Nutritional, chemical, syneresis, sensory properties, and shelf life of Iranian traditional yoghurts during storage

Tuluq and Torba yoghurts are traditional concentrates from Iran. Physicochemical, nutritional, and sensory properties of these yoghurts were studied along 60 days of storage. Results showed that, both pH and percentage of free whey decreased significantly (P < 0.05), while titratable acidity, total solid, salt, protein and fat content increased (P < 0.05) during storage. The yoghurt lipolysis decreased during the first 30 days and then increased during the storage. The indexes pH 4.6-soluble nitrogen/total nitrogen and non-protein nitrogen/total nitrogen in yoghurt samples decreased during first 30 days, possibly due to removing of low molecular weight nitrogenous compounds of Tuluq and Torba bags at late storage and then increased. Considerable alpha(s1-)and beta-casein degradation occurred in Tuluq yoghurt. This might be due to endogenous surface bacteria and yeasts activities on Tuluq bag. It was concluded that Tuluq yoghurt had long shelf-life and high quality, being a valuable dairy product114CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES302763/2014-7; 305804/2017-0não temA. S. Sant'Ana would like to thank the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) (Grants #302763/2014-7; #305804/2017-0) and to the “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior” - Brasil (CAPES) - Finance Code 001. Thanks are due to University of Aveiro and FCT/MCT for the financial support for the QOPNA research Unit (FCT UID/QUI/00062/2019, through national founds and where applicable co-financed by the FEDER, within the PT2020 Partnership Agreement. Rita S. Inácio also is grateful for the financial support from FCT through the fellowship Grant SFRH/BD/96576/2013. Thanks to GAIN (Axencia Galega de Innovación) for supporting this research (grant number IN607A2019/01