[工学]Chapter 11 MAP-2.ppt

Chapter 11 Modified Atmosphere Packaging (MAP) Outline 11.1 Introduction 11.2 Effect of modified gas atmosphere 11.3 Types of packages 11.4 MAP gases 11.5 Packaging materials 11.6 Advantages and disadvantages 11.7 Application of MAP in foods Introduction –Development of MAP Beginning of the 19th century: New demonstration End of 19th century: First patent 1929: apple were stored in the mixture of CO2 and O2 1974: Commercial application of MAP Strongly extend postharvest life maintain quality Biggest growth in use: fresh fruits and vegetables Application size ranges: Bulk storage packages (red currants) transport packages (bananas, strawberries) consumer packages (apples, broccoli) Definition of MAP The packaging of a perishable product in an atmosphere which has been modified so that its compositions is other than that of air 11.1 Effect of modified gas atmosphere Safety and perishability: most important concerns in any food product Safety：pathogen or toxic chemical Perishability：microbial degradation, enzymatic activities and /or chemical reactions Strategy of MAP slow down metabolic activity growth of microorganisms Combine with low temperature 11.1.1 Reduction of oxidative reaction Fruits and vegetables continue to live after harvest Consumption of components, spoil Energy：aerobic respiratory processes O2：enzymatic and chemical reactions Extend storage periods：reduce oxidative reaction 11.1.2 Impact on microbial growth 1. Effect on spoilage microorganisms CO2 in excess of 5% (v/v) inhibit the growth of most food spoilage bacteria Gram-negative bacteria are more sensitive to CO2 than Gram-positive bacteria Examples Pseudomonads Acinetobacter Micrococcus and Bacillus LAB: very resistant to CO2 Mould sensitive to high levels of CO2 Anaerobic atmosphere must be used with extreme caution 2. Effect on pathogenic microorganisms High levels of CO2 inhibit Staphylococcus aureus Salmonella spp. E. coli Inhibition increases as temperature dec