Set Yoghurt Research Articles

Effect of β‐glucan on the properties of probiotic set yoghurt with Bifidobacterium animalis subsp. lactis strain Bb‐12

In this study, the effects of β‐glucan from two different cereal sources (barley and oat), as prebiotics, on the viability of Bifidobacterium animalis subsp. lactis strain Bb‐12 in probiotic set yoghurt and the properties of yoghurt were studied. Physicochemical properties of yoghurt samples (including pH, titratable acidity (La%), whey separation, organic acids such as lactic and acetic acid, colour (L*, a*, b*, ΔE, C*, h*) and sensorial properties) were significantly affected by the addition of barley‐ and oat‐based β‐glucan. As a result, the survival of B. animalis subsp. lactis was maintained within probiotic and therapeutic levels (>7 log cfu/g), due to the possible prebiotic effect of barley‐ and oat‐based β‐glucan, after 28 days of cold storage of the probiotic yoghurt. In conclusion, β‐glucan can be used for the development of cereal‐based functional dairy products with sufficient beneficial effects, probiotic viability and acceptable sensory characteristics.

Viability of Probiotic Bacteria during Refrigerated Storage of Commercial Probiotic Fermented Dairy Products Marketed In Jordan

Objectives: The study aimed to measure the viability of probiotic bacteria in different probiotic fermented dairy products marketed in Jordan during their shelf lives. Methods: Ten products which were all known commercial probiotic fermented dairy drinks were purchased from main market stores at 0 day of processing, and kept under 4oC for the assigned time intervals (1, 7, 14 day). These products included 7 stirred yogurt Activia, Activia low-fat, Actimel, Baladna, Acti-Yogho, Moffedo, and Vital, and 2 set yogurt (Activia - apricot and peach, Activia light – strawberry) and one stirred yogurt (Activia- stirred). Samples were tested for probiotic count at those intervals in an unopened refrigerated bottles. Sensory evaluation using hedonic scale was carried out on the above products in an unopened package at the same indicated intervals. Morphology of probiotic bacteria in commercial products was also confirmed microscopically.Results: The results of the viability of probiotic counts in log10 remaining above 7 log until the end of shelf life (14 d) except for four products including Moffedo, vital, Activia set yogurt light – strawberry, and Activia (stirred yogurt) which decreased to 3.4, 4.9, 5.0, and 5.0 respectively at the end storage period. The pH for all products until the end of the study were between 4.1- 4.5. The best average of all sensory characteristics using hedonic scale (8.3) was for Actimel, whereas the lowest (7.1) was for both Moffedo and Activia set yogurt- Apricot and peach.Conclusion: The counts of probiotic bacteria in fermented dairy products is not always above the therapeutic dose of 6.0 log cfu/g, which urge governmental authorities to establish a standard related to these products.

Monitoring the fermentation, post-ripeness and storage processes of set yogurt using voltammetric electronic tongue

A voltammetric electronic tongue (VE-tongue) was self-developed to monitor the fermentation, post-ripeness and storage processes of set yogurt. Multifrequency rectangular pulse voltammetry (MRPV) and multifrequency staircase pulse voltammetry (MSPV) were applied as potential waveforms, and the ‘area method’ was applied to extract feature data from the original responses. The ANOVA analysis was performed to evaluate the effects of electrodes and potential waveforms on the electrochemical responses, and the visualization of the Pearson Correlation Coefficient was performed to analyze the correlations among each combination of electrode and potential waveform. Discriminant function analysis worked better than principal component analysis based on the fusion data of MRPV- and MSPV-area data in classifying set yogurts in the stages of fermentation, post-ripeness and storage, respectively. VE-tongue with support vector machine (SVM) worked efficiently and stably in predicting the fermentation time, pH and viscosity of samples during the fermentation process; while the use of VE-tongue and partial least squares regression (PLSR) should be the first choice for the prediction work during the post-ripeness and storage processes. According to the classification and prediction results, the VE-tongue with different potential waveforms was proved a promising tool for monitoring the fermentation, post-ripeness and storage processes of set yogurt.

Physiochemical, texture properties, and the microstructure of set yogurt using whey protein-sodium tripolyphosphate aggregates as thickening agents.

Polymerized whey protein-sodium tripolyphosphate can be induced to gel in an acidic environment provided during fermentation. The variety of thickening agent has an influence on texture that is an essential aspect of yogurt quality affecting consumer preference. Similar to polysaccharide stabilizers, the cold gelation properties of whey proteins can improve the body texture of yogurt products. Polymerized whey protein-sodium tripolyphosphate could be a favorable and interesting thickening agent for making set yogurt. The effects of whey protein isolate (WPI), heat-treated whey protein-sodium tripolyphosphate (WPI-STPP), heat-treated WPI and pectin on the storage properties and microstructure of yogurt were investigated. All samples were analyzed for syneresis, pH, titratable acidity, viscosity, texture profile and microstructure during storage. The results showed that incorporating heat-treated WPI-STPP had a significant impact on syneresis (32.22 ± 0.60), viscosity (10 956.67 ± 962.1) and hardness (209.24 ± 12.48) (p < 0.05) with uniform body texture. Yogurt fermented with modified WPI-STPP had higher levels of protein and better hardness compared with yogurt using pectin. The microstructure was observed to be a uniform and denser, complicated network. Heat-treated WPI-STPP may be useful for improving yogurt texture. © 2016 Society of Chemical Industry.

Microbiological and Physicochemical Characteristics of Plain Set Yoghurt Manufactured by Traditional Plants in Khartoum State, Sudan

Microbiological and Physicochemical Characteristics of Plain Set Yoghurt Manufactured by Traditional Plants in Khartoum State, Sudan

The effect of non-standard heat treatment of sheep's milk on physico-chemical properties, sensory characteristics, and the bacterial viability of classical and probiotic yogurt.

Classical and probiotic set yogurt were made using non-standard heat treatment of sheep's milk at 60°C/5min. Physico-chemical properties, sensory characteristics, and the viability of bacteria that originated from cultures in classical and probiotic yogurt were analysed during 21days of storage at 4°C. For the production of yogurt, a standard yogurt culture and a probiotic strain Lactobacillus rhamnosus GG were used. At the end of storage time of the classical and probiotic yogurt the totals of non-denatured whey proteins were 92.31 and 91.03%. The viability of yogurt culture bacteria and Lactobacillus rhamnosus GG were higher than 106cfu/g. The total sensory score (maximum - 20) was 18.49 for the classical and 18.53 for the probiotic. In nutritional and functional terms it is possible to produce classical and probiotic sheep's milk yogurt by using a non-standard temperature of heat treatment with a shelf life of 21days.

Effect of ewe’s (semi-skimmed and whole) and cow’s milk yogurt consumption on the lipid profile of control subjects: a crossover study

ABSTRACTYogurt is the most widely consumed fermented milk product worldwide. Studies have mainly used milk and dairy products from cow, which have a lower fat content than those from ewe and a different lipid profile. This study investigated the effect on the lipid profile of control subjects of three different set yogurts: (a) semi-skimmed ewe´s milk yogurt (2.8% milk fat); (b) whole ewe´s milk yogurt (5.8 % milk fat); (c) cow´s milk yogurt (3 % milk fat). A randomized crossover study included 30 healthy adults (16 women) to consume 250 g/yogurt/day during three consecutive 5-weeks periods separated by 4-week washouts. Blood samples were collected at the start and end of each period for the analysis of serum cholesterol (total, HDL-, LDL-) and triglycerides. We found no differences in the serum concentrations of lipid and lipoprotein fractions of the volunteers after the intake of any of the three types of yogurts. When the volunteers were grouped into two risk groups of risk according to their total cholesterol/HDL cholesterol ratio, the same differences between the groups in terms of the cholesterol (HDL-, LDL-) and triglyceride responses at baseline and after yogurt intake were found, with no effects due to the different types of yogurts. Moreover, we performed compositional analysis of the yogurts including determination of protein, fat, minerals and fatty acids (FA). Contents in protein, calcium, magnesium, non-protein nitrogen and some FA (mainly short-chain-FA) were higher for ewe’s than for cow’s milk yogurt. n6-n3 ratio was lower in the ewe’s milk yogurt. In conclusion, yogurt intake, from ewe’s and cow’s milk, at levels of consumption compatible with a varied diet, neither decreases nor increases plasma lipoprotein cholesterol levels in apparently healthy individuals. As ewe’s milk yogurt has a high content of macro- and micronutrients, certain target populations could benefit from its consumption.

Effect of Levels of Buttermilk on Quality of Set Yoghurt

The effect of different levels of buttermilk and storage period on quality of set yoghurt was investigated. Four batches of set yoghurt were prepared using; fresh cow milk and 3% skim milk powder (control), fresh cow milk, 2.5% skim milk powder and 5% buttermilk (sample A), fresh cow milk, 2.0% skim milk powder and 10% buttermilk (sample B), fresh cow milk, 1.5% skim milk powder and 15% buttermilk (sample C) and stored at 4°C for 15 days. The stored samples were examined for quality changes at 15 days interval. The results indicated that, the total solid, protein, fat and pH values of set yoghurt decreased significantly (P ≤ 0.05) as levels of buttermilk increased and storage time progressed. Organoleptic quality of set yoghurt revealed that, 5% buttermilk scored the best appearance, texture, flavour and over all acceptability, followed by 0.0%, 10% and the worst was recorded for sample contains 15% buttermilk. Storage period significantly (P ≤ 0.05) affected the organoleptic quality of set yoghurt. The best score was obtained at the beginning of the storage period while the worst at the end.

Syneresis and rheological behaviors of set yogurt containing green tea and green coffee powders

This study aimed to investigate the effect of added green coffee powder (GCP) and green tea powder (GTP) on syneresis behavior and consistency of set yogurts. Adding GCP (1 or 2%) decreased syneresis rate. The effect of GTP on the syneresis rate was concentration dependent. In comparison to the control, GTP decreased syneresis rate when it was added at 0.02%, but it caused an increase when added at 2%. No significant difference was observed in the syneresis rates when GTP was added at 1 and 0.01%, until 14 and 7 d of storage, respectively. The Herschel-Bulkley model parameters indicated that the consistency of control was considerably lower than that of GCP yogurts during 14 d, whereas it was higher at the end of storage. The GTP yogurt results showed that the consistency coefficients of GTP yogurts were different from those of control samples until 14 d of storage. In conclusion, GTP and GCP behaved differently in acidified gel networks of set yogurt, modifying its rheological behavior, as they have different profiles and concentrations of polyphenols.

Fractionation by microfiltration: Effect of casein micelle size on composition and rheology of high protein, low fat set yoghurt

The effects of casein micelle size on rheological properties of high protein (5.6% crude protein), low fat (≤0.2%) set yoghurt were investigated. Microfiltration with 0.20 μm membranes was used to fractionate skim milk with an average casein micelle size of ∼174 nm into a retentate and a permeate containing “large” (∼183 nm) and “small” (∼129 nm) casein micelles, respectively. The permeate containing the small casein micelles was further concentrated with 0.10 μm membranes. Yoghurt milk bases with large or small casein micelles were subjected to heat treatment at two different temperatures; 95 °C or 75 °C for 5 min. Yoghurt milk base with small casein micelles gave set yoghurts with higher storage modulus (G′) and higher firmness than yoghurt milk base with large casein micelles. Increased gelation capacity can be attributed to an increased amount of κ-casein in the yoghurt milk base containing small casein micelles.

Influence of hydrodynamic cavitation on the rheological properties and microstructure of formulated Greek-style yogurts.

With limited applications of acid whey generated during the manufacture of Greek yogurts, an alternate processing technology to sidestep the dewheying process was developed. Milk protein concentrate (MPC) and carbon dioxide-treated milk protein concentrate (TMPC) were used as sources of protein to fortify skim milk to 9% (wt/wt) protein for the manufacture of Greek-style yogurts (GSY). The GSY bases were inoculated and fermented with frozen direct vat set yogurt culture to a pH of 4.6. Owing to the difference in buffering of MPC and TMPC, GSY with TMPC and MPC exhibited different acidification kinetics, with GSY containing TMPC having a lower fermentation time. The GSY with TMPC had a titratable acidity of 1.45% lactic acid and was comparable to acidity of commercial Greek yogurt (CGY). Hydrodynamic cavitation at 4 different rotor speeds (0, 15, 30, and 60 Hz) as a postfermentation tool reduced the consistency coefficient (K) of GSY containing TMPC from 79.4 Pa·sn at 0 Hz to 17.59 Pa·sn at 60 Hz. Similarly for GSY containing MPC, K values decreased from 165.74 Pa·sn at 0 Hz to 53.04 Pa·sn at 60 Hz. The apparent viscosity (η100) was 0.25 Pa·s for GSY containing TMPC and 0.66 Pa·s for GSY containing MPC at 60 Hz. The CGY had a η100 value of 0.74 Pa·s. Small amplitude rheological analysis performed on GSY indicated a loss of elastic modulus dependency on frequency caused by the breakdown of protein interactions with increasing cavitator rotor speeds. A steady decrease in hardness and adhesiveness values of GSY was observed with increasing cavitational intensities. Numbers of grains with a perimeter of >1mm of cavitated GSY with TMPC and MPC were 35 and 13 grains/g of yogurt, respectively, and were lower than 293 grains/g observed in CGY. The water-holding capacity of GSY was higher than that observed for a commercial strained Greek yogurt. The ability to scale up the process of hydrodynamic cavitation industrially, and the ease of controlling events of cavitation that can influence final textural properties of the product, make this technology promising for large-scale industrial application. Overall, the current set of experiments employed in the manufacture of GSY, which included the use of TMPC as a protein source in conjunction with hydrodynamic cavitation, could help achieve comparable titratable acidity values, rheological properties, and microstructure to that of a commercial strained Greek yogurt.

Quality of Plain Set Yoghurt as affected by Levels of Ultrafiltration Concentration of Milk and Inoculum of Yoghurt Culture

Quality of plain set yoghurt was investigated by varying levels of ultrafiltration concentration of cow skim milk (1-without ultrafiltration, 1.5 and 2 folds) and inoculum (2, 2.5 and 3%) of yoghurt culture (Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus 1:1). Titratable acidity development and pH reduction were significantly faster during incubation of yoghurt with increasing ultrafiltration concentration level and inoculum level. Increased ultrafiltration concentration level decreased spontaneous whey syneresis, but increased water holding capacity and firmness of the product significantly. Body &amp; texture and overall acceptability scores were significantly better in yoghurts prepared from 1.5 fold concentrated milk irrespective of the inoculum level studied. Inoculum level did not show any significant effect on the quality of yoghurt, but higher inoculum level decreased the incubation period significantly. Optimized product was obtained with 1.5 fold concentrated skim milk standardized to 3.3% fat and incubated with 2% inoculum level in about five and a half hour of incubation. Optimized product had 13.60±0.02% total solids, 3.31±0.01% fat, 5.27±0.04% protein, 4.20±0.03% lactose and 0.82±0.02% ash. Whey syneresis, water holding capacity and firmness in optimized product were nil, 63.49% and 1.89 N, respectively. Thus, high quality plain yoghurt could be prepared by employing ultrafiltration, without addition of stabilizers, which is otherwise widely used commercially for the manufacture of yoghurt to control its wheying off and body.

Rheological and physical characteristics of non-fat set yogurt prepared with EPS-producing Streptococcus thermophilus and an H+-ATPase-defective mutant Lactobacillus delbrueckii subsp. bulgaricus

ABSTRACTThe rheological and physical characteristics of non-fat set yogurt produced using co-cultures of ropy EPS-producing Streptococcus thermophilus S3.3 and Lactobacillus delbrueckii subsp. bulgaricus LTM and of Streptococcus thermophilus S3.3 and Lactobacillus delbrueckii subsp. bulgaricus H+-ATPase-defective mutant L6 under different conditions were studied. Yogurts produced with mutant L6 had a higher pH and water-holding capacity and better textural properties compared to those produced with the LTM strain. The highest storage modulus (G′) and thixotropic loops were found for yogurt made with L6 at 42°C on day 21 of cold storage. This yogurt contained a network of thick, continuous protein aggregates and large void spaces.

Interaction of starch and casein

Starch was commonly used to improve the stability of set yogurt. In this research, casein and modified starches were placed in a simulated yoghurt system giving the advantage of a low variation in the environment parameters compared to a natural yoghurt system. The interactions between modified starches (phosphate starch, hydroxypropyl starch and starch ester of octenyl succinic) and casein were investigated with several independed types of measurements methods. The combination of zeta potential and fluorescence micrograph were used to research the interactions between modified starches and casein. And the results proved that modified starches not only absorbed with casein via electrostatic forces, but also had steric stabilization. Besides this, fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) were used to investigate the role of hydrogen bonds between modified starches and casein. It could be deduced that the interactions of modified starches and casein included electrostatic adhesion, steric stabilization and hydrogen bond. At the same time, electrostatic adhesion was the main interaction between phosphate starch and casein. The main role of the interactions between starch ester of octenyl succinic and casein should be steric stabilization.

Production of set yoghurt analogue through replacement of milk fat with canola and sesame oil

The aim of this study was to determine the effect of fat level and composition on chemical, textural, microbial and sensory properties of set yoghurt analogue. The best fat level for production of yoghurt analogue was found to be 2% (w/v). Studies on the effect of fat composition (canola‐to‐sesame oil ratios of 2.0/0, 1.3/0.7, 0.7/1.3, 2.0/0) indicated the superior performance of pure sesame oil. Increasing the canola‐to‐sesame oil ratio generally resulted in an inferior product. Replacement of milk fat by vegetable oils yielded yoghurts with a lower saturated fatty acid content and less firmness.

EFFECT OF SOYA AND WHEY PROTEINS ON THE SENSORY AND PHYSICOCHEMICAL PROPERTIES OF SET YOGHURT

Recently, a focus on the utilization of whey and soya proteins has been receiving significant attention due to their nutritional value and their potential to enhance the functional characteristics of the dairy products. Set yoghurt was manufactured from standardized (4% fat) buffalo milk alone (control), or fortified with whey protein concentrate (WPC), soya protein concentrate (SPC) or their combination (MIX) and stored at 5±2 °C for 10 days. Sensory properties of the resultant yoghurt were evaluated one day after manufacturing. All treatments were analyzed when fresh and during storage period for pH-value, titratable acidity(TA) and syneresis. The pH-values and titratable acidity(TA) of yoghurt samples showed that both soya and whey proteins did not alter the rate of acid production in yoghurt. Acidity of samples treated with WPC during storage was significantly (P<0.05) higher, compared to control. Also, the addition of whey proteins and soya proteins or their combination resulted in reduction in the syneresis of yoghurt samples by about 17-25%, when compared with control at zero time. Fortification with soya proteins lowered appearance, taste and odor scores by 25, 37 and 35%, respectively, compared with the control. This negative effect of soya proteins on the sensory properties of yoghurt (SPC treatment) was improved when combined with whey protein in the MIX treatment. Therefore, it is recommended to add whey proteins to improve sensory and syneresis properties of soya yoghurt.

Quality of cow milk plain set yogurt as affected by ultrafiltration process

The aim of the study was to investigate the effect of ultrafiltration (UF) process on quality of cow milk plain set yoghurt. Direct UF of cow skim milk and highly concentrated UF cow skim milk retentate addition were used to adjust the total solids (TS) of yoghurt milk, at two different UF concentration levels (UFCLs). Ultrafiltered (approximately to 1.5 and 2 fold) cow skim milk/ equivalent 5 fold UF skim milk retentate added cow skim milk were standardized to 3.3% fat and 13.8% TS. Yoghurts were prepared by inoculating with 2% yoghurt culture (Lactobacillus delbrueckii subsp. bulgaricus: Streptococcus thermophilus) and analyzed for chemical composition, spontaneous whey syneresis, water holding capacity, textural and sensory attributes. Protein, lactose and ash percentages of yoghurt prepared from direct UF milk were 5.27±0.04, 4.20±0.03 and 0.82±0.02, whereas, in yoghurt prepared from retentate added milk were 5.18±0.02, 4.28±0.03 and 0.84±0.01, respectively at 1.5 fold UFCL, which had optimum quality product. The values were not significantly different in yoghurt made by direct UF concentrated milk compared to retentate added milk. Further, it was observed that protein percentage increased and lactose content progressively decreased significantly ( p Tropical Agricultural Research and Extension 16(3): 2013: page 74-80

Screening for lactic acid bacteria based on antihyperglycaemic and probiotic potential and application in synbiotic set yoghurt

Twenty lactic acid bacteria were screened for the abilities of rat intestinal α-glucosidase inhibition, short-chain fatty acids production, utilization of prebiotics as well as gastrointestinal tract tolerance. Nine strains inhibited α-glucosidase, four of which, Lactobacillus acidophilus CCFM6, Lactobacillus plantarum CCFM47, CCFM232 and Lactobacillus rhamnosus GG (LGG) were tolerant to simulated gastrointestinal juices with survival rates up to 60% following simulated digestion. When grown on soybean oligosaccharides (SBOs), CCFM47 produced propionic (39.9 mM) and butyric (3.5 mM) acids while strain CCFM6 produced 17.2 mM propionic acid. Strains CCFM6 and CCFM47 were further tested for their viability and survival in set yoghurt supplemented with SBOs. SBOs enriched yoghurt improved probiotic survival in the simulated gastric juice and significantly improved α-glucosidase inhibition (P < 0.05). Thus strains CCFM47 and CCFM6 can be used as probiotics with antihyperglycaemic potential in the formulation of functional foods such as yoghurt.

Multi-bucket optimization for integrated planning and scheduling in the perishable dairy supply chain

This paper considers a dairy industry problem on integrated planning and scheduling of set yoghurt production. A mixed integer linear programming formulation is introduced to integrate tactical and operational decisions and a heuristic approach is proposed to decompose time buckets of the decisions. The decomposition heuristic improves computational efficiency by solving big bucket planning and small bucket scheduling problems. Further, mixed integer linear programming and constraint programming methodologies are combined with the algorithm to show their complementary strengths. Numerical studies using illustrative data with high demand granularity (i.e., a large number of small-sized customer orders) demonstrate that the proposed decomposition heuristic has consistent results minimizing the total cost (i.e., on average 8.75% gap with the best lower bound value found by MILP) and, the developed hybrid approach is capable of solving real sized instances within a reasonable amount of time (i.e., on average 92% faster than MILP in CPU time).

Comparison of Viscoelastic Properties of Set and Stirred Yogurts Made from High Pressure and Thermally Treated Milks

Viscoelastic properties of set and stirred yogurts made from raw (control), high pressure (300 and 400 MPa, 20 min, 4°C), and heat treated (80°C, 30 min) milks were investigated using a using a computer controlled rotational viscometer under oscillatory testing program, including three operating modes: a strain sweep, frequency sweep, and an isothermal time sweep. Linear, exponential, power-law, and Weltmann models were used to assess and describe the strain, frequency, and time dependent viscoelastic properties of yogurts. Their significance was analyzed using Duncan’s multiple range tests. The results indicated that the set yogurts had larger moduli (storage moduli G’ and loss moduli G”) and lower phase shift (tan δ) than stirred yogurts. High pressure treatment increased storage moduli G’ of both stirred and set yogurts significantly (p < 0.05). The influence on loss modulus was relatively lower. Unlike yogurts made from heat treated and raw milks, the ones made from pressure treated milks resulted in significantly different gel, frequency, and strain dependent properties for both types of yogurts. However, time dependent properties were not affected by pressure treatment.