ศูนย์นวัตกรรมเทคโนโลยีหลังการเก็บเกี่ยว

Physiological and Biochemical Changes In Postharvest ‘Nyoho’ Strawberries Foliar Applied with Calcium

Wasna, Na Phun

Ehime United Graduate School of Agricultural Science, Ehime University.

1999

บทคัดย่อ

  Strawberry (Fragaria X ananassa Duch.) is a very popular fruit due to its attractive red color, texture and flavor. In KawadaPrefecture, ‘Nyoho’ variety is the most popular as it can bear more fruit than ‘Toyonoka’ and the fruit is suitable not o­nly for the fresh market but also for cake topping. o­ne of the major problems besetting the strawberry protection is its extremely short postharvest life and high susceptibility to rot causing pathogens. There are several methods to prolong the storage life of the fruit such as low temperature, or controlled or calcium improves fruit quality by increasing fruit firmness, retarding the rate of fruit ripening and decreasing decay by mold. The purpose of this research is to study the effects of foliar-applied calcium o­n physiological and biochemical changes in postharvest ‘Nyoho’ strawberry which ware grown by the traditional soil culture or by a peat-bag-substrate bench culture.

I.Effects of preharvest calcium application o­n postharvest Quality of ‘Nyoho’ strawberries ware studied. Strawberries after petal fall ware sprayed with 2,000 ppm (as Ca²⁺) CaCl₂, 200 ppm Cachelate (chelated with a carboxylic acid compound extracted from plant materials), 200 ppm Cachelate plus 12.5 ppm boron or water as a control. Tween-20 was added as a wetting agent. Spraying was repeated o­nce a week for 4 times until harvest at the rate of 200 liter 1000 m² using a hand pressure sprayer. Calcium treatments significantly increasing the fruit firmness, reduced the reduced the respiration rate in storage and as a consequence prolonged the postharvest life. Ascorbic acid content in calcium-sprayed fruit was higher than that of the control not o­nly at harvest but also after 2 days at 20 ° C. The Ca-chelate alone or with boron ware as effective as CaCl₂ but at 1/10 concentration of the latter.

II.Effects of the chelating agent o­n postharvest quality of ‘Nyoho’ strawberries ware studied. Ca-chelate at 200 ppm. 150 ppm. Of the carboxylic acid compound (the chelating agent), and water ware sprayed as in Exp. I above. Strawberries treated with the Ca-chelate ware significantly higher in fruit firmness at harvest or after 2 days at 20 ° C, but the chelating agent per so did not show any consistent effects o­n the fruit quality.

III.Effects of the spray timing o­n the effectiveness of calcium spray in keeping quality of ‘Nyoho’ strawberries ware studied. Ca-chelate was applied to the strawberries for 3 times during eariler, later or 4 times throughout the growth and development stages. The later 3-times spray showed similar effects as the 4-times spray in increasing the fruit firmness at harvest and in delaying the rate of softening during storage at 20 ° C for 2 days.

IV.Effects of calcium spray part o­n the effectiveness of calcium in keeping quality of ‘Nyoho’ strawberries ware studied. Three spray parts as leaves, fruit and whole plants ware applied with 200 ppm. Ca-chelate for 3 times during the later stage of fruit growth and development. Spraying directly to the friut was the most effective in increasing the fruit firmness at harvest, reducing the rate of respiration during storage and in maintaining the fruit soundness for 2 days at 20° C calcium content both in the peel and core of the fruit ware increased most when calcium had been applied to strawberry fruits.

V.Effects of preharvest calcium application o­n postharvest quality of ‘Nyoho’ strawberries grown by beat-bag-substrate bench culture ware studied. Strawberries were planted into PE bags contained with a mixed substrate (3 peat moss : 1 rockwool) o­n 1 m high benches in a plastic house. Ca-chelate was sprayed for 4 times o­n strawberries and samples were collected separately from the north or the south side of the bench. Strawberries grown o­n the south side tended to be higher in fruit firmness and ascorbic acid content than those grown o­n the north side. Calcium applied strawberries o­n the south side had the highest fruit firmness and calcium content. Calcium treatment significantly reduced the water soluble pectin and increased the hydrochloric acid soluble pectin in accordance with increase in fruit firmness. Skin puncture force of calcium applied strawberries was higher than that of control both at harvest and after 2 days at 20 ° C. No difference was, however, found in the bundle zone puncture force. Scanning electron micrograph observation revealed that the calcium treatment decreased tissue deterioration and cell collapse.

VI.Effects of preharvest calcium application o­n the postharvest quality of ‘Nyoho’ strawberries harvested at various stages of maturity ware studied. Calcium treatment significantly increased flesh firmness of strawberries picked up not o­nly at 10, 50% but also 100% red peel color. The 10% red peel colored strawberries were higher in flesh firmness and titratable acidity. Respiration rate, weight loss and total soluble solid, however, were lower than the 100% red peel colored strawberries. Calcium treatment increased the calcium contents of all fractions such as skin, peel and flesh tissue, water soluble and NaNO₃ soluble calcium of flesh tissue, water soluble, ammonium oxalate soluble and hydrochloric acid soluble pectin of flesh tissue.

VII.Effects of preharvest calcium application and postharvest CO₂ treatment o­n the keeping quality of ‘Nyoho’ strawberried were studied. Ca-chelate was applied to strawberries 2 or 4 times before harvest and samples were stored at 0 ° C for 3 weeks under 8-15% CO₂ Both calcium and Co° treatments increased fruit firmness and maintained the fruit soundness. The combined treatment was best in keeping the quality of strawberries.

In conclusion, prehavest calcium application 3 to 4 times during the later stage of fruit growth and development, and postharvest CO₂ treatment at a low temperature are recommended as means to improve the fruit quality and to prolong the postharvest kife to ‘Nyoho’ strawberried.