Food Chemistry FDT 203 Notes PDF

Food Science Dpt. Dietetic program Level : 2 Food chemistry FDt 203 ‫اﻟﻤﺤﺎ‬ ‫ﺿﺮ‬ Prof dr.rania el gammal ‫اﻟﻤﺤﺎﺿﺮة‬ ‫اﻷوﻟﻰ‬ Introduction Introduction to to Food...

Food Science Dpt. Dietetic program Level : 2 Food chemistry FDt 203 ‫اﻟﻤﺤﺎ‬ ‫ﺿﺮ‬ Prof dr.rania el gammal ‫اﻟﻤﺤﺎﺿﺮة‬ ‫اﻷوﻟﻰ‬ Introduction Introduction to to Food Food Chemistry Chemistry  What Is Food Chemistry? Food science : the scientific study of food is one of the major branches of the life sciences. Food science deals with the physical, chemical, and biological properties of foods as they relate to stability, cost, quality, processing, safety, nutritive value, wholesomeness, and convenience. Every aspect of food is covered, integrating and incorporating concepts and information from many different fields  It draws primarily on the knowledge of chemical science (biochemistry, organic, inorganic, physical and analytical chemistry) ,  The most important building blocks of food science are food chemistry and food technology. Food chemistry: a major aspect of food science, deals with the composition and properties of food and the chemical changes it undergoes during handling, processing, and storage. Food technology covers the entire gamut from procuring food raw materials to processing them into food products to preserving, packaging and delivering the food products to the consumer market.  Enhancing the positive changes and preventing the unwanted ones, Elimination of antinutritive and toxic food components, prevention of possible contamination with substances that can pose health risks and guarantee food safety. Producing safe and nutritious food for human and animal consumption is one of the principal aims of both food chemistry and food technology.  Food Chemistry associates the most closely with chemistry and biochemistry and it is the extension of the two subjects to the food area. However, the subjects have different contents and focuses. The chemistry subject deals mainly with the composition, property, and reactions of molecules. Biochemistry focuses on the reactions and changes of various components in organisms under suitable or moderately suitable conditions.  food chemistry is interested in the changes of components occurred in such unsuitable conditions as freezing, heating, and drying, their interactions during these processes, and the effects of these changes on the nutrition, safety, and sensory properties (such as color, flavor, taste, and shape) of foods. In summary, food chemists have much in common with biological scientists, yet they also have interests that are distinctly different and are of the utmost importance to humankind.  Nutrients :refer to the indispensable substance that provides nourishment essential for maintenance of life, growth and development of human being. The human body needs a lot of nutrients. Based on chemical structure, the nutrients can be divided into six major categories, including water, carbohydrates, proteins, lipids, vitamins and minerals.  foodstuff & food A minor difference between terms foodstuff and food should be noted first. Foodstuff refers to materials containing nutrients; while foods are materials that have been processed from foodstuff (ranging from simple cleaning to a modern factory processing) in order to meet people’s nutritional and sensory requirements.  Food shall be characterized by both nutrition and sensory satisfaction. The nutritional compositions of foods can be determined easily, but sensory satisfaction is a much complex issue and is related to the color, texture, and shape, flavor of foods in addition to the cultural background and dietary habits of consumers. The chemical compositions of foods are very complex Composition of foods  Some nutrients, such as proteins, peptides and amino acids, lipids, carbohydrates, vitamins and minerals, are also sensorially active substances (e.g., sweet or bitter). The main nutrients along with other substances (certain organic acids, such as acetic and citric acids, and sugar alcohols, such as sorbitol). Nutrient classes can be categorised as either macronutrients (required in relatively large amounts) or micronutrients (required in smaller amounts).  The macronutrients include proteins, fats, carbohydrates and water; the micronutrients are minerals and vitamins. Other micronutrients include antioxidants and various phytochemicals, which are said to influence or protect some body systems. Food that does not have a significant history of consumption or is produced by a method that has not previously been used for food is called novel food. An example of a novel food is margarine containing phytosterols that help to reduce the blood cholesterol level.  Functional foods are defined as foods having disease preventing and/or health promoting benefits in addition to their nutritive or processing value. Examples of functional foods with a long history are table salt fortified with iodine or margarine fortified with vitamin D.  Another example is yoghurts with live microorganisms beneficial to the host organism (bacteria of the genus Bifidobacterium), which have advantageous effects on health and are called probiotics. Prebiotics are non-digestible food ingredients (usually oligosaccharides and other substances classified as soluble dietary fibre) that stimulate the growth and/or activity of beneficial bacteria in the small intestine. Symbiotics contain both prebiotics and probiotics.  Approach to the Study of Food Chemistry A- Quality and Safety Attributes It is essential to reiterate that safety is the first requisite of any food. In a broad sense, this means a food must be free of any harmful chemical or microbial contaminant at the time of its consumption. For example, in the canning industry, “commercial” sterility as applied to low-acid foods means the absence of viable spores of Clostridium botulinum.  B-Chemical and Biochemical Reactions Many reactions can alter food quality or safety. Each reaction class can involve different reactants or substrates depending on the specific food and the condition for handling, processing, or storage. Reactions are such as oxidation of ascorbic acid, hydrolysis of starch, or oxidation of lipids. Oxidation may involve lipids, proteins, vitamins, or pigments, and more specifically, oxidation of lipids may involve triglycerides. Chemical and Biochemical Reactions That Can Lead to Alteration of Food Quality or Safety Food type Type of reactions Carbohydrates – amino acids- Non- enzymic browning peptides- proteins reactions Fresh food Enzymic browning reactions Food contained lipids Lipid analysis Food contained lipids and lipases Lipid oxidation Food contained protein source Protein denaturation (meat – milk- egg.eg) Food type Type of reactions Food contained carbohydrates and Poly and oligosaccharides amylases enzymes hydrolysis Food contained protein and related Protein analysis proteolysis enzymes Food contained natural pigments Pigment analysis Undesirable change in some food system and affected on quality properties Quality property Undesirable change in food Texture  Loss in solubility  Loss in water binding  Tender texture  Rough texture Flavor  Rancidity ( due to oxidative or ketonic rancidity  Cooked flavor  Caramelization  Other unfavorable flavors Color Browning color Discoloration Color bleaching Nutritional value Loss in vitamins –minerals – protein and lipids  Integration of the information contained in both tables can lead to an understanding of the causes of food deterioration.  C-Factors affecting food composition Raw Materials: The content of different components in food raw materials depends on the species and variety of the animal or plant crop; on the conditions of life, and age of the farm harvesting of the plants; on the feeding, conditions of life, and age of the farm animals; and on post harvest changes that take place in the crop during storage.  Processed foods: The composition of processed foods depends on the recipe applied and on changes taking place due to processing and storage. Changes occurring in food due to processing: Leaching of soluble, desirable and undesirable components, such as vitamins, minerals and toxins occurs during washing, blanching and cooking.  During salting, pickling, frying or smoking there is leaching of nutrients and absorption of desirable or harmful compounds. Due to enzyme activity, desirable or harmful compounds are formed. Different products of oxidation of food components, mainly of lipids, pigments, and vitamins are also formed.  Cause-and-Effect Relationships Pertaining to Food Alterations during Handling, Storage, and Processing. Primary causative Secondary event Attribute influenced event Hydrolysis of lipids acids react with Texture, flavor, nutritive Free fatty protein value Hydrolysis of Sugars react with Texture, flavor, color, polysaccharides proteins nutritive value Oxidation of lipids Oxidation products Texture, flavor, color, react with many other nutritive value; toxic constituents substances can be generated Primary causative event Secondary event Attribute influenced Heating of green Cell walls and membranes Texture, flavor, color, nutritive vegetables lose integrity, acids are value released, enzymes become inactive Heating of muscle tissue Proteins denature and Texture, flavor, color, nutritive aggregate, enzymes value become inactive Bruising of fruit Cells break, enzymes Texture, flavor, color, are released, oxygen nutritive value accessible