Dairy

Dairy

Dairy Industry • largest sector of the food supply chain • physical, chemical and biochemical phenomena are the basis for the strong relation between the product quality and the process operation and design • a number of heat-induced transformations of milk components det. the functional properties of the final prdt, e.g. biological safety, shelflife, flavor, taste and texture • a reaction eng’g approach appears to be applicable to the optimal design and operation of dairy heat-treatment equipment as kinetic data of relevant transformations becomes available

Pasteurization • a process applied to minimize possible health hazards arising from pathogenic microorganisms associated w/ milk by heat treatment which is consistent with minimal chemical, physical and organoleptic changes in the product • Limitations: fouling and adherence and growth of bacteria in the equipment • 5 types  thermization (e.g. 20 s, 65°C) for inactivation of psychotropic microorganisms  low pasteurization (e.g. 20 s, 74°C) for inactivation of pathogenic microorganisms  high pasteurization (e.g. 20 s, 85°C) for inactivation of all microorganisms but not spores  sterilization to destroy spores -step1: consisting of a continuous heating step at 120–140°C for several seconds, -step2: in-bottle sterilization at 110–120°C over 10–20 mins  UHT (ultra-hightemp) treatment (e.g. 135–150°C plus holding times) to destroy spores and achieve commercial sterility

Advanced technologies ESL Technology  extended shelf-life (ESL) milk - product with a shelf-life longer than pasteurized milk under equivalent chilled distribution and storage conditions  a complete systems approach along the entire processing chain combining processing, packaging systems and distribution  the result of optimization of the temperature–time history with respect to the key components for chilled liquid milk plus hygienic methods e.g., bactofugation, microfiltration, modified ht treatment  typical shelf-life of liquid ESL products is 15–25 days stored at 7°C

Advanced technologies  innovative steam injection (ISI) - very short heating combined with very high temperatures: less than 0.1 s at 150–200°C followed by flash cooling in a vacuum vessel  a significant inactivation of heat-resistant spores can be achieved while preserving the functionality of important ingredients  costs of the technology are some 10 % higher than prevailing UHT process  To be stable for months at room temp, additional preheating step is necessary for inactivation of plasmin under chilled conditions  substantially longer shelf-life of up to 60 days.

Heat-induced reactions • 5 groups  destruction of microorganisms – propotional to T  inactivation of enzymes - desired rxn bec. of the negative effect on flavor, shelf-life; except some enzymes stimulate flavor devt  denaturation of proteins – (whey proteins) improved yoghurt texture, decreased solubility of milk powder  loss of nutrients – major nutrient loss is thiamine (vit. B1)  formation of new components – governed by Maillard rxn, a complex series of steps in w/c rxns occur bet. lactose & proteins; brown pigments; Hydroxy methyl furfural (HMF) formation

Surface Reactions • deposition of milk components on heat-treatment equipment walls from protein denaturation • adherence of microorganisms- Streptococcus thermophilus and Bacillus cereus spores; multiply on surfaces during operating and may reduce shelf-life of product