Freshness Evaluation of Leafy Vegetables with Based on the Cell Membrane Properties

Kuroki, Shinichiro (2019) Freshness Evaluation of Leafy Vegetables with Based on the Cell Membrane Properties. In: CONFERENCE PROCEEDING 3rd INTERNATIONAL CONFERENCE ON SECURITY IN FOOD, RENEWABLE RESOURCES, AND NATURAL MEDICINES 2019 (SFRN 2019). pusat penelitian dan pengabdian pada masyarakat Politeknik Pertanian Negeri Kupang. ISBN 9786025126284

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Abstract

Quality deterioration in fruits and vegetables starts from the dysfunction of cell membranes. In this study, the degree of membrane damage during storage and distribution was evaluated by transport, chemical, and mechanical properties of the cell membrane. Those measures were hydraulic conductivity coefficient (Lp), malondialdehyde (MDA) equivalent, and membrane tension at protoplast bursting (γ). Hydroponically cultivated spinach leaves (Spinacia oleracea L., cv. ‘Orai’) was used as a material. The spinach leaves were placed into an acrylic chamber and stored in an incubator at 20 °C under the dark environment for 4 days. The gas concentration in the chamber was controlled to be constant by aerating humidified gas with given concentration (O2: 5, 10, 20%; N2: balance) with 10 mL/min. Before and after storage, the mesophyll protoplasts were isolated from the sample and then used for measuring the Lp by the two laminar flows method and the γ through hypo-osmotic tolerance test. The rest of the samples were freeze-dried and used for measuring MDA equivalent with TBARS assay. Results showed that the Lp and MDA equivalent tended to increase with storage days. Low oxygen condition was adequate to suppress the increments in both measures over storage duration. Comparing the increment behavior of Lp and MDA equivalent during storage suggested that progression of lipid peroxidation in cell membranes preceded the increase of water permeability of the cell membrane. The γ decreased with storage duration, but the γ of low oxygen storage was greater than that of atmospheric condition. These findings show that the measurements of membrane integrity will be useful indicators for the freshness of spinach leaves. Our obtained knowledge will contribute to construct a freshness evaluation theory based on the dysfunction of cell membranes and to develop a novel technology for keeping freshness in fruits and vegetables.

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