One of the main objectives of food preservation is the prevention of normal spoilage of perishable foods with maximum retention of food quality which includes retention of aesthetic characteristics of the food as well as its nutritional properties. Spoiled or deteriorating food is not only unsafe to eat, but it will also lose its nutritional value. All food types inevitably deteriorate from the time they are made. Along with deterioration comes the loss of nutrients. The rate of deterioration and nutrient loss depends on several factors reviewed in Lesson 5, such as light, oxygen, temperature, pH, etc.
We often hear comments made that processed foods have all the "goodness" removed from them during processing. It is true that nutrients are lost during the processing of foods that extends their storage life, whether that processing occurs at home or manufacturing plant. However, it is important to note that the extent of nutrient loss depends on the particular nutrient and the conditions of processing. Although food processing and preservation practices do lead to some losses in nutrient content, it provides the opportunity to preserve the food for a longer period of time. In contrast, when a food spoils, the loss of nutrients is 100% because that food is no longer used for human consumption. In most cases, a significant proportion of nutrients is retained after processing. Keep in mind that nutrient losses can also occur in fresh foods even during storage in the refrigerator and during normal cooking processes commonly used at home.