Ultra-High-Temperature Processing of Milk and Milk Products

Abstract

PrefaceThis book attempts to explain the scientific basis for UHT sterilization and aseptic filling, as well as describe the processes and equipment used. I have tried to avoid producing merely a catalogue of sterilizers and aseptic fillers. Instead I have attempted to explain the principles on which the different types of plant operate, and discuss the factors which influence performance, so that information given by manufacturers may be assessed by readers in relation to their own processing requirements.Statements are generally supported by references. Where no reference is given, personal experience or my interpretation of the work of others is my justification.Although the book deals mainly with milk and milk products, I hope that the information it contains will be useful to those dealing with other products, since the principles of processing are in general the same.The book is based on more than 30 years' involvement with research into UHT processing and aseptic filling. During this time I have been fortunate to work with and to talk to many people from whom I have learned a great deal. I benefited from conta.cts with Dr T. R. Ashton (England) and Professor H. Hostettler. (Switzerland), who were pioneers in the commercial development of UHT milk. More recently I have been privileged to know and work with research workers in many countries having a common interest in UHT processing. Of these, I should mention particularly Professors E. L. Thomas, V. A.

Characterization of Aerobic Spore-Forming Bacteria Isolated From Raw Milk, Skim Milk Powder and UHT Milk

“…isolates from raw milk. According to bibliographic data, it was reported by Burton (1988) that Bacillus licheniformis is the most common spore isolated from raw milk. Pre-identification of Bacillus species isolated from skimmed milk powder:…”

A dynamic object-oriented model for efficient simulation of microbial reduction in dispersed turbulent flow

“…a factor 10) at a reference temperature T r z r = the temperature increase required from the reference temperature T r to increase the reaction rate by a factor of 10. In this study typical values for the spores of the microorganism Clostridium botulinum were used: Walstra, Geurts, Noomen, Jellema & Boekel (1999), Table 6.4, and Burton (1988), Table 2.2: D r = 12 s and z r = 10 °C, both at the reference temperature T r = 121.1 °C. Since the proposed model is based on the chemical reaction constants k 0 and E a , the following conversion was performed.…”

Evolução do índice proteolítico e do comportamento reológico durante a vida de prateleira de leite UAT/UHT

“…Dependendo da temperatura, condições e extensão da estocagem do leite, vários grupos de microrganismos podem passar por um período de crescimento intensivo, produzindo altas concentrações de enzimas, particularmente lipases e proteinases. Dentre esses grupos destacam-se os microrganismos psicrotrófi-cos [5] que, embora sejam destruídos pela esterilização, produzem enzimas proteolíticas e lipolíticas resistentes ao calor. Estas enzimas são produzidas quando a contagem de bactérias atinge 10 6 UFC/mL ou mais, e se desenvolvem em resíduos ou depósitos em leite presentes em equipamentos e tubulações de laticínios mal-higienizados [7,34].…”

“…O aquecimento é realizado em temperaturas de 130 a 150ºC por 2 a 4 seg., que pode ser responsável pela desagregação das micelas de caseína, resultando em um aumento do índice proteolítico e alterações das propriedades reológicas do leite. Nesta fase o ponto de maior controle é o binômio tempo-temperatura, que garante a esterilização comercial; temperaturas abaixo da estabelecida são indesejáveis e acima podem causar problemas tecnológicos como alterações das proteínas, interferindo no sabor, geleificação, formação de sedimentos, perda do valor nutricional e escurecimento [4,5].A qualidade da maioria dos produtos lácteos está diretamente relacionada com a qualidade microbiana do leite cru utilizado como matéria-prima. Dependendo da temperatura, condições e extensão da estocagem do leite, vários…”