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143 Crop Post-Harvest: Science and Technology , First Edition. Edited by Debbie Rees, Graham Farrell and John Orchard. © 2012 Blackwell Publishing Ltd. Published 2012 by Blackwell Publishing Ltd. 7 Pineapple Nimal Adikaram and Charmalie Abayasekara INTRODUCTION The pineapple Ananas comosus L. Merril. is the leading member of the Family Bromeliaceae native to Southern Brazil and Paraguay where wild relatives occur. The pineapple was apparently domesticated by the Indians. The plant was carried through Southern and Central Americas to Mexico and the West Indies long before the arrival of the Europeans. Pineapples are grown in Australia, Brazil, China, Hawaii, Kenya, Malaysia, Mexico, Philippines, Thailand, South Africa, Sri Lanka and West Indies. Brazil, China, Philippines and Thailand are the main pineapple producers in the world supplying nearly 50 of the total output FAO 2004. Total production of pineapple was 14 million tons in 2003 FAO 2004. Nearly 70 of the pineapple is consumed as fresh fruit in producing countries. The pineapple is a xerophytic, succulent, herbaceous plant Bartholomew and Malezieux 1994. The plant is a perennial, flowers only once and dies after fruiting; a side root then takes over. There are genetically diverse groups of pineapple: the Cayenne group, Queen group, Red Spanish, Abacaxi group and Maipure group Leal and Soule 1977; Grazia et al. 1980. The commercial varieties are classified into three groups, the Cayenne group, Queen group and Red Spanish, based on their morphological characters. Smooth Cayenne is the world’s most grown and largest commercial group Grazia et al. 1980 used in processing and fresh fruit trade. Cayenne has spineless leaves and big- ger plants, and produces fruits with shallow eyes and very sweet taste. Queen has spiny leaves and somewhat smaller plants and produces very sweet fruits with deep eyes. Spanish group plants have spiny leaves and produce medium-sized fruits with an acidic taste. Pineapple is a collective fruit made up of berry-like fruitlets developed from a whole inflorescence. The fruit is made up of 100 to 200 fruitlets which are fused together on a central axis or core. The fruit has a conical shape with larger fruitlets at the base and smaller ones at the top. Flesh of fresh or canned fruit is eaten as a dessert, and the juice has a growing demand as a beverage. The pineapple has long been one of the most popular of the noncitrus tropical and subtropical fruits, largely because of its attractive flavour and refreshing sugar–acid balance. FRUIT COMPOSITION The mature pineapple fruit contains 80–86 water and is a good source of carbohydrates. The sugars are not distributed evenly throughout the fruit; the bottom portion has more sug- ars than the top crown end because it is composed of more mature fruitlets Sinclair 1993. The fruit has 0.5–2 acids. Consumption of 100 g edible portion provides 218 KJ of energy Wenkam 1990. The fruit also has fibre. Potassium is the most prominent mineral, followed by calcium Table 7.1. Pineapple juice contains S-sinapyl-L-cysteine, N-L-γ- glutamyl-S-sinapyl-L-cysteine and S-sinapylglutathione in substantial concentrations Wen et al. 1999. Twenty-nine odour-active compounds were detected in an aroma distillate prepared from fresh pineapple, and five of these were key odorants in fresh pineapple flavour: 4-hydroxy-2,5-dimethyl-32H-furanone HDF; sweet, pineapple-like, caramel-like, ethyl 2-methylpropanoate 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.