Quality Of Fermented Dairy Products Research Articles

Influence of starter and sweetener on the syneresis intensity of fermented milk drink

Syneresis represents the appearance of separation of whey on the surface of the product and is considered an important parameter of the quality of fermented dairy products. For the production of the fermented milk drink, kombucha was used as a non-traditional starter. Two sweeteners were used, honey and sucrose.The aim of the work was to examine the influence of starter and sweetener on changes in the subsequent acidity and intensity of syneresis of the samples during storage. The results were compared with a control sample obtained by inoculation with a conventional starter culture. During storage, there was a drop in pH value and an increase in titratableacidity, as a resultof the constant metabolic activity of the microflora and the production of lactic acid in the produced samples. Honey, as a sweetener, had an effect on the lower pH value of the fermented milk drink samples. The analysis of variance showed a statistically significant difference in the titratable acidity results and the intensity of syneresis of the samples during storage.Samples that were produced with kombucha as a starter showed better structure stability during storage and better quality. During storage, sample kb4 showed the best structural stability and the lowest intensity of syneresis. KEYWORDS:stinging nettle extract;bioactive components;extraction;antioxidant

Quality assessment of buffalo milk Chakka prepared from different starter culture

Chakka is a soured dairy product that is producedby removing the whey from fermented milk (dahi, known as In-dian yogurt). The starter culture plays a significant role in deter-mining the overall elemental quality of fermented dairy products. The present study was carried to find out the suitability of three different cultures for development of chakka viz. T1 (1.5% Mixed microbial culture), T2 (1.5% bacterial culture, STI-13 freeze-dried Lactic culture), and T3 (1.5% yeast cultures). Among the different culture various quality characteristics, physico-chemical param-eters and sensory characteristics were assessed for their ability to form chakka. Curd prepared from the Lactobacillus culture(T2) was found most suitable for preparation of chakka as T2delivered highest yield of curd mass, protein, least pH value and moisture content compared to microbial culture and yeast culture. Sensory attributes of chakka also varied significantly (P0.05) among cultures. All sensory attributes rated higher for T2(Lactobacillus cultures). Therefore, result of the study concluded that T2 (1.5% Lactobacillus) culture was most appropriate for formulation of chakka.

Screening of mixed-species starter cultures for increasing flavour during fermentation of milk

Flavour is an important factor determining the quality of fermented dairy products. Three L.delbrueckii subsp. bulgaricus isolates and five Streptococcus thermophilus isolates with good fermentation characteristics were selected for evaluation as starter cultures when used in ten different combinations, and in comparison with a commercial starter. Using solid phase micro extraction-gas chromatography-mass spectrometry (SPME-GC-MS) analysis, a total of 55 volatile compounds and nine odour-active compounds were detected in milk fermented by mixed-species starter cultures C5 (L. delbrueckii subsp. bulgaricus IMAU62081: S. thermophilus IMAU40133). The results from partial least squares-discriminant analysis (PLS-DA), electronic nose (E-nose) analysis and sensory evaluation indicated that flavor composition and content of fermentation samples from the C5 mixture were closer to the commercial control than the other mixtures. These results help understand how volatile flavour compounds in yoghurt are affected by the starter culture; this will be useful in the development of value-added fermented dairy products.

Inclusion of Probiotics into Fermented Buffalo (Bubalus bubalis) Milk: An Overview of Challenges and Opportunities

Buffalo-milk-based dairy products provide various health benefits to humans since buffalo milk serves as a rich source of protein, fat, lactose, calcium, iron, phosphorus, vitamin A and natural antioxidants. Dairy products such as Meekiri, Dadih, Dadi and Lassie, which are derived from Artisanal fermentation of buffalo milk, have been consumed for many years. Probiotic potentials of indigenous microflora in fermented buffalo milk have been well documented. Incorporation of certain probiotics into the buffalo-milk-based dairy products conferred vital health benefits to the consumers, although is not a common practice. However, several challenges are associated with incorporating probiotics into buffalo-milk-based dairy products. The viability of probiotic bacteria can be reduced due to processing and environmental stress during storage. Further, incompatibility of probiotics with traditional starter cultures and high acidity of fermented dairy products may lead to poor viability of probiotics. The weak acidifying performance of probiotics may affect the organoleptic quality of fermented dairy products. Besides these challenges, several innovative technologies such as the use of microencapsulated probiotics, ultrasonication, the inclusion of prebiotics, use of appropriate packaging and optimal storage conditions have been reported, promising stability and viability of probiotics in buffalo-milk-based fermented dairy products.

Metabolic footprinting revealed key biochemical changes in a brown fermented milk product using Streptococcus thermophilus

Ultra-performance liquid chromatography coupled with a quadrupole-time-of-flight mass spectrometryElevated Energy was used to investigate changes in the metabolite profile of brown milk and fermented brown milk produced using Streptococcus thermophilus S10. Samples were analyzed in both positive and negative electron ionization modes. Data were analyzed by multivariate statistical methods for biomarker metabolites that were differentially abundant in brown milk and fermented brown milk. We identified 43 differentially abundant metabolites based on mass spectrophotometry fragmentation patterns. These metabolites included peptides, AA, fatty acids and related metabolites, carbohydrate metabolites, vitamins, and nucleosides. Some of these metabolites are known to alter the sensorial quality of fermented dairy products. Thus, it is likely that some of the currently identified differentially abundant metabolites also contribute to the unique flavor, taste, and aroma of fermented brown milk. The bitterness and astringency of fermented brown milk are likely to be due to some of these peptides, whereas the sweetness and sourness could be a result of changes in carbohydrate levels. No previous study has analyzed metabolomics changes during fermentation of brown milk. Thus, our data are a valuable reference for future development and improvement of fermented brown milk products.

The impact of bacterial cultures on changes in contents of PCB congeners in yoghurt and bioyoghurt

Persistent organic pollutants, including polychlorinated biphenyls, may pose serious health hazard to consumers due to their lipophilic character as well as their high stability and toxicity. They are common in milk and also in dairy products. Therefore, to provide consumers with food of the lowest possible level of pollutants, it is important to estimate the influence of technological processes in milk and dairy products manufacture on changes in the contents of toxic PCB congeners. The PCB congeners content was determined using gas chromatography with mass spectrometry. Our study showed that yoghurt starter cultures turned out to be an effective tool in decreasing the toxicity equivalent of yoghurts. The presence of additional two starter cultures of bacteria Lactobacillus acidophilus and Bifidobacterium sp. In the A.B.T. bioyoghurt starter culture was most likely the reason of the highest efficiency of this culture to reduce the value of toxicity equivalent (TEQPCB) in bioyoghurts (reduction by nearly 50 %). However, none of the four tested starter cultures of yoghurts and bioyoghurts ensured complete biodegradation of any of the tested PCB congeners. These cultures contributed to a distinct reduction in contents of the PCB congeners in the finished products and, simultaneously, to a significant increase in PCB 28 and PCB 77, which may result from the degradation of more chlorinated congeners. In consequence it can improve the quality of fermented dairy products.

The effect of non-conventional starter culture on lipid nutritional quality of fermented dairy products

In this study, the effects of kombucha inoculum as non-conventional starter culture on fatty acids composition of fermented milk, compared to a commercial probiotic (ABT-7) and yoghurt (YF-L812) starter cultures, during 21 days of storage was investigated. Fatty acids composition was determined by gas chromatography-mass spectrometry after the previous extraction of lipids and derivatization. The atherogenic (AI) and thrombogenic (TI) indices determined on the basis of fatty acids composition have been used for evaluation of the nutritive lipid quality of the fermented dairy products. The most significant levels of fatty acids in fermented milk products were palmitic, followed by oleic, stearic and myristic fatty acids. Fermented milk products were characterized by low atherogenic (2.14-2.39) and thrombogenic (2.91-3.18) indices, suggesting their consumption could have a favorable effect on human health. The AI and TI were comparable during the storage of fermented milk samples. Starter culture did not affect the health-related fatty acid composition of fermented milk products during storage.

Ultrasound pretreatment of fermented milk containing probiotic Lactobacillus plantarum AF1: Carbohydrate metabolism and antioxidant activity

AbstractThe effect of ultrasound (100 W, 30 kHz, 25% amplitude for 5, 10, and 15 min; US) on growth, carbohydrate metabolism, and antioxidant activity of probiotic Lactobacillus plantarum AF1 was investigated during milk fermentation. The antioxidant activity of L. plantarum AF1 was measured by 2,2′‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonate) (ABTS), 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), inhibition of the autoxidation of ascorbate, reducing ability, and superoxide anion radical scavenging activity tests. The results indicated that the cell membrane permeability of sonicated samples was increased 88–94% compared to control. Additionally, β‐galactosidase activity and population of Lactobacillus strain increased with increasing ultrasound treatment time during the fermentation after the treatment. However, no significant differences were observed in the final counts of the control and the sonicated samples at the end of fermentation (24 hr). Although the lactose content was decreased significantly (p ≤ .05) by extending sonication time, the amounts of glucose, galactose, and lactic acid enhanced significantly (p ≤ .05) as the time of fermentation and sonication proceeded. The antioxidant activity was also enhanced significantly (p ≤ .05) with increase in sonication time during 24 hr fermentation after the treatment. Therefore, the lowest and the highest antioxidant activities were seen in the control sample and the US‐15 min sonicated milk at the end of fermentation, respectively.Practical applicationsThe dairy industry is seeking methods to increase nutritional and quality of dairy products. Recently, the ultrasound has attracted significant attention in food processing generally because of the recent consumers’ trend toward functional foods. The present study provides an investigation about the efficiency of ultrasound to improve the metabolism and growth of Lactobacillus plantarum during fermentation of milk and therefore increase the quality and antioxidant activity of milk. The results show that ultrasound is a potential technique for improve metabolism of Lactobacillus strain and thus increase antioxidant activity and quality of fermented milk. Consequently, the use of ultrasound will increase the health promoting effects and quality of fermented dairy products. These results will assist in designing ultrasound procedures for optimizing the general quality of fermented milk.

Influence of fat content and starter cultures on the quality of fermented dairy products

The objective of this study was to investigate the effect of fat content and type of the starter culture (traditional or probiotic) on physico-chemical quality, rheological and textural characteristics of the fermented dairy products during 14 days of storage. Seven different fermented dairy products of two different groups: stirred and set yoghurts were used in this study. The rheological and textural characteristics of the analyzed type of fermented dairy products after the production and during storage are dependent on the chemical composition, particularly fat content.

NoxE NADH Oxidase and the Electron Transport Chain Are Responsible for the Ability of Lactococcus lactis To Decrease the Redox Potential of Milk

The redox potential plays a major role in the microbial and sensorial quality of fermented dairy products. The redox potential of milk (around 400 mV) is mainly due to the presence of oxygen and many other oxidizing compounds. Lactococcus lactis has a strong ability to decrease the redox potential of milk to a negative value (-220 mV), but the molecular mechanisms of milk reduction have never been addressed. In this study, we investigated the impact of inactivation of genes encoding NADH oxidases (noxE and ahpF) and components of the electron transport chain (ETC) (menC and noxAB) on the ability of L. lactis to decrease the redox potential of ultrahigh-temperature (UHT) skim milk during growth under aerobic and anaerobic conditions. Our results revealed that elimination of oxygen is required for milk reduction and that NoxE is mainly responsible for the rapid removal of oxygen from milk before the exponential growth phase. The ETC also contributes slightly to oxygen consumption, especially during the stationary growth phase. We also demonstrated that the ETC is responsible for the decrease in the milk redox potential from 300 mV to -220 mV when the oxygen concentration reaches zero or under anaerobic conditions. This suggests that the ETC is responsible for the reduction of oxidizing compounds other than oxygen. Moreover, we found great diversity in the reducing activities of natural L. lactis strains originating from the dairy environment. This diversity allows selection of specific strains that can be used to modulate the redox potential of fermented dairy products to optimize their microbial and sensorial qualities.

Comparative influence of medium composition on biomass growth, lactic acid and Exopolysaccharides Production by some Strains of Lactic Acid Bacteria

To promote the overall quality of fermented dairy products (FDP) which depends on the types and characteristics of the starter organisms used in the production, the effect of medium composition on biomass growth, viscosity, exopolysaccharide and lactic acid production by EPSproducing lactic acid bacteria isolates was investigated. Medium composition had profound effect on the studied parameters. Among the five medium used for the cultivation of the isolates, maximum biomass growth and viscosity production was achieved in partially de-protenised whey medium (PDW) in which Lactococcus piscium (OLHF6) and Lactobacillus plantarum (LPN1) exhibit the highest biomass growth and viscosity with concentration of 1.58 and 1.561mPa.S. Lactobacillus plantarum (LPN1) (1.58mPa.S), L.casei (LCN1) (1.475 mPa.S), L.plantarum (LPN3) (1.48mPa.S), L.plantarum (LPY80 (1.48mPa.S) and Lactococcus piscium (OLHF6) (1.185mPa.S) was found to be a good starter for development of viscous medium in the respective media. Whey was the best medium for EPS production in which L. casei (LCN1)) was the best starter (198.69mg/l). Sweet whey medium, modified MRS medium, Whey and partially deproteinised whey medium was not favourable for lactic acid production by the isolates but Semidefine medium was the best for lactic acid development in which L.plantarum (LPW10) was found to be the best starter for lactic acid development (5.57g/l).

Bacteriophages in dairy products: Pros and cons

Since the time bacteriophages were first identified as a major cause of fermentation failure in the dairy industry, researchers have been struggling to develop strategies to exclude them from the dairy environment. Over 70 years of research has led to huge improvements in the consistency and quality of fermented dairy products, while also facilitating an appreciation of the beneficial properties of bacteriophages with respect to dairy product development. With specific reference to Lactococcus lactis and cheese production, this review outlines some recently reported novel methods aimed at limiting the bacteriophage infection as well as highlighting some beneficial aspects of bacteriophage activity.