Influence of Pretreatments and Modified Atmosphere Packaging on Toughness and Quality of Asparagus Spears During Storage

Abstract

We investigated the effects of different storage methods and pretreatments on the toughness and quality of asparagus spears (Asparagus officinalis L.). Two storage methods were assessed: modified atmosphere (MA) storage using film with an oxygen transmission rate of 10,000 cc•m-2 •d-1 •atm-1 , and conventional storage (CS) using perforated film. Pretreatments were: irradiation with UV-C (UV-C), a hot water dip (HWD), pretreatment with CO 2 (CT), CO 2 injection (CI), or a control without treatment (control). In all treatments, asparagus spears were stored at a relative humidity of 85% and 4°C. Respiration and ethylene production rates were lowest after HWD treatment. In the MA storage conditions, CO 2 content within the film package was maintained at 8-11% regardless of pretreatment, thus satisfying optimal MA conditions for asparagus. Oxygen content decreased immediately after asparagus was put into storage, regardless of pretreatment methods, but later recovered to 15%. Ethylene content increased on the first day of storage, but gradually declined to 6.5-8.5 μL•L-1 by the last storage day. Regardless of pretreatment method, fresh weight loss during CS was less than 6.0%. In MA storage, asparagus packages in the CI treatment had a fresh weight loss of 0.8%, which was the highest among treatments. Asparagus tip firmness was no different across all CS conditions, regardless of pretreatment, but was lowest in MA-stored asparagus after HWD treatment. HWD-treated asparagus had the least firm stems, whether in CS or MA storage. The lignin content of both tips and stems was lowest when asparagus was pretreated with HWD. In CS asparagus, phenylalanine ammonia-lyase (PAL) activity was lowest when pretreated with HWD, but there was no difference in PAL activity between pretreatments in the MA storage condition. PAL activity was the lowest after pretreatment with HWD, regardless of storage method. In asparagus tips, there was no difference in peroxidase (POD) activity across all storage and pretreatment methods. In CS stems, POD activity was lowest after HWD treatment, but there was no difference in stem POD activity in any of pretreatment conditions in