Retention factors are a very popular area of nutritional research. In the future, retention factors expressed as percentages may be incorporated into the labels of processed foods in order to help consumers more accurately assess nutritional intake.
Although retention factors assess changes in the nutritional value, they do not relate to how much of a nutrient is absorbed or available to be absorbed after it is eaten. So, although a high nutrient food may change very little in its nutritional value after preparation, factors such as large intestinal health and interactions with other nutrients may affect the availability of the food's nutrients.
The nutritional content of foods is altered due to heating or other means of food preparation, such as pickling, soaking, and fermentation. The retention factor is the percentage of the food component remaining after preparation. To calculate this, researchers measure the vitamins and minerals in foods before and after cooking. The fraction of vitamins, minerals, fat, and other nutrients that changes during this process is expressed as the retention factor.
Components measured in retention factors include zinc, copper, potassium, calcium, and most other common vitamins and minerals. The retention factor of each of these is calculated for most popular foods. The retention factor for two different vitamins in one food may vary considerably, depending on the method of preparation. For instance, cured picnic ham has a calcium retention factor of 100%, while the retention factor for thiamin is 40%. This means that the cured picnic ham does not lose any of its available calcium during the preparation process when compared to the uncured meat, but only 40% of the thiamin is available compared to the uncured meat.
Refuse factor is a term that describes the part of a food that is inedible. For instance, the bone on a pork chop or the cob in corn would be a refuse factor.