Ozone-Ultrafine Bubbles for Reducing Concentration of Citric Acid and Sodium Chloride for Trimmed Young Coconut Preservation

Abstract

Citric acid (CA) and sodium chloride (NaCl) are used in organically trimmed young aromatic coconuts to prevent microbial growth and browning. However, the use of high concentrations of these chemicals is considered a waste and may elicit allergic reactions in the operator. This study aimed to reduce the concentration of these two substances by using a combination of ozone-ultrafine bubbles (O3UFBs). The trimmed young coconuts were dipped in 20% CA + 20% NaCl (commercial method; C20N20), 20% CA + 10% NaCl + O3UFBs (C20N10-O3UFBs), and 15% CA + 15% NaCl + O3UFBs (C15N15-O3UFBs) for one minute. All the coconuts were wrapped with PVC film and stored at 2–4 °C for 30 days and then transferred to storage at 8–10 °C for 7 days. The quality of the coconut water and coconut meat was evaluated. The whiteness, browning index, polyphenol oxidase (PPO) activity, and total phenolic content of coconut mesocarp were investigated. Titratable acidity and the total soluble solid content of coconut water were 0.038–0.095% and 6.65–7.40 °Brix, respectively, while that of the coconut meat was 0.044–0.104% and 8.00–9.80 °Brix, respectively. The mesocarp whiteness, browning index, disease score, fruit appearance, PPO activity, and total phenolic content did not differ among the treatments. C20N10-O3UFBs and C15N15-O3UFBs treatments also controlled microbial growth and the surface browning of the trimmed coconuts. In conclusion, the use of O3UFBs decreased the concentration of CA and NaCl by at least 25% of the commercial method used for treating trimmed young coconuts.