Food Chemistry 1 Final Exam Pointers PDF

POINTERS FOR FOOD CHEMISTRY 1 FINAL EXAM Food proteins are essential macronutrients composed of amino acids, vital for various bodily functions. Protein degradation is a natural process where proteins are broken down into amino acids, ensuring cellular quality control and homeostasis. The ubiquit...

POINTERS FOR FOOD CHEMISTRY 1 FINAL EXAM Food proteins are essential macronutrients composed of amino acids, vital for various bodily functions. Protein degradation is a natural process where proteins are broken down into amino acids, ensuring cellular quality control and homeostasis. The ubiquitin-proteasome pathway and autophagy-lysosome pathway are the primary mechanisms for protein degradation. Emulsion is a mixture of two or more liquids that are normally immiscible (unmixable) due to liquid-liquid phase separation. Emulsifiers are substances that stabilize emulsions, preventing them from separating. Hydrophilic - attracted to water Hydrophobic - attracted to oil Proteins are essential macronutrients that are vital for various bodily functions, including building and repairing tissues, transporting molecules, providing energy, producing hormones and enzymes, maintaining muscle mass, and supporting the immune system. DIFF. TYPES OF AMINO ACIDS THAT ARE COMMONLY FOUND IN PROTEINS; Essential amino acids: Cannot be produced by the body and must be obtained from the diet. Non-essential amino acids: Can be produced by the body and do not need to be obtained from the diet. Amino Acid Composition - amino group (-NH2): Contains nitrogen. - carboxyl group (-COOH): Contains a carbon, two oxygens, and a hydrogen. - side chain (R group): This is the unique part of each amino acid, giving it its specific properties. Protein Structure 1. Primary Structure: The linear sequence of amino acids in a polypeptide chain. 2. Secondary Structure: Local folding patterns within the polypeptide chain, such as alpha-helices and beta-sheets, stabilized by hydrogen bonds. 3. Tertiary Structure: The three-dimensional shape of a single polypeptide chain, determined by interactions between the side chains of the amino acids. 4. Quaternary Structure: The arrangement of multiple polypeptide chains (subunits) to form a functional protein complex. Protein Classification - Globular proteins: Spherical or compact in shape, often soluble in water. Examples include enzymes, hormones, and antibodies. - Fibrous proteins: Long, fibrous structures, often insoluble in water. Examples include collagen, keratin, and elastin. - Simple proteins: Composed only of amino acids. - Conjugated proteins: Contain a non-protein component in addition to amino acids, such as a metal ion, a lipid, or a carbohydrate. Lipid degradation, also known as rancidity, refers to the undesirable changes that occur in lipids over time, leading to a deterioration of their quality and functionality. These changes are primarily driven by chemical reactions, such as hydrolysis and oxidation, which alter the structure and properties of the lipid molecules. TYPES OF LIPID DEGRADATION Hydrolysis is the breakdown of lipids by water, resulting in the release of free fatty acids and glycerol. Oxidation is the reaction of lipids with oxygen, leading to the formation of free radicals and other oxidation products. Polymerization: Lipid molecules can react with each other to form polymers, leading to an increase in viscosity and a change in texture. Isomerization: The double bonds in unsaturated fatty acids can rearrange, leading to changes in the lipid's melting point and reactivity. Photolysis: Exposure to light can cause the breakdown of lipids, leading to the formation of free radicals and other degradation products. Effects of Lipid Degradation - Flavor and Odor Changes: Lipid degradation leads to off-flavors and odors, making the food unpalatable. - Texture Changes: Lipid degradation can cause changes in the texture of food, making it more viscous, sticky, or rubbery. - Nutritional Loss: Lipid degradation can destroy essential fatty acids and other nutrients, reducing the nutritional value of the food. - Formation of Harmful Compounds: Lipid degradation can produce toxic compounds like aldehydes and ketones, which can be harmful to human health. Physico-Chemical Properties of Lipids - Hydrophobicity: Lipids are hydrophobic, meaning they repel water and are insoluble in aqueous solutions. This property is due to their nonpolar hydrocarbon chains, which lack the ability to form hydrogen bonds with water molecules. - Melting Point: Lipids have varying melting points, depending on their fatty acid composition. Saturated fatty acids, with single bonds between carbon atoms, pack tightly together, resulting in higher melting points. Unsaturated fatty acids, with double or triple bonds, have less tight packing, leading to lower melting points. - Polymorphism: Lipids can exist in different crystalline forms, known as polymorphism. This property affects their melting point, texture, and stability. - Solubility: Lipids are soluble in nonpolar solvents like diethyl ether, chloroform, and hexane. This property is exploited in lipid extraction and analysis. - Surface Activity: Some lipids, particularly phospholipids, exhibit surface activity, meaning they can form stable interfaces between water and oil phases. This property is crucial in emulsifiers and detergents. - Reactivity: Lipids can undergo various chemical reactions, including hydrolysis, oxidation, and hydrogenation. These reactions are utilized in lipid processing and modification. Lipid Technology: Refinement and Modification Refinement - Degumming: Removes non-lipid impurities like gums and phospholipids from crude oils. - Neutralization: Removes free fatty acids using alkali treatment. - Bleaching: Removes pigments and other colored impurities using activated carbon or clay. - Deodorization: Removes volatile compounds responsible for off-flavors and odors using steam distillation. Modification - Hydrogenation: Converts unsaturated fatty acids into saturated ones, increasing the melting point and stability of the lipid. - Interesterification: Rearranges fatty acids within triglycerides, altering their melting point and texture. - Fractionation: Separates lipids into fractions with different melting points by controlled crystallization. - Enzymatic Modification: Uses enzymes to selectively modify lipids, creating structured lipids with specific properties. - Transesterification: Reacts lipids with alcohols to produce fatty acid esters, used in biofuels and other applications. Functions of Lipids in Foods - Flavor and Texture: Lipids dissolve flavor and odor molecules, enhancing the taste and aroma of foods. They also provide a smooth, creamy texture to foods like ice cream and cheese. - Satiety: Lipids are digested and absorbed slower than other macronutrients, contributing to satiety, the feeling of fullness. This can help keep hunger at bay for longer periods. - Cooking and Baking: Lipids are essential for cooking and baking. They act as a heat transfer medium, preventing sticking and providing a crispy texture to fried foods. They also contribute to the tenderness and flakiness of baked goods. Lipids, often referred to as fats, are a diverse group of organic molecules that are essential for various biological functions. Structure of Lipids Fatty acids can be saturated or unsaturated, depending on the presence or absence of double bonds in their hydrocarbon chains. Saturated fatty acids - typically solid at room temperature and found in animal products like butter and lard. Unsaturated fatty acids - typically liquid at room temperature and found in plant-based oils like olive oil and vegetable oils. Lipids are formed by the combination of fatty acids with various alcohols or other molecules. - Phospholipids: These lipids have a glycerol backbone with two fatty acids and a phosphate group attached. - Glycolipids: These lipids have a glycerol backbone with one or two fatty acids and a carbohydrate group attached. - Sterols: These lipids have a four-ring structure and a hydroxyl group. - Waxes: These lipids are esters of long-chain fatty acids and long-chain alcohols. Classification of Lipids 1. Fatty Acyls (FA): This category includes fatty acids, alcohols, aldehydes, amines, and esters. 2. Glycerolipids (GL): These lipids contain a glycerol backbone and include acylglycerols, alkyl, and 1-alkenyl variants. 3. Glycerophospholipids (GP): These lipids are characterized by the presence of a phosphate group esterified to one of the glycerol hydroxyl groups. 4. Sphingolipids (SP): These lipids contain a long-chain nitrogenous base as their core structure. 5. Sterol Lipids (ST): These lipids are derived from the condensation of isoprene units and are characterized by a unique fused ring structure. 6. Prenol Lipids (PR): These lipids are also derived from isoprene units but differ from sterols in their fused ring stereochemistry and methylation patterns. 7. Saccharolipids (SL): These lipids have fatty acyl groups linked directly to a sugar backbone. 8. Polyketides (PK): These lipids are a diverse group of metabolites from animal, plant, and microbial sources. COMMON CLASSIFICATION OF LIPIDS - Simple lipids: These lipids consist of two types of structural moieties, such as triglycerides, waxes, and ceramides. - Complex lipids: These lipids consist of more than two types of structural moieties, such as phospholipids, glycolipids, and sphingolipids. - Derived lipids: These lipids are the building blocks for simple and complex lipids and can occur as such or be released from the other two major groups. Role of Lipids in Food: High Energy Source / Smell and Taste The three main types of lipids are: Triacylglycerols (also known as triglycerides) make up more than 95 percent of lipids in the diet and are commonly found in fried foods, vegetable oil, butter, whole milk, cheese, cream cheese, and some meats. Sterols are the least common type of lipid. Phospholipids are crucial for building the protective barrier, or membrane, around your body’s cells. Carbohydrates are a group of organic compounds containing a ratio of one carbon atom to two hydrogen atoms to one oxygen atom. “carbo” means carbon and “hydrate” means water Glucose, the most abundant carbohydrate in the human body, has six carbon atoms, twelve hydrogen atoms, and six oxygen atoms. “saccharide,” which means sugar. The simplest unit of a carbohydrate is a monosaccharide. Carbohydrates are broadly classified into two subgroups, “fast-releasing” and “slow-releasing.” Fast-releasing carbohydrates are further grouped into the monosaccharides and dissacharides. Slow-releasing carbohydrates are long chains of monosaccharides. Monosaccharides include glucose, fructose, and galactose Dissacharides include, lactose, maltose, and sucrose. Structure of Carbohydrates Open chain structure – It is the long straight-chain form of carbohydrates. Hemi-acetal structure – Here the 1st carbon of the glucose condenses with the -OH group of the 5th carbon to form a ring structure. Haworth structure – It is the presence of the pyranose ring structure. Physical Properties of Carbohydrates Stereoisomerism – Compound shaving the same structural formula but they differ in spatial configuration. Example: Glucose has two isomers with respect to the penultimate carbon atom. They are D-glucose and L-glucose. Optical Activity – It is the rotation of plane-polarized light forming (+) glucose and (-) glucose. Diastereo isomers – It the configurational changes with regard to C2, C3, or C4 in glucose. Example: Mannose, galactose. Annomerism – It is the spatial configuration with respect to the first carbon atom in aldoses and second carbon atom in ketoses. Chemical Properties of Carbohydrates Osazone formation: carbohydrate derivatives when sugars are reacted with an excess of phenylhydrazine. Oxidation: Monosaccharides are reducing sugars if their carbonyl groups oxidize to give carboxylic acids. Reduction to alcohols: The C=O groups in open-chain forms of carbohydrates can be reduced to alcohols by sodium borohydride, NaBH4, or catalytic hydrogenation (H2, Ni, EtOH/H2O). The products are known as “alditols”. Functional Properties of Proteins Proteins are made up of a “team of amino acids”. Water-soluble proteins are referred to as hydrophillic while those that are not soluble, are called hydrophobic. The functional properties of proteins Water Absorption and Retention: Proteins that are made up of mostly hydrophillic amino acids will tend to absorb and retain more water. Solubility: Proteins that are made up of mostly hydrophillic amino acids will be more soluble. Color: Proteins react with reducing sugars to form flavors and color compounds in a process called Maillard reaction. Gelation: Some proteins have the ability to form a gel. Viscosity and Texture: Proteins can make foods not only more viscous (thicker) as we saw in the formation of gels, but also elastic. We call this property, visco-elasticity. Emulsification: Emulsifiers are substances that are able to prevent the separation of oil and water in food. Foam Formation: A food foam is formed when air bubbles are dispersed in water. Flavor-Binding: Proteins are generally odorless compounds on their own, but they can bind flavor compounds and therefore impart new flavor to foods. Curdling: Proteins can coagulate with the addition of acids. Enzymatic Browning: I talked about Maillard browning earlier. Maillard reaction is called non-enzymatic browning since it is not dependent on the work of enzyme. Remember that with Maillard browning you need only proteins and reducing sugars. Another type of browning is called enzymatic browning. That is when browning is caused by enzymes. Enzymes are proteins that speed up the rate of chemical reaction in living systems. One type of reaction that they speed up is the browning reaction. This reaction is caused by the action of the enzyme poly phenol oxidase on phenol compounds in foods, in the presence of oxygen. The result is a brown compound called melanin. Denaturation is a process in which proteins or nucleic acids lose the quaternary structure, tertiary structure, and secondary structure which is present in their native state, by application of some external stress or compound such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), radiation or heat.