Efeito do plasma frio na qualidade de maçã e araçá-boi

Abstract

Cold plasma is an alternative to traditional methods of thermal conservation and presents itself as a promising technique to preserve and retain quality parameters. Thus, the objective of this study is to evaluate the effect of two types of cold plasma (dielectric barrier discharge and glow discharge) on the qualitative aspects of apple (cube and juice) and guava (pulp). The application of dielectric barrier discharge (DBD) plasma at different frequencies: 50, 200, 400, 600, and 900 Hz for 15 min was evaluated for apple and 10, 15, and 20 min for guava, with the application of glow discharge plasma with gas flow rate between 10 and 30 mL/min for 10 to 30 min. The effects of plasma application on apple were evaluated on enzyme activity (polyphenoloxidase-PPO and peroxidase-POD), phenolic compounds, antioxidant capacity, colorimetry, concentration of sugars and organic acids. For the araçá-boi pulp the analyses evaluated were: vitamin C, hydrogen peroxide and volatile compounds profile. The application of the two types of plasma was able to partially inactivate the enzymes (PPO and POD) responsible for browning, contributed to an increase in phenolics and antioxidant activity. The DBD plasma induced a greater increase in phenolic content than the glow discharge plasma. The 50 Hz excitation frequency provided apple juice with the highest total phenolic content and antioxidant capacity. The changes in color parameters did not compromise the quality of the product. The application of glow discharge plasma induced a decrease in sucrose content and an increase in glucose, fructose and malic acid, unlike the dielectric barrier plasma which induced a decrease in sugar and an increase in malic acid content. The cold plasma technology depolymerized sucrose into glucose and fructose by cleavage at the ether bond. DBD plasma further induced the consumption of glucose and fructose, most likely through the phenylpropanoid mechanism. With this the cold plasma technology could be used to modulate the sensory characteristics of apple products by altering both sweetness and sugar-acid ratio. For guava, from process conditions studied it was observed that plasma increased the vitamin C content, reduced the hydrogen peroxide content and influenced the modification of volatile compounds. Therefore, cold plasma can be used as a technique for preservation and retention of quality parameters of studied fruits, from process conditions evaluated to achieve the specific objectives.