Suriyan Supapvanich

Effects of Salicylic Acid Incorporated with Lukewarm Water Dips on the Quality and Bioactive Compounds of Rambutan Fruit (Nephelium lappaceum L.)

This study investigated the quality attributes of rambutan cv. Rong-rien treated with salicylic acid (SA) solution and/or lukewarm water (LW). The fruit were dipped in distilled water (control), lukewarm water at 35°C, 1.0 mM sali- cylic acid solution, and 1.0 mM lukewarm salicylic acid solution (SA+LW) at 35 °C for 20 min. The fruit were packed in polyethylene containers and then held at 13±2°C for 9 days. Visual appearance, weight loss, pulp firmness, external browning score, superficial colors, total soluble solids (TSS), total acidity (TA) and bioactive compounds - namely antioxidant capacity, total phenols, total flavonoids and total ascorbic acid contents - were determined. The weight loss of the fruit was small during storage and slightly delayed by salicylic acid or/ and lukewarm water dips. SA and SA+LW dips delayed external browning and effectively inhibited the softening of the fruit. The reduction of lightness (L*) was delayed by salicylic acid and/or lukewarm water dips. All treatments had no effect on superficial colors and taste of the fruit during storage. SA and SA+LW dips clearly enhanced bioactive compounds involving antioxidant capacity, total phenols, total flavonoids and total ascorbic acid content during storage. In conclusion, SA and SA+LW treatments delayed external browning, maintained pulp firmness and enhanced the bioactive compounds of rambutan during storage.

Effects of methyl jasmonate on physicochemical qualities and internal browning of ‘queen’ pineapple fruit during cold storage

The effects of methyl jasmonate (MeJA) as a protectant against chilling injury on physicochemical qualities of ‘Trad-see-thong’ pineapple (‘Queen’ group) fruit was investigated. The pineapple fruit were immersed in 1 mM MeJA for 5 min and then stored at 10 ± 1°C for 20 days. MeJA had no effect on respiratory rate and pulp colour, but suppressed ethylene production during cold storage. Weight loss, ion leakage (IL), internal browning (IB), and loss of pulp firmness were inhibited by MeJA. The MeJA treatment also suppressed the reduction of lightness (L*) and yellowness (b*) and the increase of total phenols (TP) that commonly occurs during cold storage, and increased the polyphenol oxidase (PPO) activity of pulp adjacent to the core (PAC) tissue. Certain bioactive compounds, such as ascorbic acid (AsA) and superoxide dismutase (SOD) in PAC tissues were enhanced by MeJA. No significant difference in peroxidase (POD) activity in both pulp and PAC tissues were detected between the treated and control fruits. These results suggest that immersion in MeJA is an effective means to maintain quality, alleviate IB symptoms, and enhance certain bioactive compounds in ‘Queen’ pineapple fruit cv. Trad-see-thong during cold storage.