Classes de lipídios e triacilgliceróis em café: efeitos do tipo de café e métodos de secagem

Abstract

INTRODUÇÃO Apesar dos lipídios de café terem sido muito pouco estudados, tem-se especulado que eles podem diminuir a qualidade do café devido à hidrólise dos triacilgliceróis (TAG) com a liberação dos ácidos graxos (FA) que são, por sua vez, oxidados produzindo "off-flavour" (Spadone et al., 1990; Speer et al., 1993). Maturação e método de secagem são dois parâmetros importantes que afetam a qualidade do café mas pouco estudados. Portanto, para se entender melhor os possíveis efeitos da maturação e dos métodos de secagem sobre a composição dos lipídios, investigamos as classes de lipídios (ES: ésteres de esterois; ET:ésteres de terpenos; AGL:ácidos graxos livres; MAG:monoacilgliceróis e DAG:diacilgliceróis) e classes de TAG do três tipos (imaturo, cereja e de mistura aleatória dos tipos de sementes) de café (Catuaí Vermelho, Coffea arabica L) após serem submetidos à secagem de forno/pátio.

The effects of coffee type and drying procedures on the lipid classes and triacylglycerols were determined in coffee samples from Brazil. Three types of coffee (immature, cherry beans and a random mixture of coffee beans) were harvested and dried by two commonly used procedures (conventional oven dryer and “patio”) and the lipid classes and triacylglycerols determined. The following six treatments (T1 to T6) were carried out for the determination of lipid classes and triacylglycerols: randomly obtained mixed coffee sample dried in a conventional dryer and patio dried (T1 and T2 respectively); immature coffee beans dried in a conventional dryer and patio dried (T3 and T4 respectively) and cherry beans dried in a conventional dryer and patio dried (T5 and T6 respectively). For the six treatments the percentage of sterol esters (SE), triacylglycerols (TAG), terpene esters (TE), monoacylglycerols (MAG), diacylglycerols (DAG) and free fatty acids (FFA) varied in the intervals of 2.0-2.7, 72.1-75.2, 13.1-14.8, 2.7-4.6, 1.8-2.3 and 2.0-2.5, respectively. Twelve triacylglycerol classes with 0 to 7 double bonds were identified. The major components were distearolinolein (25.97% to 37.07%) stearooleolinolein (12.4% to 14.73%) and stearodilinolein (27.7% to 37.77%). There was a significant effect (P>0.05) of type of coffee and drying on the percentage of lipid class-TAG and DAG respectively but not for SE, TE, FFA and MAG. For the major TAG class S2D, only T3 was different from T4 (P<0.05) indicating a possible effect of drying on the immature coffee beans. However, no such effects were noted for T1 and T2 nor for T5 and T6 (P>0.05). For SMD, only T1 was different from T4 (P<0.05). For D2S, T1 was different from T2 (P<0.05) as was T5 from T6 indicating possible effect of drying on randomly obtained coffee sample and cherry bean coffee sample.