Lipid Oxidation Essay

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1.3.3 Lipid oxidation
While not a direct outcome of proteinaceous compounds, aldehydes such as hexanal and (E)-2-nonenal have been attributed to the oxidation of lipid components present in the raw material (Aaslyng et al., 1998b). They are often present in much higher concentrations in enzyme hydrolysates and have been correlated to beany off-odours described in numerous literature. Solina et al. (2005) compared the volatile components of soy protein isolate (SPI) and acid-hydrolysed soy protein and concluded that the significantly higher lipid content of SPI was responsible for green or beany odours attributed to high levels of aliphatic aldehydes and ketones. The formation of undesirable lipid-derived products may be minimised by centrifugal
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To obtain highly refined protein hydrolysates, the hydrolysis conditions may be manipulated to promote the formation of desirable taste and aroma components while suppressing potential off-flavours such as bitterness and lipid-derived products. Nevertheless, the refinement process is an arduous task as it involves meticulously characterising the identity and potential relationships between flavour compounds and complex chemical reactions. Moreover, majority of the raw protein sources are terrestrial plant crops which are largely limited by agricultural land, seasonal variation and other commercial uses. Hence, continuous research into the flavour characteristics of protein hydrolysates and exploring novel protein sources are vital in ensuring their sustainable and widespread use as flavouring and flavour-potentiating agents in the food …show more content…
From a nutritional perspective, seaweed is an excellent plant protein source as the levels of essential amino acids meet the FAO/WHO requirements of dietary proteins and exceed the levels in soybean protein, corresponding to 36% of total amino acids (Galland-Irmouli et al., 1999). While lysine, threonine, tryptophan, methionine and cysteine are present in comparatively lower levels, Holdt and Kraan (2011) concluded that their quantities are still higher than those found in terrestrial plants. Lourenço et al. (2002) reported that the levels of isoleucine and threonine in Palmaria palmata are comparable to levels found in legumes, while histidine in Ulva pertusa is present at levels similar to those in albumin. Both aspartic and glutamic acids constitute a large proportion of the amino acid fraction in seaweeds compared to soybeans and eggs, with glutamic acid being the most abundant amino acid in all species (Fleurence, 1999). According to Mabeau et al. (1992), the high proportion of aspartic and glutamic acids are responsible for the unique flavour and taste of

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