A novel and simple approach for assessing the freshness of hazelnuts

Visual inspection and sensory analysis are the only suitable ways to assess the quality of hazelnuts under routine conditions. To obtain a more objective parameter for the freshness, a fast and easy-to-use method was developed. It is based on the well-known test for the germination capacity of seeds where their vitality is determined by use of 2,3,5-triphenyltetrazolium chloride (TTC) which is reduced by flavo enzymes to 1,3,5-triphenylformazane, which appears red. For the determination, 100 hazelnut halves were embedded in TTC containing methyl cellulose gel on a glass plate and kept at 35 °C in the dark. After 6 h, the cut planes of viable nuts were stained red, the cut planes of rotten nuts were yellow or brown, and the colour of dead or mould-infected nuts remained unchanged. The colour pattern was examined either visually by counting the coloured halves or with computer support using image editing software. The ratio of the sum of coloured areas to the total area of the hazelnut cut planes gave a measure of the average degree of viability ("vitality index"). The analysis of several samples of hazelnuts of well-defined age and storage conditions confirmed the efficiency of the method.