Effect of GA3 and polyethylene film lining on the postharvest characteristics of two varieties of plantain under ambient storage conditions
Plantain is an important crop in the tropics. The crop, however, faces persistent perishability problems leading to high postharvest losses and eventual shortage and high prices of the crop and its products. The study attempted to solve this problem by providing a means of extending the shelf life of the crop particularly during the short lean period. In this regard, the post-harvest effect of GA3 and polyethylene lining on two varieties of plantain, Apem and Apentu, under ambient temperature, was investigated in a factorial experiment. Four rates of GA3 (0 mg/lit, 375 mg/lit, 750mg/lit and 1000mg/lit) were applied and three lining methods were used on card boxes as packaging materials. The three lining methods were the control/ no lining, perforated lining and unperforated lining. It was observed through the analysis that the effect of plantain variety on all the eight quality characteristics (days to ripening, weight loss, pulp to peel ratio, firmness, total soluble solids, pH, total titratable acidity, sugar to acid ratio) that were investigated were significantly different (P<0.01) except for sugar to acid ratio. Whereas Apem took a mean of 49 days to ripen (level 7 on the Dole Banana Guide), it took Apentu a mean of 23 days to ripen on the same scale. The four GA3 concentrations recorded significant differences (P<0.01) on all the eight characteristics of the plantain fruits. Plantain fruits stored longer as the concentration of GA3 was increased. The control (0mg/lit) recorded the lowest mean number of 28 days to ripening while the highest concentration of 1000mg/lit recorded the highest mean number of 42 days. Increasing the concentration of GA3 from 375mg/lit to 1000 mg/lit decreased mean weight loss from 12.37 % to 11.23 % respectively, however, the untreated fruits had the lowest mean weight loss of 9.30 %. Furthermore, pulp firmness increased as fruits were treated with GA3. The highest concentration of 1000mg/lit recorded the highest mean firmness of 5.78N as the control recorded the lowest mean of 4.72N. Total titratable acidity for fruits treated with GA3 was lower than those that were not treated. The highest mean total titratable acidity (3.94mEq) was obtained from applying 0mg/lit GA3 with 1000mg/lit recording the lowest of 2.46mEq. GA3 concentration of 375mg/lit also recorded total titratable acidity (2.56 mEq) similar to the lowest that was recorded. Polyethylene lining recorded significant differences (P<0.01) on all parameters except pH. Lined fruits stored longer than unlined ones. Fruits in unperforated lining stored longest (45 days) with fruits in unlined boxes having the lowest mean number of 22 days. Fruits in unlined packaging materials lost more weight than those in lined boxes. The highest weight loss (20.10 %) was obtained from the unlined fruits while the unperforated lining produced the lowest mean weight loss of 4.3 %. The unlined fruits became pulpier than the lined ones. The control unlined fruits recorded the highest mean pulp to peel ratio of 1.78 while the perforated lining recorded the lowest mean pulp to peel ratio of 1.13. Unlined fruits accumulated more sugar than the lined ones. The control recorded the highest mean of 3.72 (ºBrix) with the lowest 1.08 (ºBrix)) coming from fruits in perforated lining. Acidity in fruits that were lined was lower than the unlined fruits. The highest total titratable acidity (3.51 mEq) was observed from the control while the perforated lining recorded the lowest mean of 2.67 mEq. Combinations of all factors also produced significant differences (P<0.01) except for pH. GA3 was effective in delaying ripening of both types of plantain outside or within lined packaging materials at ambient temperature with higher concentrations recording longer delay in ripening. Furthermore, lined packages delayed ripening longer than unlined ones with the unperforated ones having highest influence. The combination of lining and the application of GA3 further delayed ripening of both types of plantain. Polyethylene lining and GA3 could increase shelf life of plantain fruits.
A thesis submitted to The School of Graduate Studies, Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirements for the award of Master of Philosophy in Postharvest Technology, 2016