189–196. Crop Post-Harvest: Science and Technology

144 Crop Post-Harvest: Science and Technology fruity, ethyl 2-methylbutanoate fruity followed by methyl 2-methylbutanoate fruity, apple-like and 1-E,Z-3,5- undecatriene fresh, pineapple-like Tokitomo et al. 2005. The proteolytic enzyme, bromelain, obtained from the juice or mature plant stem Nakasone Paull 1998 is used for tenderizing meat and chill proofing beer, is added to gelatine to increase its solubility for drinking and has been used for stabilizing latex paints and in the leather tanning process. In modern therapy, bromelain is used as a digestive and for its anti-inflammatory action after surgery Nakasone Paull 1998. Bromelain, is believed to cause soreness and discomfort of the mouth when excessive amount of fresh pineapple is consumed. The presence of bromelain in pineapple juice also prevents gelatinization if the juice is used as an ingredient for gelatin. Therefore, commercial pineapple juice has to be pasteurized to inactivate the enzyme. Bromelain FA2, the main proteinase component of the juice of pineapple fruit, has been purified and characterized, the molecular weight being 31 000 Daltons and the isoelectric point pH 4.6 Yamada et al. 1976. FRUIT DEVELOPMENT AND PHYSIOLOGY Fruit development Pineapples can initiate flowers only after reaching a minimum weight about 500 g for Smooth Cayenne. However, plants at this minimum weight will produce only very small flowers. Ethylene is believed to be the chemical which causes natural initiation of flowering. Plants can be artificially induced to flower at any time by applying ethylene-producing chemicals Sinclair 1993. In pineapple, and other bromeliads, it has been proposed that flowering is triggered by a small burst of ethylene production in the meristem in response to environmental cues Trusov Botella 2006. Flowering dynamics studies revealed significant differences in flowering behaviour, with transgenic plants that exhibited the silencing ACACS2 1-amino-cyclopropane- 1-carboxylate synthase gene showing a marked delay in flowering when compared with nonsilenced transgenic plants and control nontransformed plants. It appears that the ACACS2 gene is one of the key contributors towards triggering ‘natural flowering’ in mature pineapples under commercial field conditions Trusov Botella 2006. It takes approximately four months from the end of the last open flower to fruit maturity and the total time required from flower initiation to harvest is between six and seven months Nakasone Paull 1998. During maturation, the fruit size, weight, soluble solids and acidity in the flesh are increased. During ripening, the shell of the pineapple loses chlorophyll rapidly, starting at the fruit base, the pulp soluble solids increase dramatically and the fruit attains the maximum eating quality. Table 7.1 Composition of Pineapple Fruit. Nutrient Amount per 100 g edible portion Nutrient Amount per 100 g edible portion Water 80–86 g Ascorbic acid 10.00 mg Energy 218 KJ Vitamin B12 0.09 mg Protein 0.2 g Vitamin B6 50 IU Lipid 0.2 g Vitamin A, IU 53 IU Carbohydrate 13.5 g Vitamin A, RE 1.0 Acids 0.5–2 g α Tocopherol 0.16 mg Total sugars 8 g Riboflavin 0.4 mg Fibre 0.5 g Folate Total 11 mcg Ash 0.3 g Thiamin 0.9 mg Calcium 18 mg Cryptoxanthene 0 mg Iron 0.3 mg Niacin 0.036 mg Magnesium 12 mg Pantothenic acid 0.42 mg Phosphorus 12 mg Potassium 98 mg α Carotene 31 mcg Brix 10.8–17.5 Sodium 1 mg Titratable acidity 0.6–1.62 Source: Dull 1971 and Wenkam 1990.