NU FS100 Lecture Notes - Lecture 10: Case-Hardening, Shelf-Stable Food, Water Activity

• School: University of Alberta
• Department: Nutrition and Food Sciences
• Course: NU FS100
• Professor: Blanca Enriquez

Document Summary

Does not completely remove all water, as there will still be bound water (microbes will not grow because very low water activity) Rate of dehydration will influence the product characteristics and stability (faster the rate = better quality) Microbes and spores can still survive after drying process. Advantages include decrease in weight, convenient, and ultimately lower cost e. g. grapes to raisins: raisins are sweeter and shelf stable because less water = more solute concentration and low water activity. Increasing the rate of drying: surface area. The greater the surface area = the faster the dehydration rate. Have smaller pieces (reducing thickness to avoid case hardening as well: temperature. Higher temperature = higher the dehydration rate: humidity. Dry air can absorb more moisture: atmospheric pressure. Higher the pressure = higher the boiling point e. g. sea level will take longer to cook b/c higher temp there. Vacuum drying: remove water from food product at a low temperature using a vacuum.