Learning outcomes of the course unit
To describe to the student the chemical composition of foods, the characteristics of the different components, their influence on food properties, their reactivity and the transformations occurring during technological processes as well as the analytical methods for their determination. To perform lab experiments related to the theoretical studies and aimed at under standing the chemical transformations of principal and secondary food components as well as their determination and characterization. To describe the principal methods of analysis of foods.
Students should have already passed the examinations of General Chemistry, Organic Chemistry and Analytical Chemistry.
Course contents summary
The Food Chemistry course is composed of a first general part focussed on the description of food macrocomponents (water, carbohydrates, proteins, lipids) and of their chemical, physical and technological properties, the study of their general reactivity as well as of the analytical methods to assess the proximate composition of food products.
The second part takes into account several food products of animal and vegetal origin, describing their composition, the main production and storage technologies and the chemical and physical transformations occurring during processing and storage, as well as the analytical aspects linked to their characterization.
The last part of the course is focussed on more general topics, in particular: hints to food additives and their use as well as the description of the most important classes of undesirables substances linked to food safety issues.
The topics discussed during lessons are also the subject of lab experiments aimed at illustrating characteristics of food and the most used analytical techniques.
Introduction. What is Food Chemistry? Water. Water structure. Interactions of water with food components and matrices. Bound water, water activity (aw): definition and correlation with % equilibrium relative humidity. Sorption isotherms: meaning and use. Methods for the determination of % humidity of foods (dehydration, distillation, Karl-Fischer titration, IR, NIR, thermobalances), of ash (in oven o with acids) and water activity (hygrometers, lithium chloride sensors, dew point sensors). Mineral waters (potability characteristics and compositions). Lab experiments: % humidity of food products by IR thermobalance. Carbohydrates. Monosaccharides and oligosaccharides in foods: structure, properties and occurrence. Cane and beet sugar. Inverted sugar, glucose syrups: preparation and applications. Alditols: preparation and application. Decomposition of sugars in foods with acids, alkali and heat treatment. Hydroxymethylfurfural, maltol and isomaltol, lactulose. Caramellization and caramels. Maillard reaction. Methods for analysis of carbohydrates. Polysaccharides. Starch. Gelification and retrogradation. Modified starch and starch syrups. Amylases. Pectins. Pectinesterases and pectinlyases. Algal polysaccharides (alginates and carragenans). Cellulose, hemycellulose and fibers. Methods of analysis of food fiber. Gums (arabic gum, xanthan gum). Physico-chemical properties of polysaccharides and their applications in food products. Fermented products: alcoholic beverages, wine, aceto and beer. Lab experiments: determination of reducing sugars and saccharose in fruit juice with Lane and Eynon method. Determination of amylose and amylopectin in food products. Maillard reaction. Gel formation with alginates. Sugar content of must. Acidity and alcoholic grade of wine. Saccharimeters, densitometers and refractometers. Lipids. Fatty acids: structure and their occurrence in foods. Melting points and physical properties of oils and fats. Reactions of unsaturated fatty acids. Hydrogenations, margarine and trans fatty acids. Degradation oxidative reaction and rancidity (autooxydation, fotooxydation and enzymatic oxydation, lipooxygenases). Natural and synthetic antioxydants: classification, properties and mechanism of action. Control parameters for oxydation phenomena in oils. Triglycerides. Crystalline forms of triglycerides: fat melting and crystallization. Chemical composition and properties: cocoa butter and chocolate. Interesterification. Vegetal oil, milk fat, cream and butter: classification, composition, production and refinement. Emulsions. Natural and synthetic emulsifiers: characteristics and applications. HLB parameter. Sterols. Polar lipids. Cholesterol and phytosterols: chemical characteristics, occurrence and stability. Analytical methods of fats. Lab experiments: determination of fat content of foods by Soxhlet. Determination of peroxide number and acidity in oils. Determination of spectrophotometric parameters in olive and seed oil (K and K). Emulsions and emulsifiers. Determination of cholesterol in pasta samples. Determination of fatty acid composition of fats and oils by gas chromatographic analyses. Proteins. Amino acids and proteins in foods. Degradation reactions of amino acids and proteins in foods: heat and pH effects. Denaturation, racemization, isopeptides, lysinoalanine, furosine. Analytical methods. Technological properties of proteins (humectants, emulsifying, foaming, gelling, etc.). Proteinaceous foods. Milk: classification, structural components of milk, caseins and serum proteins, casein micelle structure, lipids and fat globules, lactose, thermal treatments and homogenization of milk and effects on milk components, analytical methods of milk. Cheese: classification and composition, coagulation and chemical modification during ageing, proteolysis, proteolysis index, nitrose fractions, principal analyses. Meat and fish: classification and composition, characteristics of meat proteins, post-mortem changes, anomalies (DFD, PSE), myoglobin and meat colour, additives, cured meat products (sausages), principal analyses. Eggs: composition, characteristics of egg proteins, technological properties, egg products. Cereals and derivatives: chemical composition of cereals, cereal proteins, classification and properties, gluten: formation and properties, flour and semola, rheological properties of flours, bread and pasta, bread additives, effect of heat treatment and drying. Lab experiments: determination of protein content of food by Kjehldal. Qualitative tests for proteins. Protein coagulation. Emulsifying properties of proteins. Foam formation. Gelatin. Texturalization of vegetal proteins (soy). Myoglobin: color changes upon heat treatment and use of nitrites. Food color. Molecular bases of color. Color measurement: colorimeters and spectrophotometers. Natural colors: chlorophyll, carotenoids, antocyanins, betalains, melanins, curcuma and cochineal red. Synthetic dyes. Lab experiments: pH and temperature effect on food color: chlorophyill, antocyanins. Flavour: aromas and tastes of foods. Taste: sweet, bitter, salty, acid, astringency, hot, umami. Aroma: meat, fruits, vegetables, aromatic herbs and spices, synthetic flavouring agents, off-flavor and contaminants. Sensorial analyses. Lab experiments: sensorial analyses. Additives. Classification and numbering. Chemical properties of food additives (preservatives, antioxydants, emulsifyers, ecc.). Vitamins. Classification. Properties, analyses and degradation reactions in foods. Undesirables. Toxicological aspects. Classes of undesirable components in foods. Phytotoxins. Toxins in animal products. Mycotoxins. Bacterial toxins. Allergens. Toxic residues from agriculture. Heavy metals. Toxic substances from thermal treatments. Toxic compounds from packaging. Environmental pollutants.
Texts and bibliography
T. P. Coultate, “La Chimica degli Alimenti”, Ed. Zanichelli (Bologna, 2004); P. Cabras, A. Martelli, "Chimica degli alimenti“, Ed. Piccin (Padova, 2004); H.D. Belitz - W. Grosch – P- Schieberle, “Food Chemistry”, Springer-Verlag Ed. (Berlin, Germany, 2005); O. R. Fennema, “Food Chemistry”, CRC Press Ed. (New York, USA); P. Cappelli, V. Vannucchi "Chimica degli alimenti-Conservazione e trasformazioni" Ed. Zanichelli (Bologna, 2004)
Lectures and lab experiments.
Assessment methods and criteria
Written and oral examination.
Lessons frequency is not mandatory, although strongly encouraged. Lab experiments are mandatory: the student will be admitted to the final examination only if he/she has attended all the lab experiments, eventually without one justified absence.