Ground Based Study of the Effect of Open and Close Chamber Condition on Banana Ripening Process

Abstract

Level of O₂ and CO₂ plays an important role on ethylene biosynthesis during ripening of the climacteric fruit.  Low level of O₂ and high level of CO₂ will affect ACS and ACO enzyme activities and will impede ethylene production. Thus, reduce ethylene level will eventually delay fruit ripening process. Pre-climacteric banana fruits (Musa sp.) were chosen based on ripening level, size, shape, and color similarity. Samples were put into two different chambers, open and closed, to mimic earth-like and space-like environment.  At the end of experiment, banana fruit samples were taken and stored in freezer for further genes expression analysis. Gas produced during experiment in open and close chamber were also detected using O₂ and CO₂ gas probes to obtain data of gas consumption and production during experiment. Physical characteristic and physiological analysis during fruit ripening were also conducted by examining the pulp to peel weight ratio, qualitative starch content, and qualitative  as well as quantitative sugar content. Gene characterization showed that MaACS1 in the pulp were expressed higher initially and followed by MaACO, whilst in the peel were insignificant.  It also showed that genes in the pulp was expressed higher than in the peel, which might indicate that fruit maturation in banana was started from the pulp. MaACS1 and MaACO gene expression in open condition were always higher in both pulp and peel, which might indicate the influence of O₂/CO₂ ratio in those genes expression.  This result was supported by physiological data that the O₂/CO₂ ratio was nearly invariable for the whole 8 days of experiment in the open chamber condition, the highest ratio reached 4.3 x 10^-6 while the lowest one was 3.93 x 10^-6. At the same time, the O₂/CO₂ ratio in closed chamber condition decreased logarithmically in two days, i.e. 4.0 x 10^-6 to 6.8 x 10^-8 and then slightly decrease to 3.8 x 10^-8 in the 4^th day, followed by an increase to 8.5 x 10^-8 in the last day. Ratio of pulp to peel weight in open condition increased significantly from 2.1 to 6.4 during 8 days observation, whilst in close condition only slightly increased from 2.1 to 3.8. Qualitative starch content using iodine test in open condition showed a more significant decrease than in close condition, while quantitative sugar content measured and the qualitative sugar content observed using benedict test in open condition increased higher than in close condition. Based on those qualitative experiment, it could be concluded that banana in open chamber matured earlier than banana in close chamber.