Vegetables are a group of food commodities in general is very much consumed by people, either as raw vegetables (vegetables) or by way of cooked first. Eating vegetables contribute especially vitamins A and C, and fiber that is very important for the body. Vegetables are classified as horticultural crops. Harvesting vegetables in general are relatively short (less than one year) and in general is not a seasonal crop, meaning almost all kinds of vegetables can be found throughout the year, not knowing the season.
This is slightly different characteristics with several types of fruits such as mango, durian and so are only found in certain seasons once a year. The types of vegetables are often easily found, both in traditional markets and in supermarkets include: carrots, tomatoes, mustard greens and whites, spinach, green beans, spinach, celery, leeks, squash, lettuce, eggplant, potatoes etc.
Nutrient content of each vegetable varies and is influenced by several factors: differences in varieties, weather conditions where growing, crop maintenance, harvesting, degree of ripeness when harvesting, and storage conditions.
1) Content of Water
In general, vegetables have a high water content is about 70-95%, so if it is not stored in cold conditions, these conditions lead to damage in the form of rapid wilting due to the evaporation of most of the water contained vegetables through the process of respiration.
Thus, to maintain the freshness of the vegetables, usually traders in traditional markets often sprinkled water to vegetables were sold to prevent wilting. While in supermarkets (supermarket) vegetable storage has already been placed on the shelves that maintained the temperature conditions according to the conditions of storage of vegetables, making it more resistant vegetable freshness.
2) Carbohydrates
Generally carbohydrates in vegetables are mostly found in the form of cellulose that can not be digested by the human body. With this condition, the vegetables used as a commodity good for digestion of cellulose contains. In addition in the form of cellulose, carbohydrates in vegetables is also present in the form of starch and sugar. Examples of vegetables with high starch content such as corn, potatoes, beans and other grains.
While examples of vegetables that are high in sugar content of sweet corn. The starch content in vegetables vary depending on the age of these vegetables. At the same kinds of vegetables harvesting the vegetables young age usually lower starch content than older harvesting. Often during storage of the starch contained in vegetables will turn into sugar. Changes to sugar usually in the form of glucose, fructose and sucrose.
Sucrose is a disaccharide, then by the enzyme invertase this sugar can be hydrolyzed to glucose and fructose. Glucose and fructose from sucrose by the breakdown of the invertase enzyme called invert sugar.
The proportion of the breakdown of glucose and fructose has a ratio of 1: 1. If the starch in vegetables during storage will be turned into sugar, otherwise the vegetables are high in sugar content as shown above, namely sweet corn, during storage at room temperature the sugar can turn into starch. So often sweet corn after several days of storage is no longer sweet taste. Nutrient content of some types of vegetables can be seen in the following table.
Table 5. Nutrient content of some types of vegetables
Source: Nutrition Directorate of the Ministry of Health (1972)