Effect of inulin as a prebiotic to improve growth and counts of a probiotic cocktail in fermented skim milk

Inulin was used as a prebiotic to improve quality of skim milk fermented by pure cultures of Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus and Bifidobacterium lactis, binary co-cultures with Streptococcus thermophilus, or a cocktail containing all them. Inulin supplementation to pure cultures lowered the generation time, with particular concern to S. thermophilus and L. acidophilus. The generation time of all micro-organisms decreased in the following order: mono-cultures, co-cultures, cocktail. It was demonstrated a synergism between S. thermophilus and the other strains and a bifidogenic effect of inulin. Enumerations of L. rhamnosus in cocktail markedly decreased compared to co-cultures likely because of greater competition for the same substrates. The results of this work highlight the industrial potential of the cocktail, mainly in terms of fermentation acceleration.     

Effect of prebiotic carbohydrates on the growth and tolerance of Lactobacillus

Resistance to gastrointestinal conditions is a requirement for bacteria to be considered probiotics. In this work, we tested the resistance of six different Lactobacillus strains and the effect of carbon source to four different gastrointestinal conditions: presence of α-amylase, pancreatin, bile extract and low pH. Novel galactooligosaccharides synthesized from lactulose (GOS-Lu) as well as commercial galactooligosaccharides synthesized from lactose (GOS-La) and lactulose were used as carbon sources and compared with glucose. In general, all strains grew in all carbon sources, although after 24 h of fermentation the population of all Lactobacillus strains was higher for both types of GOS than for glucose and lactulose. No differences were found among GOS-Lu and GOS-La. α-amylase and pancreatin resistance was retained at all times for all strains. However, a dependence on carbon source and Lactobacillus strain was observed for bile extract and low pH resistance. High hydrophobicity was found for all strains with GOS-Lu when compared with other carbon sources. However, concentrations of lactic and acetic acids were higher in glucose and lactulose than GOS-Lu and GOS-La. These results show that the resistance to gastrointestinal conditions and hydrophobicity is directly related with the carbon source and Lactobacillus strains. In this sense, the use of prebiotics as GOS and lactulose could be an excellent alternative to monosaccharides to support growth of probiotic Lactobacillus strains and improve their survival through the gastrointestinal tract.     

Growth and acidification performance of probiotics in pure culture and co-culture with Streptococcus thermophilus: The effect of inulin

Inulin was used as a prebiotic to improve the quality and consistency of skim milk fermented by co-cultures and pure cultures of Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus and Bifidobacterium lactis with Streptococcus thermophilus. We compared, either in the presence or absence of 4 g inulin/100 g, the results of the main kinetic parameters, specifically the generation time (t_g), the maximum acidification rate (V_max), and the times to reach V_max (t_max), to attain pH 5.0 (t_pH5.0) and to complete the fermentation (t_pH4.5). Post-acidification, lactic acid formation and cell counts were also determined and compared, either 1 day after the fermentation was complete or after 7 day storage at 4 °C. In general, inulin addition to the milk increased in co-cultures V_max, decreased t_max, t_g and t_pH4.5, favored post-acidification, exerted a bifidogenic effect, and preserved almost intact cell viability during storage. In addition, S. thermophilus was shown to stimulate the metabolism of the other lactic bacteria. Contrary to co-cultures, most of the effects in pure cultures were not statistically significant. The most important aspect of this paper is the use of the generation time as a tool to investigate the microbial response to inulin addition.     

Effect of inulin as prebiotic and synbiotic interactions between probiotics to improve fermented milk firmness

Inulin behaved as a prebiotic to improve firmness of skim milk fermented by (a) pure cultures of Lactobacillus acidophilus (La), Lactobacillus rhamnosus (Lr), Lactobacillus bulgaricus (Lb) and Bifidobacterium lactis (Bl), (b) binary co-cultures of them with Streptococcus thermophilus (St), or (c) a cocktail containing all them. Inulin addition to co-cultures and cocktail enhanced products firmness, either after 1 day (D1) or 7 days (D7) of cold storage, likely due to the increase in microbial growth induced by metabolic interactions among lactic acid bacteria and partial inulin metabolization. Co-culture firmness did in fact range from 0.33 N without inulin (St-Lb) after D1 and 0.55 N with inulin (St-Lr) after D7. Also cocktail cultures exhibited high values of firmness, ranging, as an average, from 0.43 N (D1) to 0.46 N (D7), which suggests that they could have been potentiated by the reciprocal synergistic effects of microorganisms in complex mixture.     

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.     

Preparation and evaluation of low‐calorie functional ice cream containing inulin,lactulose and Bifidobacterium lactis

This study was aimed to investigate the effects of replacing 5% fat and sugar by inulin and lactulose, respectively, on the survival of Bifidobacterium lactis and physicochemical and sensorial characteristics of the ice cream. Total solids, pH, melting rate and sensory scores of low‐fat and/or low‐sugar ice cream samples did not differ significantly from the control. Overrun and hardness of low‐fat samples were significantly higher than that of the control group (P < 0.01). The viable counts of B. lactis in the low‐sugar synbiotic ice creams were significantly lower than that of other groups at the end of 90‐day storage (P < 0.01).     

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.     

The effect of inulin as a prebiotic on the production of probiotic fibre-enriched fermented milk

We investigated the effect of inulin as a prebiotic on the production of probiotic fibre-enriched fermented milk. The kinetics of acidification of inulin-supplemented milk (0, 0.01, 0.02 and 0.04 g/g), as well as probiotic survival, pH and firmness of fermented milk stored at 4°C for 24 h and 7 days after preparation were examined. Probiotic fibre-enriched fermented milk quality was influenced both by the amount of inulin and by the co-culture composition. Depending on the co-culture, inulin addition to milk influenced acidification kinetic parameters, probiotic counts, pH and the firmness of the product.     

Improving functionality of chocolate: A review on probiotic,prebiotic, and/or synbiotic characteristics

BackgroundChocolate is consumed by people of all ages in all segments of society throughout the world. The popularity of this food is mainly associated with its potential to arouse sensory pleasure and positive emotions. Increasing awareness of the link between healthy eating and well-being is reflected in the current views of the general consumers. Consumers perceive functional foods as a member of the specific food category to which they belong. Also, in developed economies, a key trend at the moment is confectionery products that deliver functional benefits for health and well-being, such as functional chocolate.Scope and approachIn this review, studies related with production of prebiotic, probiotic and synbiotic chocolates as a functional food were investigated and positive and negative aspects of these functional products when compared with standard one were stated, which could shape the following related studies in food area and the production of prebiotic, probiotic and synbiotic chocolates in the food industry.Key findings and conclusionsWhen the studies related with this topic were investigated it could be concluded that the studies associated with chocolate which could play a role in transportation of probiotics and prebiotics might be supported by studies in which bioavailability and bioaccessibility characteristics of them in vivo and in vitro media will be determined. Moreover, in order to improve bioavailability and bioaccessibility properties product quality optimization studies might be required in the future.     

Efficiency of Bifidobacterium bifidum and Saccharomyces cerevisiae for detoxification of aflatoxin M1 in skim milk

Aflatoxin M1 (AFM1) is a carcinogenic mycotoxin mostly found in dairy products. The aim of this study was to evaluate the anti-aflatoxin effect of Bifidobacterium bifidum and Saccharomyces cerevisiae with two different concentrations (10⁸ and 10¹⁰ cfu/mL), alone or mixed, in contaminated skim milk with three concentrations of AFM1 (0.1, 0.25 and 0.5 μg/mL) and incubated at 4, 25 and 37°C for different times (30, 60, 120 min and 24 h). We found that the storage time is a key factor that significantly affects AFM1 removal. Also, removal of AFM1 was dependent on other factors such as micro-organisms' concentration, incubation temperature and toxin concentration. The effective strategy for the highest removal of AFM1 (90%) in contaminated milk spiked with 0.5 μg/mL, which was treated with mixed strains at concentration10¹⁰ cfu/mL and incubated at 37°C after 24 h. The presented methodology can be considered as a potential method for reducing the aflatoxin content of polluted dairy products.     

Influence of total solids contents of milk whey on the acidifying profile and viability of various lactic acid bacteria

The main objectives of the present study were (a) to study the effects of the different combinations of Lactobacillus delbrueckii subsp. bulgaricus (Lb), Lactobacillus acidophilus (La), Lactobacillus rhamnosus (Lr), and Bifidobacterium animalis subsp. lactis (Bl) in co-culture with Streptococcus thermophilus (St) on the rate of acid development in milk and milk-whey mixture, and (b) the effect of the level of the total solids of the different bases on the acidification profile and viability of potential health-promoting micro-organisms. The co-culture of St-Lr showed the lowest values V_max in all bases; while the co-culture St-Bl had high t_Vmax in milk and whey bases (12 and 10 g/100 g, respectively). Co-cultures St-La and St-Lb reached V_max at pH 5.5, while St-Lr and St-Bl at pH 5.91. Fermentation time to reach pH 4.5 was longer when St-Lr co-culture was used, while St-Lb had the lowest value. All the products had slight development of acid during the storage period, and lowest values were observed when the St-Bl co-culture was employed. Lb, Bl and St cultures had high counts at pH 4.5 in the three bases. The total solids affected the viability of Lb and La. The technological interest of these combinations is discussed in this article.     

Fortification of milk with plant extracts modifies the acidification and reducing capacities of yoghurt bacteria

The acidification and reducing capacities of yoghurt bacteria were evaluated in different plant extract‐enriched milk samples. The milk samples enriched with thyme and grape seed extracts exhibited the highest values of acidification capacity for Lactobacillus delbrueckii subsp. bulgaricus (LB) (0.0065 pH unit/min) and Streptococcus thermophilus (ST) (0.0068 pH unit/min). The highest values of reducing capacity were observed in thyme (?0.98 mV/min), grape (?1.92 mV/min) and green tea (?0.75 mV/min)‐enriched samples for LB, ST and mixed culture of LB + ST, respectively. The fortification of yoghurt with plant extracts modified the acidification and reducing activities of starters, thus changing the fermentation time and quality attributes of the product.     

Use of Bacillus indicus HU36 as a probiotic culture in set‐type,recombined nonfat yoghurt production and its effects on quality

Viability of a probiotic and carotenoid‐producing bacterium, Bacillus indicus HU36 in vegetative form, along with the yoghurt cultures in set‐type, recombined nonfat yoghurt and its effects on quality were determined during the storage at 4 °C. The number of B. indicus HU36 cells in yoghurt remained about 5 log cfu/mL after 14 days, but decreased to 3.5 log after 21 days. The bacterium resulted in increased yellowness, but did not affect the rheological properties of the yoghurt. Sensorial properties of the yoghurt were acceptable compared to a commercial probiotic yoghurt. B. indicus HU36 can thus be used as a probiotic culture in yoghurt production.     

Effect of milk solids concentration on the gels formed by the acidification of heated pH-adjusted skim milk

Reconstituted skim milk of 10–25% total solids was adjusted to pH values between about 6.2 and 7.1 and heated at 80 °C for 30 min. Gels were formed from the heated milks by slow acidification to pH 4.2 and the gelation process and final gels were analyzed for their rheological properties. At each milk concentration, the final acid gel firmness (final G′) and breaking stress could be changed markedly by manipulation of the pH during heating. The final gel firmness and breaking stress could also be modified by changing the concentration of the milk solids prior to heating and acidification. The results indicated that similar gel firmness and breaking stress could be achieved over a range of milk concentrations by control of the pH of the milk during heating. When expressed as a percentage change in final G′ or breaking stress relative to that obtained at the natural pH, plots of the change in final G′ or breaking stress versus pH fell close to a single curve, indicating that the same mechanism may influence the gelation properties at all milk concentrations. The final G′ and breaking stress were related to the denaturation and interaction of the whey proteins with the casein micelles, and the formation of non-sedimentable casein when the milk was heated.     

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.     

Replacement of bovine milk with vegetable milk: Effects on the survival of probiotics and rheological and physicochemical properties of frozen fermented dessert

In this study, frozen fermented desserts containing Lactobacillus acidophilus (La‐05; L) and Bifidobacterium bifidum (Bb‐12; B), were made from bovine (W), soya (S), coconut (C) and composite (i.e. combinations of coconut or bovine milks with soya milk) milks. The changes in frozen dessert eating qualities and the survival of added microbes were evaluated. The highest viscosity and melting resistance, and the lowest total sensory scores, were found in the products made using soya milk. After 90‐day storage at ?20 °C, the highest survival percentage of La‐05 was found in the products made using coconut milk (CL); and for Bb‐12, it was found in the products made using soya milk, coconut milk and a 25:75 blend of soya milk and coconut milk respectively ( samples SB, CB and SC3B) SB, SCB and CB samples.     

Influence of heat impact in reconstituted skim milk on the properties of yoghurt fermented by ropy or non‐ropy starter cultures

The paper describes studies on the influence of heat impact in reconstituted skim milk on chemical and functional properties of yoghurt products. Reconstituted skim milk was heated for 20 min at 85°C, 90°C, or 95°C. Ropy (producing exopolysaccharides, EPS) or non‐ropy strains of S. thermophilus and L. delbrueckii subsp. bulgaricus were used as starter culture for yoghurt manufacture. The studies have shown that the fermentation times decreased with increasing heat impact when the ropy starter culture was used, while they remained to a far extent unchanged if the non‐ropy starter culture was applied. The lactic acid contents of the yoghurt products were in the same range when the milk was heated at 85°C or 90°C, while they were different when milk was heated at 95°C. There was a tendency visible that an increase in preheating leads to increased L (+)‐ and decreased D (–)‐lactic acid contents if the non‐ropy culture was applied. Using the ropy culture, it was vice versa. A slightly decrease in proteolysis with increasing heat impact was to be noted with both starter cultures. Concerning the relation of proteolysis to acidification, the fermentation process could be subdivided into three sections with different slopes if the non‐ropy starter culture was used, while a linear relation was found if the ropy starter culture was applied. Regarding final product characteristics it was found that the functional properties of yoghurt decreased with increasing heat impact when the ropy starter culture was applied, while they remained to a far extent unchanged when the non‐ropy starter culture was used. It can be concluded from these studies that a preheating of milk at a temperature of 85°C (20 min) is optimal in regard to final yoghurt product characteristics.     

The effects of inulin as a prebiotic supplement and the synbiotic interactions of probiotics to improve oxalate degrading activity

This paper examines the impact of inulin, Lactobacillus spp. (candidate probiotics), and synbiotic (inulin + Lactobacillus spp.) preparation on oxalate degrading activity and viability of Escherichia coli. In this study, the lowest viability of E. coli was recorded for the synbiotic treatments of Lactobacillus fermentum BP5 (59%) and IP5 (60%). The oxalate degrading activity of L. fermentum IP5 was 38.18 and 29.60% higher than the other strains after growth in 10 mM and 20 mM MRS-ox plus 5% inulin media, respectively. The mixture of three strains demonstrated higher oxalate degrading capacity than the individual strains and showed the same good growth rates (9.43 CFU mL⁻¹) as individuals. The study concludes that the addition of prebiotics has a significant effect on probiotics; therefore, a combination of L. fermentum IP5 with inulin could be a viable probiotic-based functional food approach in administering oxalate metabolism and also treatment of E. coli-related infections.     

Viability of probiotic bacteria in fermented skim milk produced with different levels of milk powder and sugar

In this work, the effect of skim milk powder (0, 5%, 10%, 15% w/v) and sugar (0%, 10% w/v) on the viability of probiotic micro‐organisms and on the quality of fermented milks was investigated. Fermented milks were submitted to physicochemical, microbiological and sensory analyses on the 1st, 10th and 21st days after production. Sugar inclusion did not affect the probiotic growth in fermented milks, but milk powder levels of 10–15% influenced positively the probiotic counts, which were above six log colony‐forming units (cfu)/g. These findings can be useful for small dairy industries that are interested in producing flavoured fermented milks without decreasing the viability of probiotic micro‐organisms during its shelf life.     

金黄色葡萄球菌在生乳与灭菌乳中生长状况分析

目的 了解并比较金黄色葡萄球菌(S.aureus)在生乳与灭菌乳中的生长状况.方法 采用GB/T4789.37-2008<食品微生物学检验金黄色葡萄球菌检验>,测定不同温度下金黄色葡萄球菌在生乳和灭菌乳中的生长情况,利用MicroFit 1.0软件对所测数据进行分析,利用SPSS统计软件对该菌在生乳与灭菌乳中生长参数进行统计分析.结果 金黄色葡萄球菌在生乳中的最大生长速率明显低于在灭菌乳中的最大生长速率,二者的迟滞期、代时无明显差异.结论 金黄色葡萄球菌在生乳与灭菌乳中的生长情况差异显著.有统计学意义(P<0.05).