Caracterização, conservação pós-colheita, processamento mínimo e adubação na qualidade de laranja 'champagne' (Citrus sinensis L. Osbeck)

Abstract

This study aimed to characterize fruits of 'Champagne' orange harvested at different stages of maturation, evaluate the effects of different types of coatings temperatures and storage time in conservation of whole fruit of 'Champagne' oranges and different coatings and types of operation in minimally processed fruits and also investigate the influence of nitrogen and potassium fertilization on fruit quality. For characterization, fruits were harvested with 4 different coloring of the peel: totally green peel (V), green peel, predominantly green peel initiating yellowing (VA), predominantly yellow peel with traces of greenish coloration (AV) and totally yellow peel (A). These fruits and their juices were submitted to evaluation of their physical and chemical characteristics, centesimal composition and mineral composition. To investigate post- harvest conservation, the fruits were stored in polystyrene trays and covered with different coatings (control, cassava starch at 2%, cassava starch at 4%, stretchable PVC film, polyethylene film) and then stored at three different temperatures (3ºC, 8ºC and 25ºC). The fruits stored at 25ºC were evaluated every 4 days during 24 days and those under refrigeration (3 e 8ºC) were evaluated every 10 days during 60 days. For the minimum processing, mature fruits were harvested, washed and sanitized and refrigerated and they were subjected to three types of operations (whole fruit without flavedo, whole fruit without flavedo and albedo, and segmented fruit in buds). Then the fruits were packed in extended polystyrene tray (BPE) without cover; BPE with edible film of gelatin at 3%; BPE covered with polyethylene and polyesthylene plastic container with a lid and next they were stored at 5°C for 8 days. Every two days the fruits were removed from storage and evaluated. For fertilization we used the central composite design (DCCR), factorial 22 with variable nitrogen (N) and potassium (K) into five levels, a total of eleven trials. The fertilization procedure was performed for two years (crop 2010 and 2011) in four stages using urea as a nitrogen source in doses of de 86,9, 120, 200, 280 e 313,1 kg\ha year -1 and potassium chloride as a source of potassium in doses of 35,2, 60, 120, 180 e 204,84 kg\ha year -1. Subsequently leaf samples were collected for evaluation of N, K, P Ca, Mg, soil to analyse K, fruits to analyse weight, longitudinal and transversal diameters. The quality of the fruits were evaluated based on the weight loss, pH, AT- titratable acidity, SST- total soluble solids, total sugars, ascorbic acid, and in the experimento f minimally processed fruits were also evaluated the counts of psichrophilic bacteria, molds and yeasts and total and fecal coliforms. Were observed physical and chemical changes with the maturation of the fruits for many of the investigated parameters and nutritional constituents, except minerals. Highlighting the weight elevations in fruits, juice yield, pH, reducing sugars, protein, lipids and sulfur, and reduced AT, SST, ascorbic acid, dietary fiber and moisture. Besides that fruit peel color classified as AV and A reached the appropriate rates. On post- harvest storage, the refrigeration at 3ºC allowed them to keep many of the quality characteristics of fruit for up to 60 days, as long as coated with polyethylene and PVC, while at 25ºC storage maintained the external appearance of the fruits coated with polyethylene and PVC for up to 20 days. In the case of minimal processing, the ‘Champagne’ orange fruits packed with PVC film, polyesthylene plastic container with a lid and polyethylene film, independent of the operation level for which they were submitted maintained a good apperance and did not have any changes in their physicalchemical and microbiological characteristics that could compromise their quality until the 8th day of storage. Regarding to fertilization, no significant effects were observed from the combination of different doses of N and K in the physical and chemical characteristics and parameters of fruit quality, concentration of K in soil and leaf nutrient levels, except for leaf N, P and Mg.