Effect of Preharvest Multi-spray of Low Concentration Calcium-chitosan on the Internal Qualities of ‘Halla gold’ Kiwifruit during Storage
본 연구는 수확 전 키토산(100mg·L-1 동량의 염화칼슘 포함) 처리가 황육계 키위프루트 ‘한라골드’ 의 저장 중 품질과 연화에 미치는 영향을 살펴보고자 수행하였다. 키토산 처리 과실은 저장 60일까지 무처리 과실보다 경도가 높게 유지되었고, 전분도 높았지만 에탄올 불용성물질의 차이는 없었다. 수확기의 가용성고형물 함량은 칼슘-키토산 처리에서 낮았으나, 저장 중 전분의 감소와 더불어 지속적으로 증가하여 저장 1개월 후에는 처리간 차이를 보이지 않았고, 유리당(포도당, 과당, 자당) 함량도 유사한 경향이었다. 따라서 수확 전 칼슘-키토산 처리는 과실의 성숙을 지연시켰으나, 후숙 과정에서는 당 축적을 저해하지 않았다. 수확 시의 칼슘-키토산 처리 과실의 수용성 펙틴은 무처리보다 낮았지만 고분자 분획이 더 많았고 반면에 킬레이트 및 알칼리 용해성 펙틴은 대조구보다 높았다. 저장기 간 중 α-L-arabinofuransidase와 pectate lyase의 활성이 칼슘-키토산 처리 과실에서 지속적으로 낮게 유지되었으며 α-mannosidase, polygalacturonase, xylanase, β-galactosidase는 칼슘-키토산 처리의 영향을 크게 받지 않았다. 또한 칼슘-키토산 처리는 세포벽 결합 칼슘을 증가시켜주었다. 결론적으로 수확 전 칼슘-키토산 처리는 과실의 성숙 과정을 지연시키지만 경도를 높여주었고, 후숙(ripening) 이후에는 당도를 비롯한 내적 품질에 영향을 주지 않았다.
Influence of preharvest spray of chitosan and CaCl2(100 mg·L-1 each) on the physiological changes associated with fruit ripening in ‘Halla gold’ gold kiwifruit was investigated. Chitosan spray increased fruit firmness at harvest and firmness remained at higher level up to 60 days of storage. Even the amount of ethanol insoluble solids was not significantly different between treatments, starch content of fruit maintained at higher level in chitosan treatment. The soluble solids of fruit were lower in chitosan treated fruit at harvest but no difference was found after 1-month storage. Major soluble sugars were glucose and fructose, and they were increasing trend during storage. The increase of soluble sugars well agreed with the decrease of starch content. Thus, chitosan did not alter the carbohydrate accumulation in fruit even the increase of soluble sugars was delayed due to ripening delay. The content of water soluble pectic polymers was lower, and chelator soluble polymers and sodium-carbonate soluble polymers were higher in chitosan treatment in general. Elution profile of water soluble pectic polymers revealed an enhancement of high molecular weight fractions in chitosan treatment. Little difference, however, was found after 60 days of storage. Two wall hydrolase activities like α-L-arabinofuransidase and pectate lyase were consistently reduced by chitosan treatment. Others including α-mannosidase, polygalacturonase, xylanase, and β-galactosidase seemed not to be affected by chitosan treatment. A significant increase of ethanol insoluble solid bound calcium by chitosan treatment indicated in the increase of wall bound calcium. In conclusion, preharvest chitosan treatment increased fruit firmness resulting in the increase of storage potential without altering fruit quality.