Food Chemistry and Laboratory of Chemistry Applied to Food
Learning outcomes of the course unit
Knowledge and understanding
During the course the student will acquire a deep knowledge of the chemical composition of foods, of the characteristics of the different components, of their influence on the food properties, of their reactivity and of the transformations they undergo during the technological processes as well as of the analytical issues linked to their determinations.
The student should acquire the ability to correlate and integrate general aspects with specific characteristics of the different food products, understanding the correlation existing between chemical composition and quality and acquiring the ability to elaborate label informations.
These knowledges are the base to effectively operate in the production, control and analytical sector as well a sto design new products and processes.
Applying knowledge and understanding
The student must be able to utilize the acquired knowledge to understand and foreseen the molecular transformations in foods as a consequence of technological processes and storage.
During the course, the student will perform laboratory experiments linked to the theoretical part and aimed at understanding the chemical transformations of principal and secondary food components as well as their determination and characterization, showing the most important analytical methods of food and transferring operative abilities.
The student must be able to define which transformations may occur or may be induced in a food and which are the effects of the different formulations on the general properties and the quality of a food product as well as to identify the processing or storage conditions that may influence the overall quality of a product.
The student should be able to appropriately utilize the scientific language and the specific lexicon of food chemistry, showing the ability to describe and transfer in oral and written form the acquired concepts.
The lab book should be written correctly, with a synthetic but proper language and with a clear exposition and comment of the experimental data.
The student will be able to increase his/her knowledge of Food Chemistry, by self consultation of specialized texts, scientific and educational journals, also beyond the topics discussed during the lessons.
The objective is to expand the student's knowledge about chemical analysis of food. At the end of the course, the student will be able to identify the techniques of analyses and to apply these techniques to real situations.
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 focused on more general topics, in particular: hints to food additives and their use as well as the description of organoleptic characteristics of food (color and flavor).
The topics discussed during lessons are also the subject of lab experiments aimed at illustrating characteristics of food and the most used analytical techniques.
The course aims to provide students the basic knowledge of laboratory techniques ranging from general chemistry to analytical chemistry, organic chemistry, food chemistry and instrumental techniques used in a food chemistry laboratory.
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). 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. 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. Additives. Classification and numbering. Chemical properties of food additives (preservatives, antioxydants, emulsifyers, ecc.).
Different techniques will be considered for: preparing and analyzing solutions, extraction and chromatographic separation, synthesis of food-interest molecules, extraction and purification or reaction products, food analysis techniques, and finally techniques for treating of the data obtained from the analysis.
The course includes: the study of the preparation and analysis of standard solutions; extraction of active compounds from food matrices (extraction of caffeine from tea leaves); study of natural additives (carotenoids extracted from spinach leaves); synthesis of flavours of food interest (banana aroma synthesis); methods for the determination of sugars in a food matrix; methods for the determination of amino acids and proteins in foods; analysis of the fat component; application of analysis to some matrices (wine); use of instrumental techniques such as UV-Visible spectrophotometry, gas-chromatography coupled to mass spectrometry (GC-MS) and liquid chromatography (HPLC).
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).
Power point presentations of the different topics.
During the lessons, which will be done using power point projections, overheads and blackboard, the different aspects of foods and of their production will be presented and , with a particular emphasis on the chemical and physical transformations and their control.
The course will be integrated by lab experiments, with individual and practical experiments aimed at understanding theoretical and practical aspects of food behaviour, as well as at illustrating the most important analytical methods also the instrumental ones.
Lab experiments will be described by each student in a lab book, that will be an completing part of the final evaluation.
Preparation lessons and direct experience in a chemistry lab.
Assessment methods and criteria
Final examination will be written. The written examination will contain open questions on the main course topics, both on the aspects of the most important chemical reactions and on the descriptive aspects of food composition and properties and of food components.
The learning assessment will take place through a written exam and the writing of the laboratory book. The written exam consists of 6 open-response questions (4 points for a maximum of 24 points), while the laboratory book includes up to a maximum of 6 points. The total score for the written exam and book is 30 points. The obtained total score is the grade. The exam is considered passed if the test is at least sufficient, if a minimum of 14.4 points will be reached, to which the score obtained with the laboratory book will be added.
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.