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

Abstract

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<0.05) in yoghurt with increase in UF concentration/ UF retentate addition with similar TS in yoghurt milk. None of the quality parameters tested showed significant difference with UF process so that both procedures would be recommended at 1.5 fold UFCL to produce good quality yoghurt with enhanced protein content without addition of stabilizers.

Storage Stability of Texture and Sensory Properties of Yogurt with the Addition of Polymerized Whey Proteins

“…The siphon method described by Amatayakul et al [7] was used with slight modifications to determine the extent of spontaneous whey syneresis (SWS) by Narayana and Gupta [8]. A 100 mL cup of yogurt was tilted 45° immediately after being removed from the refrigerator to collect the surface whey; this was siphoned off using a graduated syringe with a needle attached.…”

Properties of Yoghurt Fortified in Lactoferrin with Effect of Storage Time

“…Spontaneous whey syneresis-SWS was also measured according to Narayana and Gupta [39] and Cais-Sokoli ńska and Walkowiak-Tomczak [40]. A plastic container with 100 mL of yoghurt was stored at 4-6 • C and immediately after removal from the refrigerator, it was tilted at an angle of 45 • to collect the surface whey using the syringe.…”

Characterization and Development of Yoghurt from Concentrated Whey

“…The appearance & color, flavor, body & texture and taste of yoghurt were assessed using the 100-point scorecard [24]. Appearance and color were given maximum 15, flavor 45, body and texture 30 and taste 10 points out of 100 points.…”