Synergistic Effect of Macadamia Nut Oil and Chitosan Coatings on Physicochemical Characteristics of Tomatoes During Storage

A significant portion of globally produced fruits are lost between the farmer and consumer, necessitating solutions like natural edible coatings for preservation due to their low cost and less toxicity. This study aimed to assess whether the combination of macadamia nut oil and chitosan posed synergistic effects on physicochemical properties of tomato fruits or the macadamia nut oil alone. A completely randomized design (CRD) with eight treatments was employed: S1 (control), S2–S4 (combined macadamia nut oil and chitosan coating), S5–S7 (macadamia nut oil coating), and S8 (chitosan). The experimental setup was conducted over 20 days at refrigeration (4°C) and postharvest shed conditions (23.8°C–30°C, 65.8%–97.5% RH). The coating solution made up of a combination of 2.5% v/v macadamia nut oil and 1% w/v chitosan showed significant differences ( p ≤ 0.05) in slowing down the changes in pH from 3.95 to 4.3, total chlorophyll content from 0.19 mg/100 to 0.12 mg/100 mL, and lipid peroxidation from 13.5 to 19.71 meq/kg. Moreover, coating solutions made by macadamia nut oil alone, especially with 1% v/v, showed the smallest increases in total soluble solids (TSS) and total sugar content, and also they exhibited the smallest decreases in titratable acidity (0.64 to 0.08 g/L), ripening index (5.78 to 84.74), total carotenoids (17.02 to 24.585 μg/g), and firmness (355 N to 130 N). Comparative analysis indicated that 1% v/v macadamia nut oil had higher mean differences ( p < 0.05) for most physicochemical parameters than coating solutions comprising 2.5% v/v macadamia nut oil and 1% w/v chitosan. However, this finding highlighted that the combination of macadamia nut oil with chitosan offers a synergistic effect on specific crucial parameters (pH, total chlorophyll content, and lipid peroxidation) compared to macadamia nut oil alone. Further studies could investigate the antimicrobial effect of tomatoes treated with a combination of macadamia nut oil and chitosan.