LIPOXIDASE ACTIVITY AND OFF‐FLAVOR IN UNDERBLANCHED FROZEN CORN‐ON‐THE‐COB^a,b

Abstract

A progressive deterioration in quality is known to occur when raw or underblanched vegetables are held in frozen storage for extended periods of time. These changes in quality, characterized mainly by the development of off-flavors, and believed to be the result of enzyme action, aTe described in a review by Joslyn (9). Various enzymes have been suggested as causative agents in off-flavor production in frozen foods, but attention has been centered around catalase and peroxidase.Comparative studies on extent of catalase and peroxidase inactivation and formation of off-flavors indicated that activity of these enzymes could be used as indices of the extent of heat inactivation of enzymes actually responsible for off-flavor formation. The use of these two enzymes in the control of blanching treatment and as an index of adequacy of blanching was due primarily to the relative ease with which their activity could be determined (5,13).Testing for adequacy of blanching in corn-on-the-cob has presented several problems not normally encountered with other vegetables (Z,14,15). Tests for catalase and peroxidase are not always reliable as criteria of adequate blanching for frozen corn-on-the-cob (3,4,5,15). This study was undertaken to determine whether or not assays for enzymes other than catalase and peroxidase might better serve this purpose, and show a better correlation with off-flavor in the frozen product.Recently the enzymes lipoxidase and lipase have been proposed as causative agents in the development of off-flavors, peroxidation of lipid matter, and chlorophyll losses in raw frozen peas (20,21,ZZ). Lipoxidase activity has been demonstrated in corn by Franke and Frehse (7) and by Fritz and Beevers (8).Residual lipoxidase activity and the extent of peroxidation of lipid matter were determined in commercial pack samples of frozen corn-on-thecob, and lipoxidase activity was correlated with flavor as determined by taste tests. The effects of processing conditions on residual lipoxidase content and flavor of the frozen product were investigated.

Gel electrophoretic analysis of peanut proteins and enzymes. II. Effects of thiol reagents and frozen storage

“…Certain enzymes such as peroxidase (Gardner et al, 1969), phenoloxidase (Anderson, 1968), lipoxygenase (Wagenknecht, 1959), and lipase (Acker and Beutler, 1965) have been shown to influence shelf-life or flavors of foods. If one could remove or reduce these enzyme activities by adding acceptable thiol-reducing reagents during the preparation of protein isolates from oilseed meals (e.g., as with phenoloxidase activity by Anderson, 1968; and the peroxidase activities in Figure 6), the stability and possibly the functional properties of the protein isolates might be improved.…”

Peroxidase and Lipoxygenase Influence on Stability of Polyunsaturated Fatty Acids in Sweet Corn (Zea mays L.) during Frozen Storage

“…However, some studies have shown that POD is not directly involved in quality deterioration of frozen unblanched vegetables and its complete inactivation may result in overblanching (Williams et al, 1986). The measure of LOX activity has been suggested as an indicator of adequacy of blanching for several vegetables (Axelrod et al, 1981;Sheu and Chen, 1991;Chen and Hwang, 1988;Williams et al, 1986;Chen and Whitaker, 1986;Wagenknecht and Lee, 1958) including sweet corn (Garrote et al, 1985;Wagenknecht, 1959). It is closely related to destruction of essential fatty acids, off-flavor development and pigment degradation.…”

Lipid Oxidation in Frozen Vegetables in Relation to Flavor Change

“…Wagenknecht and Lee (1956) demonstrated the presence of lipoxidase in fresh and frozen peas and increases in peroxide number of lipids extracted from the raw vegetable after extended periods of frozen storage. A similar finding was made in underblanched frozen corn-on-the-cob (Wagenknecht, 1959). Lee and Wagenknecht (1958) used model systems in which the enzymes lipoxidase, lipase, catalase, and peroxidase were added to enzymatically inert macerated blanched peas.…”