ELECTRONIC NOSE FAST METHOD FOR APPLES DISCRIMINATION TO DETERMINE OPTIMUM HARVEST MOMENT

Abstract

Apples should harvested before it is fully ripe, but after it has time to mature. This varies according to cultivar and different apples varieties will often ripen at different times over a three-month period. Sugars are major soluble solid in fruit juice and therefore soluble solids are often used as an estimate of sugar content. As the fruit mature, the starch changes to sugar and the aroma and flavors develops, when is generating volatile compounds. The perception of volatile compounds by the human nose is of great importance in evaluating quality of foods; therefore, similar principle as the human nose, the electronic nose, was used. An electronic nose (E-nose) was used to classify apple samples based on their smell.  Seven varieties of apples from Romania, Golden, Starkrimson, Jonathan, Gala were from Reghin region and Pinova, Fuji, Golden,too, from Insuratei area, were used. All the samples were analyzed using the E-nose FOX 4000 with 18 metal oxide coated or uncoated sensors. The resulting E-nose intensities were analyzed by Principal Component Analysis (PCA), Discriminant Factor Analysis (DFA) and Statistical Quality Control (SQC), which resulted in grouping the used varieties of apples or in grouping the types of samples (peel, homogenate or diluted homogenate from the same apple). The obtained results indicated that E-nose could discriminate successfully among varieties of apples (% of variance >> 90; percentage of recognition ≈ 100 %).  Choosing proper harvest moment for apples give us posibility of long term preservation in good quality conditions.