Improving the Antioxidant Activity and Flavor of Faba (Vicia faba L.) Leaves by Domestic Cooking Methods

Abstract

Faba leaves are an unusual vegetable which contain not only a range of functional phytochemicals, but also certain undesirable flavors, which limit their consumption. In this study, several cooking methods (microwaving, roasting, steaming, and boiling), which are expected to reduce the odd flavors, were evaluated in terms of both health benefit effects and odd flavor factors, including antioxidant activities and the content of non-volatile and volatile organic compounds (VOCs). A cooking time of 5 min was selected because of the high content of L-dopa (L-3,4-dihydroxyphenylalanine) and aim of reducing the undesirable flavors of the cooked faba leaves. Microwaving and steaming significantly increased the L-dopa content by 24% and 19%, respectively. Roasting specifically increased the content of flavonols, exhibiting a 28% increase of kaempferol-3-O-arabinoside-7-O-rhamnoside, representatively, whereas boiling decreased about 50% of most phytochemicals evaluated. Microwaving and steaming treatments significantly increased the antioxidant activities. The L-dopa content and antioxidant activities of the processed faba leaves were strongly positively correlated with either an R2 = 0.863 of DPPH radical scavenging activity or an R2 = 0.856 value of ABTS radical scavenging activity, showing that L-dopa was a key antioxidant. All cooking methods potentially improved the flavor of the cooked faba leaves compared with that of the fresh leaves, because they significantly reduced the contents of VOCs such as alcohols, aldehydes, and ketones. These VOCs were the main components (>90%) in the fresh leaves. Adverse aromatic hydrocarbons were newly formed by the microwaving treatment, typically producing p-xylene, which is known to be a harmful dose-dependent compound, but they were not detected in leaves processed by the other cooking methods; therefore, although microwaving efficiently increased antioxidant activity, the chemical safety of the aromatic hydrocarbons produced need further study.

Accumulation of Antioxidative Phenolics and Carotenoids Using Thermal Processing in Different Stages of Momordica charantia Fruit

“…The increase in antioxidant activities might be due to the variation of polyphenols in the matrix after thermal processing. The polyphenols are important antioxidant contributors [ 10 , 11 , 12 , 13 ] and the significantly increased total phenolic content in the thermally treated M. charantia can support the increased antioxidant activities, which were evaluated using three different assays ( Figure 2 and Figure 3 ). A chromatogram at 280 nm is widely used to study the polyphenols because the absorption at this wavelength is suitable for detecting a large number of such compounds [ 32 ].…”

“…Furthermore, hot-air drying is one of the most commonly employed heat treatments that alters not only the physical properties (such as hardness) but also the chemical properties (such as polyphenol decomposition) of food materials. Heat treatment increases taste preferences by promoting nonenzymatic reactions in food or inducing a change in flavor components [ 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Heat treatment can cause an increase in phenolic compounds and antioxidant activity in various fruit crops such as citrus, persimmon peel, and eggplant fruit [ 10 , 14 , 15 ].…”

Thermal Control Using Far-Infrared Irradiation for Producing Deglycosylated Bioactive Compounds from Korean Ginseng Leaves

“…This can be explained by the different progressions of thermal processing (methods, time, temperature, etc.) affecting different substances [ 13 , 37 , 38 , 39 , 40 , 41 ], as Rk3 and Rh4 are the deglycosylated products of Rg6 and F4 at C-6, respectively. Ginsenoside mutations in ginseng leaves during heat treatment have not been widely studied in the literature, especially in terms of dry-heat treatment.…”

Valorization of faba bean (Vicia faba) by-products

“…A cooking time of 5 min was recommended, as it significantly reduced the content of VOC and improved the flavour without compromising the nutritional value. Microwaving and steaming were more effective than boiling and roasting although microwaving significantly increased the p-xylene content which might have harmful effects on the human health [71].…”

“…However, the consumption of fresh faba bean leaves might be hampered by the presence of volatile organic compounds (VOC) inducing undesirable flavours. Duan et al [71] detected a total of 69 different compounds in the fresh leaves with alcohols (72%), aldehydes (14%), ketones (5%), and esters (3%) accounting for more than 90%. The authors investigated the influence of four different domestic cooking methods on the composition of the leaves.…”