Effects of ultrafiltration followed by heat or high-pressure treatment on camel and bovine yogurts
Bhawna Sobti,
Mutamed Ayyash,
Mustapha Mbye,
Meththa Ranasinghe,
Akmal Nazir,
Rabih Kamleh,
Basim Abu-Jdayil,
Afaf Kamal-Eldin
Affiliations
Bhawna Sobti
Department of Food Science, College of Agriculture and Veterinary Medicine, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates
Mutamed Ayyash
Department of Food Science, College of Agriculture and Veterinary Medicine, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates
Mustapha Mbye
Department of Food Science, College of Agriculture and Veterinary Medicine, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates
Meththa Ranasinghe
Department of Food Science, College of Agriculture and Veterinary Medicine, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates
Akmal Nazir
Department of Food Science, College of Agriculture and Veterinary Medicine, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates
Rabih Kamleh
Agthia Group, Alain Food and Beverages, Al Ain, United Arab Emirates
Basim Abu-Jdayil
Department of Chemical and Petroleum, College of Engineering, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates
Afaf Kamal-Eldin
Department of Food Science, College of Agriculture and Veterinary Medicine, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates; National Water and Energy Center, United Arab Emirates University, P.O. Box 15551, Al Ain, United Arab Emirates; Corresponding author at: Department of Food Science, College of Agriculture and Veterinary Medicine, United Arab Emirates University, Al Ain, United Arab Emirates.
The aim of this study was to assess the effects of ultrafiltration (UF) combined with high-pressure processing (HPP) or heat treatment on the quality of yogurts produced from camel milk (CM) or bovine milk (BM). Milk was concentrated by UF (0, 1, and 2-fold) before applying heat (75 °C or 85 °C for 30 min) or HPP (350 MPa or 550 MPa for 5 min). Yogurts were produced using starter cultures (Streptococcus thermophilus and Lactobacillus bulgaricus subsp. delbrückii) and pH, viscoelastic and thixotropic rheological properties, and protein profiles were determined. Compared to HPP, heat-treated yogurts, especially at 85 °C, exhibited the highest rheological storage and loss moduli signifying stronger gels. Lower storage modulus values in HPP treated CM yogurts were explained by the lack of long-range β-lactoglobulin bridges at micelle surfaces and the reassociation of pressure-dissociated caseins by hydrophobic interactions. Percent structural regeneration, which increased with increasing milk concentration, revealed higher thixotropic behavior in the case of heat- than in HPP-treated samples. SDS-PAGE electrophoresis revealed extensive proteolysis in CM compared to BM yogurts suggesting the involvement of some enzyme activities in the low gel strength.
