Question

1. You are tasked to determine if a specific brand of apple juice has microbial spoilage. What sensory characteristics and/or observation could you use in your determination?

2. Discuss three methods that are commonly used to preserve food.

3. How does determining the thermal resistance of a spoilage organism aid in characterization of a failure in food quality (i.e. why a product spoiled)?

Answer 1

1, the sensory or organoleptic characteristics and observation that one can use to identify if the food has spoiled is smell, flavour, tactile, odour, texture and colour. The spoiled apple juices shows off flavour, off odour, change of colour, loss of thickness, firmess, acidic flavour due to fermentation of sugars in fruit juices and slimy texture. Other than this if the juice is spoiled by any mould, we can visually see the mold growth on the juices.

2, Heating or boiling, drying, refrigeration are three commonly employed ways of preserving food. The increase in temperature while boiling can kill most of the microbes except for some heat resistant spore, drying decreases the complete water content of the food which is very important for microbial growth, refrigeration or using low temperature can slow down and minimise the growth of microbes or making them static. It is because most of the food spoilers are active at 37 degree Celcius (mesophiles). fermentation is also one of the common method of preservation which allows mostly friendly microbes to grow

3. The heat resistance of food spoilers vary. The vegetative cells are less heat resistant whereas spores are have high spores resistant. Mesophilic bacteria canno resist heat whereas thermophiles can resist. The number of bacteria, strain of bacteria and its characteristics according to the thermal resistance and thermal death time should be studied by the industries. And its accordingly sterilisation rechniques are selected. So proper temperature of heat is not given in the sterilistaion technique, the spolier can cope up and reactivate spoiling the food products.