Traditional Yogurt Research Articles

Fate of Escherichia coli and Kluyveromyces marxianus contaminants during storage of Greek-style yogurt produced by centrifugation or ultrafiltration

The production of Greek-style yogurts requires more processing steps than traditional yogurt, which increases the possibility of microbial contamination by pathogens or spoilage organisms. The growth and survival during storage of two microbial contaminants (Escherichia coli and Kluyveromyces marxianus) in Greek-style yogurt, produced by centrifugation or ultrafiltration, was compared with that in regular stirred yogurt. E. coli strain ATCC® BAA-1430™ was shown to be a suitable surrogate for pathogenic O157:H7 in yogurt. The increased buffering capacity of the Greek-style yogurts produced from ultrafiltered milk led to lower E. coli viability during storage. On the other hand, the Greek-style yogurt seems to promote faster growth of the dairy yeast K. marxianus at a storage temperature of 4 °C.

Physicochemical and Sensory Characteristics of Winter Yoghurt Produced from Mixtures of Cow's and Goat's Milk

Winter yoghurt is one of the most popular dairy products in Van and Hatay region of Turkey. It is made of different kinds of milk, and known as “cooked yoghurt” or “salted yoghurt” due to its high solids content and long shelf life. In this study, two different concentration methods were used to produce traditional winter yoghurt. Some physical (firmness and cohesiveness, L-, a- and b- values), chemical (total solid, fat, protein, pH, lactic acid, salt) and sensory analyses (color, odor, consistent and flavor) were made to determine the effect of production methods and storage on winter yoghurt samples at the 1st, 30th, 60th and 90th days. Significant differences were found between sensory, rheological properties and color values of winter yoghurts however no significant differences were found between physicochemical properties of the samples. Especially, winter yoghurts produced from 100% goat milk were the more appreciated samples.

Comparative studies of Listeria monocytogenes survival in bifidus and traditional yoghurt during production and storage

Traditional yoghurt (TY) (Streptococcus thermophiles+ Lactobacillus bulgaricus) and Bifidus yoghurt (BY) samples(Streptococcus thermophiles+ Lactobacillus bulgaricus+ Bifidobacterium bifidum). Traditional & Bifidus yoghurtsamples were inoculated with 106 cfu/g L. monocytogenes and stored for 21 days at 4±1oC. Samples were taken at zerotime (fresh samples) then after 3, 5, 7, 10, 14 and 21 days of storage for titratable acidity measurement and bacterial countof the culture starters and L. monocytogenes counts. The results revealed that the titratable acidity of TY & BY wasincreased during the 21 days of storage, while the population of L. monocytogenes became non-detectable level in 10thdays of storage in BY and still detected in TY till the day 14th of storage and became 2.20± 0.31 log10 cfu/g. The countof all starter cultures (S. thermophiles+ Lb. bulgaricus+ B. bifidum) in both yoghurts increased during the fermentationand cold storage and remained stable with values >6 log10 cfu/g throughout the storage period at 4±1°C.

Evaluation the effect of Lactobacillus acidophilus probiotic culture over Staphylococcus aureus during the production and storage of acidophilus yoghurt

The survival of Staphylococcus aureus in the acidophilus yoghurt (AY) was evaluated during the production and coldstorage. 21 acidophilus yoghurt samples were prepared with traditional yoghurt culture (Streptococcus thermophiles &Lactobacillus bulgaricus) with Lactobacillus acidophilus and inoculated with 106 cfu/ml S. aureus and stored for 21 daysat 4oC. Samples were taken at zero time (fresh samples), 3, 5, 7, 10, 14 and 21 days for titratable acidity, culture starters’counts and S. aureus count. The results revealed that the titratable acidity% of AY was increased and reached 0.72, 0.78,0.83, 0.87, 0.89, 1.02 and 1.45% at zero time, 3, 5, 7, 10, 14, and 21 days of storage, respectively, while the population of S. aureus reached 6.10 and 3.70 log10cfu/g at zero time and 3rd day of storage, respectively and became non-detectable level in 5th days of storage. The count of all starter cultures (S. thermophiles+ L. bulgaricus+ L. acidophilus) in acidophilus yoghurt increased during the fermentation and cold storage, S. thermophiles became 7.15, 7.35, 8.20, 8.15, 7.45, 7.45 and 6.65 log10cfu/g while L. bulgaricus 7.25, 7.55, 8.25, 8.73, 7.76, 7.47 and 6.54 log10cfu/g and L. acidophilus became 7.38, 7.70, 8.25, 8.20, 7.50, 7,46 and 6.66 log10cfu/g at zero time, 3, 5, 7, 10, 14, and 21 days of storage, respectively. It concluded that S. aureus count decreased gradually during the production and cold storage and became non-detectable level on the 5th days of cold storage. The survival of all starter cultures in yoghurt sample remained stable with values > 6 log10 cfu/g throughout the storage period at 4±1°C.

Safety evaluation and antimicrobial properties of Lactobacillus pentosus 22C isolated from traditional yogurt

Traditional dairy products are the main source of probiotic microorganisms. Hence, this study aimed to evaluate the safety and antimicrobial potential of Lactobacillus pentosus 22C, isolated from traditional yogurt from Kermanshah province, Iran. Strain 22C showed no undesirable amino acid decarboxylase and β-hemolytic activities. Virulence associated genes were detected in the isolate. The strain produced an antimicrobial molecule named pentocin 22C, a small peptide with a relative mass between 5 and 10 kDa. Bacterial inhibition was pH-independent, with greater activity at pH 4–6. Purified or semi-purified antimicrobial agents can be used as bio-preservatives, and the producing strain can be used as a starter culture to improve food safety. Therefore, a biosafety assessment should be conducted. L. pentosus 22C, isolated from a traditional dairy product, has antimicrobial ability, although its safety must be evaluated.

Characterisation and probiotic potential of lactic acid bacteria isolated from Iranian traditional yogurts

Probiotics beneficially affect human health by improving the balance of intestinal microbiota and mucosal defence against pathogens. Many probiotic bacteria, mostly belong to the genera Lactobacillus, are used in commercial probiotic fermented milks throughout the world. The aim of this study was to investigate the probiotic potential of lactic acid bacteria (LAB) isolated from various Iranian traditional yogurts. During an 18-month study from October 2013 to May 2014, 96 samples were equally collected from traditional yogurts produced from goat, sheep and cow milk in Yazd Providence, Iran. Samples were transferred into MRS broth for enrichment and then subcultured on MRS agar. Isolates were studied for morphological and biochemical characteristics, using Gram staining and catalase test. The ability to tolerate acidic pH and resistance to bile salts were used as restrictive criteria for probiotic potential. Selected LAB were further identified using 16S rDNA sequence analysis. Of 96 yogurt samples, 47 LAB were isolated; from which 12 were candidates for probiotics. Six probiotic isolates belonged to Pediococcus acidilacticii and other six isolates to Lactobacillus plantarum, L. brevis, L. fermentum and L. kefiri. In summary, LAB strains isolated from Iranian traditional yogurts were considered as viable candidates of probiotics, based on their properties such as acid and bile tolerance.

Screening and identification of lactic acid bacteria strains with high acid-producing from traditional fermented yak yogurt

A total of 57 strains of lactic acid bacteria (LAB) were isolated and purified from traditional fermented Yak Yogurt in Hongyuan-Sichuan and Yangbajing-Tibet. The strains with high acid-produced were screened by soluble calcium circle and titratable acidity determination. The five strains, 7-1, 22-1, 28-1, 34-1 and 62-1, possessed the high acid-producing and the value of titratable acidity is 196.2, 191.1, 192.2, 194.8 and 200.2 T respectively. Based on 16S rDNA sequence analysis, 22-1 was identified as Lactococcus lactis subsp. lactis , 28-1 as Lactobacillus casei , 34-1 as Lactobacillus fermentium , 7-1 and 62-1 as Enterococcus durans . This study could provide the evidence for researching fermentation strains to improve yogurt quality.

Prevention of DNA damage and anticarcinogenic activity of Activia® in a preclinical model.

Colorectal cancer is a global public health issue. Studies have pointed to the protective effect of probiotics on colorectal carcinogenesis. Activia® is a lacto probiotic product that is widely consumed all over the world and its beneficial properties are related, mainly, to the lineage of traditional yoghurt bacteria combined with a specific bacillus, DanRegularis, which gives the product a proven capacity to intestinal regulation in humans. The aim of this study was to evaluate the antigenotoxic, antimutagenic, and anticarcinogenic proprieties of the Activia product, in response to damage caused by 1,2-dimethylhydrazine (DMH) in Swiss mice. Activia does not have shown antigenotoxic activity. However, the percent of DNA damage reduction, evaluated by the antimutagenicity assay, ranged from 69.23 to 96.15% indicating effective chemopreventive action. Activia reduced up to 79.82% the induction of aberrant crypt foci by DMH. Facing the results, it is inferred that Activia facilitates the weight loss, prevents DNA damage and pre-cancerous lesions in the intestinal mucosa.

Influence of lactose hydrolysis on galacto-oligosaccharides, lactose, volatile profile and physicochemical parameters of different yogurt varieties.

Different types of reduced-lactose yogurt, obtained by lactose hydrolysis using β-galactosidase enzyme, are commercially available. The breakdown of lactose modifies the carbohydrate profile, including the production of prebiotic galacto-oligosaccharides (GOS), which could affect the survival and activity of starter and probiotic cultures and the parameters of yogurt quality. The extension of these changes is dependent on the yogurt matrix composition. This study aimed to evaluate the influence of lactose hydrolysis on GOS, lactose, volatile profile and physicochemical parameters of different yogurt varieties during storage. The presence of β-galactosidase enzyme did not affect either the global composition or the survival of cultures. Overall, the hydrolyzed products had lower acidity than traditional ones. GOS were found at similar levels in fresh hydrolyzed yogurts, whereas in traditional yogurts they were not detected. The proportion of ketones, acids and aldehydes seems to be more dependent on yogurt variety than on addition of the enzyme. Likewise, the storage period affected the volatile fraction to different degree; the increase in acid compounds was more pronounced in hydrolyzed than in traditional yogurts. This work shows that it is possible to obtain different varieties of reduced-lactose yogurt, some of them with additional benefits to health such as reduced fat, reduced calories, added with probiotic/inulin and enriched in GOS, with similar characteristics to traditional products. © 2016 Society of Chemical Industry.

AVALIAÇÃO DA QUALIDADE DE LABNEH (IOGURTE GREGO): ESTUDO COM CONSUMIDORES

O labneh (iogurte grego) é um tipo de leite fermentado caracterizado pelo processo de concentração de iogurtes tradicionais. Esse tipo de produto é relativamente novo no mercado alimentício e há poucos estudos de avaliação para seus parâmetros de qualidade. O objetivo deste trabalho foi avaliar a aceitação de três marcas comerciais de iogurte grego tradicional comercializados no município de Diamantina/MG e identificar os atributos que influenciam na qualidade do produto. Foram realizadas análises de cor (L*, a*, b*), textura, acidez titulável, pH e avaliação sensorial. Os resultados obtidos mostraram variação entre as amostras para todos os parâmetros analisados, exceto para o valor b*. Em relação à análise sensorial, por meio do teste de médias, observou-se que as marcas IA e IB foram as mais aceitas. Pelo mapa de preferência, pode-se inferir que a maior porcentagem de ácido lático da amostra IA e a firmeza de IB, foram os parâmetros responsáveis pela maior aceitação dessas marcas. Diante disso, observou-se que a textura e a acidez são atributos importantes na escolha do produto. Portanto, os resultados deste estudo podem auxiliar em trabalhos futuros de desenvolvimento de novas formulações, visando atender melhor às exigências do mercado consumidor.

Enterococcus Xinjiangensis sp. nov., Isolated from Yogurt of Xinjiang, China.

A Gram-strain-positive bacterial strain 48(T) was isolated from traditional yogurt in Xinjiang Province, China. The bacterium was characterized by a polyphasic approach, including 16S rRNA gene sequence analysis, polymerase α subunit (rpoA) gene sequence analysis, determination of DNA G+C content, DNA-DNA hybridization with the type strain of Enterococcus ratti and analysis of phenotypic features. Strain 48(T) accounted for 96.1, 95.8, 95.8, and 95.7% with Enterococcus faecium CGMCC 1.2136(T), Enterococcus hirae ATCC 9790(T), Enterococcus durans CECT 411(T), and E. ratti ATCC 700914(T) in the 16S rRNA gene sequence similarities, respectively. The sequence of rpoA gene showed similarities of 99.0, 96.0, 96.0, and 96% with that of E. faecium ATCC 19434(T), Enterococcus villorum LMG12287, E. hirae ATCC 9790(T), and E. durans ATCC 19432(T), respectively. Based upon of polyphasic characterization data obtained in the study, a novel species, Enterococcus xinjiangensis sp. nov., was proposed and the type strain was 48(T)(=CCTCC AB 2014041(T)=JCM 30200(T)).

Influence of Lactobacillus plantarum WCFS1 on post-acidification, metabolite formation and survival of starter bacteria in set-yoghurt

The objectives of this study were to evaluate the growth and survival of the model probiotic strain Lactobacillus plantarum WCFS1 in co-culture with traditional yoghurt starters and to investigate the impact of preculturing on their survival and metabolite formation in set-yoghurt. L. plantarum WCFS1 was precultured under sublethal stress conditions (combinations of elevated NaCl and low pH) in a batch fermentor before inoculation in milk. Adaptive responses of L. plantarum WCFS1 were evaluated by monitoring bacterial population dynamics, milk acidification and changes in volatile and non-volatile metabolite profiles of set-yoghurt. The results demonstrated that sublethal preculturing did not significantly affect survival of L. plantarum WCFS1. On the other hand, incorporation of sublethally precultured L. plantarum WCFS1 significantly impaired the survival of Lactobacillus delbrueckii subsp. bulgaricus which consequently reduced the post-acidification of yoghurt during refrigerated storage. A complementary metabolomics approach using headspace SPME-GC/MS and 1H NMR combined with multivariate statistical analysis revealed substantial impact of sublethally precultured L. plantarum WCFS1 on the metabolite profiles of set-yoghurt. This study provides insight in the technological implications of non-dairy model probiotic strain L. plantarum WCFS1, such as its good stability in fermented milk and the inhibitory effect on post-acidification.

Rheological properties of fermented rice extract with probiotic bacteria and different concentrations of waxy maize starch

Fermented rice extracts (FRE) obtained from bran and broken grains in a proportion of 8:92, and probiotic bacteria with different concentrations of waxy maize starch (WMS) were elaborated. Pearson correlations and multivariate analysis by Principal Component Analysis (PCA) were applied to evaluate the rheological behaviour of FRE. A completely randomized design was used, with five treatments from FRE1 to FRE5 (0, 4, 8, 12 and 16 g 100 g−1 of WMS, respectively), in four original repetitions. The multivariate analysis using PCA found that the shear stress and the WMS percentage showed a higher contribution in the first component (CP1 47.5%), and the viscosity in the second component (CP2 29.0%). The FRE5 presented the highest hysteresis, 128.12 Pa s−1. The Ostwald-de Waele model showed the best fit for the flow curves with R2 > 0.99 and a relative approximate error of 3.14%. All FRE presented non-newtonian behaviour, with n < 1. The FRE with different concentrations of WMS presented rheological behaviour similar to yogurts and lactic beverages described in the literature, indicating that such products can be comparable to traditional yogurts in relation to viscosity and to the flow characteristics. The results also suggest an improvement in the sensory properties of FRE.

Survival of Escherichia coli O157:H7 during manufacture and storage of traditional and low lactose yogurt

Yogurt has been considered safe due to its low pH, although recent researchers have demonstrated the survival of Escherichia coli O157:H7 in dairy products. In this context, the aim of the study was to verify survival of E. coli O157:H7 in yogurts with different lactose content. Six different yogurts were prepared: Traditional yogurt (TY); Pre hydrolyzed yogurt (PHY); Lactose free yogurt (LFY); Traditional inoculated yogurt (TIY); Pre hydrolyzed inoculated yogurt (PHIY); and Lactose free inoculated yogurt (LFIY). Three of them were inoculated with E. coli O157:H7 (TIY, PHIY and LFIY). The survival of E. coli, carbohydrates, lactic acid and pH of yogurts were determined during fermentation and storage. HPLC showed lactose content of 3.13, 0.47, 0.27, 3.02, 0.22 and 0.44 g.100 mL−1 after 24 h of storage for TY, PHY, LFY, TIY, PHIY and LFIY respectively. It was also observed that E. coli counts decreased during fermentation and that E. coli was able to survive for 10 days in TIY and PHIY, and for 22 days in LFIY. LAB counts were with minimum of 7 log cfu g−1 in all groups. These results suggest that contamination by E. coli O157:H7 before fermentation increases its survival, especially in lactose free milk.

Aflatoxin M1 Contamination in Traditional Yoghurts Produced in Guilan Province, Iran

Aflatoxin M1 is a major carcinogenic compound that may be existed in dairy products. The aim of this study was to determine the occurrence of AFM1 in traditional yoghurt samples in Guilan Province (Northern Iran). Ninety samples of traditional yoghurts were collected during summer and autumn 2014. Enzyme linked Immunosorbentassay (ELISA) which is a rapid and sensitive method was used to determine the presence and levels of AFM1. 100% of the yoghurt samples were contaminated with 5 and 83 ng/kg of AFM1. In general, AFM1 in 20 samples (22.22%) were higher than the maximum tolerance limit (50 ng/kg) accepted by the European Union. It was therefore concluded that, high occurrence of AFM1 in yoghurt is a serious risk for public health.

Effects of peptides derived from traditional Greek yoghurt on expression of pro- and anti-inflammatory genes by ovine monocytes and neutrophils

ABSTRACTThe objective of the present study was to examine the effect of yoghurt peptides on expression of various pro- and anti-inflammatory genes by ovine monocytes and neutrophils. A total of eight commercial traditional-type Greek yoghurts made with ovine or bovine milk were used. Water-soluble extracts (WSEs) were obtained from all samples. Peptides present in WSE induced cyclooxygenase-2 gene expression and down-regulated inducible NO synthase, Interleukin-1 Receptor Antagonist and Ιnterleukin-12β gene expression in both cell types. Treatment of neutrophils with WSE resulted in a decrease in Interleukin-1β gene expression relative to control. There was a different response from monocytes and neutrophils regarding Transforming Growth Factor-β1 gene expression with an increase by monocytes and a decrease by neutrophils relative to control. Expression of Ιnterferon-γ and Ιnterleukin-10 remained unaffected. In conclusion, peptides derived from Greek yoghurt exhibited a mixed effect (pro- and anti-inflammatory) on two immunocompetent cell populations, although the anti-inflammatory effect was more pronounced.

Effects of fermentation with Lactobacillus rhamnosus GG on product quality and fatty acids of goat milk yogurt

The effect of fermentation with Lactobacillus rhamnosus GG on the product quality of goat milk yogurt using traditional yogurt starter was studied through single-factor experiments and orthogonal experiments. The optimum fermentation condition was evaluated by the titratable acidity of goat milk yogurt, water-retaining capability, sensory score, and texture properties; the fatty acids of the fermented goat milk were determined by a gas chromatograph. Results indicate that high product quality of goat milk yogurt can be obtained and the content of short-chain and medium-chain fatty acids can be decreased significantly when amount of sugar added was 7%, inoculation amount was 3%, the ratio of 3 lactic acid bacteria—Lactobacillus delbrueckii ssp. bulgaricus, Streptococcus thermophilus, and L. rhamnosus GG—was 1:1:3, and fermentation temperature was 42°C.

Effect of indigenous Lactobacillus rhamnosus isolated from bovine milk on microbiological characteristics and aromatic profile of traditional yogurt

The indigenous Lactobacillus rhamnosus DSA LR1 was isolated from milk that was obtained from a restricted geographical area in northeast Italy and it was chosen, among other isolated strains on the bases of its resistance to the pH of gastric juices, the bile salts, the antibiotics and its lipolytic and proteolytic activities. The indigenous isolated potential probiotic bacteria were then added in combination with starter bacteria to the milk used for yogurt production. The results showed that L. rhamnosus DSA LR1 was able to maintain its viability for the entire shelf-life period without affecting on the viability or acidification capacity of starter culture.At the end of the fermentation period, the yogurt that had been co-fermented with L. rhamnosus DSA LR1 presented an aroma profile that was qualitatively similar to the control yogurt but less intense from a quantitative point of view. However, all of the major volatile compounds tended to increase during storage at 4 °C for 20 days, yogurt with L. rhamnosus had absolute areas larger than the areas of the control yogurt for all major carbonyl compounds.

Identification, typing and functional characterization of dominant lactic acid bacteria strains from Iranian traditional yoghurt

Interest in the microbiota of traditional fermented dairy products, such as yoghurt, continues due to the need for new lactic acid bacteria (LAB) strains that can complement or replace currently-in-use starters. In this work, five traditional yoghurts and one milk sample (for making yoghurt) from different areas of the Khorasan-e-Razavi region, Iran, were subjected to microbial characterization. Among the 102 isolates recovered, which included 29 from milk, the thermophilic LAB species Streptococcus thermophilus (34) and Lactobacillus delbrueckii (36) (with similar numbers of the subsp. bulgaricus and lactis) were the majority bacteria in all samples. Wide intra-species phenotypic and genetic diversity was encountered among the isolates. The safety and technological features of 29 strains belonging to the species S. thermophilus, L. delbrueckii and Lactobacillus helveticus, all candidates for use in yoghurt-making, were examined. In culture, two S. thermophilus strains produced the biogenic amine histamine from histidine (its precursor amino acid), and five L. delbrueckii strains showed atypical resistance to tetracycline (MIC ≥ 8 μg mL−1). The remaining strains coagulated milk, producing a coagulum of good appearance and pleasant acidic aroma. None of them produced appreciable amounts of exopolysaccharides in milk under the incubation conditions. After fermentation of milk with individual and mixed strains, major yoghurt aroma volatile compounds (i.e. acetaldehyde, diacetyl and acetic acid) were detected. Also as being used in the design of commercial starters, the thermophilic LAB strains characterized in this study might be used to help improve the safety of traditional yoghurts, while maintaining their original qualitative and sensorial characteristics.

Growth and viability of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus in traditional yoghurt enriched by honey and whey protein concentrate.

The ability of whey protein concentrate (WPC) (1% w/v) and/or honey (2% and 4% w⁄v) to improve lactic acid bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) growth and viability in yoghurt during a 21 day period of storage was investigated. Another focus of this study was to examine fermentation kinetics and post-acidification rates through pH and lactic acid content measurements over the 21 day period. The addition of WPC and acacia honey accelerated fermentation and improved lactic acid bacteria (LAB) growth over the 21 days, but honey proportion did not significantly affect the viability of LAB. Moreover, adding honey and WPC did not support the overproduction of lactic acid, which positively influenced yoghurt stability during the 21 day storage period.