Hazelnut by-products

Antioxidant Activities and Phytochemicals in Hazelnut Corylus avellana L.) and Hazelnut By-Products... 

Although antioxidant activity and phenolic constituents of hazelnut (hazelnut kernel) [4,26-28] and some of its by-products [29-31,100] have been reported, little is known about phenolic phytochemicals and their potential health benefits in hazelnut and hazelnut by-products. Therefore, this chapter provides detailed information on nutraceuticals, phytochonicals, and health aspects of hazelnut and hazelnut by-products and evaluates their antioxidant activities by a number of indicators. Taxanes present in hazelnut by-products are discussed in detail. Where possible, the health benefits of relevant phytochemicals are described. 

Five soluble phenolic acids (free and esterifled), one of which is a hydroxylated derivative of benzoic acid (gallic acid) and four are cinnamic acid derivatives (caffeic, p-coumaric, ferulic, and sinapic acids), have been studied and tentatively identified in ethanolic extracts of hazelnut kernel and hazelnut by-products (Table 13.2) [31]. The order of total phenolic acid concentration was as follows hazelnut hard shell > hazelnut green leafy cover > hazelnut tree leaf > hazelnut skin > hazelnut kernel. Different phenolic acids predominate in each plant part examined. Among the identified phenolic acids, p-conmaric acid was most abundant in hazelnut kernel, hazelnut green leafy cover, and hazelnut tree leaf, whereas gallic acid was most abundant in hazelnut skin and hazelnut hard shell, possibly implying the presence and perhaps the dominance of tannins in the latter samples (Table 13.2). The same number, but different concentration, of phenolic acids have also been reported in hazelnnt kernel and hazelnut green leafy cover [30]. 

High tannin content in hazelnut by-product extract (skin and hard shell) was reported by Contini et al. [ 100]. Total tannins represented the principal fraction of the phenolic substances of the extracts, containing nearly 60%-65% of the total phenol [100]. As a general rule, the highest amount of total tannins was detected in the extracts with the highest amount of total phenols. Hence, the high antioxidant activity in hazelnut by-product extracts maybe due to these polyphenolic compounds since they are expected to have powerful antioxidant activity [100]. 

Recently, Shahidi et al. [31] found that total antioxidant activity of hazelnut extracts ranged from 29 to 148 xmol TE/g of ethanolic extract, with lowest activity in hazelnut kernel aud highest in hazelnut tree leaf (Table 13.1). The total antioxidaut activity of hazelnut by-product extracts were approximately 4-to5-fold higher than that of hazelnut kernel at the same extract concentration. At a given concentration, hazelnut by-product extracts would serve as a more effective antioxidant than hazelnut kernel extract. Consideration of defatted hazelnut (on an extract basis) and hazelnut (as is weight basis) make the quantitative comparison between the studies of Wu et al. [4] and Shahidi et al. [31] impossible. 

Contini et al. [100] also observed that different solvents [80% (v/v) methanol, 80% (v/v) ethanol, and 80% (v/v) acetone] used for the extraction had different capacities in extracting substances and phenols from hazelnut by-products. The most suitable phenolic solvents for hazelnut by-products were either 80% acetone or 80% ethanol [100]. These results are in agreement with that of Alasalvar et al. [30]. 

Several free radical scavenging activity tests (hydrogen peroxide, superoxide, and DPPH) have been employed to evaluate the extracts of hazelnut kernel and hazelnut by-products. This information... 

BHA, BHT, Trolox, and a-Tocopherol Equivalent Antioxidant Capacity of Hazelnut By-Product Extracts... 

FIGURE 13.2 Antioxidant activity in extracts of hazelnut kernel and hazelnut by-products in the 3-carotene-linoleate model system. (From Shahidi, R, Alasalvar, R, and Liyana-Pathirana, C.M., J. Agric. Food Chem., 55,1212, 2007. With permission.)... 

Retention (%) of Supercoiled DNA in Extracts of Hazelnut Kernel and Hazelnut By-Products in Free Radical Induced Strand Scission... 

Despite small amounts of taxanes present, hazelnut by-products could have an industrial value for the production of paclitaxel [99]. The reason behind this is that the hazelnut trees grow much faster than the Pacific yew (a slow-growing plant in limited quantities in the Pacific Northwest). This could reduce the cost of the commercial drug and make it more readily available. Commercial supphes of Taxol are now manufactured by a semisynthetic method that relies on extracts from leaves of other yew species. Although pachtaxel has been synthesized artificially in the laboratory without using any yew parts, this method is currently too complex and expensive to implement commercially. 

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