Harnessing the untapped potential of indigenous cow milk in producing set-type yoghurts: case of Thamankaduwa White and Lankan cattle.

This research paper assessed textural, microstructural, sensory and colour properties of set-yoghurts produced using milk from two indigenous cattle types, Thamankaduwa White (TW) and Lankan cattle (LC) compared to two generic cattle breeds, Friesian and Jersey. Instrumental texture profile (firmness, adhesiveness, cohesiveness and springiness), colour space (L* a* b*) and scanning electron micrographs of set-yoghurts during 21 d of storage (4 ± 1°C) were evaluated. Sensory quality attributes were evaluated with 40 untrained panellists using a five-point hedonic scale. Set-yoghurts prepared using indigenous cow milk showed higher (P < 0.05) firmness, cohesiveness and apparent viscosity values compared to those prepared using generic cow milk. As revealed by micrographs, set-yoghurts made from TW milk had lesser and smaller void spaces and a dense protein gel network than gels made from LC and the two generic breeds. The gel network made from Friesian milk showed a comparatively larger porous gel structure and thinner protein strands resulting in a weaker gel than other milk gels. The highest lightness (L*) and yellowness (b*) were observed from set-yoghurt produced from Friesian and LC milk, respectively. Set-yoghurts from TW milk had the highest (P < 0.05) sensory scores for all sensory attributes. The lowest sensory acceptance was recorded in set-yoghurt made from Friesian milk. Thus, milk from TW and LC is likely to be suitable in producing set-yoghurts with superior textural, microstructural and sensory properties, compared to milk from Jersey and Friesian. Our results suggest the merits of using indigenous cow milk in producing set-yoghurts and, thereby, prioritizing the preservation of the genetic pool of these indigenous breeds.

Quality indices of the set-yoghurt prepared from bovine milk treated with horseradish peroxidase.

Horseradish peroxidase (HRP, EC 1.11.1.7) was applied to treat whole bovine milk in the presence or absence of ferulic acid (FA). The treated milk exhibited different rheological properties from the control milk, and was used to prepare set-yoghurt with commercial direct vat set starter. Some chemical, textural and rheological properties of the yoghurt prepared were measured and compared. Compared to that prepared with the control milk, the yoghurt prepared with the HRP- or HRP and FA-treated bovine milk exhibited an increased hardness and adhesiveness, lower syneresis extent, higher apparent viscosity, and higher storage modulus and viscous modulus. Observation of the microstructure of the yoghurt samples under scanning electron microscopy illustrated that HRP treatment of bovine milk led to the prepared yoghurt a more compact and uniform structure. The results in the present work stated that treatment of bovine milk with HRP in the presence of ferulic acid could be applied to improve the quality of set-yoghurt.

Quality attributes of set yogurt made from lactoperoxidase system activated cow's milk.

The study aimed to assess the quality attributes of set yoghurt made from cow's milk preserved by lactoperoxidase system (LPs). Fresh cow's milk was collected from Datto milk collection center and samples were grouped to control and LPs activated. Set yoghurt was prepared immediately for the controlled samples, but in LPs activated milk, sample was kept for 9 h at 25 °C ± 2 before yoghurt was made. LP enzyme was activated within 2 h after milking by adding 1 mg/ml of sodium thiocyanate (SCN_) and hydrogen peroxide (H2O2). Totally, 36 L of cow's milk was used and the experiment was done in triplicates. Titratable acidity (TA) and pH were assessed every 30 min until coagulation formed. Yoghurt samples were stored for 21 days and different parameters were assessed including incubation duration, pH, TA, microbiological quality and sensory attributes. The results revealed that LPs partially suppressed the rate of acid production during incubation of cultured milk. Yoghurt made from LPs treated milk had significantly (P < 0.05) higher pH and lower TA values. Similarly, yoghurt made from LPs treated milk had lower total bacterial counts at 24-h, 72-h and 7-days of storages. Additionally, yoghurt from LPs activated milk had lower yeast and mold counts at 24-h and 7-days. Yoghurt made from LPs activated milk received better scores for the sensory attributes. In general, LPs activated milk can be used for making set yoghurt without a negative effect. Further studies are needed to illustrate the LPs activated milk fitness in making other cultured milk products.

Effects of Commercial Polysaccharides Stabilizers with Different Charges on Textural, Rheological, and Microstructural Characteristics of Set Yoghurts.

The study investigated the preparation of set yoghurts by adding three common commercial polysaccharide stabilizers, namely sodium alginate (SA), gellan gum (GG), and konjac gum (KGM), in milk fermentation to evaluate their effects on the texture, rheology, and microstructure of set yoghurts. The physicochemical properties, water-holding capacity (WHC), texture, low-field nuclear magnetic resonance (LF-NMR), rheology, and microstructure of set yoghurts added with different kinds and quantities of polysaccharides were compared and analyzed. The results showed that the set yoghurts added with anionic polysaccharide GG had more obvious effects on improving WHC, firmness, and rheological properties compared with the set yoghurt added with KGM and SA. The firmness of set yoghurts with 0.02% (w/v) GG increased from 1.17 N to 1.32 N, which significantly improved the gel structure. The transverse relaxation time (T2) of set yoghurts added with GG was the closest to that of the control. Compared with the set yoghurts added with 0.02% SA and KGM, the free water area (A23) of the one added with 0.02% GG decreased most significantly. Moreover, all samples showed shear-thinning behavior, and the apparent elastic and viscous modulus (G', G″) increased with the increase of GG concentration. The G' and G″ of set yoghurts with 0.005% SA and KGM were higher than those in the control, decreased when adding 0.010%, and then increased with the increase of SA and KGM. Additionally, the microscopic observation demonstrated that the addition of GG in set yoghurts significantly promoted the formation of larger protein clusters and showed a tighter and more uniform protein network comparing with the other two polysaccharides (SA, KGM).

In situ exopolysaccharides from Lactobacillus helveticus MB2-1 in Sayram ketteki yoghurt: Set yoghurts properties and interactions with sodium caseinate.

The effects of high exopolysaccharides (EPS) - producing Lactobacillus helveticus MB2-1 on the structure and storage stability of set yoghurts, and the interactions between its EPS (molecular weight 9.34 × 104 Da) from Sayram ketteki yoghurt (SKY) and sodium caseinate (CAS) were studied. The rheology, microstructure, texture and storage stability of the three set yoghurts including control yoghurt (Control), adding-probiotic yoghurt (APY) and SKY were investigated, which showed that the SKY exhibited less shear thinning than the Control and APY, and the textural indexes and storage stability of the SKY were significantly better than that of other two yoghurts (p < 0.05). Moreover, the increased turbidity, decreased ζ potential and surface hydrophobicity of EPS/CAS complex coacervation were determined at EPS/CAS mass ratio of 3 (corresponding to 0.33 g/L of CAS and 1 g/L of EPS), mainly owing to the electrostatic attraction of the two biopolymers to form aggregates. Besides, the higher sizes and more aggregation of EPS/CAS complexes were formed at pH 3.5. Taken together, the results indicated that the high EPS-producing characteristic of L. helveticus MB2-1 could positively influence the qualities of set yoghurts, and the EPS/CAS complex coacervation in dairy products was closely related to the EPS/CAS mass ratio and pH condition.

Impact of type and level of stabilizers and fermentation period on the nutritional, microbiological, and sensory properties of short-set Yoghurt.

This study aimed to produce short set yoghurt with different stabilizers at different concentrations and determine the effects of the stabilizers and length of fermentation on the nutritional, microbiological, and sensory properties of short set yoghurt. Stabilized yoghurt samples were produced using 0%, 0.5%, and 1.0% concentrations of carboxyl methylcellulose (CMC), corn starch, and gum acacia with different fermentation periods (1-5 hr), respectively. Samples were analyzed for the proximate, physicochemical, microbial, and sensory properties using standard laboratory methods. Results showed that an increase in stabilizer concentration and fermentation time decreased the moisture content but increased the total solids, protein, fat, ash, sugars, pH level, and total titratable acidity. The viscosity of the yoghurt samples significantly (p < .05) increased with the addition of stabilizers (1.48 ± 0.03 cP to 275.57 ± 4.08 cP), with CMC having the highest increase (p < .05) and gum acacia the least. However, the lactic acid production reduced as the concentration of stabilizers increased but showed an increase with fermentation time. The total viable count (TVC) reduced significantly (p < .05) with an increase in the concentration of stabilizer and fermentation time. Hence, short set yoghurt samples containing CMC yielded highest protein (0.5%), fat (1.0%), and ash contents (1.0%). Yoghurt samples produced with a 1.0% concentration of gum acacia gave an optimum pH (0.5%), TTA, mouthfeel, appearance, flavor, and taste. In contrast, yoghurt produced with corn starch produced the most desirable overall acceptability, viscosity, total solids at 1.0%, and TVC (at 0.5%) concentration.

Incorporation of omega-3 fatty acid-rich grape seed oil in yoghurt: Response surface optimization of physicochemical, textural, and sensory attributes during refrigerated storage.

The demand for consuming low-fat or nonfat dairy products, especially fat-free yoghurt, has increased considerably because of the effects of high-fat diet on human health during the two past decades. Generally, consumers prefer low-fat products to the same high-fat products. For this reason, manufacturers are looking for an ideal source for replacing fat substitute. In this research, the effect of grape seed oil (GSO) as a fat replacement on different quality attributes of the produced set yoghurt was determined. The effect of diverse ratios (3:0, 1.5:1.5, and 0.5:3%) of milk fat and GSO on the change in the quality attributes of the set yoghurt for up to 22 days of refrigeration period (4 ± 1°C) was investigated. Statistical analysis revealed that increase in GSO concentration leads to a significant increase (p < .05) in viscosity, acidity, and water-holding capacity (WHC), whereas syneresis and pH value decreased during the storage time. Furthermore, increasing the proportion of fat replacement to 3% (w/w) in set yoghurt increased the samples hardness while in case of cohesiveness; negative effect was observed because of the action of fat globules within the protein system. Result of fatty acid analysis revealed that the yoghurt samples containing GSO have higher unsaturated fatty acid content than the control yoghurt sample. In conclusion, the best fat replacement concentration of GSO in producing low-fat yoghurt was found in 1.5%, which also had the highest overall acceptance score between different yoghurt samples containing different levels of GSO.

Okra polysaccharide: Effect on the texture and microstructure of set yoghurt as a new natural stabilizer.

Four plant-derived polysaccharides including okra polysaccharide (OP), apple pectin (AP), sodium alginate (SA) and konjac glucomannan (KGM) were studied in yoghurt formulation to investigate their effect on gelling characteristics. The results indicated that OP, KGM and AP enhanced the water-holding capacity, firmness and elasticity of yoghurt while SA demonstrated the opposite effects. Gel structure was better improved with OP, the firmness of yoghurt increased from 9.01 g to 14.86 g when 0.08% OP was added. The yoghurt with OP achieved the closest transverse relaxation time (T2) to the control. The free water area (A23) decreased from 1592 for control to 1414 for yoghurt with 0.08% OP addition. All samples exhibited shear-thinning behavior, both apparent viscosity and elastic modulus (G', G″) increased with increasing concentrations of OP and KGM, with peak values at 0.06% OP and 0.015% KGM. Both G' and G'' reduced significantly as pectin concentration rose to 0.1%, while modules went up with the increasing concentration of SA. Microscopy results showed that addition of OP and AP reduced the porous structure of gel and promoted formation of larger protein clusters, which eventually led to more compact protein network. This study provided new insights for food application with plant-derived polysaccharides.