Probiotic viability and physico-chemical and sensory properties of plain and stirred fruit yogurts made from goat's milk

Probiotic plain and stirred fruit yogurts were made from goat's milk using bacterial cultures comprising, Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and Propionibacterium jensenii 702. The products were stored at 4°C for 4weeks, during which time the viability of the yogurt starter culture and probiotic bacteria was analysed weekly. P. jensenii 702 demonstrated the highest viability (10(8)cfu/g) in all types of yogurt throughout the storage period, while the viability of the bifidobacteria (～10(7)cfu/g) also remained above the minimum therapeutic level. The viability of L. acidophilus LA-5 fell below 10(6)cfu/g in yogurts, however, the addition of fruit juice appeared to support the viability of lactobacilli, with higher microorganism numbers observed in fruit yogurts than in plain yogurt throughout the shelf life. Addition of fruit juice significantly increased the syneresis, and decreased viscosity and water holding capacity of yogurts (p<0.05), and also enhanced their sensory acceptability.     

The effects of commercial starter culture and storage temperature on the oxidative stability and diacetyl production in butter

In this study, the effects of four different direct-vat-set (DVS) commercial starter cultures (CHN11, CHN22, EZAL BT001 and MM100) and storage temperatures (4  ±  1 and −18  ±  2°C) on the oxidative stability and diacetyl production in butter during a 4-month period were investigated. Samples were taken from butter on days 3, 30, 60, 90 and 120. Analyses of titration acidity, peroxide value, free fatty acids and diacetyl contents of the samples taken were carried out. The effects of the starter cultures on the peroxide value and diacetyl contents were found to be significant ( P  < 0.01) while the storage temperatures significantly affected all parameters tested. Interaction between the type of culture and storage temperature was significant for free fatty acids ( P  < 0.05) and diacetyl content ( P  < 0.01).     

Evaluation of volatile compounds and free fatty acids in set types yogurts made of ewes’, goats’ milk and their mixture using two different commercial starter cultures during refrigerated storage

Six different types of yogurt were manufactured from Damascus goat milk, Awassi ewe milk and a mixture of equal portions of the 2 species of milk using 2 types of commercial yogurt cultures (CH-1 and YF-3331). Yogurts were chemically analysed at 1, 7, 14 and 21 days of storage. Results showed that cultures significantly affected acetaldehyde (P < 0.05), acetone (P < 0.05) and diacetyl (P < 0.001) contents. Type of milk significantly influenced acetaldehyde (P < 0.05), diacetyl (P < 0.001), acetoin (P < 0.001) and ethanol (P < 0.05) levels. Significant variations occurred in acetaldehyde (P < 0.001) and acetoin (P < 0.05) contents during the storage. Short-chain free fatty acids were the highest in ewes’ milk yogurt made with culture YF-3331, and increased during storage, while the levels of medium-chain free fatty acids, except for decanoic acid, were unchanged and the amount of long-chain free fatty acids decreased during storage. Cultures used and types of milk had no effect on long-chain free fatty acids in yogurts.     

Characterization of functional, biochemical and textural properties of synbiotic low-fat yogurts during refrigerated storage

This study examined the influence of exopolysaccharides (EPS) produced in situ on the viability of Streptococcus thermophilus, Lactobacillus delbrueckii ssp. bulgaricus and probiotics, the proteolytic and ACE-inhibitory activities, and textural and rheological properties of inulin-containing probiotic yogurt during refrigerated storage. Two types of yogurt were prepared using strains of S. thermophilus not producing EPS (NEPY) and producing EPS (EPY). The yield of crude EPS increased (by 2.4 times) until day 21 of storage. Presence of EPS showed a protective effect on the survival of L. delbrueckii ssp. bulgaricus and Lactobacillus acidophilus but not on S. thermophilus, Lactobacillus casei and Bifidobacterium longum. No changes in post-acidification, lactic acid content or the ACE-inhibition activity of the two types of yogurt were observed. Overall, EPS containing yogurts exhibited higher proteolysis in the presence of inulin and probiotics (0.698 units) than the corresponding control (0.563 units). The storage and loss moduli (Pa), yield stress (Pa), consistency index (Pa s) and thixotrophic behaviour (Pa s⁻¹) of both samples were similar at day 1 and the influence of EPS was observable only after day 7. Such a variation of the effect of EPS on the textural and rheological properties of low-fat yogurt appears to be partially due to the presence of probiotics.     

Monitoring the chemical and textural changes during ripening of Iranian White cheese made with different concentrations of starter

The effect of the concentration of starter inoculated to milk on the composition, free tyrosine-tryptophan content, microstructure, opacity, and fracture stress of Iranian White cheese (IWC) was studied during 50 d of ripening in brine. Three treatments of cheese were made using 1-fold (IWC1S), 2-fold (IWC2S), and 4-fold (IWC4S) concentrations of a direct-to-vat mesophilic mixed culture containing Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. lactis as starter. As ripening progressed, moisture and protein contents of the treatments continuously decreased, whereas their total ash, salt, and salt in moisture contents increased. Fat content and pH of cheeses remained stable during ripening. The pH of cheese milk at the time of renneting, which decreased by increasing the concentration of starter (6.57, 6.49, and 6.29 for IWC1S, IWC2S, and IWC4S, respectively), significantly affected most of the chemical characteristics and opacity of cheese. Lower pH values at renneting decreased moisture and ash contents, whereas cheese protein content increased. The concentration of free tyrosine-tryptophan in curd increased at first 29 d but decreased between d 29 and 49 of aging. The changes observed in cheese whiteness followed the changes in moisture content of the treatments. As the concentration of starter inoculated to milk increased, the value of fracture stress at a given ripening time significantly decreased, leading to a less resistant body against applied stress. A similar trend was also observed for fracture strain during cheese ripening. The micrographs taken by scanning electron microscopy provided a meaningful explanation for decrease in the value of fracture stress. As the cheese ripening progressed or the concentration of starter increased, the surface area occupied by the protein fraction in cheese microstructure decreased, leading the way to lower the force-bearing component in cheese texture.     

An economic evaluation of freeze-dried kefir starter culture production using whey

An economic study is presented in which industrial-scale production of freeze-dried kefir starter culture is discussed based on results on a laboratory scale. Industrial scale-up was based on a 3-step process using 3 bioreactors of 100, 3,000, and 30,000 L for 300 kg of freeze-dried culture/d of plant capacity. The major cost component of the total investment was the freeze-drying machinery, which consisted of 57% of the total investment. Production cost was reduced from €15.4/kg ($18.5/kg) to ∉2.9/kg ($3.5/kg) when the production capacity was increased from 30 to 900 kg/d. An economic analysis revealed a 3.5-fold increase in production cost compared with the corresponding production cost of the wet product, with an added value of up to ∉10.8 × 10⁹ ($13.0 × 10⁹) within the European Union.     

The effects of some starter cultures on the properties of Turkish White cheese

White cheese samples were manufactured from bovine milk using three different commercial direct vat starter cultures (DVS-1, -2 and -3) and a lyophilized culture, and ripened at 4 ± 1°C for 90 days. The composition, titratable acidity and ripening indices of the cheese samples were determined on the 2nd, 30th, 60th and 90th days of ripening. The ratios of total solids, protein and fat were higher for cheeses manufactured using DVS-2 and lyophilized cultures but the titratable acidity in cheese produced using DVS-3 and lyophilized cultures was higher (P < 0.01). The mean value of the ripening indices of the cheese produced using the lyophilized culture was lower than the cheeses produced with added DVS cultures (P < 0.05). The total solids, ash, salt ratios, titratable acidity and ripening indices values increased for all types of white cheeses during ripening (P < 0.05).     

Influence of an autochthonous starter culture and a commercial starter on the characteristics of Tenerife pasteurised goats’ milk cheese

Two batches of Tenerife cheese were produced from pasteurised goats’ milk, one with a commercial starter and another with an autochthonous starter consisting of three selected strains of lactic acid bacteria isolated from artisanal Tenerife cheese. Influence of starter on the characteristics of the cheeses was evaluated. Owing to the composition of the starters, lactobacilli and leuconostocs varied significantly between both cheeses. However, the type of starter did not significantly affect the physicochemical and proteolytic properties of the cheeses. In general, cheeses made with autochthonous starter received higher scores for sensory attributes, especially for aroma, than those made with commercial starter.     

发酵剂对熏马肠成熟过程中蛋白质降解的影响

对熏马肠发酵成熟过程中蛋白质的降解变化进行了研究。结果表明,非蛋白氮含量在加工过程中持续增加,并且发酵剂组的非蛋白氮值上升较快;通过SDS-PAGE图谱分析,肌浆蛋白和肌原纤维蛋白均发生了降解,发酵剂组的蛋白降解程度明显高于空白组,尤其是肌浆蛋白,分子质量在14.4 ku、27～35 ku、66～90 ku附近的蛋白条带均降解消失;通过对组织蛋白酶B和L活力测定,得出空白组的酶活力高于发酵剂组。     

Changes in gastric resistance of Lactobacillus casei in flavoured commercial fermented milks during refrigerated storage

This study investigated the gastric acid resistance ofLactobacillus caseiin commercial fermented milks during refrigerated storage. Samples of fermented milks (natural, strawberry, fruits of the forest, vanilla and multifruits) were obtained from three different manufacturers. In vitro gastric acid resistance (GAR) was assessed in samples upon arrival to the laboratory and after 10 and 20 days of refrigerated storage at 5 °C and 12 °C. The GAR ofL. caseiin fermented milks may increase or decrease during storage in relation to the flavour and storage conditions. The occurrence of this phenomenon in commercial fermented milks containing probiotic bacteria may induce changes in their functionality after consumption.     

Effect of starter cultures on properties of soft white cheese made from camel (Camelus dromedarius) milk

This experiment was conducted to investigate the effect of starter cultures on the physicochemical properties, texture, and consumer preferences of soft white cheese (SWC) made from camel (Camelus dromedarius) milk. The experiment was laid out in a completely randomized design with 5 treatments [starter cultures; i.e., 1 thermophilic (STI-12), 2 blended (RST-743 and XPL-2), and 2 mesophilic (R-707 and CHN-22) cultures]. Starter cultures STI-12 and RST-743 were inoculated at 37°C, whereas XPL-2, R-707, and CHN-22 were inoculated at 30°C. Camel milk inoculated using STI-12 and RST-743 cultures resulted in faster acidification than XPL-2, R-707, and CHN-22 cultures. Camel milk SWC made using STI-12 and CHN-22 cultures gave lower pH (4.54) and titratable acidity (0.59), respectively, whereas R-707 culture resulted in high cheese yield (13.44 g/100 g). In addition, high fat (20.91 g/100 g), protein (17.49 g/100 g), total solids (43.44 g/100 g), and ash (2.40 g/100 g) contents were recorded for SWC made from camel milk made using RST-743 culture. Instrumental analysis of cheese texture revealed differences in resistance to deformation in which camel milk SWC made using RST-743 culture gave higher firmness (3.20 N) and brittleness (3.12 N). However, no significant difference was observed among camel milk SWC adhesiveness made using different starter cultures. Consumer preference for appearance, aroma, taste, and overall acceptances of SWC were affected by inoculation of starter cultures. Considering curd firmness, cheese yield, compositional quality, and textures using STI-12, RST-743, and R-707, these cultures were found to be better for the manufacture of camel milk SWC.     

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.     

Genotypic identification of some lactic acid bacteria by amplified fragment length polymorphism analysis and investigation of their potential usage as starter culture combinations in Beyaz cheese manufacture

In this study, 2 different starter culture combinations were prepared for cheesemaking. Starter culture combinations were formed from 8 strains of lactic acid bacteria. They were identified as Lactococcus lactis ssp. lactis (2 strains), Lactobacillus plantarum (5 strains), and Lactobacillus paraplantarum (1 strain) by amplified fragment length polymorphism analysis. The effects of these combinations on the physicochemical and microbiological properties of Beyaz cheeses were investigated. These cheeses were compared with Beyaz cheeses that were produced with a commercial starter culture containing Lc. lactis ssp. lactis and Lc. lactis ssp. cremoris as control. All cheeses were ripened in brine at 4°C for 90 d. Dry matter, fat in dry matter, titratable acidity, pH, salt in dry matter, total N, water-soluble N, and ripening index were determined. Sodium dodecyl sulfate-PAGE patterns of cheeses showed that α_S-casein and β-casein degraded slightly during the ripening period. Lactic acid bacteria, total mesophilic aerobic bacteria, yeast, molds, and coliforms were also counted. All analyses were repeated twice during d 7, 30, 60, and 90. The starter culture combinations were found to be significantly different from the control group in pH, salt content, and lactobacilli, lactococci, and total mesophilic aerobic bacteria counts, whereas the cheeses were similar in fat, dry matter content, and coliform, yeast, and mold counts. The sensory analysis of cheeses indicated that textural properties of control cheeses presented somewhat lower scores than those of the test groups. The panelists preferred the tastes of treatment cheeses, whereas cheeses with starter culture combinations and control cheeses had similar scores for appearance and flavor. These results indicated that both starter culture combinations are suitable for Beyaz cheese production.     

Growth inhibition of foodborne pathogens by kimchi prepared with bacteriocin-producing starter culture

Kimchi (starter kimchi) was prepared with Leuconostoc citreum GJ7, a bacteriocin producer, with the objective of preventing growth and/or survival of foodborne pathogens such as Escherichia coli O157:H7, Salmonella Typhi, and Staphylococcus aureus. Numbers of the pathogens inoculated to 5.41 to 5.63 log CFU/mL into the filtrate of freshly made starter kimchi remained stable for the first 12 h of incubation at 10 °C. Reductions of 2.69, 2.88, and 3.42 log CFU/mL were observed 48 h after inoculation with E. coli O157:H7, S. Typhi, and S. aureus, respectively. Use of the bacteriocin-producing starter culture for kimchi fermentation significantly reduced the numbers of pathogens in the filtrate. Reductions of 3.85, 4.45, and 5.19 log CFU/mL were observed 48 h after inoculation for E. coli O157:H7, S. Typhi, and S. aureus, respectively. Presumably, the antimicrobial activity came from the ingredients of kimchi such as sulfur-containing compounds, low pH (approximately pH 4.5) produced by the conversion of sugars into organic acids and the bacteriocins potentially produced by lactic acid bacteria (LAB), such as kimchicin GJ7. Together, these data suggest that addition of a starter culture capable of producing bacteriocins could serve as a strategy to protect the fermented product from delivering pathogens upon consumption and that the kimchi filtrate itself may be used as a food preservative. Practical Application: The adaptation of the starter fermentation into kimchi induced a faster die off of the pathogens as compared to natural fermentation. The in situ bateriocin-production by Leuc. citreum GJ7 in kimchi would act with antimicrobial kimchi ingredients in a synergistic manner to protect the fermented product from delivering pathogens upon consumption.     

Evaluation of physical properties during storage of set and stirred yogurts made from ultra-high pressure homogenization-treated milk

The effects of ultra-high pressure homogenization (UHPH) on cow's milk were investigated and its suitability for yogurt manufacturing was compared with the conventional process currently applied in the yogurt industry. Yogurts were prepared from UHPH-treated milks at 200 and 300 MPa at 40 °C, and yogurts prepared from heat-treated milk at 90 °C for 90 s, homogenized at 15 MPa and enriched with 3% of skim milk powder were used as control samples. This study included determination of titrable acidity, water-holding capacity (WHC), and textural and rheological evaluation of gels in both set-type and stirred yogurts. In order to follow the evolution of yogurts during storage at refrigeration temperature (4–6 °C), all analyses were carried out weekly (1, 7, 14, 21 and 28 days). Results showed that yogurts from UHPH-treated milk presented higher WHC and firmness values compared with the conventional yogurts. However, the disruption of the network from UHPH-treated milk into stirred gels resulted in yogurts with higher consistency, less syneresis but coarser structure than the conventional ones.     

直投式发酵剂制备的哈尔滨风干肠在成熟过程中的理化及微生物特性变化

采用三种由自然发酵分离鉴定出的微生物,按一定比例混合制备复合发酵剂,将其用于哈尔滨风干肠中,研究其对风干肠的理化性质、微生物变化和游离氨基酸含量的影响。实验分为三组,分别为对照组,添加普通发酵剂组和添加直投式发酵剂组。结果表明:添加发酵剂的风干肠pH明显低于对照组,且添加直投式发酵剂的pH最低(P<0.05);添加发酵剂会使产品的游离氨基酸含量显著提高(P<0.05)、感官品质也较好(P<0.05),而各组水分活度变化差异不明显,这说明直投式发酵剂具有很好的活力和发酵性能,能够显著提高风干肠的质量,缩短发酵时间。     

中国不同地区老酵头对馒头质构和感官品质的影响

目的探讨中国不同地区传统老酵头对馒头品质特征的影响,筛选产品品质较为优良的老酵头。方法收集10个地区的传统面食发酵剂为实验材料制作老酵馒头,测定不同地区老酵面团在发酵过程中微生物的变化及馒头的品质指标,并进行感官评价。结果不同地区老酵馒头的品质指标间具有显著性差异(P0.05),老酵头制作面团发酵过程中不同地区间酵母菌和乳酸菌的生长趋势相似且具有一定的规律性,在发酵前期,酵母菌迅速生长至面团成熟期后,其数量趋于稳定;乳酸菌在发酵前期经过短暂的适应期后进入快速生长期,至面团成熟期后乳酸菌数量显著下降。综合馒头的质构指标、物性指标及感官评价来看,5#老酵头制作出的馒头其综合品质最佳,感官评分最高为89分。结论本研究结果为传统发酵剂在馒头工业化生产中的合理利用提供了理论依据。     

Levels of Se,Zn, Mg and Ca in commercial goat and cow milk fermented products: Relationship with their chemical composition and probiotic starter culture

We determined Se, Zn, Mg and Ca levels in 42 samples of goat and cow fermented milks which are widely consumed in Spain were determined. Atomic absorption spectrometry (hydride generation for Se and flame atomisation for remaining elements) was used as an analytical technique. Reliability of the procedure was checked. Only Mg levels in goat fermented milks were significantly higher to those found in cow fermented milks (p < 0.022). Important similarities in concentrations and behaviours for Mg and Ca have been observed. Mg contents were significantly correlated with Zn (r = 0.590; p < 0.001) and Ca (r = 0.344; p < 0.028) concentrations, Zn, Mg and Ca levels with protein content (r = 0.554, r = 0.479, r = 0.388, respectively), Mg levels with fats (r = 0.403; p = 0.011) and Se levels with carbohydrates (r = −0.379; p = 0.031). Mineral and macronutrient levels in yogurts with traditional probiotic starter cultures were not significantly different to those found in fermented milks with additional probiotic microorganisms (p > 0.05). It was concluded that goat fermented milks are a better source for Mg than cow samples.