The combined effect of probiotic cultures and incubation final pH on the quality of buffalo milk yogurt during cold storage

The effect of jicama (Pachyrhizus erosus L.) starch on the properties and probiotic potential of L. plantarum SN13T fermented milk

Objective

This study investigated the application of Jicama starch (Pachyrhizus erosus L.) as a stabilizing agent to enhance the longevity and integrity of fermented milk.

Materials and Methods

Lactobacillus plantarum SN13T (6 gm/100 ml) and Jicama starch (2 gm/100 ml) were added into pasteurized milk (65°C, 30 min) and then incubated under anaerobic conditions at 37°C for 18 h. The fermented milk was stored at 4°C. The evaluation on proximate composition, pH, titratable acidity (TA), viscosity, water holding capacity (WHC), syneresis, total lactic acid bacteria (LAB), and hedonic sensory evaluation was conducted at 1, 7, 14, 21, and 28 days of storage.

Results

Throughout the storage period, fermented milk enriched with Jicama starch significantly (p < 0.05) increased pH, TA, population dynamics of LAB, viscosity, WHC, and syneresis. It effectively sustained WHC and mitigated syneresis, thus ensuring the preservation of vital product quality. Furthermore, the quantity of LAB within the fermented milk consistently met the probiotic threshold of 84.50 × 108 CFU/ml. The hedonic sensory evaluation results indicated that fermented milk showed consistent sensory attributes throughout storage, except for overall acceptance, which declined on day 28.

Conclusion

The addition of Jicama starch revealed a promising health probiotic product, presenting a viable avenue for delivering probiotic benefits to consumers while maintaining the palatability and efficacy of the product.

High performance poly(L-lactic acid)-based film by one-step synthesis of poly (L-lactic acid-co-butylene itaconate-co-glycolic acid) for efficient preservation of yogurt storage

Biodegradable poly(L-lactic acid) (PLLA) has seldom used for dairy packaging due to medium permeability and brittleness. Novel PLLA copolymers, poly (L-lactic acid-co-butylene itaconate-co-glycolic acid) (PLBIGA), were developed by integrating glycolic acid (GA) and poly(butylene itaconate) (PBI) into PLLA's structure using low molecular weight PLLA as a key initiator. Then, packaging materials with better barrier and mechanical properties were obtained by blended PLBIGA with PLLA. Both PLLA/PLBIGA films and polyethylene nylon composite film (PE/NY) were used for stirred yogurt packaging and storage at 4 °C for 25 days. Results revealed that yogurt packed by PLLA/PLBIGA films maintained stabler water-holding capacity, color, and viscosity over the storage period. Moreover, the integrity of the gel structure and the total viable count of lactic acid bacteria in yogurt packaged in PLLA/40-PLBIGA8 were also found to be superior to those in PE/NY packages, highlighting its eco-friendly advantages in dairy packaging.

Physiochemical and Microbial Analysis of Tibetan Yak Milk Yogurt in Comparison to Locally Available Yogurt

Yak yogurt, which is rich in microorganisms, is a naturally fermented dairy product prepared with ancient and modern techniques by Chinese herdsmen in the Qinghai-Tibet Plateau. The objective of this research was to assess the impact of Lactobacillus bulgaricus and Streptococcus thermophilus starter cultures on the quality and shelf life of yak yogurt, as well as the genetic stability across multiple generations, in comparison to commercially available plain yogurt and peach oat flavor yogurt. Following that, the samples were evenly divided into four treatment groups denoted as T1 (treatment 1), T2, T3, and T4, with each group employing a distinct source of yogurt formulation. T1 included L. bulgaricus, T2 comprised S. thermophilus, T3 consisted of plain yogurt, and T4 represented peach oat yogurt flavor. The findings indicate that T1 yogurt consistently presents a lower pH and higher acidity compared to the other three yogurt types throughout the entire generation process. Moreover, the fat content in all generations of the four yogurt types exceeds the national standard of 3.1 g/100 g, while the total solid content shows a tendency to stabilize across generations. The protein content varies significantly among each generation, with T1 and T4 yogurt indicating higher levels compared to the T2 and T3 yogurt groups. In terms of overall quality, T1 and T4 yogurt are superior to T2 and T3 yogurt, with T1 yogurt being the highest in quality among all groups. The findings revealed that the inclusion of L. bulgaricus led to enhanced flavor, texture, and genetic stability in yak yogurt. This study will serve as a valuable source of data, support, and methodology for the development and screening of compound starters to be utilized in milk fermentation in future research and applications.

Milk fermentation by monocultures or co-cultures of Streptococcus thermophilus strains

Direct vat-set starter cultures are the key ingredient for the production of fermented dairy products. The characteristics of the strains used for fermentation determine the fermentation time, texture and flavor of the fermented milk products. In this study, a large-scale analysis of the acid production rate, texture, carbon source utilization characteristics of Streptococcus thermophilus strains was conducted. All 100 S. thermophilus strains were divided into six groups according to the acid production rate and into two groups according to the consistency texture. A universal medium, basing on the carbon sources metabolic properties were optimized (0.5% lactose and 3.5% glucose), to culture all of the tested strains. Among them 40 strains were used to test pH-controlled conditions using this universal culture medium. After 5-7 h of fermentation, the optical density (OD) values of all fermented products exceeded 10, suggesting the potential for high-density cultivation of S. thermophilus. Although the OD could be further increased by adding more glucose, this may have hindered subsequent lyophilization because of high residual lactic acid in the fermented product. Next, the application of Streptococcus thermophilus strains in fermented milk was studied. Monocultures and co-cultures of strains were evaluated and compared. The results revealed the existence of symbiotic or competitive relationships between different S. thermophilus strains. Based on the findings, the mixing ratio of three symbiotic S. thermophilus strains was optimized. A co-culture of these three strains yielded fermented milk with high viscosity, low post-acidification, good sensory properties and processability.

Fortification of cocoa semi-skimmed milk formulations with native lactic acid bacteria: Cell viability, physicochemical and functional properties for developing novel foods

This study aimed to evaluate several cocoa semi-skimmed milk formulations (CSMFs) as potential carriers of native lactic acid bacteria (LAB) strains to obtain novel probiotic beverages (PBs) with improved technological and functional characteristics, and satisfactorily organoleptic acceptance. The viability of two native LAB (Lactiplantibacillus plantarum UTNGt2 and Lactiplantibacillus pentosus UTNGt5) was assessed in comparison with two references (Lactococcus lactis subsp. lactis ATCC11474 and Limosilactobacillus reuteri DSM17938) strains in supplemented CSMFs throughout storage with refrigeration. The optimum conditions to produce novel beverages supplemented with native LAB were pH 6.6, 42°C, and 1 h of fermentation. Moreover, the effect of LAB strains fortification on pH, titratable acidity, total solids (°Brix), total polyphenolic compounds (TPC), antioxidant capacity (AOX), and ascorbic acid content (AAC), total proteins and fat, at initial and final storage was evaluated. The addition of two native LAB strains did alter the physicochemical quality of CSMFs to a lesser extent, where the bioactive molecules improved significantly (p < 0.05) with the increase of cocoa concentration and depending on the supplied strain. Although a statistically significant (p < 0.05) decrease in cell counts was recorded during storage, the LAB cells were found to be viable up to 21 days of storage at 4°C (>6 logCFU/ml), which is sufficient in number to prove their stability in vitro. Overall organoleptic results suggested that LAB supplementation had a significant impact on sensory attributes with satisfactory acceptability (>78%) of PBs containing the native strains and 1-2% cocoa, while CSMFs counterparts were less appreciated (40%) as perceived off-flavor. It appears that supplying bacteria to CSMF preserves flavor in the final product. Furthermore, the final beverages were free of harmful bacteria; thus, they comply with consumer safety regulations. This study concludes that CSMF can be used as a carrier of native LAB strains, maintaining cell viability, unaltered physicochemical properties, and improved functional and sensory characteristics, for which final beverages can be regarded as functional food. From the application standpoint, these formulations are an alternative to delivering native LAB strains and could help the cocoa and dairy industry to develop more attractive products for the growing regional market.

Digital technologies to assess yoghurt quality traits and consumers acceptability

BACKGROUND

Sensory biometrics provide advantages for consumer tasting by quantifying physiological changes and the emotional response from participants, removing variability associated with self-reported responses. The present study aimed to measure consumers' emotional and physiological responses towards different commercial yoghurts, including dairy and plant-based yoghurts. The physiochemical properties of these products were also measured and linked with consumer responses.

RESULTS

Six samples (Control, Coconut, Soy, Berry, Cookies and Drinkable) were evaluated for overall liking by n = 62 consumers using a nine-point hedonic scale. Videos from participants were recorded using the Bio-Sensory application during tasting to assess emotions and heart rate. Physicochemical parameters Brix, pH, density, color (L, a and b), firmness and near-infrared (NIR) spectroscopy were also measured. Principal component analysis and a correlation matrix were used to assess relationships between the measured parameters. Heart rate was positively related to firmness, yaw head movement and overall liking, which were further associated with the Cookies sample. Two machine learning regression models were developed using (i) NIR absorbance values as inputs to predict the physicochemical parameters (Model 1) and (ii) the outputs from Model 1 as inputs to predict consumers overall liking (Model 2). Both models presented very high accuracy (Model 1: R = 0.98; Model 2: R = 0.99).

CONCLUSION

The presented methods were shown to be highly accurate and reliable with respect to their potential use by the industry to assess yoghurt quality traits and acceptability. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Physicochemical properties, sensory characteristics, and antioxidant activity of the goat milk yogurt probiotic Pediococcus acidilactici BK01 on the addition of red ginger (Zingiber officinale var. rubrum rhizoma)

Background and Aim:

Yogurt contains beneficial probiotics. Addition of red ginger to yogurt as an antioxidant source becomes a way to improve the flavor and functional properties of yogurt. This study aimed to examine yogurt processing and the effect of adding red ginger (Zingiber officinale var. rubrum rhizoma), as an antioxidant source, on Pediococcus acidilactici BK01. It sought to observe the physicochemical and sensory qualities during storage (4°C).

Materials and Methods:

Goat milk was obtained from local farmers in Lubuk Minturun, Padang, West Sumatra, Indonesia. The yogurt was divided into two factors. Factor A was supplemented with red ginger in various concentrations: A (0% – as control), B (1%), C (2%), and D (3%). On the other hand, Factor B was subjected to variations in storage time: A (1 day), B (15 days), and C (30 days). Each treatment was conducted in triplicate. Physicochemical properties (pH, titratable acidity [TTA], and proximate analysis), sensory characteristics, and antioxidant activity (2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity) were measured using the standard tests. The data were analyzed through analyzing multivariate (analysis of variance) supported by Duncan’s multiple range test.

Results:

The addition of red ginger juice increased the antioxidant activity, TTA, and water holding capacity (WHC) (p<0.05), while syneresis was significantly decreased; however, it had no effect on the total lactic acid bacteria. At the end of this research (day 30), the yogurt was still suitable for consumption, with the following composition: Antioxidant activity 48.39%, pH 4.3, TTA 1.716, water content 80%, protein 3%, fat 3%, syneresis 28%, WHC 63%, and total lactic acid bacteria 89×10⁸ colony-forming units/mL. Furthermore, yogurt supplemented with red ginger changed its color into red blush.

Conclusion:

Yogurt red ginger juice is recommended as a functional drink, as it contains probiotics P. acidilactici BK01 and antioxidants to support human health. The addition of up to 3% ginger juice and a storage period of 30 days are still favored by the panelists and meet the quality standard of yogurt. We have not conducted the study on active compounds so, further research could be conducted on the components of the active compounds found in red ginger yogurt.

The Potential of Olive Leaf Extract as a Functional Ingredient in Yoghurt Production: The Effects on Fermentation, Rheology, Sensory, and Antioxidant Properties of Cow Milk Yoghurt

Background: Yoghurt has been traditionally consumed for its high nutritional value and health-promoting benefits. The addition of plant extracts as a source of phenolic compounds and bio-flavonoids has attracted much attention recently since milk and dairy products are deficient in these health-protecting components. Accordingly, olive leaf extract (OLE) has been considered due to the presence of bioactive compounds, primarily polyphenols. Thus, the aim of this research was to investigate the possibility of adding OLE into cow milk yoghurt as a potential functional ingredient. Methods: Yoghurts enriched with OLE (1.5, 3, and 5% v/v) were produced and compared with yoghurt without OLE. In all samples acidity, viscosity, colour, syneresis, water holding capacity (WHC), microbiological parameters, sensory properties, total phenols, and antioxidant activity (DPPH and FRAP methods) were determined. Results: The addition of OLE resulted in shorter fermentation and lower pH, but it had no adverse effect on the viability of yoghurt starter bacteria. OLE-enriched yoghurts showed increased syneresis, higher total phenols content, and antioxidant activity, while WHC and viscosity decreased. Sensory properties were slightly poorer for yoghurts containing higher OLE concentrations. Considering all of the obtained results, the addition of 1.5% OLE appeared to be optimal.

Comparative effects of probiotic and paraprobiotic addition on microbiological, biochemical and physical properties of yogurt

Paraprobiotics are inactivated probiotics that exert various health and technological benefits making them suitable for production of functional yogurt. In the present study, probiotic yogurt containing Lactobacillus acidophilus ATCC SD 5221 and Bifidobacterium lactis BB-12 and paraprobiotic yogurt containing inactivated form of the mentioned bacteria were produced and were compared regarding microbiological, biochemical, and physical properties during 28 days of storage at refrigerated temperature. Results revealed that the greatest mean pH drop rate, mean acidity increase rate, mean redox potential increase rate, final acidity and final redox potential were observed in yogurt containing inactivated L. acidophilus added before fermentation. The highest lactic acid after 28 days of storage was obtained in samples prepared by addition of paraprobiotic form of L. acidophilus after fermentation. Yogurt samples with B. lactis and L. acidophilus added after fermentation showed the highest and lowest acetic acid level, respectively after 28 days of storage. The samples containing L. acidophilus and B. lactis had the highest acetaldehyde on day 0 while on day 28, L. acidophilus had more impact on acetaldehyde generation in yogurts. Addition of paraprobiotics increased viability of starter cultures. In addition, incorporation of inactivated probiotic cells into yogurt resulted in lower syneresis and the higher WHC compared to probiotic yogurt samples. Regarding color parameters, it was observed that color parameters (a*, b* and L*) were not influenced by paraprobiotic in probiotic and paraprobiotic yogurts. Overall, it can be concluded that incorporation of paraprobiotics into yogurt involves less technological challenges and can be considered as a suitable appropriate alternative for probiotics in development of functional yogurt.

Biological reduction of aflatoxin B1 in yogurt by probiotic strains of Lactobacillus acidophilus and Lactobacillus rhamnosus

The present study was conducted to investigate the ability of two probiotic strains, L. acidophilus PTCC 1643 and L. rhamnosus PTCC 1637, to bind aflatoxin B1 (AFB1, 20 ng/ml) in comparison with yogurt starter cultures, at equal bacterial count (~ 109 LogCFU/ml) during a 21-day storage period at 4 °C. All assessed treatments exhibited high percentages of AFB1-binding, ranged from 64.56 to 96.58%. However, the ability of probiotic bacteria was statistically higher than yogurt starter cultures. Aflatoxin binding ability of the selected lactic acid bacteria was dependent on both time and bacteria species. The highest and the lowest percentages of AFB1-removal was observed at 11th day of cold storage by L. rhamnosus (96.58 ± 3.97%) and at the first day of storage for yogurt starter cultures (64.56 ± 5.32%), respectively. The stability of bacterial cells-AFB1 complex was remarkable, since only 0.84-26.75% of bounded AFB1 was released from bacterial cells after 3 times washing during the storage period.

Effect of commercial yogurt starter cultures on fermentation process, texture and sensoric parameters of white yogurt

In this work, we have compared and described the fermentation process of two commercial yogurt starter cultures during the white yogurt production. We used freeze-dried thermophilic starter culture YoFlex® YF - L812 and deep-frozen starter culture Delvo® Fresh YS – 241 for the production of white yogurts. We analysed titration acidity, active acidity, total viable counts, texture, and sensory parameters of white yogurts produced in laboratory conditions. This research was performed for dairy company Mliekareň Kopanice Selce, s.r.o., Slovakia. We did not found statistically significant differences (p >0.05) in titration acidity of both yogurts after 7 hours of fermentation. We did not found statistically significant differences (p >0.05) in the pH of both yogurts after 7 hours of fermentation. We found statistically significant differences (p <0.05) in all textural parameters (hardness, consistency, cohesion, and viscosity). The total viable count of microorganisms in yogurts after 24 hours of fermentation was 6.28 x 107 and 7.14 x 107 respectively.

Probiotic Potential and Technological Properties of Bacteriocinogenic Lactococcus lactis Subsp. Lactis UTNGt28 from a Native Amazonian Fruit as a Yogurt Starter Culture

A native Lactococcus lactis subsp. lactis UTNGt28 (GenBank accession no: MG675576.1) isolated from Amazonian fruit of the tropical Caimitillo (Chrysophyllum oliviforme) tree and the commercial strain Lactococcus lactis subsp lactis ATCC11454 (LacAT) were targeted ex vitro in whole milk in combination with Streptococcus thermophilus ATCC19258 to obtain a fermented probiotic beverage. Concomitant with cell viability determination during storage (28 days), the pH, titratable acidity, syneresis, protein and fat were evaluated. The results indicated that neither UTNGt28 nor LacAT displayed a high capacity to ferment whole milk and survive during storage; a statistically significant difference (p < 0.05) in cell viability was registered for UTNGt28 compared with LacAT when inoculated alone or in combination with S. thermophilus. A principal component analysis showed a clear difference between the yogurt formulations at day 1 and 28 of storage. The PC 1 explained 46.8% of the total variance (day 28), was loaded in the negative (-) direction with titratable acidity (% lactic acid), while the PC 2 explained 22.5% (day 1) with pH. PC 1 was loaded in the positive (+) direction with pH, cell viability, syneresis, fat and protein. Overall results indicated that UTNGt28 has the technological properties for further development of a new probiotic product.

Evaluation of Physicochemical and Antioxidant Properties of Yogurt Enriched by Olive Leaf Phenolics within Nanoliposomes

Olive leaf extract is a rich source of phenolic compounds and oleuropein which is well-known regarding its antioxidant and antimicrobial attributes. However, the mentioned phenolic compounds will lose their beneficial properties during storage and induce undesirable aftertaste in food products. In this study, olive leaf extract-bearing nanoliposomes were produced via the ethanol injection method and using phosphatidyl choline plus cholesterol as the reagents for the wall material. Later, the prepared nanocarriers were examined in regard to their zeta potential, stability, encapsulation efficiency, and particle size. Moreover, the prepared nanoliposome-loaded yogurt samples were examined considering syneresis, antioxidant activity, pH, acidity, color, and sensorial properties. The mean particle size of the fabricated nanoliposomes was in the range of 25-158 nm. Also, the entire formulation had a negative charge. The encapsulation efficiency was between 70.7 to 88.2%. Besides, the application of nanoliposomes in yogurt improved the antioxidant activity, and unlike the yogurt with nonencapsulated olive extract, no significant changes in color and sensorial attributes were observed and even the syneresis rate was minimized. To conclude, olive leaf phenolics can be entrapped within nanoliposomes with a considerable encapsulation efficiency for application in food products like yogurt to increase their nutritional value and public acceptance.