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About Food Chemistry

About Food Chemistry#

P.F. Fox, PhD
School of Food and Nutritional Sciences, University College, Cork, Ireland

Importance of Food Chemistry
Foods are very complex chemical systems. Most commodities, e.g., drugs, fuels, metals, glass, ceramics, textiles and paper consist of one, or a few, chemicals, but most natural foods contain hundreds of compounds and its characteristics may be due to a minor rather than to its macro-constituents. Many of a food’s constituents interact chemically or physically during the processing and storage of the food, the results of which dominate the physical and organoleptic properties of the food. Foods are unstable systems being susceptible to chemical, biological and physical deterioration and act as vectors for pathogenic and food-poisoning micro-organisms and of indigenous or contaminating toxins or anti-nutrients. Food safety is of utmost importance and in this respect, at least three aspects are important: (i) freedom from toxins, indigenous, endogenous or contaminants, (ii) freedom from pathogenic and food-poisoning micro-organisms, and, (iii) balance of nutrients.

Food chemistry is the study of composition, chemical processes and interactions of all biological and non-biological components of foods. The principal groups of foods are milk and dairy products, meat, fish, cereals, fruits and vegetables. The main components of foods are carbohydrates, lipids, proteins and water, with lesser amounts of vitamins, minerals, enzymes, additives, flavours and pigments. Food Chemistry also encompasses how foods change under certain processing techniques and ways either to enhance or to prevent changes from happening. An example of enhancing a process is to encourage the fermentation of dairy products with micro-organisms that convert lactose to lactic acid; an example of preventing a process is preventing browning on the surface of freshly cut apples using lemon juice or other acid.

Evolution of Food Chemistry
The scientific approach to food and nutrition evolved from agricultural chemistry in the works of J. G. Wallerius, Humphry Davy and others. Davy published Elements of Agricultural Chemistry, in a Course of Lectures for the Board of Agriculture (1813) in the United Kingdom which went to a fifth edition. One of the pioneers was Carl Wilhelm Scheele who isolated tartaric acid from grapes (1769), lactic acid from sour milk (1780), citric acid from grapes (1784) and malic acid from apples (1785).

The adulteration of foods, frequently with very toxic materials, was widespread up to the end of the 19th Century. This practise was exposed through the work of Frederick Accum, Thomas Wakley (founder of The Lancet) and Arthur Hassall and led to a series of Acts to prevent it [Food Adulteration Act, 1860 (revised in 1862); Sale of Food & Drugs Act, 1875]. The Society of Public Analysts was founded in 1874, with Hassall as its first President; each county in the UK was required to appoint at least one Public Analyst. Food analysis seriously commenced with the enactment of the Sale of Food & Drugs Act 1875 and the appointment of Public Analysts.

Factors that affected the Development of Food Chemistry
The development of colleges and universities worldwide, most notably in the United States, facilitated expansion of food chemistry. Research by Harvey W. Wiley at the United States Department of Agriculture during the late 19th century was a key factor in the creation of the United States Food and Drug Administration in 1906. The American Chemical Society established its Agricultural and Food Chemistry Division in 1908 and the Institute of Food Technologists established its Food Chemistry Division in 1995.

Food chemistry concepts are often drawn from rheology, theories of transport phenomena, physical and chemical thermodynamics, chemical bonds and interaction forces, quantum mechanics and reaction kinetics, biopolymer science, colloidal interactions, nucleation, glass transitions and freezing, disordered or non-crystalline solids, and thus has Food Physical Chemistry as a foundation area.

Foods are subjected to a wide variety of analytical procedures for various reasons. A food sample is very rarely subjected to the full range of analyses; the analytical methods used depend the objective of the investigation

Food Constituents
The principal constituents of foods, water, carbohydrates, proteins and lipids, have been studied thoroughly in general by chemists and biochemists and in food systems by food chemists since the mid-19th century.

Water
Water is the principal constituent in most foods, ranging from about 50 to 75% in meat (depending on fat content), about 85% in milk to 95% in many fruits and vegetables. Water is a simple molecule, H2O, with very interesting properties, which have been the subject of research in various aspects of science for a very long time. Water is the universal solvent in biological systems, including foods. It is an excellent medium for bacterial growth and food spoilage if it is not properly processed. The reactivity of water is usually expressed as water activity (aw) which is defined as the ratio of the vapour pressure exerted by water in a food system to that of pure water at the same temperature. Water activity is very important for the shelf-life of many foods and one of the keys to food preservation is reduction of the amount of water or water activity by dehydration, freezing, refrigeration or the addition of sugar or salt which reduce water activity. The significance of water in foods is a very active area of research.

Carbohydrates
Carbohydrates, ranging in size from monosaccharides (altohexoses, ketohexoses, altopentoses and ketopentoses) through disaccharides and oligosaccharides (3 to 10 monosaccharides) to polysaccharides are major constituents of living systems and foods and have been popular research subjects since the 17th century.

Monosaccharides
There are 8 aldohexoses, two of which, glucose and galactose, are major constituents of foods and 4 ketohexoses, one of which, fructose, is a major constituent of foods. Glucose was isolated by Andres Marggraf in 1747. Its structure and that of many other monosaccharides was described by Emil Fischer in the 1890s; fructose was discovered by Augustin-Pierre Dubrufacet in 1847 and galactose by Louis Pasteur in 1856.

  • Disaccharides
    Three principal disaccharides occur in foods, sucrose, maltose and lactose. Sucrose, which contains glucose and fructose, is by far the principal food disaccharide, It has been prepared from sugar cane or sugar beet for more than 2,000 years. Marggraf discovered sucrose in sugar beet in 1747 and described its structure. Current production is about 190 million tonnes per annum. Lactose, which consists of glucose and galactose, is unique to milk; it was first isolated by Fabrizio Bartoletti in 1633, identified as a sugar by Carl Wilhelm Steele in 1780 and its structure determined by Emil Fischer in 1894. About 450,000 tonnes of lactose are produced per annum. It has many interesting properties. Although maltose, which contains two molecules of glucose, has been used since ancient times in China and Japan, it does not occur naturally in large quantities and is produced commercially by the hydrolysis of starch. Its structure was confirmed by Cornelius O’Sullivan, a brewer, in 1872. Maltose is one of the sugars produced from starch during the malting step in the production of beer and alcoholic spirits and serves as the substrate for yeast with the production of ethanol.
  • Oligosaccharides
    Oligosaccharides (OSs) are polymers of 3 to 10 monosaccharies in quite complicated structures. Generally, they occur at low coneentrations and there are no rich natural sources. One of the best sources is human milk which contains about 200 OSs at a total concentration of about 10 to 25 mg per 100 ml. Elephant milk also contains a fairly high level but the milk of other species contains a low level of OSs. The OSs in bovine milk partition into the whey from which they can be concentrated by nanofiltration. OSs possess a number of important biological functions and are attracting considerable research interest.
  • Polysaccharides
    The principal polysaccharides in foods are starch and glycogen, with lesser amounts of dextran, cellulose, pectin, agar and xanthan gum.

Starch, the principal storage carbohydrate in food plants (eg., cereals and potatoes), is a large polymer of glucose (several thousand units) linked by α-1-4 glycosidic bonds Two types of polymer occur, amylose (about 20%) and amylopectin; the former is linear while the latter has some branches. Large amounts of starch are produced, mainly from cereals for use as food additives, mainly as thickeners in soups, gravies, etc. They are also used for the production of glucose, maltose and oligosaccharides by enzymatic or acid hydrolysis. Starches may also be chemically modified.

Glycogen, the principal storage carbohydrate in animal cells, is also a large polymer of glucose linked by α-1-4 glycosidic bonds; it is more highly branched than starch. Glycogen is catabolized to lactic acid in meat post-mortem and therefore has a major effect on the properties and quality of meat, Glycogen is not produced commercially.

Dextrans are also polymers of glucose, linked by α-1-6 glycosidic bonds produced by micro-organisms, especially lactic acid bacteria. . Their principal uses are in medicine as blood extenders and in microsurgery. Dextrans have been known for their viscosifying, emulsifying, texturizing and stabilizing attributes in food applications. Dextrans have the potential to be used as a novel ingredient to replace the commercial hydrocolloids in bakery and other food industries. Prebiotic oligosaccharide production by hydrolysis of dextran is a rather new field, attracting research and industrial attention.

Cellulose, a linear polymer of glucose molecules linked by β 1-4 glycosidic bonds, is the principal structural element in plant tissue. It is not digestible by humans and causes reduction of food quality. It was discovered in 1838 by Anselme (French), who also determined its structure. It is used to produce various artifical polymers, eg., rayon and cellophane. Carboxymethyl (CMC) is a chemically modified form of cellulose in which a carboxy group (CH3COOH) group is esterified on some of the –OH groups of cellulose. CMC is used in foods under the E Number E466 or E469, as a viscosity modifier or thickener and to stabilize emulsions in various products, including ice cream. It is also a constituent of many non-food products.

Pectin is a structural acidic heteropolysaccharide contained in the primary cell walls of plants. Its main component is galacturonic acid, a sugar acid derived from galactose, linked by α 1-4 glycosidic bonds. It was first isolated and described by Henri Braconnet in 1825. It is extracted commercially from citrus fruits and used in foods as a gelling agent, especially in jams and jellies but also in dessert fillings, medicines, sweets, as a stabilizer in fruit juices and milk drinks, and as a source of dietary fiber.

Agar is a mixture of two components, a linear polysaccharide, agarose, and a heterogeneous mixture of smaller molecules called agaropectin, with agarose making up about 70% of the mixture. Agarose is a linear polymer of agarobiose, a disaccharide consisting of D-galactose and 3,6-anhydro-L-galactopyranose. Agaropectin is a heterogeneous mixture of smaller molecules that occur in lesser amounts, and is made up of alternating units of D-galactose and L-galactose modified with side-groups, such as pyruvate and sulfate. Agar forms the supporting structure in the cell walls of certain species of red algae and is released on boiling.

Agar may have been discovered in Japan in 1658 by Mino Tarōzaemon, an innkeeper in Kyoto, who is said to have discarded surplus seaweed soup and noticed that it gelled on cooling. Over the following centuries, agar became a common gelling agent in several Southeast Asian cuisines. Agar was first subjected to chemical analysis in 1859 by the French chemist AnselmePayen, who had obtained agar from the marine algae Gelidium corneum Beginning in the late 19th century, agar began to be used heavily as a solid medium for growing various micro-organisms

Agar can be used as a laxative, an appetite suppressant, a vegetarian substitute for gelatin, a thickener for soups, in fruit preserves, ice cream and other desserts.

Xanthan gum was discovered by A. R. Jeanes, United States Department of Agriculture in the 1960s It was approved for use in foods in 1968, with E number E415 and CAS number 11138-66-2. Xanthan gum is produced by Xanthomonas campestris. It is composed of pentasaccharide repeat units, comprising glucose, mannose and glucuronic acid in the molar ratio 2:2:1.

Xanthan gum is used in wide range food products, such as sauces, dressings, meat and poultry products, bakery products, confectionery products, beverages and dairy products. It helps to create the desired texture in ice cream, thicken commercial egg substitutes made from egg whites, to replace the fat and emulsifiers found in egg yolks. In gluten-free baking, xanthan gum is used to give the dough or batter the stickiness that would otherwise be achieved with gluten, In most foods, it is used at concentrations of 0.5% or less.

Lipids
The term lipid comprises a diverse range of molecules and is a catch-all for water-insoluble (ether-soluble) or non-polar compounds of biological origin, including triglycerides, waxes, fatty-acids, phospholipids, sphingolipids, glycolipids, retinoids and steroids. In 1823, Michel Chevreul discovered the composition of stearn and olein, the solid and liquid fractions of fats and isolated stearic and oleic acids. In 1844, T.J Pelouze synthesized a lipid, tributyrin and in 1853, M. Bertholot synthesized tripalmitin and tristearin. The principal lipids are triglycerides which represent 98% of the total lipids in milk. Triglycerides are esters of the trihydroxy alcohol, glycerol, and three carboxylic acids (referred to as fatty acids, FAs). Most lipids contain characteristic amounts of about 20 FAs; up to 400 FAs have been reported in bovine milk, most of which are at low or trace concentrations. Lipids are important constituents of foods as sources of energy and food quality (flavour and texture) and methods were developed early for determination of the lipid content of foods. The first method for the determination of fat in foods (and tissues) was developed by Franz von Soxhlet in 1879 (he also proposed the pasteurisation of milk in 1886). Since this method is not applicable to liquid samples, including milk, a modified ether-extraction method was developed by B. Roese in 1884 and modified by E. Gottlieb in 1892, which is still the standard method for determination of the fat content of milk and dairy products. The Roese-Gottlieb method is slow and not suitable for the analysis of large numbers of samples, such as at creameries. Two principles were used in such situations: (i). the amount of butter produced from a representative sample of milk or cream, or (ii). the volume of fat released on dissolving the milk protein and destabilising the fat emulsion initially by concentrated NaOH, which was soon replaced by conc. H2SO4 as used in the methods of S.M. Babcock and N. Gerber, developed in 1890 and 1891, respectively.

Butter was the most expensive fat, and consequently was the target for adulteration with cheaper fats/oils. The fatty acid profile of milk fat is unique and before it became possible to determine its total fatty acid (FA) profile (by gas chromatography around 1950) methods were developed to determine characteristics of the FA profile, i.e.

  • The Reichert-Meissl number, a measure of the volatile water-soluble FAs, mainly butanoic acid.
  • The Polenske number, a measure of the volatile water-insoluble FAs, mainly hexanoic and octanoic acids.
  • The Kirschner number, a measure of the soluble silver salts of the FAs, butanoic acid

Milk fat has high R-M and Kirschner numbers but a low Polenske number; coconut and palm oils have low R-M and Kirschner numbers and a high Polenske number. For all ather fats and oils these three numberes are very low.

Most foods contain some lipids which affect the texture, flavour and stability of the food. Some isolated lipids are also produced commercially as food ingredients or for cooking, eg., deep-fat frying; such products include butter, butteroil (ghee), lard and tallow from pig and cattle carcasses, respectively, plant oils (maize, sunflower, safflower, rapeseed, soybean olive, palm) and fish oils.

Lipids and lipid-rich foods are susceptible to two causes of deterioration: hydrolytic and oxidative rancidity. The former is caused by enzymes (lipases) indigenous to the food or produced by contaminating microorganisms. Oxidative rancidity is caused by the addition of free-radical oxygen to the double bond(s) of fatty acids and through a series of steps forming highly flovoured carbonyl compounds. The reaction is catalyzed by light, metals (Fe or Cu) or enzymes (lipoxygenases).

Most lipids are consumed as indigenous components of foods: milk and dairy products, meat and fish or cereal-based products but extracted/isolated lipids form three very important products also: (i) cooking fats, especially oils and butter, (ii) as ingredients for bakery products, especially oils and butter and lard (shortenings), and (iii) spreads, butter and hydrogenated vegetable oils; the rheology of butter and other spreads and their modification, eg., by interesterification has been a very active area of research.

Food lipids are active subjects of research of which the following are the principal areas: fatty acid profile (probably now known for most cases), hydrolytic and oxidative stability. Milk lipids are a special case; in milk the lipids occur as globules (0.2 – 20 µm in diameter, mean ~ 4µm), stabilized by a membrane composed of special proteins and phospholipids, derived from the apical membrane of the secretory mammary cells. The creaming of milk fat globules and the composition and structure of the milk fat globule membrane are active areas of research. The rheological properties and spreadability of butter and its modification were major research subjects and still are of some interest.

Most lipids have some polar character in addition to being largely non-polar. Generally, the bulk of their structure is non-polar or hydrophobic, meaning that it does not interact well with polar solvents like water. Another part of their structure is polar or hydrophilic and tend to associate with polar solvents like water. This makes them amphiphilic molecules (having both hydrophobic and hydrophilic portions). In the case of cholesterol, the polar group is a mere -OH (hydroxyl or alcohol).

Lipids act as carriers of the fat-soluble vitamins, A, D, E andK.

Proteins
Proteins are highly complex molecules that are present in all living organisms and foods derived therefrom. The importance of proteins was recognized by chemists in the early 19th century, including the Swedish chemist Jöns Jacob Berzelius, who in 1838 coined the term protein, a word derived from the Greek prōteios, meaning “holding first place.” Proteins are species-specific; that is, the proteins of one species differ from those of another species. They are also organ-specific; for instance, within a single organism, muscle proteins differ from those of the blood or liver. Owing to their biological importance, proteins have been the subject of research by chemical, biochemical, medical and food scientists for more than 100 years and are now well characterized. A protein molecule is very large polymer of many hundreds of amino acids, about 20 different forms of which occur naturally in proteins, linked by peptide bonds. The sequence of amino acids is referred to as the primary structure of a protein but the polymer folds into certain conformations, referred to as the second and tertiary structures and many proteins aggregate/associate to form quaternary structures. Many proteins contain/bind inorganic atoms, eg., calcium, iron, copper, zinc, molybdenum or phosphate which have major effects on their properties.

In foods, proteins are essential for growth and survival, and requirements vary depending upon a person's age and physiology. Protein is commonly obtained from animal sources: eggs, milk, meat and fish, and plant sources, eg., nuts, grains and legumes. The unique physicochemical and functional properties of foods depend mainly on the proteins it contains. Research on food proteins falls into the following principal aspects: quantitation, fractionation and isolation, structure and function, characterization and denaturation.

Proteins contain about 16% nitrogen and determination of nitrogen content was the original, and still is the reference, method for the quantitation of proteins in foods and tissues. The first method was developed in 1833 by Jean Baptiste Dumas, followed in 1873 by Johann Kjeldahl. These methods are still the reference methods for determination of the concentration of protein in food products although they have been replaced by more rapid methods for routine applications. These include absorption of UV light at 280 nm by the aromatic amino acids contained in proteins (this principle is not used for foods), dye binding methods which react with certain amino acids and recently by IR spectrophotometric principles, Research in this area continues.

The fractionation and isolation of proteins commenced in the late 19th century. Various chemical methods based on differential solubility were developed initially but these have been replaced in many cases by various forms of chromatography (adsorption, ion exchange, size exclusion, hydrophobic, affinity, etc.). Preparative gel electrophoresis, including electroblotting, is very useful for the small-scale isolation of proteins. Probably, the earliest fractionation of a food protein system is that of the Swedish chemist Olav Hammarsten in 1880 for the fractionation of milk proteins by isoelectric precipitation of the caseins; this principle is still used for the laboratory- and industrial-scale fractionation of milk proteins.

Characterization of proteins

Proteins are very large complicated molecules and their characterization requires a number of techniques. The most basic step involves determination of the amino acid composition which requires hydrolysis of the protein by concentrated (6 N) acid (HCl) at 120 oC for about 6 h. The hydrolyzate is analysed by ion exchange chromatography, for which a dedicated instrument, an amino acid analyzer, has been developed. The next step is determination of the sequence of amino acids (the primary structure) in the protein. Basically, this involves cleaving off one amino acid at a time from the carboxy terminal, using a decarboxylase enzyme, or from the amino terminal using an aminopeptidase. A typical protein is too large to determine the complete sequence at once and it is necessary to initially cleave the protein into a set of polypeptides using a proteinase of known specificity. The peptides are fractionated and the AA sequence of each determined. The peptides are then placed in order using a second set of overlapping peptides.

Depending on its primary structure, the polypeptide adopts specific secondary, tertiary and quaternary structures (conformations). These higher structures determine the functionality and overall properties of a protein and are characterised by techniques such as circular dichroism, optical rotary dispersion, viscosity and light scattering. Many food processing operations alter these native structures (i.e., cause denaturation) and alter the physico-chemical properties of the protein. Quantifying the extent of protein denaturation is a fairly routine procedure in food analysis and can be assessed by changes in solubility, optical or biological properties.

The principal food groups contain several proteins with different structures and characteristics. These systems have been studied intensely for about 100 tears and are now well characterized chemically, physically and biologically but are still the subjects of research.

Enzymes
Enzymes are proteins which function as biochemical catalysts for the various processes that occur in biological systems. Enzymes, which may be indigenous, endogenous or exogenous in a food, play very important roles in food processing, quality and stability. The indigenous enzymes are constituents of the living tissue from which the food is produced, some may cause spoilage, e.g., lipase and plasmin, have anti-bacterial properties, e.g., lysozyme, lactoperoxidase or xanthine oxidoreductase, serve as markers of mastitis, and hence of quality, e.g., N-acetyglucosaminidase, and especially serve as markers of heat treatment, and hence of safety or quality, e.g., alkaline phosphatase, lacotperoxidase, -glutamylpeptidase and catalase. The isolation, characterisation and quantitation of indigenous enzymes in milk have been an important research activity for more than 100 years; lactoperoxidase was isolated from milk by C. Arnold in 1881, i.e.., before the word “enzyme” was coined and before it was known that enzymes are proteins; it is now known that milk contains about 60 indigenous enzymes. Today, several standardised and automated colourimetric or fluorometric assay methods are used routinely for the indigenous enzymes.

The endogenous enzymes are produced by micro-organisms that grow in the food and secrete enzymes into the environment or release intra-cellular enzymes after death and lysis. Most of these enzymes have negative effects on food quality but some have desirable/essential effects, eg., in fermented foods such as cheese, fermented meats or fermented vegetables.

The exogenous enzymes are those added to foods to induce specific changes. Examples include rennets used in the production of rennet-coagulated cheeses (~75 % of all cheese), proteinases for the tenderization of meat or chill-proofing of beer, malt in the production of beer, amylase in baking, lipases in the production of certain cheeses or the modification of lipids., cellulases in the clarification of fruit juices.

Study on various aspects of enzymes is a very active area of Food Chemistry.

Vitamins
Vitamins are nutrients required in small amounts for essential metabolic reactions in the body. The term vitamin is derived from the word vitamine, coined in 1912 by the Polish biochemist, Casimir Funk, who isolated a complex of micronutrients essential to life, all of which he presumed to be amines. When this presumption was determined not to be true, the "e" was dropped from the name. All vitamins, 13 for humans, were discovered (identified) between 1913 and 1948. The vitamins are classified either as fat-soluble (A, D, E and K) or water-soluble, 9 B vitamins). An adequate supply of vitamins can prevent diseases such as beriberi, anemia and scurvy while an overdose of vitamins can produce nausea and vomiting or even death.

Apart from determining the concentration of vitamins in foods and their destruction by various food-processing operations, food chemists probably do not engage in research on vitamins. However, Vit E is a potent anti-oxidant, Vit C may function an anti-oxidant or pro-oxidant depending on its concentration. As a precursor of carotene, Vit A affects the colour of foods and does riboflavin (Vit B2).

Inorganic elements (minerals)
Dietary minerals in foods are numerous and diverse with many functions but some trace elements can be hazardous if consumed in excessive amounts. Minerals with Recommended Daily Allowance (RDA) of more than 200 mg/day include calcium, magnesium and potassium; important trace minerals (RDA less than 200 mg/day) are copper, iron and zinc. These are found in many foods, and may also be taken in dietary supplements.

Many of the inorganic elements are components of proteins, including enzymes; others are present in free form. The functional properties of metal-containing proteins is very strongly influenced by the presence of the metal, e.g., casein, myoglobin, hemoglobin and several enzymes. Some metals, eg., Fe and Cu are pro-oxidants of lipids.

Determination of the concentrations of minerals in foods is a routine study, usually accomplished by atomic absorption spectroscopy. The effects of minerals on the properties of proteins and the stability of lipids are substantial research subjects. The physiological function of minerals, which is undertaken by nutritionists, is also a major research area.

Food Analysis
During the 20th Century, a progression of increasingly more sophisticated techniques for the compositional analysis of foods and the characterization of food constituents have been developed. Depending on the objective, any one of several analytical principles and almost all physical, chemical, biological, microbiological and sensory/organoleptic methods may be used in food analysis. Some methods have been developed specifically for food analysis but most are generally-applicable methods, modified, if necessary, for application to foods. Some methods are used in food factory laboratories for quality control/assurance of the product and/or process, others are used primarily in industrial or academic/institutional laboratories to characterize the composition, properties and functionality of foods and food constituents.

The authentication of foods is very important for the avoidance of fraudulent practices; as mentioned above, this was the principal reason for introducing food legislation in the 19th century. Important examples of adulteration in the dairy industry are: addition of water to milk (detected and quantified by elevation of the freezing point), adulteration of butter with cheaper vegetable fats (detected and quantified by fatty acid analysis) or adulteration of sheep, goat or buffalo milk with cheaper bovine milk [accomplished by gas chromatography (GC), polyacrylamide gel electrophoresis, immunological principles or molecular biology techniques]. A recent challenge in the area of food adulteration is the detection of genetically modified micro-organisms (GMOs) or the products of GMOs in foods, a practice prohibited in many countries; this is best accomplished by using molecular biology techniques involving polymerized chain reaction (PCR).

A very wide range of characterization techniques have been used. The classical techniques of organic chemistry for elemental analysis, functional group determination, mass determination by various methods and infrared spectroscopy have been used to characterise low MW compounds, e.g., sugars, lipids, amino acids and vitamins. Various forms of chromatography have been used to identify unknown compounds by comparison with known standards. Electrophoresis may also be useful, especially immunoelectrophoresis. Initially, mass spectrometry was used mainly to identify low MW, volatile compounds, usually in GC eluates, but mass spectrometers are now available which can be used to determine the mass of very large molecules, e.g., proteins.

The principal constituents of most foods are macromolecules, lipids, polysaccharides and proteins. Characterisation of these involves identification of the molecular units and bonds by which they are polymerised. In the case of proteins, the amino acid composition and the sequence of amino acids (primary structure) are key characteristics and are now determined routinely by chromatographic methods

Food Quality
For most consumers, the ultimate criteria of food quality are its sensoric properties, colour/appearance, flavour (aroma/taste) and texture. These properties can be assessed subjectively using a trained or untrained taste panel in-house or at dedicated laboratories; probably all food producers engage in some form of sensoric assessment of their products and this work may become highly scientific with large food processors or food marketing companies. An important aspect of sensory analysis involves comparison of a company’s products with those of its competitors. Trained taste panels are subjective, expensive to operate and are limited as to the number of samples they can assess at a sitting. Consequently, attempts have been made for at least 50 years to develop objective methods for quantifying food flavour, more usually aroma, by analysing the volatiles released from a sample of the food; this has become increasingly sophisticated over time and has involved GC, GC-MS, olifactory-GC, proton-transfer-reaction mass spectrometry (PTR-MS), the electronic nose, etc. Colour may be quantified relatively easily using colourimetres and various aspects of texture may be quantified by rheological methods integrated as texture profile analysis (TPA) using conditions that simulate the mastication of a piece of food in the mouth; such objective measurements of food texture are essentially confined to research laboratories. Food producers usually rely on subjective assessment of food texture by trained or untrained panellists.

Food processors modify the flavour of foods by the addition of salt, sugar or an acid which also function as preservatives. Vanilla is used to modify the flavour of ice cream. A range of esters are used to simulate or enhance natural flavours, eg., manzate (apple), diacetyl, acetion (buttery), isoamyl acetate (banana), methyl anthranlate (grape), ethyl decadienoate (banana) and limonene (orange).

Umami or “savory” flavourants, commonly called flavour enhancers, are largely based on amino acids and nucleotides and are usually used as sodium or calcium salts. Umami flavourants approved by the European Union include:

Glutamic acid salts
This amino acid's sodium salt, monosodium glutamate (MSG), is one of the most commonly used flavour enhancers in food processing. Mono- and di-glutamate salts are also commonly used.
Glycine salts
Simple amino acid salts typically combined with glutamic acid as flavour enhancers
Guanylic acid salts
Nucleotide salts typically combined with glutamic acid as flavour enhancers
Inosinic acid salts
Nucleotide salts created from the breakdown of AMP, due to high costs of production, typically combined with glutamic acid as flavour enhancers
5'-ribonucleotide salts
Nucleotide salts typically combined with other amino acids and nucleotide salts as flavor enhancers

Certain organic and inorganic acids, eg.acetic, ascorbic, citric, fumaric, malic, lactic, phosphoric and tartaric, may be used to enhance sour tastes; each acid imparts a slightly different sour or tart taste that alters the flavor of a food.

Food colouring may be added to enhance or change the colour of a food for sensory purposes. Common examples are annatto (from the annatto bean, Bixaorellana) for cheese, a red dye ( eg., FD&C Red No 40, or Allura Red AC) for ketchup, or Caramel (prepared by heating a sugar) , which is the most widely used food colouring, eg., for soft drinks, soya sauce and pickles.

Digestibility and Nutritional value of Foods
In addition to the above more or less widely applicable analytical methods, numerous specific methods are used only in certain cases, eg., digestibility by in vivo or in vitro methods that simulate in vivo digestion; toxicity testing in vivo or using tissue cultures and assessing the nutritional quality of proteins by in vivo feeding trials.

Conclusion/Summary
In this article I have attempted to demonstrate that Food Chemistry is a very diverse and complex subject. A very wide range of chemical, physical and biological methods are used to characterize a wide range of small and large molecules which usually occur in mixtures and must be isolated and purified before study. Many food processing operations induce interactions and changes which are important subjects of study in their own right.

FoodChem Board Members#

Patrick F Fox, PhD

Advisory Board

School of Food and Nutritional Sciences, University College, Cork, Ireland

Fulgencio Saura-Calixto, PhD

Advisory Board

Food Companies Scientific Advisor, Former Research Professor, ICTAN-CSIC, (Spanish National Research Council), Madrid, Spain

Pei Chen, PhD

Advisory Board

Research Chemist, USDA, Washington D.C

Navam Hettiarachchy, PhD

Advisory Board

Department of Food Science, Institute of Food Science and Engineering, University of Arkansas, AR

Pingfan Rao, PhD

Advisory Board

Professor and Director of CAS.SIBS-Zhejiang Gongshang University, Joint Center for Food and Nutrition Research, Fuzhou University of China, China


FoodChem Experts#

Fulgencio Saura-Calixto, PhD

Keynote Speaker

Nutriantioxidants and Science FDI (Scientific Advisor), Former Research Professor, CSIC ( Spanish National Research Council), Spain

Jan A. Delcour, PhD

Keynote Speaker

Professor and Head of the Laboratory, Katholieke Universiteit Leuven, Belgium

Joe Vinson, PhD

Keynote Speaker

Emeritus Professor of Chemistry, University of Scranton, PA

Pei Chen, PhD

Keynote Speaker

Research Chemist, USDA, Washington D.C

Eva Reinhard, PhD

Keynote Speaker

CEO Agroscope, Federal Department of Economic Affairs, Bern, Switzerland

Navam Hettiarachchy, PhD

Keynote Speaker

Department of Food Science, Institute of Food Science and Engineering, University of Arkansas, AR

Pingfan Rao, PhD

Keynote Speaker

Professor and Director of CAS.SIBS-Zhejiang Gongshang University, Joint Center for Food and Nutrition Research, Fuzhou University of China, China

Nikolai Kuhnert, PhD

Keynote Speaker

Professor of Chemistry, Department of Life Sciences & Chemistry, Jacobs University Bremen gGmbH, Germany

Christine Morand, PhD

Keynote Speaker

Research Director, National Institute for Agricultural Research (INRA), France, & Editor-in-Chief of Food & Function.

Franco Pedreschi, PhD

Keynote Speaker

Professor of Chemical Engineering and Bioprocesses, Pontifical Catholic University of Chile (UC), Chile


FAQ/Networking

MEET THE EXPERTS

Meet the expert’s forum provides an opportunity to students, company representatives, start-ups and agencies to interact with experts and decision-makers at FoodChem-2021 to solve the complex research problems and collaborate with them to potential partners.

INVESTMENT OPPORTUNITES

Industry prospectors are looking for breakthrough technologies that are ready for licensing, corporate partnering, or investment opportunities. This can include prototypes, demonstrations, and display booths to showcase your innovative solutions at FoodChem-2021. Pitch your idea to an industrial expert jury to raise the capital you need to get started.

CORPORATE PARTNERING

FoodChem- 2021 help commercialize your innovations and build your business development pipeline through corporate partnering. We will arrange one-on-one partnering meeting on request. We will share all the conference attendees list with you, a month before the conference and arrange for one-on-one meeting with selected corporate representatives.

STUDENT MARKETING

FoodChem-2021 not only open doors to your career, but also open your eyes to future opportunities, new cultures, and international perspectives. With the majority of the students interested in doing higher studies abroad, students' marketing forum provides an opportunity for Postgraduate and Undergraduate students to have formal communication with University representatives from around the world. Postgraduate student recruitment is increasingly becoming a strategic priority for higher education institutions. FoodChem-2021 provides an excellent networking opportunity for potential collaboration with businesses and organizations for students.