High-temperature acidification upgraded the stability of acidified milk through fibrillation of casein micelles

Acidification at 90 °C prevented whey separation in acidified milk. • Acidification at 90 °C enhanced the gel strength and viscosity of acidified milk. • Fibrils appeared in the acidified milk obtained at 90 °C. • When casein micelles were acidified at 90 °C, fibrillation occurred. • Fibrillation of casein micelles improved the acidified milk stability. Whey separation usually occurs to traditional acidified milk beverages. Therefore, this work aimed to improve stability of acidified milk beverages through high-temperature acidification, because high-temperature acidification might induce fibrillation of milk protein. The stability was enhanced when milk was acidified at 90 °C. Atomic force microscopy analysis revealed that the traditional acidified milk gel was particulate, whereas fibrils appeared in acidified milk obtained at 90 °C. Moreover, when the whey protein solution and the casein micelle suspension were acidified at 90 °C, respectively, no fibrils were observed in the whey protein solution, while casein micelles became fibrils. These results suggested acidification at 90 °C mainly induced casein fibrillation and thus improved stability of acidified milk. Thioflavin T fluorescence showed that longer treatment time enhanced casein fibrillation, which aligned with improved stability of acidified milk products at 90 °C through extended acid-heat treatment. This correlation also suggested that casein fibrillation enhanced acidified milk stability. Acidification at 90 °C for ≥3 h induced fibrillation of casein micelles and improved the acidified milk stability. Download: Download high-res image (105KB) Download: Download full-size image