Qualidade, aceitação e aplicação de revestimento comestível à base de amido para conservação de frutos de umbuzeiro

Abstract

The umbuzeiro is a fruit tree native to the Caatinga, whose fruits have peculiar properties that allow them to be sold fresh and processed. Prevalent to extractivism, the growth of commercial cultivation with the insertion of new umbuzeiros demands characterization that enhances its use. Furthermore, as the fruit is highly perishable and consumption is limited to the period between harvests, technologies, such as the use of edible coatings based on different sources of starch and cellulose nanofibrils, become an interesting alternative to extend its shelf life. In this context, the objective was to characterize the quality and acceptance of fruits of umbuzeiro accessions produced in the Southwest of Bahia and to expand the post-harvest conservation of umbu 'BRS-68' through starch-based coatings, containing cellulose nanofibrils, associated with refrigeration. Thus, two experiments were carried out. In the first experiment, the fruits of the accessions EPAMIG-05, EPAMIG-07, EPAMIG-09, EPAMIG-13, BGU-44, BGU-45, BGU-47, BRS-48, BGU 30 and IFBaiano-01 were arranged in an entirely randomized design with three replications to evaluate the physical characteristics of diameter, mass, pulp yield, skin color and pulp firmness; the chemical characteristics of pH, titratable acidity, soluble solids content and relationship between soluble solids and titratable acidity; and the sensory acceptance and purchase intention test. In the second experiment, starch-based coatings were developed using the casting method with glycerol and cellulose nanofibrils. The experiment was arranged in a completely randomized design and plots divided over time, with three replications of ten fruits. In the plots, the use of coatings was studied, including: uncoated fruits, coated with cassava starch, rice, regular corn and whaxy corn, in the plots. In the subplots, storage periods of 0, 3, 6, 9 and 12 days were studied, at 18 ± 2°C and 85 ± 5% RH. The morphology of starch granules and cellulose nanofibril and the characteristics of mass loss, pulp firmness, skin color, soluble solids content, titratable acidity, soluble solids ratio and titratable acidity and pH of the fruits were characterized. The fruits of accessions BGU-44 and BRS-48 had a larger transverse diameter and, together with EPAMIG-05, a larger longitudinal diameter and mass. The pulp yield exceeded 70% for all, highlighting BGU-45 (75.88%) and BGU-44 (74.35%). The average luminosity was 61.89, with the BRS-48 shell being brighter. The fruits of accessions EPAMIG 05 (38.43) followed by BGU-30, EPAMIG-09 and BRS-48 showed greater color intensity and the °Hue varied from 111.29 to 106.12, expressing a bright green hue. The soluble solids content ranged from 9.6 (BGU-45) to 12.2°Brix (BGU-30), being suitable for fresh consumption and processing. The fruits of accessions BGU-44, BGU-45, BGU-47 and BRS-48 showed higher pH and lower acidity, adjusted to fresh consumption. Lower pH and higher acidity, suitable for industry, were expressed by the accessions IFBaiano-01 and EPAMIG-09. Greater sweetness was recorded in BGU-44, which, similarly to EPAMIG-05, presented lower pulp firmness. The acceptance rate for the evaluated sensory attributes exceeded 70% for all accessions. The fruits were similar in terms of flavor, with emphasis on BGU-44, EPAMIG-07 and EPAMIG-09. The fruits of the studied umbuzeiro accessions have commercialization potential and reach new markets, supported by the evaluation of physical and chemical characteristics, sensory acceptance and purchase intention, being EPAMIG-05, BGU-44, EPAMIG-09, EPAMIG-13 and BRS-48 more suitable for processing and BGU-45, BGU-47, BGU-30 and IFBaiano-01 for fresh consumption. The results of experiment II reveal starch granules with different shapes and sizes, enabling the formation of coatings with better gelatinization, barrier and reinforcement properties. The nanofibrils presented long fibers with an average width of 62.88 nm. The largest and smallest decreases in firmness after 12 days of storage were, respectively, for uncoated fruits (75.30%) and those coated with cassava starch (44.84%). The cassava starch-based coating provided less mass loss in the fruits (8.53%), followed by rice starches (10.54%), regular corn (12.11%), whaxy (15.18%) and without coating (20.00%). The coating based on different sources of starch, cellulose nanofibril and glycerol increases the shelf life of fruits from the BRS-68 accession, preserving the green color of the skin, the physical and chemical properties when stored at 18 ± 2°C and 85 ± 5% RH, with cassava and rice starches being more efficient in reducing mass loss and maintaining firmness.