Effect of Maturity at the Harvest and Low Temperature Distribution on Keeping Quality of Strawberry Fruits

Abstract

Recently interest has increased in strawberry fruits harvested at the full-ripe stage (complete coloring) and shipped at low temperature to obtain strawberry fruits with higher quality.
The present experiments were designed to study the influence of ripening of strawberry fruits upon their quality. The ripe stage was determined by color development. Strawberry fruits were harvested at various stages of coloring: quarter-colored, half-colored, three-quarters-colored and fully-colored. The quality of fruits harvested at the various stages was determined on the basis of anthocyanin content, total sugar, titrable acidity, total ascorbic acid and firmness. Four studies were made, in January, February, March and April. Two cultivars, ‘Hokowase’ and ‘Donner’ were used as material.
A relationship between fruit coloring and quality was found. As fruit color deepened, anthocyanin content and the sugar-acid ratio increased markedly, and the fruit tissue became soft. Total sugar and total ascorbic acid content increased slightly, and titrable acidity decreased slightly, during color development.
In fruits harvested on January 18 and February 21, respectively, the correlation coefficients between the anthocyanin content and the sugar-acid ratio gave correlations of -0.61 and -0.69, regression of anthocyanin content vs. total sugar gave correlations of -0.28 and -0.48, and anthocyanin content vs. titrable acidity gave correlations of -0.62 and -0.12.
Further experiments were designed to simulate conditions in transportation and distribution facilities. Strawberry fruits were harvested at the fully-colored stage and held at 3°C for two days, or at the half-colored stage (conventional maturity for shipping) before being held at room temperature (15-20°C) for two days. Their taste was tested by 100 panelists, and other quality changes were again determined by measuring total sugar, titrable acidity, total ascorbic acid, anthocyanin content and softness. These experiments were carried out three times (in March, April, and May).
The taste of strawberries harvested at the fully-colored stage and held at 3°C was judged to be superior to that of those harvested at the half-colored stage and held at room temperature. Sixty-eight %, 91%, and 65% of the panelists attested the superiority in sweetness and freshness of fruits held at 3°C in taste tests in March, April, and May, respectively. Fruits held at 3°C for two days contained 5.67% total sugar and 0.42% titrable acidity, whereas those held at room tern perature for two days contained 4.9% total sugar and 0.55% titrable acidity. However, there was no difference in total ascorbic acid and anthocyanin content between the two groups. The fruits which were harvested at incomplete coloring colored completely during storage at room temperature for two days, but total sugar content scarcely increased, and titrable acidity decreased but little.
In test simulating transportation conditions, bruising was found in less than 20% of the fruit held at 3°C, whereas bruising occurred in more than 50% of the fruit held at room temperature.