Trolox equivalent antioxidant capacity of Coffea arabica L. seeds

ABSTRACT The causes of the low desiccation tolerance and low longevity of coffee seeds have not yet been fully elucidated, and a full understanding of their complex physiology is of great interest. Among several alternatives, the loss of antioxidant capacity in seeds may be related to their rapid loss in quality during storage. The objective of this study was to determine the total antioxidant capacity of coffee harvested at different ripeness stages before and after the storage of seeds with different water contents and to relate antioxidant capacity to physiological quality. Seeds in the greenish-yellow or cherry stages, recently harvested or stored for nine months at 10 °C with 40, 30, 20 and 12% water content (wet basis - wb), were submitted to physiological and biochemical quality evaluations, and the Trolox equivalent antioxidant capacity (TEAC) was determined. The germination and root protrusion of coffee seeds from greenish-yellow and cherry fruits were not affected by drying, but seeds harvested at physiological maturity had greater vigor when the moisture content was lower. The quality of coffee seeds decreased during storage, and this decrease was greater in seeds stored with higher water contents. Coffee seeds in the greenish-yellow stage had a higher antioxidant capacity than those in the cherry stage when recently harvested, but there was a substantial reduction in this capacity during storage at both maturation stages. Coffee seed deterioration is related to a reduction in antioxidant capacity, and the isoenzymatic profiles of the antioxidant process are little affected by the seed maturation stage. The deterioration of coffee seeds during storage is related to a reduction in their total antioxidant capacity, regardless of their maturation stage, being more pronounced in the greenish-yellow stage.摘要 咖啡种子脱水耐性（desiccation tolerance）与储存寿命偏低的成因尚未完全阐明，全面解析其复杂生理机制具有重要研究价值。在诸多潜在影响因素中，种子抗氧化能力的丧失可能与其储存过程中品质快速劣变存在关联。本研究旨在测定不同成熟度采收的咖啡种子，在不同含水量（湿基，wet basis, wb）储存前后的总抗氧化能力，并探讨抗氧化能力与生理品质的相关性。选取刚采收的绿黄色成熟阶段或樱桃成熟阶段的咖啡种子，分别以40%、30%、20%、12%的湿基含水量，于10℃下储存9个月，随后对其开展生理与生化品质评价，并测定Trolox等效抗氧化能力（Trolox Equivalent Antioxidant Capacity, TEAC）。实验结果表明：干制处理未影响绿黄色与樱桃成熟阶段咖啡种子的萌发及胚根伸出，但生理成熟期采收的种子在含水量降低时活力更高。咖啡种子的品质在储存过程中逐渐下降，且储存时含水量越高的种子，品质下降幅度越大。刚采收时，绿黄色成熟阶段的咖啡种子抗氧化能力高于樱桃成熟阶段，但两种成熟阶段的种子在储存期间其抗氧化能力均出现显著降低。本研究证实，咖啡种子劣变与抗氧化能力降低密切相关，且抗氧化过程的同工酶谱（isoenzymatic profiles）受种子成熟阶段的影响较小。无论成熟阶段如何，咖啡种子储存期间的劣变均与其总抗氧化能力降低相关，且该现象在绿黄色成熟阶段表现更为显著。