Improving hawthorn fruit pulp processing and quality through optimized freeze-thaw cycles

Abstract

Hawthorn fruit is firm, making it difficult to process into fruit pulp. To improve the processing suitability of hawthorn fruit pulp, one, two, and three freeze-thaw cycles (FTCs, frozen at −18 °C for 24 h, then thawed at 5 °C or 25° C for 6 h) were performed on hawthorn fruit in this study. Using unfrozen specimens as the controls, the study assessed fruit softening characteristics and rheological properties, taste traits, and nutritional components of the fruit pulp. Freeze-thaw treatments decreased fruit firmness and cell-wall stability, increased juice yield during pulp processing, and reduced the viscosity, sourness, and astringency of hawthorn fruit pulp, likely by enhancing pectin solubility. The treatment effect was influenced by both FTC number and thawing temperature. Two FTCs with a thawing temperature of 5 °C were most effective, promoting the transformation of protopectin into water-soluble pectin (WSP) to the fullest extent. The treatment reduced firmness to about 25 % of the initial value, increased juice yield by about 22 %, increased the sugar-acid ratio to 11.6, and reduced the sourness and astringency of the fruit pulp. It increased the contents of total flavones and anthocyanidins without affecting the contents of vitamin C. Therefore, the use of two FTCs with a thawing temperature of 5 °C can facilitate the preparation of hawthorn fruit pulp while preserving its nutritional properties and improving its taste profile.