No abstract

Developing effective and economically viable treatments that replace chemical phytosanitary and quarantine practices is urgently needed for the coffee bean industry to maintain competitiveness in domestic and international markets. The objective of this study was to determine coffee bean heating uniformity and quality as influenced by radio frequency (RF) treatments for postharvest disinfestations. A pilot-scale, 27 MHz, 6 kW RF unit was used to study RF heating uniformity, develop a treatment protocol, and evaluate quality attributes in treated coffee beans. After comparing three selected electrode gaps, an appropriate gap of 14 cm was obtained to raise the central temperature of 2.75 kg samples to 48°C using RF energy by 4.6 min, compared to more than 237 min for samples to reach only 45°C when using forced hot air at 48°C. RF heating uniformity in bean samples was improved by adding forced hot air and back and forth movements on the conveyor at 0.89 m min -1 . The final temperatures reached 50.4°C in the interior of the sample and 50.6°C on the sample surface, resulting in small uniformity index values of 0.023 to 0.060 for the interior temperature and 0.073 for surface temperature distributions. RF treatments combined with forced hot air at 48°C to hold the target temperature for 10 min followed by forced room air cooling through a 3 cm product layer provided good bean quality. No significant differences in weight loss, moisture content, and color were observed between RF treatments and unheated controls.

In this study, the antifungal effects of 12 preservatives or disinfectants against Fusarium concentricum on asparagus spear, as well as their inhibiting characteristics, were investigated. Results showed that dehydrogenation sodium acetate at 0.5 g/L, sodium ethyl p‐hydroxybenzoate at 0.3 g/L, sodium hypochlorite at 0.2 g/L, and cinnamic aldehyde at 0.4 g/L could completely inhibit the sporulation. The concentrations of cinnamaldehyde, sodium hypochlorite, H2O2, and ethyl p‐hydroxybenzoate that completely inhibited spore germination were 0.1, 0.1, 0.2, and 0.3 g/L, respectively. High molecule chitosan (HMC) at 0.25 g/L and water‐soluble chitosan (WSC) at 2 g/L could inhibit spore germination and 90% of mycelium growth. Moreover, asparagus treated with HMC or WSC at 0.5 g/L showed hyphae growth with no soft rot, which indicated that pectinase might be damaged. This results might provide an important basis for further study into the uses of preservatives for control of postharvest diseases of asparagus. Novelty impact statement The screened antifungal agents from food additives showed prominent inhibitory effect on F. concentricum, which were expected to be used for postharvest asparagus preservation in the future.