Thermal Stability of l‐Ascorbic Acid and Ascorbic Acid Oxidase in Broccoli (Brassica oleracea var. italica)

Abstract

The results reported in this study are applicable for both domestic and industrial processing of vegetables into products such as juices, soups, and purees. In this report, we have demonstrated that processing crushed broccoli in a temperature range of 30 to 60 degrees C could result in the conversion of l-ascorbic acid to dehydroascorbic (DHAA), a very important reaction in regard to vitamin C degradation because DHAA could be easily converted to other compounds that do not have the biological activity of vitamin C.

Effect of microwave assisted blanching on the ascorbic acid oxidase inactivation and vitamin C degradation in frozen mangoes

“…5; from the comparison between the two isorate contour plots it is clear that AAO is more heat sensitive than L-AA. Similar trend has been identified regarding the AAO and L-AA in the case of whole broccoli florets blanching, while in the case of crashed florets treatement L-AA found to be also thermosensitive (Munyaka et al, 2010). This can be considered as a key tool to select blanching conditions, optimum blanching processing of mango would require the highest possible inactivation of AAO while maintaining the maximum possible L-AA content.…”

“…As reported, AAO present in fruits is detected in the cell wall, in the extracellular matrix and in the vacuole and therefore intact cell structure protects AAO from thermal inactivation and leaching (Munyaka et al, 2010). In a recent study regarding mango matrices it was also observed that AAO in whole pieces of mango was in some extent heat resistant and a part of remaining activity was observed after processing (Guiamba, 2016).…”

“…Although there are available data in the literature regarding thermal inactivation kinetics of AAO, the residual activity of this enzyme after thermal treatment of broccoli, pumpkin (Cucurbita maxima), carrots (Daucus carota subsp. sativus) and others indicate that inactivation kinetics can be different with respect to the origin of the matrix (Leong & Oey, 2012;Munyaka et al, 2010;Porto et al, 2006). To our knowledge, there is not available information in literature regarding the thermal inactivation kinetics AAO present in mango.…”

“…Depending on whether the product is emerged in water or not, heat can be transferred by water or electromagnetic energy. During water blanching the food matrix is interacting directly with the blanching medium and the physicochemical properties of the matrix such as porosity, nutrient solubility, composition, density and others are influencing the characteristics of the final product (Munyaka et al, 2010;Ramesh, Wolf, Tevini, & Bognár, 2002).…”

“…Blanching is a common mild thermal pretreatment prior to freezing aiming to inactivate deteriorative enzymes, decrease the microbial load and remove the air from the pores which subsequently can affect the nutritional characteristics of the fruits and vegetables upon storage (Munyaka, Makule, Oey, Van Loey, & Hendrickx, 2010;Xanthakis & Valdramidis, 2017).…”