Heat-stable peptidases released in refrigerated raw milk by psychrotrophic bacteria are responsible for UHT milk gelation. K-casein-derived caseinomacropeptides, identified by mass spectrometry, were constantly detected in gelled milk by capillary electrophoresis. Strains of Pseudomonas fluorescens, Ps. poae and Chryseobacterium joostei, selected among aprX-positive strains from raw milk, were incubated in milk up to 6 days at 4 °C before sterilization (98 °C/4 min). Samples were then stored at 25 or 40 °C, visually observed for gelation, and analysed for presence of caseinomacropeptides throughout 90 days of storage. Depending on cold pre-incubation time, caseinomacropeptides accumulated well before gelation onset in milk stored at 25 °C. Caseinomacropeptides were successively degraded, especially in milk stored at 40 °C, due to extensive proteolysis, and an abundant sediment developed instead of a gel. The caseinomacropeptides are here presented as an early indicator of UHT milk gelation and a mechanism explaining this phenomenon is proposed.

Bacterial proteolysis of casein leading to UHT milk gelation : an applicative study / P. D'Incecco, M. Brasca, V. Rosi, S. Morandi, P. Ferranti, G. Picariello, L. Pellegrino. - In: FOOD CHEMISTRY. - ISSN 0308-8146. - 292(2019 Sep), pp. 217-226.

Bacterial proteolysis of casein leading to UHT milk gelation : an applicative study

P. D'Incecco
Primo
;
V. Rosi;L. Pellegrino
Ultimo
2019-09

Abstract

Heat-stable peptidases released in refrigerated raw milk by psychrotrophic bacteria are responsible for UHT milk gelation. K-casein-derived caseinomacropeptides, identified by mass spectrometry, were constantly detected in gelled milk by capillary electrophoresis. Strains of Pseudomonas fluorescens, Ps. poae and Chryseobacterium joostei, selected among aprX-positive strains from raw milk, were incubated in milk up to 6 days at 4 °C before sterilization (98 °C/4 min). Samples were then stored at 25 or 40 °C, visually observed for gelation, and analysed for presence of caseinomacropeptides throughout 90 days of storage. Depending on cold pre-incubation time, caseinomacropeptides accumulated well before gelation onset in milk stored at 25 °C. Caseinomacropeptides were successively degraded, especially in milk stored at 40 °C, due to extensive proteolysis, and an abundant sediment developed instead of a gel. The caseinomacropeptides are here presented as an early indicator of UHT milk gelation and a mechanism explaining this phenomenon is proposed.
AprX; Capillary zone electrophoresis; Caseinomacropeptides; Milk gelation; Psychrotrophic bacteria; Analytical Chemistry; Food Science
Settore AGR/15 - Scienze e Tecnologie Alimentari
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/642145
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