甜樱桃采后热空气处理抑制青霉病的工艺优化

为确定热空气处理控制采后甜樱桃果实青霉病的最优条件,采用响应曲面法研究了不同温度-时间的热空气处理对甜樱桃采后青霉病的抑菌效果和果实品质的影响。甜樱桃果实采后用不同温度热空气(40~48℃)和不同处理时间(60~180 min)处理后,接种青霉菌在20℃、相对湿度90%~95%的条件下贮藏5 d,贮藏结束后测定果实的病斑直径、硬度、抗坏血酸含量和固酸比,建立了4个响应值的二次多项数学模型,分析了拟合程度,并利用模型的响应面对甜樱桃的抗病性和果实品质进行了探讨。结果表明,热空气处理控制采后甜樱桃果实青霉病的较优条件为热处理温度为44℃、热处理时间为114 min,该条件显著(P0.05)抑制了甜樱桃采后青霉病的扩展,与对照组相比,热处理较好的保持了甜樱桃果实品质,显著(P0.05)减缓了硬度、抗坏血酸含量和固酸比的下降,为热空气处理在甜樱桃贮藏保鲜中的应用提供理论依据。

Process optimization of hot-air treatment on inhibition of blue mould infection for postharvest sweet cherry fruit

Sweet cherry (Prunus avium L.), an economically important temperate fruit, is popular for its attractive red colour and high value of nutrients. However, sweet cherry is highly perishable and susceptible to mechanical injury and fungal decay. Penicillium expansum, the causal agent of blue mould, is a widespread fungal pathogen and causes considerable losses in sweet cherry fruit. Traditionally, the control of postharvest mould decay is mainly dependent on synthetic fungicides. However, the increasing resistance of fungal pathogens and growing concern of the public over chemical residues make it crucial to research alternative approaches to inhibit mould decay. Heat treatment, as a physical method, has acquired increasing attention and has been widely used to control fruit decay and maintain quality. There are 3 methods in use to heat fruit and vegetable: Hot air, hot water and hot water vapor. However, there is no information concerning the condition of hot air on inhibiting blue mold decay in sweet cherry fruit using the response surface methodology (RSM). RSM is a collection of mathematical and multivariate statistical techniques that are useful for the modeling and analysis of problems, in which a response of interest is influenced by several variables and the objective is to optimize the response. In order to determine the optimum condition of hot-air treatment on the inhibition of blue mould decay in postharvest sweet cherry fruit, the effects of different temperature-time combinations on inhibition efficiency of blue mould decay and fruit quality were investigated using the RSM. The fresh harvested sweet cherry fruits were treated in hot air at different temperatures (40-48℃) for different treatment time (60-180 min), then the fruits were inoculated with the spores of Penicillium expansum (5×104 CFU/mL) and stored under the condition of approximately 90%-95% relative humidity at 20℃ for 5 d. At the end of storage, lesion diameter of blue mould decay, fruit firmness, content of ascorbic acid and ratio of TSS (total soluble solids) to TA (titratable acidity) were measured. Four second-order quadratic equations of lesion diameter of blue mould decay, fruit firmness, content of ascorbic acid and ratio of TSS to TA were established, and the fitting degrees were also analyzed through the RSM. The key factors and their interactions affecting the inhibition efficiency of blue mould decay and fruit quality were also discussed through the RSM. By analyzing the response surface graphs and corresponding contour graphs as well as solving the quadratic equations, the results suggested that the optimum condition for combined treatment of hot air in sweet cherry fruit was that the temperature was 44℃, and the treatment duration was 114 min. Results of demonstration and comparison tests showed that the optimum condition (44℃, 114 min) obtained via the RSM effectively inhibited the blue mould decay in sweet cherry fruit and maintained the fruit quality. In comparison with the control fruit, hot-air treatment delayed the decline of firmness and ascorbic acid content and maintained a higher level of TSS/TA. The present study showed that the optimum parameters of hot-air treatment obtained by the RSM are feasible, which can provide a theoretical foundation for further research of the application of hot-air treatment in sweet cherry fruit preservation.