Introduction to Food Chemistry

• Food chemistry studies the chemical processes of biological and non-biological components in food.
• It dates back to the 1700s with important discoveries in food chemicals.
• Food undergoes changes during handling, processing, and storage, which Food chemistry studies.
• This field focuses on food safety, quality, flavor, texture, aroma, and temperature effects.
• Food chemistry is closely related to chemistry, biochemistry, botany, zoology, and microbiology.
• It applies chemistry to understand and control chemical systems in food.
• The goal is to improve nutritional value, safety, and culinary presentation.
• Food chemistry provides the molecular background for understanding food and its interactions with the human body.
• Key study areas include defining food chemistry, its history, food components, quality and safety properties, chemical reactions affecting food, cause-and-effect relationships in food processing, and applications.

What is Food Chemistry?

• Understanding food science is vital before delving into food chemistry.
• Food science studies the physical, chemical, and biological properties of foods, forming the basis for food processing and preservation.
• It is a branch of biological science, integrating microbiology, chemistry, biology, and engineering.
• Food chemistry is a key part of food science focused on the composition, properties, and chemical changes in food during handling, processing, and storage.
• It is similar to biochemistry, focusing on carbohydrates, lipids, proteins, water, vitamins, minerals, enzymes, food additives, flavors, and colors.
• It uses knowledge from various sciences to study and control biological substances in food effectively.
• The primary interests include reproduction, growth, and changes that foods undergo.
• It encompasses how food products change under certain food processing techniques.
• Enhancing fermentation to converts lactose to lactic acid is an example of enhancement.
• Preventing browning on apples with lemon juice is an example of prevention.
• Professionals in food chemistry study biological substances in postharvest physiology of plants and postmortem physiology of muscle and their reactions to environmental conditions.
• Also studies disrupted food tissues (flour, juices, manufactured foods), single-cell foods (eggs, microorganisms), and milk.
• Food chemistry shares common aspects with biology and is important to mankind.

History of Food Chemistry

• The 18th and 19th centuries were transformative, with food science emerging as a separate discipline in the second half of the 19th century.
• Chemistry developments laid the groundwork for food chemistry.
• French chemist Lavoisier established combustion principles/organic analysis, determined alcohol composition, reported organic acids
• Swedish pharmacist Scheele discovered chlorine, glycerol, and isolated citric and malic acid.
• Liebig perfected analytical methods and classified foods as nitrogenous/non-nitrogenous.
• His 1847 book, "Researches on Chemistry of Food," is an early food chemistry text.
• Louis Pasteur's discovery of microorganisms advanced the field due to knowledge of fermentation processes.
• Newer analytical methods and progress in physiology/nutrition led to the existing knowledge of food's chemical constituents until the end of the 19th century.
• The Industrial Revolution led to public health issues, poor food quality, and adulteration due to expansion.
• Institutions were established to control food composition, starting in Amsterdam and spreading across Europe and North America.
• Food chemistry led to agricultural units, control laboratories, research institutions, journals, and specialized education programs.

Composition of food

• Food is composed of major components like water, carbohydrates, proteins, and lipids, along with vitamins, minerals, colorants, flavors, bioactive substances, and food additives.

Water in Food

• Water is a major component in food, ranging from 50% in meat products to 95% in tomato products.
• If not processed well, it can cause bacterial growth and food spoilage.
• The measurement of the water activity is an important point in the shelf life of food during processing.
• Reducing water or altering the water's characteristics enhances shelf-life.
• Methods include dehydration, freezing, and refrigeration.

Carbohydrates

• A carbohydrate is a biological molecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms.
• The simplest version of a carbohydrate is a monosaccharide which possesses carbon, hydrogen, and oxygen in a 1:2:1 ratio under a general formula of CnH2nOn where n is a minimum of 3.
• Glucose is an example of a monosaccharide, and also fructose.
• A chain of monosaccharides form to make a polysaccharide.
• Such polysaccharides include pectin, dextran, agar, and xanthan.

Proteins

• Proteins are macromolecules consisting of one or more long chains of amino acid residues.
• They also play a fundamental role in the structure and function of cells and consist mainly of carbon, nitrogen, hydrogen, oxygen, and some sulphur.
• They may also contain iron, copper, phosphorus, or zinc.
• Food proteins are easily digestible, nontoxic, nutritionally balanced, functionally useable, abundant, and sustainable agriculturally.
• Protein commonly comes from animal origins: eggs, milk, and meat.
• Nuts, grains, and legumes provide vegetable sources of protein, and combining vegetable sources achieves complete protein nutritional quotas.

Lipids

• Lipids comprise a range of molecules and includes water-insoluble/nonpolar compounds of biological origin.
• These include waxes, fatty acids (including essential fatty acids), fatty-acid derived phospholipids, sphingolipids, glycolipids and terpenoids such as retinoids and steroids.
• Some lipids are aliphatic molecules; others have ring structures, some are aromatic/flexible/rigid.
• Lipids have polar character in addition to being largely nonpolar.
• Their structure is nonpolar/hydrophobic ("water-fearing"), meaning it does not interact well with polar solvents like water.
• The structure is polar/hydrophilic ("water-loving") and will tend to associate with polar solvents like water making them amphiphilic
• Lipids in food include the oils of corn, soybean, from animal fats, and parts of many foods such as milk, cheese, and meat.

Vitamins

• Vitamins are organic compounds vital for metabolic reactions, broken down in nutrition as water/fat-soluble.
• They are necessary for normal growth.
• A shortage of them in the body results in deficiency diseases
• From a food chemistry point of view several of the vitamins influence the chemical nature of food, by functioning as reducing agents, radical scavengers, reactants in browning reactions, and as flavor precursors.
• Maximize retention of vitamins in food.

Minerals

• Minerals are naturally occurring inorganic substances in foods that are large and diverse with many of them required for the normal functioning of the body.
• They occur in different chemical forms commonly referred to as species and include compounds, complexes, and free ions.
• They're present in low concentrations with key functional roles in both living systems and foods.
• Minerals are found in foods such as meat, cereals, fish, milk and dairy foods, vegetables, fruit and nuts.

Enzymes

• Enzymes are biochemical catalysts in converting processes from one substance to another.
• They reduce the amount of time and energy required to complete a chemical process.
• Many aspects of the food industry use catalysts, including baking, brewing, dairy, and fruit juices, to make cheese, beer, and bread.

Colour

• Food coloring is added to change the color of any food substance.
• It is mainly for sensory analysis purposes, and simulates the natural color as perceived by the customer, such as red dye in ketchup.
• Caramel is a natural food dye and industrial form called caramel coloring.
• Caramel is the most widely used food coloring in soft drinks, soy sauce, bread, and pickles.

Flavours

• Flavour in food is important in how food smells and tastes to the consumer, especially in sensory analysis.
• Some of these products occur naturally like salt and sugar.
• Flavour chemists develop many of these flavors for food products.
• Artificial flavors include lactic acid which gives milk a tart taste.

Food additives

• Food additives preserve flavor, improve taste/appearance, by adding vinegar for pickling or using emulsifiers for mixtures like mayonnaise.
• They are listed by "E number" in the European Union or GRAS ("generally recognized as safe") by the United States Food and Drug Administration.

Determining properties of food quality and safety

• Key point to note here, is that analysis of the chemistry of foods includes all of the following information
• A food must be free of harmful chemical or microbial contaminants upon consumption.
• Steps to prevent microbial growth may or may not interfere with other quality attributes.

Alterations in food

• Texture can be altered by loss of solubility /water-holding capacity, toughening, and softening.
• Flavour changes from development of rancidity/cooked/caramel flavors, presence of off-flavors, and appearance of desirable flavors.
• Color alterations involve darkening and bleaching.
• The desirable colors appears with the browning of baked goods.
• Nutritive Value includes loss, degradation, and altered bioavailability of proteins, lipids, vitamins, minerals, and other health-promoting components.
• Safety alterations: generation, development, and inactivation of toxic substances.

Reactions Influencing Foods

• Chemical and biochemical reactions can change food quality and safety.
• Each reaction can involve different substrates based on food and handling/storage.
• Reactions are influenced by substrates present, not limited to individual foods.
• Non-enzymatic browning involves carbonyl compounds reacting, arising from existing reducing sugars/diverse reactions like oxidation of ascorbic acid, hydrolysis of starch, or oxidation of lipids.
• Oxidation may involve lipids, proteins, vitamins, or pigments.
• Lipid oxidation may involve triacylglycerols in one food or phospholipids in another.

Chemical and Biochemical Reactions

• Table showing some chemical and biochemical reactions leading to alteration of food quality or safety.
• Non-enzymatic Browning Examples: Baked goods, dry, and intermediate moisture foods
• Enzymatic browning: Cut fruits and some vegetables
• Oxidation: Lipids (off-flavors), vitamin degradation, pigment decolorization, proteins (loss of nutritive value)
• Hydrolysis: Lipids, proteins, vitamins, carbohydrates, pigments
• Metal interactions: Complexation (anthocyanins), loss of Magnesium from chlorophyll, catalyisis of oxidation
• Lipid Isomerization: cis → trans isomerization, non-conjugated → conjugated
• Lipid cyclization: Monocyclic fatty acids
• Lipid oxidation-polymerization: Foaming during deep-fat frying
• Protein denaturation: Egg white coagulation, enzyme inactivation
• Protein crosslinking: Loss of nutritive value during alkali processing
• Polysaccharide degradation: In plants postharvest
• Glycolytic changes: Animal postmortem, plant tissue postharvest

Transformations in Foods

• Attributes of food and possible alterations have been learnt.
• Food changes have a series of primary events followed by secondary events, evident as altered attributes.
• A single quality attribute can be altered as a result of several primary events.

Alterations By Event

• Hydrolysis of lipids
  • Primary Event: Free fatty acids react with protein
    • Texture, flavour and nutritive value
• Hydrolysis of polysaccharides
  • Primary Event: Reaction of sugars with protein
    • Texture, flavour, colour and nutritive value
• Oxidation of lipids
  • Primary Event: Reaction of oxidative products with many constituents
    • Texture, flavour, colour and nutritive value
• Bruising of fruit
  • Primary Event: Damage to cell membranes
    • Texture, flavour, colour and nutritive value
  • Primary Event: Release of enzymes
    • Texture, flavour, colour and nutritive value
• Heating of food products
  • Primary Event:Release of acids and inactivity of enzymes
    • Texture, flavour, colour and nutritive value
• Heating of muscle tissue
  • Primary Event:Denaturation of protein
    • Texture, flavour, colour and nutritive value
  • Primary Event:Inactivation of enzymes
    • Texture, flavour, colour and nutritive value

Application of Food Chemistry

• Food chemistry studies chemical components of food items to detect nutritional and non-nutritional compounds.
• Knowing the nutritional value helps develop food products with essential nutrients.
• Food chemistry helps transform food into nutritious, safe materials.
• Varieties of flavors, preservatives, emulsifiers, thickeners, stabilizers, sweeteners and colors are produced.
• Food chemistry is credited for natural and artificial food preservatives.
• Study of preservation methods has resulted in synthesizing industrial preservatives.
• Research leads to new food products for industries.
• Studying food substances initiates reactions, forming new/improved products with taste enhancement, new aroma, color, or increased shelf life.

Conclusion

• Food chemistry makes food safe, nutritious, and appealing from production to consumption.
• It's integrating Chemistry, Botany, Microbiology and Engineering.
• The objective is understand innate properties of food components and their interactions to human use.
• Food chemistry is important to stability, cost, quality, processing, nutritive value, wholesomeness and convenience.