不同干燥方法对核桃贮藏过程中内种皮褐变的影响

收稿日期：2024-05-09

基金项目：甘肃省自然科学基金项目（22JR5RK1049）；甘肃省高校教师创新基金项目（2024B-333）；甘肃省高等学校创新创业教育改革项目[甘教高函（2023）14号]；甘肃省大学生就业创业能力提升工程项目[甘教学函（2023）29号]

作者简介：王一峰（1986-），男，甘肃礼县人，硕士，副教授，研究方向为植物生理生态。（E-mail） wangyifeng0305@163.com

“Qingxiang” as the experimental material. Four drying methodswereemployed：natural sun-drying（CK），hot-air drying（T1），vacuumdrying（T2），andvariable-temperaturevacuumdrying（T3）.Duringstorage，changes in the appearance of the kernel and browning indices of the endotesta were measured.Path analysis was used to identify themain factors affecting endotesta browning in walnuts. The results indicated that with the extension of storage

time，thecolorofthekernelsinalltreatmentsgraduallydarkenedandthedegreeofbrowningincreased.Comparedwith CK，thekernelsinT2andT3treatmentshadlightercolorandlowerdegreeofbrowning.Therelativeelectricalconductivity andthecontent of malondialdehyde（MDA）graduallincreased with the extensionof storage time.The increase was the highestinCK，whiletheincrements inT2andT3 treatments wererelativelysmaler.Thetotalphenoliccontentinthewalnut endotesta decreasedat 3Odays of storage，increasedat 6Odays，and thendecreased again at90 days.However，the magnitudeofthese increasesanddecreaseswasnotsignificant.Throughoutthestorage period，the totalphenoliccontentin the walnutendotestaremainedatarelativelyhighlevel.ComparedwithCK，thetotalphenoliccontentintheendotestaof walnutsin T2 and T3 was generally higher.The activities of polyphenol oxidase（ PPO ），superoxide dismutase（ SOD ）and Na⁺/K⁺ -ATPase in walnut endotesta increased first and then decreased. Compared with CK，the activities of SOD and Na+/ （204 K⁺ -ATPase in walnut endotesta under T2 and T3 treatments were generally higher，and theactivity of PPO was generally lower.Theperoxidase（ P（DD ）activity of walnut endotesta showed a downward trend as a whole.Compared with CK，the activity of walnut endotesta in T2 and T3 treatments was generally higher. The activities of catalase （ CAT ）and lipoxygenase （ LOX ）showed an upward trend.Compared with CK，the activity of CAT was higher and the activity of LOX was lowerinT2andT3treatments.Thepathanalysisresultsindicatedthatdiferentdrying methodshaddifferent efectsonwalnutbrowningduring storage.Forwalnutsin theCK，themainfactors influencing browning were theactivitiesof PPO ， （2 PD ，and Na⁺/K⁺ -ATPase.For walnuts in T1 treatment，the main factors influencing browning were the total phenolic content， CAT activity，and Na⁺/K⁺ -ATPase activity. For walnuts in T2 treatment，the main factors influencing browning were the activities of SOD ， ，and Na⁺/K⁺ -ATPase.For walnuts in T3 treatment，the main factors influencing browning were the total phenolic content， activity，and Na⁺/K⁺ -ATPase activity.

Key words： walnut；endotesta；drying methods；storage；browning

核桃是世界四大干果之一[1]，因其核仁富含营养物质和具有一定的保健、美容及药用价值而被大量种植和消费[2]。核桃在中国栽培历史悠久，分布广泛，已形成西北、西南、华中和东南沿海栽培区域。近年来，核桃种植面积及产量逐年攀升，对其采后商品化处理和贮藏提出了新的要求。核桃果实在采后贮藏期间品质会下降，表现在外观、色泽等方面，可能会出现褐变、裂果等现象，其中褐变问题是影响其品质的最重要因素。褐变是果实发生的生理失调现象，其发生原因众多，如果实衰老、机械损伤、环境胁迫、能量匮乏等，而且往往是多种原因共同造成的[3]。目前，普遍认为褐变包括酶促褐变和非酶促褐变，核桃贮藏过程中发生的褐变多为酶促褐变。底物酚类和氧化酶区域分布学说是当前最为认可的酶促褐变机制之一，当细胞区室化丧失，底物酚类会与酶结合生成黑色物质，进而造成褐变[4]。核桃内种皮含有丰富的酚类物质（核桃内种皮多酚含量远高于核仁）[5]，对富含脂肪的种胚起到了关键保护作用，核桃在贮藏过程中内种皮褐变逐渐加重，使得种胚失去保护，导致油脂酸败和蛋白质氧化损伤，从而降低核仁品质，且种皮颜色是评价核桃商品最直观的品质指标。……