Food Industry Engineering Master Degree Lecture Notes PDF
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Università degli Studi di Padova
Sara Spilimbergo
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Summary
These lecture notes cover the fundamentals of food preservation, with an emphasis on pasteurization and thermal processing methods. It details methods for food preservation such as water activity reduction, pH reduction, and the use of additives. The aim is to outline the principles and procedures applied to preserving food products.
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Master Degree in Food Industry Engineering A. Pasteurization Thermal treatments in the food industry Lecturer: Prof. Sara Spilimbergo Content index Lesson 1. Introduction. Preservation principles by heat treatment: sterilization and pasteurization. Lesso...
Master Degree in Food Industry Engineering A. Pasteurization Thermal treatments in the food industry Lecturer: Prof. Sara Spilimbergo Content index Lesson 1. Introduction. Preservation principles by heat treatment: sterilization and pasteurization. Lesson 2. Processing standards. Introduction to heat treatment validation methods. Lesson 3. Pasteurization and sterilization systems of packaged foods. Lesson 4. Studies of temperature distribution and heat penetration. The general method for calculating cumulative lethality. Practical cases. Master Degree in Food Industry Engineering A. Pasteurization Lesson 1 Thermal treatment: Intro and preservation principles Lecturer: Prof. Sara Spilimbergo Methods of Food Preservation Food Spoilage Water activity reduction Physical Lowering pH Chemical Use of preservatives Enzymatic Microbiological Cold Heat treatment New non-thermal technologies (HPP, ultrasound,...) Methods of Food Preservation (1). Inhibition principle Food Spoilage Use of additives Physical Water activity reduction Chemical pH reduction Enzymatic Cold Microbiological (2). Killing principle Heat treatment Irradiation Uses of gases New non-thermal technologies (HPP, ultrasound,...) Food preservation by lowering water activity Lowering of water activity can be achieved by: Addition of high content of salt: Sodium chloride and sometimes nitrats and nitrites Addition of high content of sugar Drying: sun/air drying; electrical drying or freeze drying The salting procedure The salting procedure can be performed in four ways: 1. Dry cure in which the meat or fish is rubbed with salt 1. Pickling: The products are immersed in pickle of brine, usually containing about 15% salt. 1. The injection cure: concentrated salt injected to muscles 1. Direct addition method Food preservation by lowering pH Many food products can be preserved by lowering pH so that the growth of spoilage and pathogenic bacteria is prevented The lowering of pH can be achieved by addition of acids and fermentation Fermentation is the breakdown of carbohydrates under anaerobic conditions into alcohol or lactic acid and carbon dioxide Food preservation by use of low temperatures Low temperatures are used to retard chemical reactions and actions of food enzymes and to slow down or stop the growth and activity of microorganisms in the food. Chilling and freezing to arrest microbial growth and multiplication Chilling is keeping food at temperatures between 0-15oC. The commom chilling temperatures ranges between 4-5oC Freezing is keeping food at temperatures between at a temperature below 0oC. Spores are not usually injured at all by freezing. Water unavailable due to ice formation Portion of organisms remaining can grow when food is thawed Storage life of some foods Food product Storage life (days) at 21oC Raw beef and mutton 1-2 Raw fish 1-2 Raw poultry 1-2 Dried salted or smoked 360 or more meat and fish Fresh fruits 1-7 Dried fruits 360 or more Leafy vegetables 1-2 Root crops 1-20 Dried seeds 360 or more Methods of Food Preservation (1). Inhibition principle Food Spoilage Water activity reduction Physical pH reduction Chemical Use of additives Enzymatic Cold Microbiological (2). Killing principle Heat treatment Irradiation PEF Uses of gases HPP, ultrasound,... Thermal Treatment OBJECTIVES: Pathogen destruction Microorganisms and enzymes Cooking Quality factors retention TIME-TEMPERATURE ENVIRONMENTAL FACTORS Thermal Processing PASTEURIZATION STERILIZATION New trends in thermal processing TT optimization. Modeling of the effect on the different compounds. Faster and more efficient heating: Microwave and ohmic Combination with other new technologies (US, HPP, PEF,...) Preservation Principles of thermal processing When determining the conditions of a heat treatment, consider: Microorganism/spore/ target enzyme and its thermoresistance pH of the food Heating conditions Thermo-physical properties of the food Size and shape of the food / container Storage conditions after treatment Preservation Principles of thermal processing Foods are divided into four pH groups: High acidity, pH
