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Phenolic Chemicals Found in Raw and Roasted Nuts and Their Skins

October 01, 2022

In the UK and across the world, people eat nuts often not just because they taste good but also because they are good for you. Nuts are a wonderful source of phytochemicals in addition to their distinct makeup, which is low in sugar and high in unsaturated fatty acids, vitamins, and minerals. The majority of the phytochemicals found in nuts, including flavonoids, phenolic acids, tannins, stilbenes, lignans, and phenolic aldehydes, are phenolic compounds.

The most popular nuts consumed worldwide are almond, Brazil nut, cashew, hazelnut, macadamia nut, pecan, peanut, pistachio, and walnut. They might be eaten unprocessed or after processing. The phenolic profiles, total phenolic levels, and antioxidant activity of both the kernels and, primarily, the skins of natural (raw) nuts are credited with the health advantages of these foods. Processes, particularly roasting, alter foods' antioxidant activity and phenolic component concentration while also removing the skin. Skins are beginning to be recommended for reconsideration in sectors including food, medicine, and cosmetics since they are a phenolic compound-rich component of nuts.

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As a study published in the ScienceDirect we will write:

Nuts and CVD | British Journal of Nutrition | Cambridge Core:  Almond, Brazil nut, cashew, hazelnut, macadamia nut, pecan, pine nut, pistachio, and walnut are some of the edible nuts that are frequently eaten. The skins of nuts have the highest concentration of phenolic chemicals. For instance, total phenolic content (TPC) in almonds with skins was reported to be 239 mg GAE/100 g fresh weight, compared to 47 mg GAE/100 g fresh weight in almonds without skin. Depending on the type, it was discovered that the TPC of peanut seed coverings was 60–120 times greater than that of their cotyledon components. TPC was observed to be 577.7 mg catechin equivalent/g of extract for the ethanol extract of hazelnut skin and 13.7 mg catechin equivalent/g of extract for the hazelnut kernel with skin.


Nuts can be eaten in their natural state (raw) or after processing. The majority of walnuts are eaten raw, with the skins still on. According to the desired outcome, the other frequently eaten nuts are often roasted, although they can also be stir-fried, oil-fried, or boiled. Blanching and a subsequent peeling procedure might be used to remove the skin from nuts. The eventual effect of roasting will be the removal of the skin, whether it is applied to nuts with skin or nuts without skin. When blanching and after the skin is peeled off, nuts' antioxidant activity (AOA) and TPC levels drop. Due to the release of bound phenolic compounds and the creation of Maillard reaction products such as melanoidins, roasting may raise TPC and AOA. However, roasting may also cause phenolic chemicals to degrade or disappear. Skins are valuable by-products whose reevaluation studies have grown recently because of their AOA, TPC, and phenolic profile.


Natural and roasted nuts' phenolic profiles, total phenolic content, and antioxidant activity

The two main phenolic acids and flavonoids found in natural almonds were discovered to be chlorogenic acid and isorhamnetin-3-O-rutinoside (with skin). Roasted almonds were not found to contain any flavonoid glycosides. However, after roasting, phenolic acids (gallic, protocatechuic, 5-hydroxybenzoic, chlorogenic, and vanillic acid) and flavonoid aglycones (eriodictyol, quercetin, naringenin, kaempferol, and isorhamnetin) gradually increased. In natural Brazil nuts, the phenolic acids gallic, vanillic, and ellagic were measured (without skin). According to reports, natural cashews (without the skin) contain condensed tannins, gallic acid, catechin, epicatechin, and epigallocatechin.

Except for catechin and epicatechin, heat treatments reduced their levels. Epicatechin-3-gallate, procyanidin dimers, trimmers, and tetramers, as well as catechin and epicatechin, were discovered to be abundant in natural hazelnuts. Hazelnuts have been shown to contain the hydrolysable tannins glansreginin A and glansregin B. Along with p-coumaric and ferulic acids, protocatechuic and gallic acids are the most prevalent phenolic acids in hazelnuts. Although the concentration of other phenolic compounds declined with roasting, gallic and protocatechuic acids rose as a result of the destruction of polymerized polyphenols, such as hydrolysable tannins. The isoflavones detected in natural and roasted peanuts in nearly equal amounts were biochanin A and genistein.


Nut skins' phenolic composition

The most often identified phenolic acids in the skins of almond, hazelnut, peanut, and pistachio include caffeine, chlorogenic, coumaric, ferulic, gallic, hydroxybenzoic acids, protocatechuic, and vanillic acids. The two most prevalent hydroxybenzoic acids found in hazelnut, pistachio, and peanut skins are gallic acid and protocatechuic acids. The prevalent hydroxybenzoic acid in hazelnut and peanut is coumaric acid.


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Nuts are available in a range of flavours. They can be eaten raw or roasted. Our cheese cashew will surely replace your kids' current list of favourite snacks. If you enjoy sweet foods, you might also want to try Honey Roasted Cashews, Honey Cinnamon Pecan, Honey & Cinnamon Cashews, Honey Coffee Cashews, Honey Raspberry Cocoa Dusted Almonds, or Honey & Chilli Cashews. As part of our unique Mediterranean preparation, we also salt them. To view all fresh Nuts types and all flavours, please visit our online store.



Recent years have seen a near-complete characterization of the phenolic chemicals found in raw and roasted almond, hazelnut, peanut, and pistachio. However, the specific phenolic components of natural Brazil nut, cashew, macadamia, and pine nut need to be clarified before the identification and quantification of phenolic compounds can be completed. The biggest contributors to the overall phenolic content of nuts are the skins, which are typically removed as a result of roasting. Since nut skins are viewed as a cheap source of phenolic chemicals, reevaluating them is a hot issue. Phenolic chemicals that are naturally present in nut skins can be exploited to add value.

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