Abstract
The macadamia tree (Macadamia integrifolia Maiden & Betche) produces a nut of highly commercial value, distinguishable from other nuts by its delicate flavour and oil quality. This study aimed to compare the oxidative stability of dried nuts, with the application of hot air microwave energy, in relation to conventional drying. The analyses were performed at the beginning stage (time zero), at 90 days, and 180 days of storage, to evaluate the percentage of free fatty acids, peroxide values, induction period, fatty acid composition, and tocopherol/tocotrienol content. The percentage of free fatty acids varied from 0.095 (MW1) to 0.124 (MW3) and from 0.123 to 0.148 (CVL); peroxide values (meq O2 kg-1 oil) ranged from 0.77 (MW2) to 2.57 (MW1) and from 1.52 to 3.29 (CVL); the induction period (h) from 16.7 (MW2) to 13.6 (MW4) and from 11.9 to 10.6 (CVL); and the ?-tocotrienol (mg 100 g-1) content from 1.75 to 2.19 (MW1) and from 2.14 to 2.19 (CVL), for microwave and conventional drying, respectively. The fatty acid composition values did not change during storage, in relation to the drying processes applied. The microwaves drying method was more efficient, regarding the macadamia nuts oxidative stability, when compared to the conventional drying method.
Highlights
The macadamia tree (Macadamia integrifolia Maiden & Betche) produces a nut of highly commercial value, distinguishable from other nuts by its delicate flavour and oil quality
Avaliando-se o tempo de armazenamento, em cada tratamento, para os ácidos graxos livres, verificou-se que não houve diferença significativa (p ≤ 0,05), durante os 180 dias de armazenamento, com teor médio de ácidos graxos livres de 0,106%, no tratamento MW1; 0,110%, no MW2; 0,110%, no MW3; 0,105%, no MW4; e 0,136%, no CVL
Os valores encontrados em ácidos graxos estão de acordo com aqueles observados por Cavaletto (1983), Dierberger & Marino Netto (1985), Duke (1989), Mason & MccConachie (1994), Kaijser et al (2000), Sousza et al (2007) e Freitas & Naves (2010)
Summary
The macadamia tree (Macadamia integrifolia Maiden & Betche) produces a nut of highly commercial value, distinguishable from other nuts by its delicate flavour and oil quality. O teor de ácidos graxos livres (%) das amêndoas de noz macadâmia variou de 0,095 (MW1) a 0,124 (MW3) e de 0,123 a 0,148 (CVL); os índices de peróxidos (meq O2 kg-1 de óleo) entre 0,77 (MW2) e 2,57 (MW1) e de 1,52 a 3,29 (CVL); o período de indução (h) de 16,7 (MW2) a 13,6 (MW4) e entre 11,9 e 10,6 (CVL); o teor de α-Tocotrienol (mg 100 g-1) de 1,75 a 2,19 (MW1) e de 2,14 a 2,19 (CVL), respectivamente, para a secagem com micro-ondas e convencional. O objetivo deste trabalho foi avaliar a estabilidade, durante 180 dias de armazenamento, de amêndoas de noz macadâmia seca, após aplicação de energia de micro-ondas com ar quente, e compará-la com a de amêndoas secas pelo processo convencional (secagem convectiva)
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