Nondestructive analysis of phytochemicals present in fruits and vegetables by Photoacoustic techniques

Fruits and vegetable have long been regarded as having considerable beneficial effects on health, due in part, to the presence of bioactive compounds or phytochemicals. Their amount and composition in plant foods is strongly dependent on a number of factors as genotype, ripening, environmental conditions, climate, cultivation practices, harvesting modalities and storage methods. Moreover, phytochemicals are responsible for the organoleptic characteristics of foods such as colour, aroma and taste. In the human organism, these bioactive compounds are involved in several cellular processes. For example, they are able to neutralize or reduce the oxidative stress, to interact and modulate multienzymatic systems, to inhibit platelet aggregation, to counteract the carcinogenesis, to reduce the formation of inflammatory molecules through different mechanisms. Therefore, the daily and continuous introduction of these substances is of particular importance for human health. All these properties confer to phytochemicals an important role as biomarkers of nutritional, healthy and commercial quality. Nowadays, both the food industry and the agricultural sector need of rapid screening tools that make it possible the quality control along the whole chain of production (from farm to finished product). In this respect is desirable a non-destructive analytical approach, which allows to correlate the information obtained from direct analysis of bioactive compounds content in plant foods with the stadium of ripeness, freshness, shelf life of products. In the recent years, the Photoacusitc (PA) and Photothermal (PT) techniques have been applied for quantifying phytochemicals present in fruits and vegetables. In particular, these techniques have allowed the direct quantitative analysis of carotenoids (α- and β-carotene, lycopene) and flavonoids (mainly anthocyanins) in fresh produce products such as tomatoes, carrots, brassicaceae, oranges, cherries, apricots, grapes, wine, etc, with little or no manipulation of the sample. In this context we obtained preliminary data from PA signals measurements in peel of apple fruits belonging to two different varieties: Golden Delicious apple and Pink Lady apple. The results revealed that PA signals were in agreement with different apple peel colours due to the different distribution and content of chlorophylls (a and b), carotenoids and anthocyanins in apple peel.