Enhancing the export competitiveness of the Philippine super mango: postharvest behavior and quality of irradiated 'carabao' mango fruits under controlled or modified atmosphere conditions

Results from three laboratory trials that established irradiation dose-storage responses showed the following: 1) irradiation dose of 150 Gy (max) gave the best results in terms of peel and pulp quality regardless of storage system used; 2) the higher the irradiation dose the slower the rate of peel development but at 300-600 Gy, high incidence of physiological disorder, such as internal breakdown (IB), and pulp/peel browning were evident regardless of storage system used; 3) at the table ripe stage (TRS), all fruits, regardless of treatments (irradiation, storage condition and duration), did not exhibit significantly different % TA, TSS and pH values. In terms of firmness, no significant differences were observed using CA [controlled atmosphere]/MA [modified atmosphere] in combination with irradiation doses. In both storage methods and duration, non-irradiated fruits (0 Gy) had significantly the highest disease severity rating, implying that irradiation has a controlling effect on disease development, however, the irradiation dose-effect relationship was found to be insignificant. In general, non-irradiated fruits stored in MA or CA were the most preferred by panelists in the sensory tests. The following conditions and protocols for MA/CA storage of irradiated mangoes were generated/established. For MA, the use of 38-mm polyethylene or 20-mm zeolite film with 52 or 44 pinholes, respectively, for packing 5 kg fruit in a bag with a surface area of approximately 0.80 sq m if held at 12.5 deg C, at these conditions, the desired level of O2 was attained to give favorable fruit responses. For CA storage, the optimized conditions were: oxygen level range of 5-7% and a low temperature (10-12 deg C) regime. For both storage systems, the mangoes must have reached the appropriate maturation stage gauged by flotation or calendar method. The green mature mangoes must undergo combined heat and postharvest dip treatments (52-55 deg C, 5-10 min dipping, 600 ppm prochloraz) to effectively control latent diseases like anthracnose and stem-end rot. These sets of optimized MA or CA conditions and protocols, when applied in subsequent MA/CA storage pilot scale trials of mango fruits irradiated at the optimum dose of 150-250 Gy, resulted in the following: 1) a significant delay in ripening-CA storage retarded the ripening of irradiated mangoes for five weeks (35 d), whereas, MA storage extended the shelf-life of irradiated mangoes up to 36-39 days, upon withdrawal from the storage of CA chamber or MA plastic bag, average peel color index (PCI) of 4.0 and 3.8 upon opening of the CA and plastic bag, respectively; irradiated CA- and MA-stored fruits ripened normally at ambient and at 18 deg C ripening rooms with no significant differences in titratable acidity (TA), total soluble sugars (TSS) and pH values relative to non-CA/MA stored fruits, peel/pulp discoloration was evident in irradiated fruits whether they were CA or non-CA stored; regardless of the ripening room temperature, mango fruits stored under CA or MA had firmer sensory texture at the table-ripe stage (TRS) than the non-CA/MA stored fruits; for both CA and MA storage, disease incidence and severity was none to low upon removal from storage but disease severity and incidence progressed during ripening at ambient. An actual sea shipment to a distant market like Dubai, UAE, was done in order to verify the technical feasibility of the modified atmosphere technology in extending the shelf life of mango, and also to determine the economic soundness of exporting the Philippine Super mango to a distant market by refrigerated sea shipment and under the MA technology.