The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes.
Antimicrobial resistance has become a global public ...health concern, and antibiotic resistance genes (ARG) in food are a research focus. In China, probiotics and pasteurized yogurts are the 2 main types of commercially available yogurt, but the distribution and differences of antibiotic-resistant bacteria and gene types in these products are not well known. This study used a shotgun metagenomic approach to analyze 22 different types of yogurt collected from 9 main yogurt-producing areas in China; each type of yogurt included 8 different batches of samples. The abundance and diversity of bacteria identified in probiotic yogurt were significantly higher than those in pasteurized yogurt, with Acetobacter, Raoultella, and Burkholderia identified as unique and highly abundant genera in probiotic yogurt. Similarly, the abundance of Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. was higher than that in pasteurized yogurt. A total of 1,149 ARG subtypes belonging to 16 ARG types were identified, with the highest abundance of rifampicin, multidrug efflux pumps, and quinolone resistance genes detected. Network analysis revealed significant nonrandom co-occurrence relationships between different types and subtypes of ARG in yogurt samples. A total of 44 ARG subtypes in pasteurized yogurt were potentially hosted by 36 bacterial genera, and in probiotic yogurt, 63 ARG were expected to be hosted by 86 bacterial species from 37 genera. These findings indicate potential safety issues in fermented dairy products and emphasize the need for a more hygienic environment when processing probiotic yogurt.
The present study investigated the effects of three strains of probiotic Lactobacillus spp. such as Lactobacillus rhamnosus (Lr), Lactobacillus casei (Lc), or Lactobacillus plantarum (Lp) in ...co-cultures with Streptococcus thermophilus (St) and Lactobacillus delbrueckii subsp. Lactis (Ll) on the changes of post-acidification, viability of lactic acid bacteria (LAB), total phenolic and flavonoid contents, and antioxidant activity of cashew milk (W) - based yogurt (Y) during 0, 7, 14, & 21 days of storage. In addition, sensory evaluation of all yogurt samples was run during the first day of storage. The addition of Lr decreased significantly the pH in cashew milk-based yogurt compared to control-yogurt (C-Y; containing only St and Ll) throughout 21 days of storage. Cashew milk-based yogurt showed an increment in LAB counts, total phenolic and flavonoid contents, and antioxidant capacity content which is relatively dependent on the probiotic Lactobacillus spp. strains. WLp-Y showed lower sensory attributes scores. In conclusion, L. rhamnosus, L. casei, and L. plantarum could be used as a starter culture in cashew milk-based yogurt production with a potential source of natural antioxidants.
•WLr-Y decreased significantly the pH compared to control-yogurt.•WLr-Y exhibited the highest TFC and among other treatments.•WLr-Y exhibited the highest DPPH scavenging activity.•WLp-Y showed the highest FIC and FRAP values at 21 days of storage.•L. plantarum lower taste, flavor, and overall acceptability scores of yogurt.
Fermented foods and beverages possess various nutritional and therapeutic properties. Lactic acid bacteria (LAB) play a major role in determining the positive health effects of fermented milks and ...related products. The L. acidophilus and Bifidobacteria spp are known for their use in probiotic dairy foods. Cultured products sold with any claim of health benefits should meet the criteria of suggested minimum number of more than 10⁶ cfu/g at the time of consumption. Yoghurt is redefined as a probiotic carrier food. Several food powders like yoghurt powder and curd (dahi) powder are manufactured taking into consideration the number of organisms surviving in the product after drying. Such foods, beverages and powders are highly acceptable to consumers because of their flavor and aroma and high nutritive value. Antitumor activity is associated with the cell wall of starter bacteria and so the activity remains even after drying. Other health benefits of fermented milks include prevention of gastrointestinal infections, reduction of serum cholesterol levels and antimutagenic activity. The fermented products are recommended for consumption by lactose intolerant individuals and patients suffering from atherosclerosis. The formulation of fermented dietetic preparations and special products is an expanding research area. The health benefits, the technology of production of fermented milks and the kinetics of lactic acid fermentation in dairy products are reviewed here.
Two major quality defects of yogurt are syneresis and the presence of large particles, and several reasons have been extensively discussed. Vibrations during fermentation, particularly generated by ...pumps, must be considered as a further cause as latest research showed that both ultrasound and low frequencies induced visible particles. The aim of this study was to investigate the impact of sonication during fermentation with starter cultures differing in exopolysaccharide (EPS) synthesis on the physical properties of set (syneresis, firmness) and stirred yogurt (large particles, laser diffraction, rheology). Skim milk was fermented with starter cultures YC-471 (low EPS) or YF-L 901 (high EPS) (Chr. Hansen) and sonicated for 5min at pH5.2. Sonicated set gels exhibited syneresis and were softer than respective controls. The mechanical treatment was adjusted to quantify visible particles (d≥0.9mm) in stirred yogurts properly. Sonication significantly increased particle numbers, however, the effect was less pronounced when YF-L 901 was used, indicating EPS as a tool to reduce syneresis and particle formation due to vibrations. Rheological parameters and size of microgel particles were rather influenced by starter cultures than by sonication.
•Impact of short-time sonication (35kHz) during yogurt fermentation was investigated.•Comparison of two starter cultures differing in exopolysaccharide (EPS) production•Investigation of physical properties of both set and stirred yogurts•EPS prevented syneresis and the formation of large particles due to sonication•The mechanism of particle formation is discussed.
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Aim: The aim of this study was to encapsulate red pepper waste (RPW) bioactives and monitor their stability in yogurt.
Methods: RPW extract was encapsulated in whey protein using spray and ...freeze-drying techniques. Physicochemical characteristics of encapsulates were evaluated, and better encapsulates were used to develop functional yogurt. Retention of bioactives was followed over 21 days of storage, and sensory analyses were assessed.
Results: Freeze-dried encapsulates (FDE) showed better characteristics like water activity, moisture content, solubility, flowing and colour properties, and, therefore, incorporated in yogurt. Yogurt with FDE successfully retained carotenoids (71.43%) and caused increasing of polyphenol retention (up to 123.73%). This yogurt exhibited higher sensory and general acceptability scores compared to control sample. The fortification of yogurts had a positive influence on maintaining the initial number of lactic acid bacteria during storage.
Conclusion: Freeze drying and utilisation of pepper waste are efficient for functional food development, with improved nutritional, colour and bioactive properties.
Novel complexed microgels with enhanced pH and ion stability were constructed using heat-denatured soy protein isolate (SPI) and Chitosan (CS). Their characteristics and their effects on the ...textural, rheological, and tribological properties of soy yogurt were investigated. The complexed microgels showed larger particle sizes, lower surface hydrophobicity, and higher turbidity than pure SPI microgels. Incorporating the SPI-CS complexed microgels into the yogurts increased their protein content from 3.94% to 5.07% and reduced their fat content from 2.17% to 1.99%. Additionally, incorporating the microgels enhanced the texture of the yogurts, including increased firmness, elasticity, and viscosity, alongside improved water holding capacity (WHC). The incorporation of 0.8% SPI-CS microgels led to the optimum physicochemical characteristics. Rheological analyses demonstrated that incorporating SPI-CS microgels led to an increase in apparent viscosity and shear modulus. Furthermore, the presence of the SPI-CS microgels significantly improved the lubrication properties. Microstructural analysis showed subtle differences in the gel structure of the yogurts after microgel addition. The three-dimensional network structure within the microgel-fortified yogurts was more compact than that in the control. Thus, SPI-CS microgels potentially improve the nutritional profile and quality attributes of plant-based yogurt products.
•Soy protein isolate (SPI)-chitosan (CS) microgels were prepared and characterized.•Properties of soy yogurt after incorporation of SPI-CS microgels were investigated.•SPI-CS microgels can make up for the textural and structural deficiencies of soy yogurt.•SPI-CS microgels significantly improved the lubrication properties of soy yogurt.
The fermentation and quality characteristics of yogurt were investigated according to the inoculation concentration of Bifidobacterium longum. The total sugar content of yogurt decreased as the ...fermentation time increased, and with an increased concentration of B. longum treatment the fermentation time decreased rapidly. As fermentation progressed, the lactose content decreased rapidly at the beginning and gradually decreased as the pH decreased. Depending on the B. longum treatment concentration, the lactose content varied from 0.29 ± 0.01 to 0.47 ± 0.01% and was 0.5% or less in all experimental groups. The experimental group inoculated with 0.0015% of B. longum displayed the best results in all categories, including pH, total acidity, lactic acid content, solid non-fat content, and total lactic acid bacteria count, which are factors that determine the quality of yogurt. In summary, the experimental group inoculated with 0.0015% of B. longum was determined to be the highest quality yogurt.
► Propionibacteria and bifidobacteria maintained high viability in yogurts during storage. ► Fruit juice appeared to help sustain the viability of L. acidophilus LA-5. ► Addition of fruit juice tends ...to enhance the sensory properties of goat’s milk yogurts.
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 (108cfu/g) in all types of yogurt throughout the storage period, while the viability of the bifidobacteria (∼107cfu/g) also remained above the minimum therapeutic level. The viability of L. acidophilus LA-5 fell below 106cfu/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.
Proto-cooperation between Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus is one of the key factors that determine the fermentation process and final quality of yoghurt. In ...this study, the interaction between different proteolytic strains of S. thermophilus and L. delbrueckii subsp. bulgaricus was investigated in terms of microbial growth, acidification and changes in the biochemical composition of milk during set-yoghurt fermentation. A complementary metabolomics approach was applied for global characterization of volatile and non-volatile polar metabolite profiles of yoghurt associated with proteolytic activity of the individual strains in the starter cultures. The results demonstrated that only non-proteolytic S. thermophilus (Prt−) strain performed proto-cooperation with L. delbrueckii subsp. bulgaricus. The proto-cooperation resulted in significant higher populations of the two species, faster milk acidification, significant abundance of aroma volatiles and non-volatile metabolites desirable for a good organoleptic quality of yoghurt. Headspace SPME-GC/MS and 1H NMR resulted in the identification of 35 volatiles and 43 non-volatile polar metabolites, respectively. Furthermore, multivariate statistical analysis allows discriminating set-yoghurts fermented by different types of starter cultures according to their metabolite profiles. Our finding underlines that selection of suitable strain combinations in yoghurt starters is important for achieving the best technological performance regarding the quality of product.
•S. thermophilus Prt+ did not show associative interaction with L. bulgaricus.•Only S. thermophilus Prt− performed proto-cooperation with L. bulgaricus.•Non-volatile polar metabolite profile of yoghurt was revealed by 1H NMR.•Overall yoghurt metabolite profile was determined by combining GC/MS and 1H NMR.•Multivariate analysis allows discriminating yoghurts based on metabolite profile.
One approach to avoid production of acid whey during the manufacture of high-protein yogurt and related products is to concentrate the milk before fermentation. However, the resultant gels are firm ...so that stirring in the tank and further processing are difficult on an industrial scale. We hypothesize that power ultrasound (US) during fermentation softens the gel because sound waves cause cavitation and strong shear forces in the fluid. Skim milk was standardized to different protein contents up to 12%, heated (85°C, 30 min), and acidified with thermophilic or mesophilic starter cultures. An excessive increase in gel firmness as a function of protein content was detected. In the next series of experiments, US was applied during fermentation. Milks (10% protein) were acidified at 43.5°C and sonicated from pH 5.8 to 5.1 with a sonotrode (20 kHz, 20 W). Immediately after fermentation, gels were agitated using a rheometer with a vane geometry. The maximum torque required to break the gel was reduced by 75% following US, and gel firmness was reduced by 80%. Gels were then processed into stirred yogurt and analyzed. Sonicated samples were smoother with fewer large aggregates. Confocal laser scanning microscopy images suggested a less cohesive structure and more compact microgel particles, resulting in reduced viscosity. We concluded that US is a promising tool to weaken the gel and facilitate further processing. This enables new approaches for the manufacture of Greek yogurt, particularly in regard to avoiding production of acid whey and developing products with novel textures.
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