Effect of 'Porotan' Storage Conditions on the Quality of Kanroni

Kanroni, a highly popular Japanese food made with chestnuts, is prepared by stewing chestnuts in syrup. The Japanese chestnut (Castanea crenata Sieb. et Zucc.) 'Porotan' has excellent peelability and the frozen fruit is easily cracked by heating. In this study, we examined the effect of different 'Porotan' storage conditions on the quality of the prepared kanroni. Six chestnut processing strategies were tested: (i) immediate use after purchase (Cont), (ii) refrigeration (R), (iii) freezing (F), (iv) refrigeration for 1 month followed by freezing (RF), (v) refrigeration for 1 month followed by peeling and freezing (RPF), or (vi) freezing of RPF under vacuum packaging (RPF-V). For strategies (ii)-(iv), the chestnuts were peeled after storage. The most suitable strategies to prevent fruit cracking were R, RPF, and RPF-V. Kanroni prepared using frozen fruit (F, RF, RPF, or RPF-V) exhibited lower maximum stress and brittleness than when prepared using fruit from the Cont and R groups, indicating that frozen fruit would yield less firm kanroni. Furthermore, 'Porotan' storage conditions had only a slight effect on the color of the prepared kanroni. Notably, fruits processed by RPF-V showed higher maximum stress than those processed by RPF. These results indicate that RPF and RPF-V are the most suitable 'Porotan' storage conditions for the prepared kanroni.