Consumer perceptions of food and beverage flavour -- Physiological impacts of odour compounds. Thammasat University Library Your cart is empty. Login: Password:. Parker, J.
Elmore and L. Contributor s : Parker, J. Jane K. Elmore, Stephen Methven, L. Material type: Book Call no. ISBN: ; Tags from this library: No tags from this library for this title. Log in to add tags. Includes bibliographical references and index. Log in to your library account to post a comment.
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LC—MS-based methodologies have been proposed to be best suited for the identification of novel bioactive compounds in plant foods because of the compatibility of LC separation with the diversity of metabolites present Johanningsmeier et al. GC—MS-based methods have been broadly applied for the analysis of food volatiles and may also be applied to the study of derivatised, non-volatile polar components such as mono- and di-saccharides, sugar alcohols, organic acids, amino acids, and long-chain fatty acids. Headspace techniques are now regularly being used to study the volatile aroma composition of food products.
Each technique has its own advantages and limitations and these are highlighted in more detail for specific flavour compound groups in Sect. For a more detailed overview of the wide range of methodologies we can refer to the many recent chapters in Antonio Xu et al.
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Feng et al. Kaneko et al. Lee et al. Lin et al. Elmore et al. Moreover, the complexity of the food matrix provides the greatest challenge. Lipids, proteins, and carbohydrates in the food matrix can positively or negatively affect the flavour of food products. The release of aroma compounds from foods is determined by the partition coefficient between the air phase and food matrix and here also between the hydrophobic and hydrophilic phases.
For instance, fat composition, concentration, emulsion characteristics and temperature, can each significantly modify interactions between lipids and small molecules Piraprez et al. The retention of different aroma compounds in lipid matrices is strongly influenced by their molecular weight and chemical structure Piraprez et al. Lipid oxidation produces a variety of aldehydes that can participate in carbonyl—amine condensation and aldol condensations, potentially competing for reactive intermediates with the Strecker aldehydes.
In addition, studies have shown that carbohydrates can also influence the retention and release of volatile flavour compounds Naknean and Meenune Generally, mono- and disaccharides usually increase the vapour pressure, which causes an increase in volatility of flavour compounds relative to water.
Proteins have also been shown to bind covalently to thiols and disulphides Adams et al. Studying the behaviour of these flavour-matrix interactions will enable us to understand better the dynamics of the formation and release of flavour compounds in food. In metabolomics studies, the complexity of food matrices has become a crucial aspect for method development, especially for untargeted analyses.
Non-enzymatic reactions occurring in the formation of aroma compounds during food processing include Maillard reactions, caramelization, oxidative and thermal degradation of lipids, as well as degradation of sugars, proteins, ribonucleotides, pigments and vitamins. Once again, the interactions between degradation products can also result in additional chemical reactions.
The Maillard reaction, lipid degradation and a combination of both are particularly important for aroma formation in process flavours. Louis-Camille Maillard first reported the reactivity of reducing sugars with peptides in Maillard The Maillard reaction is a complex of hundreds of possible reactions. Even with the simplest sugars and amino acids, hundreds of different volatile and non-volatile compounds can be formed. This extremely complex reaction has been the subject of much research by food scientists seeking to discover new mechanisms of formation and to identify new compounds that provide the desired flavour and colour characteristics of heated foods Nursten ; Jaeger et al.
The chemistry has been comprehensively reviewed by Ledl and Schleicher and more recently by Nursten Many authors also reviewed the importance of flavour formation through Maillard reactions in different processed foods Manzocco et al. Hodge divided the chemistry of the browning reaction into three stages, now generally adopted as the three stages of the Maillard reaction.
These are: i the early stage sugar-amine condensation, the Amadori rearrangement ; ii the intermediate stage sugar breakdown and dehydration, Strecker degradation and iii the final stage aldol condensation, aldehyde-amine condensation and formation of heterocyclic nitrogen compounds. Two reactions occur during the early stage, the condensation of an aldose sugar and an amino compound N -glycosylamine formation , and the rearrangement reaction leading to the Amadori compound the N -substituted 1-aminodeoxyketose or the Heyns compound if the reducing sugar is a ketose.
While the first reaction is reversible, the second is not and is thought to be acid-catalysed. There is no formation of any aroma or colour at this stage. Sugar fragmentation and release of the amino group occurs, and Strecker aldehydes, among others, are formed Rizzi ; Fig. These corresponding Strecker aldehydes contain one less carbon atom than the original amino acid Whitfield and can be colourless or yellow.
They are considered important contributors to the aroma of food products. Many patents have been granted which involve Strecker degradation to produce flavouring materials of foodstuff such as maple syrup, chocolate, coffee, tea, honey, mushroom and bread Morton et al. The final stage of the Maillard reaction is comprised of many complex and interconnected reactions of dehydration, fragmentation, cyclization, condensation and polymerisation, in which amino groups again participate.
Heterocyclic ring systems, such as pyridines, pyrazines, pyrroles, and imidazoles, have also been shown to be present in food materials after these reactions Nursten However, little is known about their mechanisms of formation. Here we present a schematic overview of the Maillard reaction, based on Hodge and van Boekel , that shows the main-end products contributing to flavour. The control of Maillard products during food processing is essential to prevent the formation of undesired products like carcinogenic compounds and off-flavours and to facilitate the production of savoury compounds.
For this, we first need to learn more about the chemical reactions and mechanisms during processing conditions. Metabolomics now represents a new approach to help correlate pathway analysis, non-enzymatic conversions and food processing steps Klevorn and Dean Importantly, lipids influence the aroma and flavour of other components, are precursors of odour and flavour compounds and many even have odours and flavours themselves Forss Lipids are generally associated with more negative qualities of food flavour, as they are responsible for rancidity in oils or lipid-containing foods.
However, they can also play a positive role as flavour enhancers depending on product characteristics. For example, short chain fatty acids are mainly responsible for rancid flavours in milk whereas the same acids are essential flavour constituents in cheese. Moreover, lipids also play an important role in food texture i. During food processing, non-enzymatic auto oxidation of lipids may occur, and degradation pathways will lead to the formation of a great number of secondary aroma-related metabolites that can affect flavour.
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Understanding the mechanisms underlying thermal lipid processing needs more attention. Most lipids are hydrophobic, non-polar compounds. Phospholipids and triglycerides are disassembled during heating releasing short-chain fatty acids with reduced saturation. At elevated temperatures, autoxidation of fatty acids occurs and hydroperoxides are produced. This process involves a free radical mechanism which can be divided into three stages: initiation, propagation and termination Fig. The initiation reaction is activated by direct thermal dissociation, metal catalysis or exposure to light, forming hydroperoxides Frankel which are then decomposed via many routes leading to a broad variety of volatile and non-volatile secondary products.
A better understanding of hydroperoxide formation and rearrangement is needed. GC—MS analysis provides information regarding the structures of individual oxygenated fatty acids, typically as methyl esters, isolated from oxygenated triacylglycerols TAGs , while LC—MS techniques allow analysis of intact oxygenated TAGs and yields information on the position of the oxygenated acyl chain on the glycerol backbone Xia and Budge Lipids and their breakdown products are often hugely influential to the overall quality and flavour of food.
Flavour Development Analysis And Perception In Food And Beverages 2014
These compounds can have both a positive or a negative influence on off- flavour. Here we present an overview of the lipid degradation pathway: a provides an overall picture of the different fatty acid degradation routes and b illustrates the complexity using two specific examples of important common fatty acids and their diversity in breakdown products of sensory relevance. Hydroperoxide decomposition forms an alkoxy radical which mostly transforms into aldehydes, ketones, alcohols and furans.
Which products are formed depends on the fatty acids present, the hydroperoxide isomers formed, and the stability of the decomposition products. However, the formation of hydroperoxides is not the only oxidation mechanism involved. According to Schaich , alternative pathways to the hydroperoxide can occur from competing reaction cycles to form peroxides.
These peroxides can then either re-enter the traditional propagation stage or undergo alternate reaction pathways thus increasing the complexity of both the kinetics and the product mixture. Most of the research related to food science has been focused on the autoxidation of the most common relevant acids; oleic acid, linoleic acid and linolenic acid. Frankel and Ho and Chen list the expected decomposition products from linoleate and linolenate hydroperoxides Fig. The rate of autoxidation increases with the degree of unsaturation. An overview of the lipid degradation pathways that lead to flavour formation is shown in Fig.
All of these products are of broad importance in off flavour determination—for example, 2,4-Decadienal is known to be one of the most important flavour contributors to deep-fat fried foods. Both lipid degradation and Maillard reactions lead to the formation of a great number of compounds with a similar range of physicochemical properties. Lipid—Maillard interaction products have been mostly identified in cooked meat, French-fries, peanuts and beverages such as coffee, tea and cocoa.