Introduction • 7
tomatoes, since the availability of hydrophobic carotenoid increases after heat processing. Both lycopene and β-carotene are antioxidants, important components of a healthy diet. The composition of the tomato fruit and important fruit-quality components are shown in Tables 1.1 and 1.2. There have been frequent complaints about the quality (especially the flavor) of modern fresh tomatoes. Handling and transporting fruit contribute significantly to this problem. To prevent serious losses during shipping and sales of fruit that are harvested ripe or nearly ripe, most fresh-market tomatoes produced in the field are picked before they are ripe. To lower costs, producers reduce the number of harvests,
which results in a significant proportion of immature fruit in a single harvest. Picking fruit before they start to ripen can have an adverse effect on the flavor when they finally ripen. Another potential contributor to the quality problem can be refrigeration. Tomatoes are sensitive to chilling, and when fruit are stored at temperatures less than 50°F (10°C), flavor is adversely affected. The rapid increase in the production and consumption of greenhouse tomatoes is likely fueled by the lack of satisfaction with field- grown fresh tomatoes. Greenhouse-grown tomatoes are generally picked with color and have improved handling, since they are a higher-priced product.
Fig. 1.13. Volume of tomato exports by China. Much of the increase in Chinese production occurred in the northwestern province of Xinjiang. (Based on data from FAOSTAT)
Table 1.1. Approximate composition of ripe fruit of a typical tomato cultivar (per 100 g fresh weight)a Component
Amount
Component
Amount
Total solids Total carbohydrates Sugars Glucose Fructose Sucrose Polysaccharides Cellulose, hemicellulose Pectic compounds Protein Amino acids Gamma aminobutyric Asparagine Aspartic Glutamic Glutamine Serine
6.0 3.9 2.9 1.3 1.5 100.0 1.0 600.0 400.0 300.0 350.0 70.0 10.0 45.0 100.0 60.0 10.0
Ash Calcium Chloride Magnesium Phosphorus Potassium Sodium Organic acids Citrate Malate Lipids Ascorbic acid Carotenoids Lycopene β-carotene Other compounds
500.0 15.0 40.0 10.0 25.0 250.0 5.0 800.0 600.0 200.0 100.0 23.0 4.8 4.5 150.0 20.0
a
g g g g g mg g mg mg mg mg mg mg mg mg mg mg
Adapted from Stevens and Scott, 1988.
mg mg mg mg mg mg mg mg mg mg mg mg mg mg µg mg