INFLUENCE OF TRADITIONAL AND MICROWAVE TECHNOLOGY ON GARLIC SULFUR-COMPOUNDS IN GARLIC AROMATIZED OILS AND ON THE STABILITY OF OLIVE OIL TO OXIDATION

In this paper the influence of the different techniques of extraction on garlic volatile compounds, during the preparation of garlic aromatized olive oils, was studied. The aroma compounds were extracted from whole peeled garlic or chopped cloves in olive oil for 16-18 h (infusion) at room temperature and for 0-20 min. at 50-degrees divided-by 100-degrees-C (conventional heating, microwave). For the analyses, the garlic aroma compounds were stripped from the oil by the head-space technique and then analysed by GC/MS. The qualitative analysis showed that the aromatized oil prepared by microwave at 90-degrees-C for 5 min, contained the most sulphuric compounds. Prolonging heat treatments, a decrease of diallyl disulphide was noted, which was probably caused by unknown substances in the oil and not by heat treatments. During heat treatments no off-aroma phenomenon was observed. The quantitative analysis was carried out by S.I.M. technique, determining diallyl disulphide which is the most abundant and characteristic component of garlic aroma. The results pointed out that with microwave technique the extraction of diallyl disulphide was 5 times quicker than traditional methods in the first 5 min. of treatment. Using U.V. technique, the influence of heat treatments on the stability to oxidation Of the aromatized oils was also estimated. Using the microwave, the aromatized oils had induction times of oxidation longer than conventionally heating and untreated oils.