Ethephon-induced changes in macadamia nuts: implications for dietary indicators, nutritional quality, and postharvest shelf life = Okulawula ukukhula kokwenziwa kwesihlahla okunomthelela emantongomaneni iMacademia: Isiphakamiso esimayelana nezinkombaluhlelo zokudla, izingabunjalo lomsoco nobude besikhathi sokuyigcina emva kwesivuno.

Abstract

The thriving macadamia nut industry, prized for its nutritional value, grapples with the challenge of inconsistent abscission seasons, leading to variable harvest times and increased operational costs. To address this, the traditional application of ethephon induces uniform nut abscission and streamlines harvesting. However, it is crucial to investigate how ethephon impacts the nutritional quality and postharvest shelf life of macadamia nuts. This study focuses on the effect of ethephon on the postharvest quality of the ‘788’ and ‘Beaumont’ cultivars, comparing various categories: nuts that successfully abscised due to ethephon (ED), those manually picked from ethephon-treated trees (ET), nuts naturally dropped from control trees (CD), and those manually picked from control trees (CT). Guided by industryrecommended doses, Ethephon 480 SL® was administered using a Cima mist blower to facilitate nut abscission, specifically targeting physiologically mature nuts. The research explores the influence on fatty acids, dietary indicators, biochemical components, and polyphenol oxidase (PPO) activity. Various parameters, including total phenolics, flavonoids, antioxidant activities, sucrose, and total protein, were assessed across treatments using standardized procedures. samples were collected over a 72-day accelerated storage period. The study further assessed the effect of Ethephon on the physical attributes of macadamia during a 56-day accelerated storage, analyzing mass, diameter, colour (L*, a*, b*, and hue angle), and texture. Kernels were roasted at 125 °C for 15 minutes using a hot air oven dryer post drying and dehusking. Models were then developed to predict the firmness and colour parameters of macadamia nuts harvested with ethephon from the ‘788’ and ‘Beaumont’ cultivars based on drying days and storage conditions. The aim was to determine the minimal processing requirements for achieving satisfactory postharvest nut appearance. Input parameters considered included storage temperature, drying temperature, and storage days, vi while the resulting outputs were firmness and colour parameters (L*, a*, b*, and hue angle). The range of the input parameters spanned from -22℃ to 25℃ for storage temperature, 35 to 57℃ for drying temperature, and 0 to 70 days for storage duration. Significant changes were observed in the fatty acid profiles of macadamia nuts exposed to ethephon treatment. Notably, ethephon led to a substantial increase in stearic acid content, reaching 24,622 µg/g in (ED) after 72 days, compared to 16,764 µg/g in (CD), thereby impacting their nutritional quality. Conversely, ED nuts exhibited a reduction in unsaturated fatty acids (USFAs). Hierarchical clustering analysis identified strong correlations between ED and saturated fatty acids (SFAs) in both ‘Beaumont’ and ‘788’ cultivars, with coefficients of 0.78 and 0.80, respectively. This was accompanied by an increase in atherogenic indices, thrombogenic index, and saturation index, along with a decrease in the hypocholesterolemic/hypercholesterolemic ratio. Concurrently, a robust correlation (0.97) between sucrose and Polyphenol Oxidase (PPO) was observed in ‘Beaumont’, underscoring the influence of ethylene treatment. Notably, ED ‘Beaumont’ nuts exhibited the highest sucrose content at 18.63 mg/g, coupled with elevated PPO activity at 1.06 U g-L. For the physical attributes, ED exhibited a notable influence on the ‘Beaumont’ cultivar, particularly affecting parameters such as a*, b*, mass, and diameter. Conversely, in the ‘788’ cultivar, Principal Component Analysis (PCA) revealed that CD treatment held prominence, showing elevated values for firmness, a*, and b*. Furthermore, model development demonstrated significance, with high coefficients of determination ranging between 0.83 and 0.97. Notably, under reduced drying days and optimal storage temperature, the models predicted maximum L* values of 76.253 and 79.748 for the ‘788’ cultivar. This study provides a theoretical framework for identifying optimum set points crucial for the effective preservation of both the ‘788’ and ‘Beaumont’ varieties of macadamia nuts, particularly in preventing external discolouration. The proposed set points aim to enhance the quality and overall market value of these macadamia nut varieties. The overall findings offer a comprehensive perspective on the effects of ethephon application on macadamia nuts. Stakeholders, producers, and processors in the macadamia nut industry can leverage this research to make informed decisions that enhance overall efficiency and quality while ensuring optimal nutritional value and extended shelf life for macadamia nuts.

Iqoqa.

Imboni yokukhiqiza amantongomane abizwa ngemacadamia ibhekene nezinkinga ngenxa yezikhathi ezingenayo inhlalanjalo zokuwohloka kwamahlamvu ezihlahla eyenzeka noma yinini, okwenza isivuno singazinzi kahle futhi kunyuke nezindleko. Ukusetshenziswa komuthi i-ethephon kusiza ekutheni ukuwohloka kwamahlamvu ezihlahla kwenzeke ngesikhathi sonyaka esifanele, nokho umphumela walo muthi ezingeni lokudla nesikhathi sokugcinwa kwakho awaziwa. Lolu cwaningo lucubungula imiphumela ye-ethephon mayelana nezinga lokudla osekuvuniwe i-788 nezitshalo ezahlukene zeBeaumont. Izinhlobo ezahlukene zamantongomane, okufaka nalawo awiswe yi-ethephon, nathathwa ezihlahleni ezilashiwe, naziwele ngokwawo, kwahlolwa futhi kwaqhathaniswa. I-ethephon yasetshenziswa kulandelwa imigomo ebekiwe yezimboni, kubhekwa amantongomane asevuthiwe. Lolu cwaningo lwaluhlola isimuncwane esinafutha, izinkomba zokudla, amakhemikhali nepolyphenol oxidase (PPO). Amasampula ocwaningo aqoqwa esikhathini esiyizinsuku ezingama-72 sokugcinwa kwawo, ukucubungula izinto ezibonakalayo njengesisindo, umnqamulankaba, umbala kanye nobunjalobotho. Imifanekisomumo iqagule ukuzinza nemibala emihle ngezikhathi ezinzima namazinga okugcineka kokudla, ukuhlonza nokugcina isikalo esibekiwe. Inguquko ekwakhekeni kwamfutha yabonakala yenzeka, amantongomane afakwe i-ethephon akhombisa ukwenyuka kwesimuncwane esigcwele amafutha nokuncipha kwesimuncwane esinamafutha angagcwele. Kwatholakala ubudlelwane obuqinile phakathi kokusetshenziswa kwe-ethephon kanye nesimuncwane samafutha aphelele. Kwatholakala kunokwenyuka kwesakhi sikashukela kamoba noma webhithrudi kanye noksebenza kwe-PPO emantongomaneni eBeaumont alashwe kusetshenziswa i-ethephon. Ukuhlaziya okukhulu kocwaningo kwaveza imiphumela ehlukile ngokwakheka kwesitshalo ngasinye esasicwaningwa. Indlela ecwaninga ukukhula yaveza ukwenyuka kwesibalo, esasifinyelela phezulu emibaleni ngendlela eyayilindekile. Indlela yokubheka ukuzinza yayibaluleke kakhulu ezitshalweni ze-788. Lolu cwaningo luza nomhlahlandela mayelana nokugcinwa kwamantongomane emacadamia, ukuthuthukiswa kwezinga kanye namanani okudayisa. Abathintekayo bangasebenzisa le miphumela yocwaningo ukuthuthukisa indlela yokusebenza kahle, izinga, kanye nokukwazi ukugcina ukudla isikhathi eside futhi kuqinisekiswe nokuthi ukudla kunomsoco odingekayo.