Physicochemical and Sensory Properties of Yogurt Supplemented with Corni fructus during Storage

Effect of pulsed electric field treated on quality of curd

Pulsed electric field (PEF) is a potential pre-treatment technique to improve the quality of milk by reducing its microbial load. The present study aims at addressing this issue with respect to a popular fermented dairy product, that is, curd. Milk was treated with high voltage and frequency (55 kV and 90 Hz) square waves of pulse width 900 µs for 100 s. Curd samples were prepared with conventional heat treatment (CHT), PEF-treated milk subjected to CHT (PT-CHT), and PEF-treated milk (PT). PT samples resulted in curd with higher acidity (0.17 ± 0.005% LA) and microbial load (6.65 ± 0.27 log CFUg-1), while the PT-CHT samples resulted in curd with better whey holding capacity. The firmness recorded for CHT, PT-CHT, and PT was 1.15 ± 0.05, 1.32 ± 0.04, and 0.91 ± 0.03 N, respectively. PT-CHT showed a higher viscosity index, that is, 0.207 ± 0.005 g. Sensorial properties showed the acidic nature of PT-curd with greater syneresis and softer texture resulted in its poorer sensory scores for texture. Shelf-life analysis showed no significant difference between curd prepared using the CH and PT-CHT up to 12 days. The study demonstrated the potential of employing PEF with CHT for improving the texture and shelf life of curd without impacting its quality.

Physicochemical, sensory and microbiological characteristics of coriander seed powder yogurt

Yogurt is a fermented food obtained by the bacterial fermentation of milk. In the present work, the effect of different concentrations (1, 3 and 5% w/w) of coriander (Coriandrum sativum) seed powder on physicochemical, sensory characteristics and viability of Bifidobacterium bifidum and Lactobacillus acidophilus of probiotic yogurt were investigated at 4 °C for 21 days. Laboratory-made yogurts were obtained by inoculating milk with yogurt bacteria (mixed culture of Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus) and two probiotic cultures (Lactobacillus acidophilus and Bifidobacterium bifidum). According to the results, the viability of B. bifidum and L. acidophilus increased in synbiotic stirred yogurts with 5% CSP (coriander seed powder) up to 9.15 ± 0.09 log CFU/g at 11 days of the storage period, whereas probiotic bacteria count decreased to 9.02 ± 0.01 by the end. Therefore, our results confirmed that the addition of probiotics and CSP powder improved the physicochemical and sensory characteristics of stirred yogurt and exerted a beneficial effect on probiotic bacteria.

Probiotic Yogurt Fortified with Chickpea Flour: Physico-Chemical Properties and Probiotic Survival during Storage and Simulated Gastrointestinal Transit

In the present study, probiotic yogurt with Lactobacillus acidophilus LA5 and Bifidobacterium BB12 was produced via fortification with chickpea flour (0, 1, 2.5, 5% w/v). During refrigerated storage for five weeks, probiotics maintained a viable count above the minimum therapeutic level (106 CFU/g) in all yogurt types. Although there was no significant (p > 0.05) positive effect of chickpea flour on probiotic viability during storage, the addition of chickpea flour has beneficial effects on the viability of both probiotic species in the presence of gastric and intestinal juices, with 0.3% bile. This study also evaluated the physio-chemical properties of probiotic yogurt during storage. Some physicochemical properties of yogurt, such as water holding capacity and susceptibility to syneresis, were enhanced by the addition of chickpea flour. Hence, chickpea flour could be an attractive pulse ingredient in the production of probiotic yogurts for health-conscious consumers.

Jujube mucilage as a potential stabilizer in stirred yogurt: Improvements in the physiochemical, rheological, and sensorial properties

Here, the mucilage of jujube was extracted and used as a natural stabilizer in the production of stirred yogurt. Yogurts were enriched with different concentrations of jujube mucilage (i.e., 0, 0.1, 0.15, and 0.2%), and their physical, chemical and sensory attributes were analyzed during 21 days of storage at 4°C. The results showed that the protein and fat contents of the yogurts were not significantly different compared with each other, while higher ash contents were obtained in yogurts which contained higher concentrations of the mucilage. The acidity and proteolysis of the stirred yogurts were enhanced in the presence of mucilage, and they exhibited lower concentrations of diacetyl and acetaldehyde, although the differences were not significant among the samples of different treatments. The storage time had adverse and direct effects on the amounts of acetaldehyde and diacetyl, respectively. The effects of storage time and the presence of jujube mucilage in yogurts caused a significant decrease in the percentage of syneresis, while their viscosity and WHC values increased. The magnitudes of dynamic moduli (G, G''), complex viscosity (η*), and loss tangent (tan δ) of stirred yogurts increased by increasing the concentration of jujube mucilage. The yogurts which had been enriched with mucilage were preferred slightly less by tasters during the storage period, but these differences did not amount to a statistical significance. Generally, the results of the present study showed that the jujube mucilage can be potentially used as a natural stabilizer in stirred yogurt.

Texture and sensory characterization of functional yogurt supplemented with flaxseed during cold storage

In this study, flaxseed was used as a functional ingredient in yogurt formulations. The goal of this study was to produce prebiotic yogurt supplemented with flaxseed and investigation of its texture and sensory properties. Yogurt samples containing 0%-4% flaxseed was produced and stored at refrigerator (4-5°C) for 28 days. Textural properties were determined by texture analysis, and sensory characteristics were assessed by 26 trained panelists. Addition of flaxseed to yogurt samples increased the hardness, gumminess, chewiness, cohesiveness, and springiness values in produced yogurt samples. However, adhesiveness level was reduced in a sample enriched with flaxseed. By increasing flaxseed concentration, the color of samples was significantly different than the control sample; L* value was diminished and a* and b* value increased. Sensory scores including taste and mouthfeel, appearance, and overall acceptance showed reduction trend in samples containing a high level of flaxseed. In general, results showed that the addition of 2.63% flaxseed into yogurt samples lead to produce functional food with satisfactory texture, sensory characteristics that sustained these properties until 17.17 days after cold storage.

Effect of Resistant Cassava Starch on Quality Parameters and Sensory Attributes of Yoghurt

Resistant starch is known to impart a number of health benefits to consumers. It is therefore desirable to increase the content of resistant starch in popular foods such as yoghurt. The current research investigated the effect of cassava resistant starch synthesized by heat-moisture treatment of starch from I92/0057 cassava variety on physico-chemical properties and sensory attributes of yoghurt. Cassava starch rich in resistant starch was incorporated into yoghurt in the proportions of 0, 0.1%, 0.5% and 1%. Corn starch (0.6%) was used as control. Yoghurt was stored at 4oC for 21 days and the effect of starch modification on resistant starch content, viscosity, syneresis, total solids, acidity, lactic acid bacteria count and sensory properties were determined on weekly basis. Applying cassava starch rich in resistant starch into yoghurt in the proportions of 0.5% and 1% had significantly higher (p≤0.05) resistant starch content of yoghurt reaching 3.40 g/100 g and 5.58 g/100 g on day one and 1.92 g/100 g and 4.47 g/100 g on day 21, respectively. There was a significant correlation (p≤0.05) between resistant starch concentration and the physico-chemical properties of yoghurt. Yoghurt treated with 1% resistant starch enriched cassava starch had the highest viscosity during cold storage which was determined as 2721.5 mPa s, mPa s, 2650.0 mPa s and 1034.5 mPa s at day 1, day 7, day 14 and day 21 respectively and it had the least syneresis (22.25%). Addition of cassava starch rich in resistant starch significantly increased (p≤0.05) the total solids content of yoghurt but did not significantly (P>0.05) change the sensory properties of yoghurt. The application of 1% of resistant starch enriched cassava starch as yoghurt thickener produces significant quantity of resistant starch in yoghurt with acceptable sensory and physico-chemical properties.