Effect of Different Drying Methods on Physical and Chemical Attributes of Blanched Green Bell Pepper

Abstract

Changes in total chlorophyll and ascorbic acid (AsA) contents and total color difference (TCD) of blanched green bell peppers during hot air and microwave drying were investigated. The dehydration kinetics of unblanched and blanched green bell peppers at 60℃ were determined. Total chlorophyll and AsA contents as well as TCD were determined in the range of 40 _ 70℃ for hot air drying and 500 _ 800 W for microwave drying. The decomposition rates of total chlorophyll, AsA and TCD followed first order reaction kinetics. Each rate constant exhibited an Arrhenius-type temperature dependence. The activation energies (E) of total chlorophyll, AsA contents and TCD were determined for hot air drying.Keywords: green bell pepper, drying, chlorophyll, ascorbic acid, total color difference, reaction kinetic IntroductionThe bell pepper (Capsicum annuum L.) is an important vegetable crop that can be grown in temperate or tropical regions.The color of ripe bell peppers can be white, red, yellow or orange, while unripe bell peppers are green in color (Simonne et al., 1997).Green bell peppers contain large amounts of vitamin C (76 mg/100 g) and minerals, such as potassium (190 mg/100 g), calcium (11 mg/100 g) and iron (0.4 mg/100 g) (STAJ, 2002).Green bell peppers are consumed raw or cooked as well as in dehydrated form.The green bell pepper, like other vegetables, is highly perishable; thus, dehydration plays an important role in extending its shelf life. Dehydration can be accomplished by several methods, including hot air, microwave and vacuum drying. However, losses of chemical compounds and physical properties, such as chlorophyll and water-soluble vitamins (mainly ascorbic acid (AsA)) and total color difference (TCD) occur during vegetable drying (Guine and Barroca, 2012;Di Scala and Crapiste, 2008;Marfil et al., 2008;Ozkan et al., 2007;Maharaj and Sankat, 1996).Chlorophyll pigments (mainly chlorophyll a) are responsible for the green color of the green bell pepper and are extremely sensitive to heat. Undesirable changes in the color of the green bell pepper during drying may decrease its quality. Boyer and Huff (i) reported that most vegetables should be blanched before drying.According to Fellows (2000), the addition of sodium carbonate (0.125% w/w) to the blanching water prevents the loss of chlorophyll and retains the color of green vegetables. The main function of blanching is to destroy the enzymatic activity of vegetables; blanching also reduces the drying time and kills many spoilage organisms (Boyer and Huff (i);Fellows, 2000). Peroxidase (POD) is the most heat-stable enzyme in fruits and vegetables, and the POD content is widely used as an index of blanching (MoralesBlancas, et al., 2002;Fellows, 2000;Negi and Roy, 2000;Gunes and Bayindirli, 1993). Okoli et al. (1988) reported that blanching L. V. Man et al. 776 spinach at 95℃ for 1 min was sufficient to inactivate POD. Imaizumi et al. (2013) investigated the applicability of microwaving (MW) for blanching taro and yam. According to Gunes and Bayindirli (199...

Effects of Microwave Utilization on the Color Properties of Food: A Review

“…Hot air-drying activation energies (E) for total chlorophyll, AsA, and TCD were calculated. [58] This study compared the effects of 915 MHz microwave-assisted thermal pasteurization and conventional hot water pasteurization (F10 90 = 10 min) on chlorophylls in green beans stored at 10, 7, and 2 °C for 100 days. Vacuum-sealed N2-flushed containers processed frozen-cut green beans.…”

Energy consumption and thermal properties of drying banana (musa ssp) under varied relative humidity

“…Where M e M, and M o and are the equilibrium moisture content of the initial moisture content and dry basis respectively at time t; k is the drying constant. For the analysis of MR, the equilibrium moisture content was assumed to be zero (Man et al, 2014). At time (t), the drying rate (DR) of banana slices was calculated as follows:…”