Enzyme Inactivation Analysis for Industrial Blanching Applications:  Comparison of Microwave, Conventional, and Combination Heat Treatments on Mushroom Polyphenoloxidase Activity

Abstract

Browning reactions in fruits and vegetables are a serious problem for the food industry. In mushrooms, the principal enzyme responsible for the browning reaction is polyphenoloxidase (PPO). Microwaves have recently been introduced as an alternative for the industrial blanching of mushrooms. However, the direct application of microwave energy to entire mushrooms is limited by the important temperature gradients generated within the samples during heating, which can produce internal water vaporization and associated damage to the mushrooms texture. A microwave applicator has been developed, whereby irradiation conditions can be regulated and the heating process monitored. Whole edible mushrooms (Agaricus bisporus) were blanched by conventional, microwave, and combined heating methods to optimize the rate of PPO inactivation. A combined microwave and hot-water bath treatment has achieved complete PPO inactivation in a short time. Both the loss of antioxidant content and the increase of browning were minor in the samples treated with this combined method when compared to the control. This reduction in processing time also decreased mushroom weight loss and shrinkage.

Naturally occurring tyrosinase inhibitors: mechanism and applications in skin health, cosmetics and agriculture industries

“…Another alternative approach is the use of microwave energy, but it also suffers from the main disadvantage that a temperature gradient is generated within the sample (Decareau, 1985), which causes enzyme in-activation in overheated regions only and in colder regions the enzyme may not be completely inactivated; moreover, it causes internal water vaporization with associated damage to the mushroom texture (Rodriguez-Lopez, 1991). The application of a combined microwave-hot water treatment is slightly better in terms of final product quality (Devece et al, 1999). In any case, microwave blanching is not very successful in the food industry except for some isolated applications.…”

Prediction of Polyphenol Oxidase Activity Using Visible Near-Infrared Hyperspectral Imaging on Mushroom (Agaricus bisporus) Caps

“…Brown discoloration is largely confined to the skin tissue of the 33 mushroom, where levels of phenols and polyphenol oxidase are higher than in other parts 34 of the fungi (7). PPO inactivation has been the target of several postharvest treatments 35 including thermal or microwave heating (8), irradiation (9) and addition of inhibitors (10). 36 However, consumer preference for fresh produce makes the management of PPO activity a 37 problem in the production, distribution and retail of fresh mushrooms.…”

Influence of Polyphenol and Ascorbate Oxidases during Cooking Process on the Radical-Scavenging Activity of Vegetables

“…The economic and nutritional loss induced by enzymatic browning is of concern to food processors and researchers. Therefore, numerous studies have been devoted to the biochemical and catalytic properties of polyphenol oxidase and to the inhibition of polyphenol oxidase activity in several fruits and vegetables including apple (Murata et al, 1992), peach (Chang et al, 2000), banana (Cano et al, 1990;Galeazzi et al, 1981), potato (Chen et al, 1992), mushroom Devece et al, 1999), eggplant (Pérez-Gilabert & Carmona, 2000, Chinese cabbage (Nagai & Suzuki, 2001), and lettuce (Fujita et al, 1991;Cantos et al, 2001). In eggplant, burdock and lettuce, enzymatic browning results from the enzymatic oxidation of chlorogenic acid (5-caffeoylquinic acid), which exists in large quantities (Fujita & Tono, 1988;Fujita et al, 1991).…”