Effect of Roasting on Phenolic Content and Antioxidant Activities of Whole Cashew Nuts, Kernels, and Testa

Abstract

The effect of roasting on the content of phenolic compounds and antioxidant properties of cashew nuts and testa was studied. Whole cashew nuts, subjected to low-temperature (LT) and high-temperature (HT) treatments, were used to determine the antioxidant activity of products. Antioxidant activities of cashew nut, kernel, and testa phenolics extracted increased as the roasting temperature increased. The highest activity, as determined by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity, oxygen radical absorbance capacity (ORAC), hydroxyl radical scavenging capacity, Trolox equivalent antioxidant activity (TEAC), and reducing power, was achieved when nuts were roasted at 130 °C for 33 min. Furthermore, roasting increased the total phenolic content (TPC) in both the soluble and bound extracts from whole nut, kernel, and testa but decreased that of the proanthocyanidins (PC) except for the soluble extract of cashew kernels. In addition, cashew testa afforded a higher extract yield, TPC, and PC in both soluble and bound fractions compared to that in whole nuts and kernels. Phenolic acids, namely, syringic (the predominant one), gallic, and p-coumaric acids, were identified. Flavonoids, namely, (+)-catechin, (-)-epicatechin, and epigallocatechin, were also identified, and their contents increased with increasing temperature. The results so obtained suggest that HT-short time (HTST) roasting effectively enhances the antioxidant activity of cashew nuts and testa.

Effect of malting conditions on phenolic content, Maillard reaction products formation, and antioxidant activity of quinoa seeds

“…On the other hand, it has been mentioned that reducing power in extracts reflected the presence of compounds that were electron donors, which can act as primary and secondary antioxidants (Yen and Chen 1995). Thus, the increased reducing power observed in this study was due to the ability to donate electrons, not only of released phenolic compounds, but also due to the development of reductone-like compounds formed during Maillard reaction (Maillard et al 1996;Chandrasekara and Shahidi 2011).…”

“…The observed increase in phenolic compound levels during malting process could be due to the action of endogenous esterases synthesized during germination process, which can lead to the release of phenolic compounds originally bounded in the seed matrix (Maillard et al 1996) or through de novo synthesis (Krahl et al 2008). Moreover, roasting process might induce structural changes in plant cell walls provoking as consequence a release of previously-glycosylated/esterified phenolic compounds (Dewanto et al 2002;Chandrasekara and Shahidi 2011).…”

“…It is well known that advanced and final MRPs have antioxidant activities (Matiacevich and Buera 2006;Chandrasekara and Shahidi 2011), therefore, an estimation of their contents in malted quinoa seeds was carried out. Formation of fluorescence compounds as well as crosslinking products were formed at advanced stages of Maillard reaction, which can be estimated by measuring the maximal fluorescence emission at 340-370 nm excitation wavelengths of samples (Matiacevich and Buera 2006), whereas melanoidins (the final products of Maillard reaction) due to brown colour were commonly estimated as absorbance value at 420 nm.…”

Phenolic Acid Content and Free Radical-Scavenging Activity of Two Differently Processed Carob Tree (<i>Ceratonia siliqua</i> L.) Pod

“…Most of these thermal processes result in a degradation of phenolic compounds, although there are some exceptions. For example, it has been observed that immersion of pre-cut celery (Apium graveolens L.) in water at 50˚C for 90 s resulted in a reduction in total flavonoid content of about 22% [23]; roasting of tartary buckwheat extracts at 120˚C for 20 min and at 160˚C for 30 min led to reductions in total flavonoid content of 12% and 16%, respectively [24,25]; and sand roasting and microwave cooking (at 280˚C for 20 s) reduced the phenolic content of barley by 8% [26]; while an increase in temperature (40˚C  70˚C) during apple-juice processing resulted in a 50% rise in flavonoid content [27]; and roasting increased the total phenolic content of cashew nuts and peanuts [28,29].…”

Cashew nut roasting: Chemical characterization of particulate matter and genotocixity analysis

“…The nuts are oven-roasted, where the shell itself acts as the fuel. The fuel generated from cashew nut roasting releases cashew nut shell liquid, a highly flammable caustic phenolic oil that releases compounds into the atmosphere (Agila and Barringer, 2011;Chandrasekara and Shahidi, 2011). The smoke generated during cashew nut roasting is inhaled daily by family groups that take part in the activity for periods that may exceed 10 h/day.…”