Factors affecting microbial heat resistance in foods

- Moisture: moist heat is more lethal than dry heat, greater protein denaturation - Fat content: low aw, water excluded from fat, microbes more heat resistant - Salt: lower aw in foods, microbial heat resistance increases - Carbohydrates: lower aw, increased microbial heat resistance - pH: extremes of pH + heat are more lethal to microbes - Number of microbes: large # give protection, production of protective substances - Growth temperature: greater resistance in microbes with high growth temperature - Age of microbes: older cells more resistant, stationary phase cells more resistant than exponential, long term survivor cells the most resistant - Inhibitory compounds - Heating temp and time - Prior environmental stress: certain stresses can increase heat resistance of microbes (sub lethal heating, starvation, desiccation), production of stress proteins