ประสิทธิภาพของสารสกัดจากเคี่ยมร่วมกับไคโตซานต่อการยับยั้งเชื้อราก่อโรคหลังการเก็บเกี่ยวและการรักษาคุณภาพของผลเงาะ

Abstract

The effects of Kiam (Cotylelobium lanceolatum Craib) crude extract combined with chitosan on postharvest fungal diseases and quality of rambutan fruit were conducted in ‘Rongrien’ rambutan grown in Nasan district, Surat Thani Province. The results of fungal isolation showed that Diaporthe sp., Phomopsis sp. 1, Phomopsis sp. 2 and Phomopsis sp. 3 were the most dominant fungi causing fruit rot disease in the rambutan fruits collected from Nasan area. According to the pathogenicity test by wound-inoculation, rambutan fruits infected by Phomopsis sp. 3 showed the highest disease severity. The efficacy of branch and leaf extracts from Kiam was investigated on PDA medium containing crude extracts at concentrations of 0 (control), 500, 1,000, 2,000, 4,000, 6,000 and 8,000 μg/mL. The results found that the most effective concentration for controlling Diaporthe sp. Phomopsis sp. 1 and Phomopsis sp. 3 was at 8,000 μg/mL of Kiam extract, which the percentage of inhibition was 39.16, 54.24 and 42.51 % respectively. For Phomopsis sp. 2 the highest percentage of inhibition (41.48 %) was observed at the concentration of 6,000 μg/mL of the branch extract. These results suggest the potential of Kium extract, especially from branches better than from leaves, for controlling postharvest fungal disease. The postharvest quality of rambutan fruit effected by the branch extract combined with chitosan were examined during storage at 25 C for 8 days. It was found that the rambutan fruits treated with 6,000 μg/mL crude extract combined with 10 ppm chitosan could reduce the percentage of weight loss, delay fruit softening, browning of peel and spintern, fruit rot disease, total soluble solids (TSS) and titratable acidity (TA). Therefore, application of Kium extract together with chitosan could be an optional treatment to develop in order to replace chemical usage in postharvest treatment of rambutan and other fruits.