Peaches electrical bioimpedance assessment to control freeze induced texture changes: a easy and not expensive method to discover fruits undeclared cold treatments

Peach (Prunus persica) is a fruit of agricultural relevance for its economic value as well as its relevance in human health as an important source of henolic compounds, cyanogenic glucosides and phytoestrogens. Despite peaches cold storage delays their ripening, peaches are subject to a low-temperature internal breakdown that may limit the time fruit can be held and still ripened normally. Since it has been found that changes in electrical impedance of peaches behaved differently depending on the frequency of the current injected into them, in these experiments the resistive component of the electrical impedance of some sardinian (Italy) cultivar peaches has been assessed by injecting into fruit’s mesocarp an alternate electrical current (1mA, 65 KHz). Peaches tested were117 subdivided in 4 groups, each from 21 and 39 samples, and were stored 12 hours in a freezer with constant temperature respectively of 7°C,-2°C,-8°C and-17°C. Bioimpedance assessment was done12 hours after thawed. Results found a linear significant regression equation (P=0.027) in which each temperature unitary change (1°C) induced a 10.9 Ω of change in the resistive component of the peaches bioimpedance. It was concluded that electrical-bioimpedance technique could be a good indicator of possible previous passages through frozen/thawing protocols in peaches exposed for sale.