Chitosan-liquid smoke-based composite coating for extending the shelf life of cherry tomatoes

Cherry tomatoes are climacteric fruits that are highly perishable during storage. In this study, an edible coating was developed to extend the shelf life of cherry tomatoes during preservation at room temperature. The edible coating was made from liquid smoke enriched with chitosan and durian seed starch. The liquid smoke used was derived from durian rinds pyrolyzed at 340 °C (T1), 380 °C (T2), and 420 °C (T3). Next, 2%–6% liquid smoke was blended with chitosan and durian seed starch to form various formulations of edible coating. Cherry tomatoes were soaked in the edible coating for 15 minutes and then dried in an air-circulating oven. The properties of the edible coating were characterized using Fourier transform infrared (FTIR) spectroscopy and X-ray fluorescence (XRF). The FTIR analysis showed no new functional groups, while the XRF analysis indicated that the elemental compositions of the edible coating did not significantly differ across the various formulations. The antibacterial effect of the edible coatings was tested against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus. In particular, respiration rate and colorimetric tests were performed to evaluate the feasibility of the edible coating as a cherry tomato preservative. The various formulations demonstrated moderate antibacterial properties, with inhibitory zone diameters ranging from 6 mm to 7.67 mm against the four bacteria. Results showed that applying edible coatings effectively decreased both the respiration rate. The color changes (L∗, a∗, b∗) of cherry tomatoes coated edible coatings revealing differences in lightness, redness, and yellowing compared to control samples, with coating treatments slowing the typical ripening process. Moreover, the T3C2 edible coating, made from liquid smoke incorporating chitosan and durian seed starch, could extend the shelf life of cherry tomatoes to 12 days at room temperature.