Revestimentos à base de amido na conservação pós-colheita de pedúnculos de caju anão precoce CCP-76 e goiabas Paluma

Abstract

The objective of this work was to prolong the post-harvest life of cashews of the clone - CCP-76 and guavas Paluma by means of a modified atmosphere obtained with coatings based on starches. The study was divided into two stages. Firstly, xanthan pruni was obtained for use as coat stabilizer; and rice, bean and cassava starches modified by low moisture heat treatment - TTBU (24% water/110°C/60 min). The native and modified starches were characterized as moisture content, swelling power (PI), paste clarity, crystallinity index and morphology of the granules. Subsequently, films were produced by casting, being evaluated for morphology. The gels or pastes of modified starch presented reduction in swelling power, pulp clarity and crystallinity index. TTBU generated films with better matrix continuity compared to native starch films. The second stage consisted of three experiments, with application of coatings in fruits, being two in peduncles of dwarf cashew clone - CCP-76 and other with guavas Paluma. In the first cashew experiment, two coatings based on native starches and xanthan were tested: (T1) 3.0% rice starch (RS), 0.3% xanthan and 3.0% sorbitol (w/v); (T2) 3.0% bean starch (BS), 0.3% xanthan and 3.0% sorbitol (w/v), uncoated fruits served as controls. The fruits were covered by immersion and stored at 7±1°C, 90±5% RH, for 8 days. Mass loss (ML), pulp firmness (N); external appearance (EA); soluble solids (°Brix), titratable acidity (TA), pH, vitamin C and coloration (L*, c* and °Hue). Uncoated fruits served as controls. Coatings increased appearance, but were not efficient to retard ML. In the second cashew experiment, four coatings based on physically modified starches (MS), xanthan or chitosan were tested: (T1) 4.0% rice starch 0.3% xanthan; 2.0% sorbitol and 0.02% calcium phosphate (w/v); (T2) 4% rice starch, 0.7% chitosan, 2.0% sorbitol and 0.02% calcium phosphate (w/v); (T3) 4% cassava starch (CS), 0.3% xanthan, 2.0% sorbitol and 0.02% calcium phosphate; (w/v); (T4) 4.0% cassava starch, 0.7% chitosan, 2.0% sorbitol, 0.02% calcium phosphate (w/v). Previously, casting films were prepared, evaluating the thickness, water vapor permeability (WVP), water solubility, opacity. The combination of the starches with chitosan generated thinner films, with lower WVP. The solutions applied as coatings were effective in delaying degradation of vitamin C for up to four days of storage under conditions similar to the previous experiment. For the experiment with guavas Paluma, four types of native and modified starch-based coatings of cassava and chitosan were studied: (1) 3.0% cassava starch (CS), 0.3% chitosan (Ch); 0.9% sorbitol (S) w/v; (2) 3% MCS, 0.3% Q, 0.9% S (w/v); (3) 2.7% CS, 0.6% Q, 0.9% S (w/v); (4) 2.7% MCS, 0.6% Q, 0.9% S (w/v). The properties of cast films, including moisture, water solubility, thickness, WVP, tensile strength and elongation and morphology were investigated. The combination of the lower starch concentration and the higher chitosan concentration (T3 and T4) made the films more tensile and elongation resistance, but the use of the modified starch resulted in lower luminosity and increased opacity. The coatings applied in guavas provided LM reduction throughout the storage (8±1 and RU 90±2%) for 20 days, compared to the fruits of the control treatment. The composite coating with the highest native starch concentration (T1) was the most efficient, providing a 34% reduction in relation to uncoated fruits. 11 For color, after eight days of storage up to 20 days the best performance was achieved by the use of the coating with the lowest modified starch concentration, a fact evidenced by the lower values of chroma and higher values of ºHue. With the advancement of storage, time the coated fruits maintained higher total carotenoids and total chlorophyll content when compared to uncoated fruits.