Hydrothermal and high-pressure processing of chestnuts - Dependence on the storage conditions

Abstract

High-pressure processing (HPP) is an emergent technology for nonthermal pasteurization of foods, which here demonstrates the potential to be used by the chestnut industry. This study evaluated HPP as a post-harvest processing technology to control molds and insect larvae proliferation in chestnuts (Castanea sativa Mill.) and improve the fruit's shelf-life. Chestnuts were processed by HPP (400, 500, and 600 MPa for 5.0 min at 20 °C) and the conventional hydrothermal technology (HT, 50 °C for 45 min). Untreated chestnuts were also used as a control group. Shelf-life studies were conducted for 60 d at i) 25 °C and 40 % relative humidity (RH); and ii) 5 °C and 70 % RH. After the treatment and over the storage period, parameters such as color, texture, weight loss, nutritional composition, ascorbic acid, and fungal load were evaluated. The results showed that immediately after the HPP treatments, the chestnuts became slightly softer than HT samples. Fruit treated by HPP maintained their nutritional composition and ascorbic acid content. During the first 30 d of storage, no changes of color were observed in treated fruit. Also, the shelf-life of chestnuts treated at 600 MPa was extended by 40 d, compared to HT, where no molds at a detectable level and insect larvae were observed when stored at 5 °C. This storage condition also reduced the fruit weight losses. Compared with HT, HPP has short processing times, which is an important advantage. In addition, the observed changes of texture as softening and easy peeling can be useful for obtaining ready-to-eat products since chestnuts looked partially cooked. However, its possible application at the industrial level should be adequately investigated based on the promising results obtained.