible through judicious selection of inoculum species, the folate levels remain relatively low in terms of recommended daily allowance.     

The viability of three probiotic organisms grown with yoghurt starter cultures during storage for 21 days at 4°C

This study investigated the viability of probiotic ( Lactobacillus acidophilus LA5, Lactobacillus rhamnosus LBA and Bifidobacterium animalis subsp . lactis BL-04) in milk fermented with Lactobacillus delbrueckii subsp . bulgaricus LB340 and Streptococcus thermophilus TAO (yoghurt – Y). Each probiotic strain was grown separately in co-culture with Y and in blends of different combinations. Blends affected fermentation time(s), pH and firmness during storage at 4°C. The product made with Y plus B. animalis subsp . lactis and L. rhamnosus had counts of viable cells at the end of shelf life that met the minimum required to achieve probiotic effect. However, L. acidophilus and L. delbrueckii subsp . bulgaricus were inhibited.     

Survival and activity of selected probiotic organisms in set-type yoghurt during cold storage

The growth and metabolism of two probiotic organisms (L. acidophilus LAFTI^® L10 and Lactobacillus casei LAFTI^® L26) and a regular yoghurt culture (L. delbrueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus St1342) were studied in yoghurt containing 0.5%, 1.0%, and 1.5% (w/v) of high amylose corn starch powder (Hi-maize^®) or inulin. Viable cell counts of probiotic organisms, their metabolites and proteolytic activities, and viscosity of the yoghurts were determined during refrigerated storage for 28 d at 4 ^oC. In the presence of inulin, cultures showed better retention of viability (8.0 log cfu g⁻¹) in comparison with that of Hi-maize, which had a reduction by one log cycle. Lower concentrations of 0.5–1.0% Hi-maize improved (P<0.05) the production of propionic acid and also increased proteolytic activity of probiotic organisms substantially. A greater release of free amino acids may have sustained better growth of the organisms in yoghurts. Supplementation with either Hi-maize or inulin increased the viscosity of probiotic yoghurts significantly (P<0.05).     

Effect of the addition of pulse ingredients to milk on acid production by probiotic and yoghurt starter cultures

Pulses contain carbohydrates, proteins, minerals and vitamins which are essential requirements in the human diet and which could also serve as growth nutrients for probiotic and yogurt starter cultures. In this study, milk supplementation with pulse ingredients is examined as a means to increase the nutritional properties of yogurt and probiotic type beverages. The acid production rate of two yogurt starters (A and B) and two probiotic cultures (Lactobacillus rhamnosus and Lactobacillus acidophilus) was followed in milk supplemented with the following soy and pulse ingredients: pea protein, chickpea flour, lentil flour, pea fibre, soy protein concentrate and soy flour. The pulse ingredients had no negative effect on the acidification trends of the fermented milks. On the contrary, with yogurt culture B, pea fibre, pea protein and lentil flour significantly enhanced the acidification rate. All ingredients used for supplementation improved the acidification rate of probiotic cultures, and the highest effects were obtained with lentil and soy flour. Lentil flour had the lowest pH after 12 h which was significantly lower than the product enriched with the same quantity of skim milk powder. The effect of ingredient supplementation on the microbial composition (ratio of cocci to bacilli) of the yoghurt products was also examined. The ratio of cocci to bacilli was between 1.8 and 2.5 for all supplemented yogurt samples obtained with culture A, and these variations were not judged to be statistically significant (p < 0.05). With yogurt products obtained from culture B, however, there was a higher proportional level of lactobacilli in all supplemented samples, as compared to the milk control; the enhanced growth of the lactobacilli was particularly noted when lentil flour was added to milk.     

Effect of packaging materials and dissolved oxygen on the survival of probiotic bacteria in yoghurt

The effects of packaging materials on the dissolved oxygen and the survival of the probiotic bacteria in yoghurt were studied. Oxygen adapted and non‐oxygen adapted strains of Lactobacillus acidophilus and Bifidobacterium spp. were incorporated in yoghurts, which were packaged in oxygen permeable high‐impact polystyrene (HIPS), oxygen‐barrier material (Nupak^TM) and Nupak^TM with an oxygen scavenging film (Zero₂^TM). During storage the dissolved oxygen increased steadily in HIPS packaged yoghurt whereas it remained low in yoghurts packaged in Nupak^TM and Zero₂^TM. In all yoghurts, no significant decreases were observed in the viability of either oxygen adapted or non‐oxygen adapted cells of L. acidophilus and Bifidobacterium spp. Thus, although the dissolved oxygen in yoghurt can be influenced by the type of packaging material, it may not affect the survival of probiotic bacteria in yoghurts.     

Effect of refrigerated storage time on the viability of probiotic bacteria in fermented probiotic milk drinks

The viability of Lactobacillus acidophilus and Bifidobacterium lactis in fermented milks A, B and AB, containing respectively these strains separately and mixed, was studied over 21 days of storage at 5°C. Samples were analysed for titratable acidity and viable cell counts of probiotics. Milks A and AB showed post-acidification mainly due to the β-galactosidase activity of L. acidophilus . Generally, the viability of the probiotics decreased during storage, whereas, in some cases, the proteoletic activity of L. acidophilus resulted in a higher survival rate of the probiotics even with the adverse effects of low temperature and organic acids.     

Production of traditional Greek yoghurt using Lactobacillus strains with probiotic potential as starter adjuncts

Lactobacillus plantarum ACA-DC 146 and L. paracasei subsp. tolerans ACA-DC 4037 were examined for their potential application as adjuncts in the production of traditional Greek set-type yoghurt. Both strains displayed low milk acidification activity, while no inhibition was observed towards or from the yoghurt starters used. Yoghurt produced with L. paracasei subsp. tolerans ACA-DC 4037 exhibited the best sensory properties, with a rich traditional smooth taste, and the strain was selected for further trials. Yoghurt produced with this strain as an adjunct had good physicochemical properties. After 2 weeks of refrigerated storage, microbial loads (>7.0 log cfu g⁻¹) were in accordance with international recommendations and guidelines for probiotic and starter cultures in milk products. Increasing the microbial load further, using concentrated and encapsulated inocula (10–11 log cfu g⁻¹), gave yoghurt with long fermentation times and poor organoleptic properties.     

酸乳中益生细菌活性影响因素的研究概况

阐述了发酵型酸乳中益生菌的种类，特性和活性条件。重点讨论了益生菌的（特别是酸乳中常用的乳酸细菌）保健功能，探讨了酸乳中益生菌活性抑制因素和提高益生菌活性的方法，目的在于探求和开发生产高质量，高活性益生菌酸乳途径。     

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.     

泡菜中益生性乳酸菌的筛选和鉴定

以筛选具益生特性的泡菜发酵剂为目的,从15个泡菜样品中通过比较溶钙圈的大小分离出59株产酸能力较强的菌株。通过测定发酵液的酸度以及耐酸性和耐胆汁盐试验,再从中筛选出2株产酸能力和在胃肠道生存能力都强的菌株A18和B17。经形态特征及16S rDNA序列分析,确定A18和B17均属于植物乳杆菌。     

益生菌对黄曲霉毒素的作用

益生菌的功能性引起了广泛的关注。介绍益生菌对强致癌物黄曲霉毒素作用的研究情况,包括益生菌对黄曲霉毒素产生的抑制作用及对黄曲霉毒素的去除作用。     

Effect of acidification on the activity of probiotics in yoghurt during cold storage

The viability of Lactobacillus acidophilus LAFTI^® L10, Bifidobacterium lactis LAFTI^® B94, and L. paracasei LAFTI^® L26 and their proteolytic activities were assessed in yoghurt at different termination pH of 4.45, 4.50, 4.55, and 4.60 in the presence of L. delbrueckii ssp. bulgaricus Lb1466 and Streptococcus thermophilus St1342 during 28 days of storage at 4 °C. All strains achieved the recommended level of 6.00 log cfu g⁻¹ of the product with L. acidophilus LAFTI^® L10 and L. paracasei LAFTI^® L26 exceeding the number to 8.00 and 7.00 log cfu g⁻¹, respectively. Lactobacilli strains showed a good cellular stability maintaining constant concentration throughout storage period regardless of termination pH. On the other hand, the cell counts of B. lactis LAFTI^® B94 decreased by one log cycle at the end of storage. The presence of probiotic organisms enhanced proteolysis significantly in comparison with the control batch containing L. delbrueckii ssp. bulgaricus Lb1466 and S. thermophilus St1342 only. The proteolytic activity varied due to termination pH, but also appeared to be strain related. The increased proteolysis improved survival of L. delbrueckii ssp. bulgaricus Lb1466 during storage resulting in lowering of pH and production of higher levels of organic acids, which might have caused the low cell counts for B. lactis LAFTI^® B94.     

酸乳发酵菌的分离及酸乳发酵工艺的研究

采用选择培养基对酸乳发酵菌种分离、筛选出优良酸乳生产菌株，并用生理生化指标对其进行鉴定。初步鉴定为嗜热链球菌和保加利亚杆菌。并采用2种混合发酵实验，结果表明：接种量4％、发酵时间5h，2种菌种比例为2：l，发酵酿制的酸乳质量较佳。     

Effects of fructooligosaccharide and whey protein concentrate on the viability of starter culture in reduced-fat probiotic yogurt during storage

ABSTRACT:  Viability of yogurt starter cultures and Bifidobacterium animalis was assessed during 28 d storage in reduced-fat yogurts containing 1.5% milk fat supplemented with 1.5% fructooligosaccharide or whey protein concentrate. These properties were examined in comparison with control yogurts containing 1.5% and 3% milk fat and no supplement. Although fructooligosaccharide improved the viability of Streptococcus thermophilus , Lactobacillus delbrueckii subs. bulgaricus, and Bifidobacterium animalis , the highest growth was obtained when milk was supplemented with whey protein concentrate in reduced-fat yogurt ( P < 0.05). Supplementation with 1.5% whey protein concentrate in reduced-fat yogurt increased the viable counts of S. thermophilus , L. delbrueckii subs. bulgaricus, and B. animalis by 1 log cycle in the 1st week of storage when compared to control sample. Similar improvement in the growth of both yogurt bacteria and B. animalis was also obtained in the full-fat yogurt containing 3% milk fat and no supplement. Addition of whey protein concentrate also resulted in the highest content of lactic and acetic acids ( P < 0.05). A gradual increase was obtained in organic acid contents during the storage.     

Effect of cryoprotectants,prebiotics and microencapsulation on survival of probiotic organisms in yoghurt and freeze-dried yoghurt

The survival of probiotic microorganisms including Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus rhamnosus and Bifidobacterium spp. was evaluated in yoghurt and freeze-dried yoghurt after processing and storage. The effectiveness of microencapsulating probiotic organisms as well as adding cryoprotectants and prebiotics in improving their viability was also investigated. The viability of Bifidobacterium infantis 17930 and L. rhamnosus GG was reduced by 0.07 log, while that of L. casei 1520 and Bifidobacterium longum 1941 was reduced by 0.28 and 0.39 log, respectively. There was a 7% improvement in the viability of L. casei 1520 when cryoprotectant ‘Unipectine™ RS 150’ was added at 2.5% (w/v). The prebiotic ‘Raftilose^®P95’ when added at 1.5% w/v to yoghurt improved the viability of the combined selected probiotic organisms by 1.42 log during four weeks of storage at 4 °C. Microencapsulation with alginate improved viability of combined selected probiotic organisms by 0.31 log in freeze-dried yoghurt stored at 21 °C.     

益生菌酸奶的工艺研究

以保加利亚乳杆菌(Lb)、嗜热链球菌(St)、干酪乳杆菌(Lc)、罗依氏乳杆菌(Lr)混合菌发酵,得到益生菌酸奶.正交结果表明,干酪乳杆菌、罗依氏乳杆菌可以应用于酸奶发酵,发酵工艺为:保加利亚乳杆菌:嗜热链球菌:干酪乳杆菌:罗依氏乳杆菌为3:3:2:2,发酵温度39℃,接种量0.25%(DVS),加糖量8%,凝乳时间5h.     

Rheology and sensory profiling of set-type fermented milks made with different commercial probiotic and yoghurt starter cultures

Varieties of set-type probiotic fermented milks and yoghurt were made from recombined skimmed milk powder, anhydrous milk fat and commercial starter cultures (direct-to-vat inoculation, DVI). Serum separation of fermented milks and yoghurt with high initial rates of syneresis proceeded more slowly than separation of those with low initial rates of syneresis; the decrease during the storage period was linear and the rate of decrease was dependent on the type of starter culture used. The firmness of these products increased over the time period, and the rate of increase was linear and independent of the starter culture. The production of exopolysaccharide material by the starter microflora also influenced syneresis and firmness of the probiotic fermented milks. The average profiles of organic acids of all the products were similar with the exception of two starter cultures that generated the highest level of acetic acid. After cross-validation, classification of the starter type using the organic acids values correctly predicted the type of starter culture used for 23 out of 24 samples. All the sensory attributes were influenced by the type of starter culture used and the trial, with the exception of viscosity character; acetic acid production by the microbial species of the starter cultures had the greatest influence on the flavour attribute.     

Effect of encapsulated Lactobacillus plantarum as probiotic on dry-sausages during chilled storage

The impact of free and encapsulated Lactobacillus plantarum addition on the physicochemical and microbiological properties during chilled storage (60 days) of dry-fermented sausages have been studied. Control (C) treatment was performed without probiotic incorporation, and the reformulation was comprised of L. plantarum as free cells (F) in alginate spheres (EA), in water-in-oil simple emulsion (ESM) and in water-in-oil-in-water double emulsion (EDM). After 60 days of storage, lower (P < 0.05) lipid oxidation was observed in F and EA (0.602–0.625 mg MDA kg⁻¹) while it was higher (P < 0.05) in EDM (1.949 mg MDA kg⁻¹). Treatments C and ESM presented intermediate TBARS levels compared to other treatments at the end of storage. All dry-fermented sausages presented high levels of lactic acid bacteria during the whole chilled storage (8.06–9.29 log CFU g⁻¹ at day 0 and 8.02–9.35 log CFU g⁻¹); however, EA treatment presented the highest L. plantarum viability even at 60 days of storage (8.34 log CFU g⁻¹). Therefore, the strategy of L. plantarum inoculation in alginate spheres seems to be the best strategy for the delivery of probiotics during chilled storage of dry-fermented sausages.     

不同混生模式对酸奶发酵剂球杆菌比例的影响

目的:探讨了酸奶菌株的混合发酵特性及最佳的混合模式。方法:在2.5L罐中观察不同发酵温度、pH、接种比例和接种时段对德氏乳杆菌保加利亚亚种KLDS1.9201和唾液链球菌嗜热亚种KLDS3.021混合培养的影响。结果:不同的混生模式均关系到酸奶菌株之间共生的问题。培养条件为42℃和pH6.2,接种比例为KLDS1.9201∶KLDS3.0201=2∶1,或是KLDS3.0201推迟2h接种,将有利于发酵剂菌株混合培养时的球杆菌比例平衡。结论:不同的混生模式是促进酸奶混合菌株协同生长的重要前提。