Targeted and Non-Targeted Analyses of Secondary Metabolites in Nut and Seed Processing

Abstract

Tree nuts and related seeds such as peanuts and oilseeds contain large numbers of secondary metabolites. These compounds have beneficial qualities for human health and wellness, but the reports on them are scattered. The growing field of metabolomics aims to characterize these compounds in a systematic way so that the mechanism of their formation can be better understood. This review gathers current studies using both targeted and non‐targeted approaches to the analysis of secondary metabolites from tree nuts and related oilseeds. Almonds, Brazil nuts, hazelnuts, macadamia nuts, pecan, pine nuts, pistachios, walnuts, peanuts, rapeseeds, and sesame seeds are included along with some lesser known products. The changes with roasting are also discussed. Phenotypic data of this type is useful for identifying specific genetic markers that could be used for crop improvement. High value crops such as tree nuts, peanuts, and oilseeds would benefit from these advances in the understanding of the development of secondary metabolites as they are crucial to seed development, growth, and characteristic flavors. Practical Applications: Tree nuts and seeds are sources of high quality protein and oils worldwide. This review gathers information about more recent studies of the secondary metabolites that are present in these products. The identification and understanding of the mechanism of their formation is needed for expanding the role of tree nuts and related seeds in nutrition and health. A critical review allows for the collection of research on this topic to increase access of the results to those in the field who continue to advance these studies. Nuts and seeds undergo a series of processing steps to produce consumer products. Nuts are harvested from trees, or in the case of peanuts, from plants, either mechanically or by hand. Shelling and cleaning to remove protective outer shells is usually done and then most nuts or seeds are roasted to form desired flavors. Some nuts such as almonds, walnuts, and pecan are often consumed raw. Roasting operations can be either continuous or batch operations. After cooling, nuts are inspected to remove unwanted material and then packaged for retail sale.

Bioactive phytochemicals of tree nuts. Determination of the melatonin and sphingolipid content in almonds and pistachios

“…In turn, the fatty acids vary in chain length (14-30 carbon atoms), degree of unsaturation, and presence or absence of a hydroxyl group on the carbon atom (Canela et al, 2016). Unlike mammalians, plant sphingolipids are mainly cerebrosides (mono-and oligohexosylceramides) containing glucose, galactose, mannose and inositol as head groups (Markham, Lynch, Napier, Dunn, & Cahoon, 2013, Dean, 2018. Health-promoting effects of dietary sphingolipids have been demonstrated in vivo; in particular, their anticancer activity has been documented in a number of animal models (Canela et al, 2016).…”

Breba Fruits Characterization from Four Varieties (Ficus carica L.) with Important Commercial Interest in Spain

“…This fact is not unusual, since protective effects of cell structures against UV radiation are attributed to this compound, as well as a high influence on the coloring of the fruits, where ‘Cuello de Dama Negro’ presented a pulp with a much more intense coloration [ 36 , 37 ]. Cyanidin 3-rutinoside is mainly attributed to antioxidant functions, defense against pathogens, and pigmentation [ 38 , 39 ], so its higher content in ‘Cuello de Dama Negro’, in comparison with the other varieties, would again be related to its specific intense coloration. The results were in line with those reported by Wojdyło et al [ 31 ] for the varieties ‘Colar’, ‘San Antonio’, and ‘Cuello de Dama Negra’ grown under similar conditions.…”

Monitoring changes in the volatile fraction of roasted nuts and seeds by using comprehensive two-dimensional gas chromatography and matrix templates

“…Numerous volatile compounds are generated, mainly through: (i) the Maillard reaction, where nitrogen derivatives are produced, essentially pyrazines, and other compounds such as furans and aldehydes; (ii) the caramelization of sugars, responsible for the appearance, among others, of derivatives of furan; and (iii) the degradation of lipids that, although it is usually associated with the formation of unpleasant aromas, also favors the appearance of certain aldehydes and ketones that provide sweet and fruity notes [ 4 , 5 ]. Other important chemical groups that appear are alcohols, hydrocarbons and certain phenolic derivatives [6] , [7] , [8] . The best way to know the global perception experienced when smelling a product is through a sensory analysis [9] , through the so-called tastings which, however, entail a series of drawbacks, among which the need to use a panel of tasters stands out, trained, and formed by a considerable number of individuals, as well as a high cost (of money and time), among other factors.…”