The effects of ohmic and conventional blanching on the nutritional, bioactive compounds and quality parameters of artichoke heads

Abstract

The effect of ohmic (24 V/cm, 80 °C) and conventional hot water (100 °C) blanching on peroxidase (POD) and polyphenol oxidase (PPO) inactivation, colour parameters [L, hue (h), Chroma (C), ΔE*], texture (maximum compression force) as well as total protein and phenolic content of artichoke heads immediately after blanching as well as during storage by canning was investigated.The experimental results have shown that ohmic blanching inactivates both enzymes at lower processing times than conventional blanching, with total inactivation times of 360 s and 480 s, respectively. The colour of the raw product was well preserved after ohmic heating, while after water blanching it changed significantly from a yellow/green to a brownish/green. In addition, when compared to the artichokes blanched by ohmic treatment, the samples treated by the conventional method appeared heterogeneously softened showing a lower softening in the inner region but excessive softening in the outer part.Finally, the results have revealed that the blanching method also affects the nutritional and bioactive compounds in artichokes immediately after blanching and during storage by canning, with the losses in both protein and polyphenolic content in conventionally pre-treated samples being greater than those measured in samples pre-treated by ohmic blanching.