Flavour chemistry

Code

Course teacher

Associate teachers

Status of the course

Course objectives

Acquisition of basic knowledge of flavour chemistry, understanding of the activation of receptors of smell and taste, knowledge of the structure of organic compounds of the typical flavours and their division, knowledge of the basic mechanisms of flavour formation and the flavour isolation methods.

Course enrolment requirements and entry competences required for the course

Learning outcomes expected at the level of the course (4 to 10 learning outcomes)

After passing the course, students will be able to:
- describe the basic concepts, types of flavours, gustatory active molecule, legal regulations related to the flavour toxicological assessment and allowed concentration of biologically active substances
- illustrate ways of flavour perception (smell and taste), the mechanisms of development of natural flavour, the division of flavouring substances based on the chemical structure
- demonstrate basic procedures of flavour isolation from solid and liquid samples (headspace, volatile, semivolatile and nonvolatile substances)
- identify appropriate mechanisms of flavour origin by specific patterns, particularly flavourings derived from carbohydrates and proteins and lipid oxidation flavours
- propose appropriate methods of the sample processing taking into account the fundamental principles of distillation and extraction and the possibility of artefacts formation, structural linkage between aromatic compounds and suitable mechanism for their origin
- choose the correct chemical approach to solving problems in the field of flavour chemistry, starting from the acquired knowledge in organic chemistry and biochemistry

Course content broken down in detail by weekly class schedule (syllabus)

Introduction to the chemistry of flavour. Classification of flavours. Natural, natural identical and artificial flavouring substances. Flavouring preparations. Thermal process flavourings. Smoke flavour. Blends of flavours. Review of the quality of flavour. (3 hours); A short overview of the development of flavour chemistry. Legal regulations. Natural, natural identical and artificial flavours – differences between the United States and the EU. New EU legislation. (3 hours); Croatian law on flavourings (NN) with emphasis on chemical specifications of flavours and maximum allowed values of biologically active substances in flavoured food. Croatian regulations on food additives (NN). Sweetening agents. Flavour enhancers. (3 hours)
The sense of smell. Activating receptors of smell. The sense of taste - basic taste qualities. Activation of taste receptors. Example of aromagram. (3 hours); Molecules with sensory effects - examples of chemical structures: stinging molecules; molecules for cooling; strong, sharp molecules with heating and hot stimuli, the molecules with the contraction, shrinkage. The taste active molecule - examples of structures: sweeteners (nutritive, nonnutritious sweeteners, natural carbohydrates, noncarbohydrates, artificial sweeteners), salt, acid, bitter and umami substances (monosodium glutamate, inosine monophosphate). (3 hours)
The division of the flavour substances according to the chemical structure: flavouring substances I (C, H, O compounds: alcohols, phenols, acids, ketones, carotenoids, ionones and related compounds, hydrocarbons) - examples; the flavouring substances II (heterocyclic compounds with oxygen: oxiranes, furans, hydrofurans, pyrans and oxepines; heterocyclic compounds with nitrogen and/or sulphur) - examples, flavouring compounds III (compounds containing sulphur: thiols, thioethers, sulphides, heterocyclic compounds with sulphur) - examples (3 hours)
Mechanisms of flavour formation from the starting compounds. Terpenes (biosynthesis through MVA and DXP). Norisoprenoids (the mechanism of degradation of carotenoids). Phenylpropanoic derivatives (shikimate biogenetic pathway). (3 hours); Flavours derived from carbohydrates and proteins. Maillard reactions. Aldol reactions and retro-aldol reactions. Strecker degradations (cysteine, methionine). Comparison of Strecker degradation and Amadori rearrangement. (3 hours); Independent pathways occurrence of Strecker aldehydes. Amadori rearrangement by transamination and Strecker aldehydes formation by decarboxylation of α-oxocarboxylic acids. Strecker degradation and Amadori modelling in the development of flavour and colour. (3 hours); Heterocyclization (formation of furfural, hydroxymethylfurfural, 5-methyl-4-hydroxy-3(2H)-furanone, formyl furol, isomaltol, pyrazine, oxazole and thiazole). Flavours of thermal degradation of vitamin B1. (3 hours); Flavours of lipid oxidation. Triplet and singlet oxygen. Lipid oxidation by radicals (initiation, propagation and termination). Hydroperoxides and hydroperoxides breakup. Lactones. (3 hours); Non-radical lipid oxidation. Enzymatic lipid oxidation (lipoxygenation). Flavours caused by enzymatic reactions and by microorganisms (diacetyl from lactose, the flavours of onion and garlic). (3 hours)
Isolation methods for flavourings. Solvent extraction. Accelerated solvent extraction. Supercritical fluid extraction. The fractionation of the extracts. Concentration of the extracts. (3 hours); Distillation methods. Headspace isolation techniques (static, dynamic). Thermal desorption. Sorption techniques: headspace solid-phase microextraction; headspace extraction and extraction from the stirring stick. (3 hours)
Examples of chemical flavour profiles of selected food products: Honey flavour. Flavour of roasted coffee. Flavour of wine. Flavour of meat products. Cheese flavour. (3 hours)

Format of instruction:

Student responsibilities

Students are required to attend classes (lectures and seminars) and actively participate in the teaching process, which will be evaluated in the final assessment by the weight coefficient of 5%.

Optional literature (at the time of submission of study programme proposal)

K. A. Smith, Advances in Flavours and Fragrances, Royal Chemical Society, 2001.

Quality assurance methods that ensure the acquisition of exit competences

Quality assurance will be performed at three levels:
(1) University Level;
(2) Faculty Level by Quality Control Committee;
(3) Lecturer’s Level.

Other (as the proposer wishes to add)