Effects of nitrogen and selenium treatments on the texture parameters of ‘Qingcui’ plum fruit

Abstract

‘Qingcui’ plum fruit becomes soft at harvesting. In this study, we assessed the effect of the following different treatments on various fruit texture parameters: three concentrations of nitrogen (NH4NO3 0%, 0.5% and 1%) and three forms of selenium (selenomethylcysteine [C5H9NO2SSe/SeMeCys], sodium selenate [Na2SeO4] and sele-nomethionine [SeMet]). The fruit texture parameters evaluated were fracture, hardness, cohesiveness, springiness, gumminess, chewiness and initial modulus under 4oC. Results showed that the optimal N concentration was 1% and the optimal Se form was SeMeCys. Fruits treated with SeMeCys had similar fruit texture parameters as those of the group under cysteine treatment. We then sprayed the fruit with approximately 2 mL/fruit of the following treatments: five different combinations ratios of Se (SeMeCys; 10 mg/L) and N (NH4NO3; 1%) (2:18; 4:16; 10:10; 16:4; 18:2), after which the fruit was stored at 4oC for 13 days. The parameters of fruit texture, fruit color, and other fruit qualities were measured. Linear correlations were observed between parameters, and main sensory qualities were analyzed. We observed that a combination of Se and N in a ratio of 18:2 produced the best results in terms of fracture, first hardness and second hardness, preventing the softening of the fruit. The parameters of soluble protein, titratable acid and soluble solids had significant linear relationships with three fixture parameters. The fruit color parameters of a* (greenness) and b* (yellowness) also had significant linear correlations with fracture and first hardness. These findings may offer a promising strategy to prolong fruit storage and maintain fruit crispness and hardness.