Survival of probiotic microflora in Argentinian yoghurts during refrigerated storage

The survival of Bifidobacterium bifidum BBI and Lactobacillus acidophilus LAI in reduced-fat (liquid) and full-fat (set) yoghurts produced with two commercial lactic starter cultures (SID and SISD) was investigated. The viability of the probiotic bacteria was also assayed in milk acidified with lactic acid at different pH values. Samples were stored at 5°C for up to 4 weeks. There was a great variability in the survival ability of the probiotic cultures in the two yoghurt types. L. acidophilus LAI demonstrated, in general, a lower resistance to the yoghurt environment than B. bifidum BBI. On the other hand, the full-fat yoghurt was a more inhibitory medium than the reduced-fat one, especially for B. bifidum BBI. Regarding the lactic starters used, the results showed that the culture SISD was clearly more inhibitory for both probiotic organisms than the culture SID. The loss of cell viability in yoghurt samples was different (higher in some cases and lower in others) from that due to lactic acid only. In general, pH values of 4.5 or lower jeopardised the cell viability of the probiotic organisms in yoghurt stored at 5°C. This work shows the importance of selecting a suitable combination of probiotic strains and starter cultures when different yoghurt types are formulated.     

Probiotic stability of yoghurts containing Jerusalem artichoke inulins during refrigerated storage

Experimentally prepared Jerusalem artichoke inulins (JAI) were compared with two commercial chicory root inulins for their prebiotic potentials in media broth model and growth-sustaining ability in non-fat yoghurts. Experimental yoghurts were made with 12% reconstituted skim milk (RSM) supplemented with 4% inulin powders, inoculated with mixed cultures of Lactobacillus casei LC-01, Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (1:0.5:0.5 based on supplier’s recommendation) and incubated overnight at 37 °C. Non-supplemented yoghurt was prepared from 16% RSM and used as control. The survival and acidifying activity of lactic and probiotic cultures in all yoghurts were investigated on weekly intervals during the shelf life of 28 days at 4 °C. Incorporation of JAI resulted in improved viability of LC-01, maintaining >7.0 log CFU/g during cold storage but did not affect the viability of yoghurt bacteria in comparison with the control.     

Growth characteristics of agrowaste‐immobilised lactobacilli in soymilk during refrigerated storage

We aimed at evaluating agricultural wastes as solid supports for the immobilisation of lactobacilli in a liquid media, namely soymilk. Lactobacillus acidophilus FTDC 1331, L. acidophilus FTDC 2631, L. acidophilus FTDC 2333, L. acidophilus FTDC 1733 and L. bulgaricus FTCC 0411 were immobilised on solid supports produced from durian (Durio zibethinus), cempedak (Artocarpus champeden) and mangosteen (Garcinia mangostana). The immobilised cells were inoculated into soymilk and stored at 4 °C over 168 h. Soymilk inoculated with non‐immobilised cells was used as the control. Immobilised cells showed higher survivability over 168 h compared to the control, accompanied by higher reduction of simple sugars and oligosaccharides in soymilk. Higher growth and higher utilisation of substrates also led to the higher production of lactic and acetic acids, which lowered the pH in soymilk compared to the control. Our results illustrated that agrowastes could be used as immobilisers to enhance the growth of lactobacilli in a liquid medium.     

Quality and microbial stability of partially baked bread during refrigerated storage

Partially baked bread was prepared and stored at 1 °C or 7 °C for 28 days. Periodically, this product was subjected to moisture, hardness, and microbiological analyses. After storage, the baking process of part-baked bread was completed and product evaluated according to microbiological, physical, and sensorial tests, as well as hardness analysis. Part-baked breads stored at 7 °C showed mold growth at day ninth, while the product stored at 1 °C did not show mold growth through 28 days. The full-baked bread obtained from part-baked samples stored at 1 °C showed higher values of hardness and change in crumb hardness, and lower sensorial quality than bread from part-baked samples stored at 7 °C. Moisture content, specific volume, and width/height ratio in the full-baked bread were not affected by storage time and temperature.     

鲜切生菜贮藏期病原真菌的分离及鉴定

以鲜切生菜为试材,采用传统的微生物分离手段分离纯化在4℃贮藏过程中引起腐烂的主要病原真菌,通过回接试验验证其致病性。通过形态学观察、分子生物学鉴定以及系统发育学分析其分类地位。结果表明:从货架期终点的鲜切生菜中共筛选出菌落形态差别比较明显的病原真菌4株,经鉴定其依次为短柄帚霉(Scopulariopsis brevicaulis)、扩展青霉(Penicillium expansum)、翅孢壳霉(Emericellopsis sp).和暗孢节菱孢(Arthrinium phaeospermum),4种病原真菌中扩展青霉为主要致病菌。     

Effect of probiotic cultures on the stability of anthocyanins in blueberry yoghurts

Dependent on anthocyanin pigments, colour is one of the main quality factors of berry products. In this paper we assess the influence of probiotic bacteria on the degradation rate of anthocyanins in yoghurts with a highbush blueberry preparation during storage. Four types of yoghurts were prepared: first with the yoghurt starter culture YC-X16 only (Steptococcus thermophilus and Lactobacilllus delbrueckii subsp. bulgaricus) and three more, each with the starter culture YC-X16 and one of the three probiotic cultures: Bb-12, La-5 and LCP, respectively (Bif. animalis subsp. lactis – Bb-12; Lactobacillus. acidophilus – La-5 and Lactobacillus. paracasei subsp. paracasei – LCP).Derivatives of malvidin were the predominant anthocyanins in the tested yoghurts. Degradation of pigments occurred in accordance with the first-order reaction and its half-life time depended on the bacterial cultures. Anthocyanins in the probiotic yoghurt made with LCP culture were characterized by lower stability than those made with the other bacterial cultures. The impact of lactic bacteria or their metabolic products on the stability of anthocyanins in berry yoghurts shows that an appropriate selection of culture for production of yoghurt is recommended.     

Influence of addition of raffinose family oligosaccharides on probiotic survival in fermented milk during refrigerated storage

The influence of the addition of raffinose family oligosaccharides (RFOs) extracted from lupin seeds on the survival of Bifidobacterium lactis Bb-12 and Lactobacillus acidophilus La-5 in fermented milk during 21 days of storage in refrigerated conditions was studied. For this purpose, viability and metabolic activity (expressed as pH, lactic and acetic acid production and utilization of soluble carbohydrates) of probiotic bacteria were determined. Retention of viability of B. lactis Bb-12 and L. acidophilus La-5 was greater in fermented milk with RFOs. The pH of probiotic fermented milk at 21 days of storage was lower (4.27) compared with probiotic fermented milk with RFOs (4.37). The highest levels of lactic and acetic acid were produced in probiotic fermented milk without RFOs compared with probiotic fermented milk with RFOs during storage at 4 °C. Soluble carbohydrates were utilised in fermented milk with and without RFOs, respectively, for maintaining B. lactis Bb-12 and L. acidophilus populations during refrigerated storage. In conclusion, all these experiments provide convincing evidence that RFOs have beneficial effects on the survival of these probiotic cultures in dairy products. As a result, such stored dairy products containing both probiotics and prebiotics have synergistic actions in the promotion of health.     

Effect of long‐chain inulin on the texture profile and survival of Lactobacillus paracasei ssp. paracasei in set yoghurts during refrigerated storage

The effects of adding inulin at 20 g/L as a fat replacer and probiotic bacteria on the physicochemical and textural characteristics of yoghurt were studied. The ability of long‐chain inulin to improve the probiotic (Lactobacillus paracasei ssp. paracasei) bacteria viability in yoghurt was investigated. The addition of inulin made the texture (firmness, cohesiveness, adhesiveness and gumminess) of skimmed yoghurt similar to that of whole yoghurt, demonstrating the role of inulin as a fat replacer. However inulin increased syneresis and did not influence the viability of probiotic bacteria in the yoghurts. The addition of probiotic bacteria in yoghurts improved syneresis and increased firmness and gumminess.     

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.     

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。     

Suitability of whey and buttermilk for the growth and frozen storage of probiotic lactobacilli

The growth of six probiotic commercial strains of lactobacilli was assessed in reconstituted dried whey and buttermilk supplemented with yeast extract, meat peptone, soy peptone, tryptone or casein acid hydrolysate at 0.3%, 0.6% or 1%. The addition of 1% glucose was also tested. Growth and acidification kinetics were determined at 37°C using MRS broth and a commercial culture medium as references. The suitability of whey and buttermilk as cryoprotectants at –20°C and –70°C was also assessed. Whey and buttermilk with 0.3% yeast extract were chosen for the growth of probiotic lactobacilli, since no satisfactory growth was observed without an external nitrogen source, whereas glucose did not improve the growth of any of the strains assayed. In general, buttermilk performed as satisfactorily as the reference media. The effectiveness of these media as cryoprotectants was strain dependent: skimmed milk and whey were the most suitable ones, especially for long-term storage at –20°C. However, at –70°C, no significant differences were observed between the culture media assessed. The use of whey or buttermilk as culture media for the production of probiotic lactic acid bacteria and for their cryopreservation implies a novel use of these low-cost products, offering an alternative way of utilizing the by-products of the dairy industry, helping to minimize their negative impact on the environment.     

Oxidative stability of gelatin coated pork at refrigerated storage

As consumers are chiefly concerned with odor and appearance, refrigerated meats have a greater possibility of rejection due to their perishability. A treatment was designed to preserve the quality parameters such as color and oxidation rate. The treatment encompassed coating pork loin samples with aqueous porcine gelatin solutions (175 bloom) at three concentrations (0%, 10% and 20%) and studying its effect on lipid oxidation, protein oxidation, oxidation pre-cursors, color and purge of meat. Vacuum packed Longissimus dorsi muscle was cut into 10 × 5 × 1 cm samples and randomly dipped in one of three solutions. Samples were stored at 4 °C and analyzed for thio-barbituric acid reactive substances, metmyoglobin content, protein carbonyls, heme iron content and color change. There was a significant difference (p < 0.05) for TBARS values, protein carbonyls, heme iron content, total color change, metmyoglobin content with treatments maintaining values more similar to a fresher product when compared to control on days 3, 5 and 7. There was no significant difference (p > 0.05) between 10% and 20% gelatin coating on any of the parameters between storage days.     

Effect of refrigerated storage temperature on the viability of probiotic micro-organisms in yogurt

The effect of refrigerated storage temperature was studied at 2, 5 and 8°C on the viability of probiotics in ABY ( Lactobacillus acidophilus, Bifidobacterium lactis BB-12 and yogurt bacteria. Bulgaricus , i.e. Streptococcus thermophilus and Lactobacillus delbrueckii ssp. Bulgaricus ) probiotic yogurt. The study was carried out during a 20-day refrigerated storage period to identify the best storage temperature(s). Also, the viability change of the probiotic micro-organisms was analysed at 5-day intervals throughout the refrigerated storage period. After 20 days, storage at 2°C resulted in the highest viability of L. acidophilus , whereas for Bifidobacterium lactis the highest viability was obtained when yogurt was stored at 8°C.     

Effect of chitooligosaccharide from squid pen on gel properties of sardine surimi gel and its stability during refrigerated storage

Effect of chitooligosaccharide from squid pen prepared using lipase (COS-L) at various concentrations (0–30 g kg⁻¹) on gel properties of sardine surimi gel was investigated. Breaking force (BF) and deformation (DF) of gel were increased, when COS-L level was increased up to 10 g kg⁻¹ (P < 0.05). Water holding capacity and whiteness of gel were improved with the addition of COS-L than those of control. Gel added with 10 g kg⁻¹ COS-L had denser network with higher likeness score for all sensory attributes, compared to control. When gel incorporated with 10 g kg⁻¹ COS-L was stored at 4 °C, BF, DF and whiteness were maintained during 10 days of storage. Textural properties of surimi gel added with COS-L were higher than those of control throughout storage. Thus, incorporation of 10 g kg⁻¹ COS-L could improve gel properties of sardine surimi gel and retarded the deterioration of gel properties during refrigerated storage.     

Quality changes of fish patties produced from anchovy during refrigerated storage

Quality changes of anchovy patties at the storage temperature of 4 °C were investigated. After patties had been prepared using minced anchovy meat they were stored in a refrigerator. Quality control analyses were conducted for every day of storage. Total volatile basic nitrogen and thiobarbutiric acid values increased, and acidity and sensory scores decreased during the storage. The peroxide value significantly increased until the fifth day of storage then decreased on days 5 and 6 of storage. Anchovy patties were consumable up to 6 days.     

Proteolytic degradation of ewe milk proteins during fermentation of yoghurts and storage

Yoghurts are mostly produced from cow milk and to a very limited extent from ewe milk. The evolution of caseins and whey proteins in ovine milk submitted to different thermal treatments (63 degrees C/30 min; 73 degrees C/15 min; 85 degrees C/10 min or 96 degrees C/5 min) was followed during fermentation of yoghurts and during their storage up to 14 days, using two different sets of starters. One set of starter LAB was a "ropy" culture (YC-191), which is a well-defined mixed strain culture containing Streptococcus thermophilus ST-143 and Lactobacillus delbrueckii subsp. bulgaricus (LB-18 and LB-CH2). The other set of starter bacteria (YC-460) was a standard yoghurt culture("non-ropy") containing mixed strain culture of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Contents of free amino groups in produced yoghurts increased gradually during the fermentation, up to a maximal value obtained after 4 h fermentation, then they did not change significantly during storage of yoghurt produced with YC-191 starter. In contrary, a large drop in the amount of free amino groups was observed in the first 24 h of storage in the case of yoghurt made with YC-460 indicating that microorganisms continue still to grow in low temperatures. During fermentation and storage of both yoghurt types, alpha-lactalbumin was hydrolyzed to a slightly bigger extent than beta-lactoglobulin. During fermentation, beta-casein was slightly more degraded than alpha(s)-caseins; however, the opposite was observed during storage up to 14 days. Generally, a more intense heat pretreatment led to a higher degradation of whey proteins and caseins during fermentation and storage. Differences in proteolytic activity between the two starters used (whey proteins more degraded by YC-191; caseins more degraded by YC-460) may lead to improvement in production and formulation of yoghurts differing in their physicochemical and rheological properties.     

啤酒中疏水性蛋白质提取鉴定及其对于泡沫性能的影响的研究

利用蛋白疏水层析色谱法(HIC)从啤酒泡沫中分离疏水性蛋白,研究发现,HIC依次分离的蛋白组分表面疏水性增强的同时,泡沫稳定性随之增强,说明HIC分离得到强疏水性多肽对于啤酒泡沫稳定性具有较明显的积极作用,而弱疏水性多肽的影响效果不明湿.此外通过质谱(Mass Spectrometry)鉴定结果显示所得到的疏水性蛋白质为蛋白质乙,通过对啤酒酿造过程中的关键控制点的跟踪,确定了啤酒酿造过程中,发酵阶段疏水性蛋白质的损失最为严重,对啤酒泡沫质量的影响最大.     

自然发酵酸菜中乳杆菌的分离鉴定与多态性分析

以自然发酵的东北酸菜汁液为实验样品,对其中的乳杆菌进行了分离纯化,共得到乳杆茵34株:使用生理生化实验对其中的10株乳杆菌进行了鉴定;并采用16S rDNA PCR-RFLP方法对这10株乳杆菌进行了遗传多态性的分析.结果表明它们分属5个遗传型.     

东北酸菜中产胞外多糖乳杆菌的分离筛选及其在酸乳中的应用

从东北酸菜中分离出97株乳杆茵菌株,并筛选出两株产酸快、产胞外多糖(EPS)的乳杆茵2号菌株和9号菌株.初步鉴定前者为干酪乳杆茵,后者为植物乳杆茵.在发酵剂(保加利亚乳杆菌和嗜热链球茵,LS)中混入等量的菌株2或9培养物(脱脂乳),所制备的酸乳中EPS质量浓度达34 mg/L.活茵总数可迭2×108mL-1以上.酸乳物性测定结果显示,产EPS菌株发酵的酸乳弹性好,相对粘度高,持水力强,乳清析出少.感官评定结果显示,与没有添加产EPS茵株发酵的酸乳相比,产EPS茵株LS+2与LS+9组合发酵酸乳风味分值较高,组织状态的分值差别较大,而酸度上没有显著差异.与物性测定结果一致.