Biochemical analysis and activity profiling of fruit ripening enzymes in banana cultivars from Kerala

Bananas are the most important fruit crop enriched with various vitamins, minerals, β-carotenes and fibres. But the short shelf life of the fruits is the major limiting factor for post harvest storage. Textural changes lead to softening of fruit, mainly due to the cumulative action of a group of cell wall hydrolyzing enzymes like polygalacturonase (PG), pectin methyl esterase (PME), cellulase and xylanase. Banana is a multiploidy crop and breeders need knowledge on the ploidy level for varietal improvement of this crop. Mainly there are two types of banana genome, AA genome (Musa acuminata) and BB genome (Musa balbisiana); and AAB—triploid of M. acuminata and M. balbisiana; AAA- triploid of M. acuminata and AB- diploid of M. acuminata and M. balbisiana. In this background the present study was carried out to understand the activity of five major fruit ripening enzymes (PG, PME, cellulase, invertase and xylanase) in the fruits of eight M. acuminata cultivars viz. M. acuminata cv. Palayancodan (triploid, AAB), Nendran (triploid, AAB), Poovan (triploid, AAB), Robusta (triploid, AAA), Red banana (triploid, AAA), Kadali (diploid, AA), Matti (diploid, AA) and Njalipoovan (diploid, AB) at early ripened, ripened and late ripened stage of fruit maturation. Preliminary biochemical estimation was carried out in the fruits from the selected cultivars for total carbohydrates, reducing sugar, amino acids, total proteins, and β-carotenes in early ripened, ripened and late ripened stages. Carbohydrate content was maximum in Red banana (2689.6 µg/g tissue) and minimum in Matti (1267.16 µg/g tissue). Amino acid content was maximum in Kadali and minimum in Red banana and Poovan. Maximum protein was observed in Kadali (698.4 µg/g tissue) and minimum in Red banana and Poovan. β-carotene content was maximum in Nendran (412.16 µg/g tissue) and least in Matti (124.03 µg/g tissue). The cell wall hydrolyzing enzymes except invertase showed maximum activity in ripened fruits of Palayancodan. Invertase activity is maximum in Njalipoovan and this can be linked with its higher non-reducing sugar content. Present study confirmed that the chemical composition and nutritional value of bananas are different for each cultivars and showed significant difference during the ripening period.