ผลของการเคลือบกล้วยด้วยไคโตซานผสมวานิลลินและน้ำมันอบเชยต่อการยับยั้งเชื้อ Colletotrichum spp. และ Fusarium spp. และการเปลี่ยนแปลงคุณภาพของกล้วย

Abstract

This research aims to study the effect of chitosan coating incorporated with vanillin and cinnamon oil on inhibiting Colletotrichum spp. and Fusarium spp. and quality changes of bananas in terms of biochemical, physical, and sensory during storage. This research composes of 4 parts, including Part 1: The study of the efficiency of vanillin and cinnamon oil (VC) and cinnamon oil (C) in inhibiting Colletotrichum spp. and Fusarium spp. by poisoned food bioassay technique and vapor phase diffusion technique. In poisoned food bioassay technique, plant extracts at concentrations of 20, 100, 200, and 1000 µL/L were tested and the results showed that VC and C at 100 µL/L could completely inhibit Colletotrichum spp. At 20 µL/L, C and VC inhibited Colletotrichum spp. by 38.98% and 42.33%, respectively. Therefore, vanillin enhances the inhibition effect of cinnamon in inhibiting Colletotrichum spp. In vapor phase diffusion technique, VC and C at a concentration of 100 µL were dropped on a filter paper with 9 cm diameter and placed on the Petri dish lid. This concentration could completely inhibit Colletotrichum spp. At 20 µL vapor, C and VC inhibited Colletotrichum spp. by 30.34% and 54.73%, respectively. This experiment demonstrates that vapor of VC at 20 µL is more effective in inhibiting Colletotrichum spp. compared with cinnamon vapor alone. In addition, 100 µL of VC and C completely inhibited Fusarium spp. At 20 µL/L, C and VC inhibited Fusarium spp. by 48.98% and 6.65%, respectively. This reveals that C at 20 µL/L is more effective than VC. In vapor phase diffusion technique, the use of 100 µL VC dropped on a filter paper could completely inhibit Fusarium spp. While 20 µL C and VC vapor inhibited Fusarium spp. 8.60% and 50.68% respectively. The results indicate that VC vapor had greater efficacy in inhibiting Fusarium spp. From GC-MS analysis, the main constituents of cinnamon oil consist of 3-allyl-2-methoxy phenol, benzoyl benzoate, caryophyllene, acetyl eugenol, trans-cinnamyl acetate, β-linalool, cinnamaldehyde, and safrole. While the principal components of vanillin mixed with cinnamon oil contained benzaldehyde and 3-hydroxy-4-methoxy, which were the compositions of vanillin. Both constituents exhibited inhibitory effect against Colletotrichum spp. and Fusarium spp. Therefore, chitosan film mixed with vanillin and cinnamon oil had more effectiveness in inhibiting Colletotrichum spp. and Fusarium spp. Part 2: Properties of chitosan coating incorporated with VC and C. The results showed that VC significantly increased viscosity of chitosan and pH values of chitosan coating solutions were in the range of 6-6.5. The chitosan coating combined with VC exhibited a higher binding ability percentage on banana peel when compared to both chitosan coating and chitosan coating combined with C. Part 3: Properties of chitosan coating film. The chitosan coating was formed into film sheets including chitosan film (CH), chitosan film incorporated with vanillin and cinnamon oil (CHCV), and chitosan film incorporated with cinnamon oil (CHC). All films were tested in term of thickness, color, microscopic structure, vapor permeability, gas permeability, and chemical structure. It was found that adding vanillin and cinnamon oil into the chitosan coating increased the thickness of the film and affected the film color. Films containing plant extracts tended to turn yellow. The surfaces of the banana peel coated with all film formulations were smoother than the uncoated peel. The chitosan film and the chitosan film incorporated with vanillin and cinnamon oil had a rougher surface compared with chitosan film incorporated cinnamon oil. The water vapor permeability values among all three film formulas were comparable. The chitosan film exhibited the highest vapor permeability at 0.62±0.03 g mm/m2 h kPa, and its permeability slightly decreased when vanillin and cinnamon oil were added. The CHCV had the lowest vapor permeability at 0.29±0.05 g mm/m2 h kPa. This might be due to the molecular interaction of vanillin in chitosan matrix and the aldehyde group (CHO) of vanillin interacting with the amino group (NH2) of chitosan, resulting in the formation of an amino acid (NC) and a hydroxymethyl group (CH2OH) of chitosan. The gas permeability test revealed that CHCV had the lowest permeability at 0.65±0.13 cm3/m2x 24 hrs, followed by the CHC (0.72±0.02 cm3/m2x 24 hrs), and the chitosan film (0.87±0.08 cm3/m2x 24 hrs). The reduction of gas permeability value of CHCV might be attributed to the interactions of vanillin and cinnamon oil in chitosan matrix. When analyzing the chemical composition of CH, CHC, and CHCV using FTIR technique, the FT-IR spectra of CH, CHC, CHCV exhibited characteristic peaks for CH stretching vibrations at 3046.98 cm-1 (CH), 3027.69 cm-1 (CHC) and 3026.73 cm-1 (CHVC) Adsorption bands were in the range of 3000-3600 cm-1 due to the stretching vibration of N-H and OH functional groups of chitosan. Adding cinnamon oil into chitosan film showed the changes of the band at 3046.98 cm-1 (CH) to 3027.69 cm-1 (CHC) (-OH and -NH2 stretching), and observed a new peak at 1746.23 cm-1, which indicated the presence of carbonyl group C=O. This suggests the interaction of cinnamon oil components. When vanillin was added to a chitosan film, the new peak at 1215.9 cm-1 appeared which indicated the formation of the hydroxyl group of vanillin. Part 4: Evaluation of physicochemical and sensorial qualities of ripe bananas. The coating had done in 2 ways; whole fruit coating and calyx coating and stored at 25 ºC. Quality parameters were measured including; weight loss, decay, total soluble solids, respiration rate, peel color, malic acid content, and ethylene production. Calyx coating with chitosan incorporated with vanillin and cinnamon oil at 20 µL/L resulted in lower weight loss compared with control treatment over 14 days. No fungal growth was observed on the bananas treated with CHCV Calyx coated bananas with chitosan incorporated with vanillin and cinnamon oil started ripening on days 12-14, whereas the control treatment began ripening on day 6. Chitosan coated banana had significantly lower amounts of water soluble solid than control. Chitosan coating enhanced the respiration rate of bananas. Calyx coated bananas with chitosan incorporated with vanillin and cinnamon oil gradually increased in titratable acidity compared to untreated bananas. This indicates that calyx coating with chitosan incorporated with vanillin and cinnamon oil can extend the shelf life of bananas. However, in whole fruit coating with chitosan incorporated with vanillin and cinnamon showed the delay in ripening and then decay. Calyx coated bananas with chitosan incorporated with vanillin and cinnamon oil also showed the gradually increase in ethylene content, with the ethylene peak occurring on day 12, compared to the control bananas which reached the peak on day 6. In sensory test, the preference scores of appearance, aroma, and taste were consistent in the same direction. Banana coated at the calyx with CHVC had yellow peel with acceptable brown spots. Whole fruit coating exhibited burnt brown peel with bruising marks after 1 day storage, resulting in unacceptable appearance scores. Calyx coated bananas with CHVC at 20 µL per 20 ml of the coating solution can extend the shelf life for 14 days at 25 ºC with acceptable sensory characteristics.