Jackfruit (Artocarpus Heterophyllus lam) a potential Source of pectin

Abstract

Jackfruit is widely cultivated in tropical areas. The fruit is mainly grown and consumed fresh. Approximately 65% of jackfruit is inedible and this part is commonly fed to animals or discarded. However, jackfruit waste can be processed into pectin for use in food processing. The characteristics of pectin vary between and within sources implying a deeper understanding of a pectin source is needed if its efficient utilization is to be achieved. This research assessed the potential of jackfruit as source of pectin. A survey was conducted in five selected districts of Uganda (Jinja, Kamuli, Kayunga, Luuka and Mityana) to establish the existing jackfruit types, production levels, maturity period and utilization. Jackfruit samples of varying flake color were picked and the fruits kept for 2-3 days to ripen. Fruit dimensions, fruit part proportions and flake physico-chemical properties were determined. The different types of fruit were divided into parts. Pectin was extracted from each of these parts and the physico-chemical properties of the pectin analyzed. The pectin was used to prepare gels whose hardness, gelling time and gelling temperature were determined. Results showed that jackfruit is widely grown in the study areas but on subsistence scale mainly for house hold consumption and to a small extent, the flakes are dried into chips or fermented into jackfruit wine. Farmers on average owned 2-7 jackfruit trees on their farm land. About 57% of the jackfruit trees were purposely planted, 12% were inherited, 11% grew on their own and 20% did know how the trees came about. The study areas were estimated to have about 1.7 million fruiting jackfruit trees yielding between 20-120 fruits per tree per season with an average weight of 11 kg per fruit. The annual production for Jinja, Kamuli, Mityana, Kayunga and Luuka districts was estimated at 0.403, 0.345, 0.309, 0.297 and 0.172 million tons, respectively. Farmers revealed that they categorize jackfruit based on the flake color (white, orange and yellow) and texture (hard or soft). Respondents reported two peak harvesting periods, namely March - April and November – December, with more harvest made in the latter period. About 78% of the harvest was for home consumption, 16% was sold in local markets, and 5% was fed to animals while 1% processed into dried chips or wine. Jackfruit types studied showed variation in physico-chemical properties of the flakes, proportions of different parts and maturation time. Yellow flaked fruit types had the biggest flake size (17kg) followed by the white and orange flaked fruit types (p < 0.05). The period to maturity varied with flake type (p<0.05) and ranged between 95 to 113 days. Jackfruit flakes contained 1.6-4.3mg/100g ascorbic acid, 0.3-2.4mg/100g carotenoids and total soluble solids 17-26 obrix, with TSS: acid ratio of 44-65. Flake hardness was 12.1±1.2 N/mm in white flakes 10.5±1.0 N/mm in yellow flakes and 6.6±0.7 N/mm in orange. Flake resilience exhibited a trend similar to that of flake hardness. Orange flakes were associated with high carotenoids and TSS content compared to yellow and white flakes. The average equivalent weight (EQW) for yellow, orange and white flakes pectin was 917, 868 and 662g/mol respectively. The methoxyl content (MeO) for the majority of jackfruit pectins studied was above the critical limit 7%. Anhydrogalacturonic acid (AUA) content was below 65%. The degree of esterification (DE) for all pectin types was about 50%. The pectin yield and ash content 15-30% and 2-12% respectively. Generally, all jackfruit parts showed high solubility at pH 2 and beyond pH 8. However, among the pectin sources, flake pectin exhibited the least solubility at all the pH levels studied. Pectin from different jackfruit parts and types varied in gelling properties when tested at different Ca2+ levels with pectin from orange and white flaked jackfruit types gelling at 35 mg/100ml [Ca2+] at room temperature. At this [Ca2+] jackfruit pectin formed hard gels whereas the reference pectin did not. The results of this study, suggest that the study areas have potential for jackfruit production if the crop is produced in a more organized way. It is more economical to use jackfruit flakes for consumption purposes and the waste for pectin extraction. Based on the properties of jackfruit pectin, the pectin could be recommended for industrial application