Rheological properties of fermented milk from heated and high pressure-treated camel milk and bovine milk

Abstract

Gelation of camel milk is a challenge to the industrial utilization. This study investigated the impact of low-temperature long-time (LTLT) and high-temperature short-time (HTST) pasteurization, ultra-high temperature (UHT) treatment, and high-pressure processing (HPP), at 300 and 600 MPa, on the rheological properties of the fermented milk. Both camel and bovine milk were fermented by Lactiplantibacillus plantarum and Ligilactobacillus salivarius. Both milk treated at 300 and 600 MPa showed the highest Lb. plantarum and Lb. salivarius numbers, with ∼9 log.HTST and UHT-treatment increased particle size in bovine milk but decreased it in camel milk. HPP-treatment decreased particle size in both camel and bovine milk. All fermented milk showed shear-thinning behavior, regardless of milk type, processing, culture type and storage time. For both camel and bovine milk, fermented UHT-treated milk had the highest viscosity followed by fermented HPP-treated milk. Lowest viscosities were observed for fermented LTLT-treated and HTST-treated milk. Small deformation rheology showed consistently lower tan δ values for fermented HPP-treated camel milk than for fermented heated camel milk, with the latter only giving tan δ < 1 at elevated frequencies. UHT- and HPP-treatment of milk can enhance the rheological properties of fermented camel milk compared with other heat treatments.