Ntd2003 Food Chemistry Protein Lecture Notes PDF

NTD2003-Food Cemistry PROTEIN ECENUR ÖZKUL ERDOĞAN 1  Protein  They are components that have an important physiological effect on the realization of vital functions.  In addition to carbon, hydrogen and oxygen, they contain significant...

NTD2003-Food Cemistry PROTEIN ECENUR ÖZKUL ERDOĞAN 1  Protein  They are components that have an important physiological effect on the realization of vital functions.  In addition to carbon, hydrogen and oxygen, they contain significant amounts of nitrogen (15-18%) and sometimes sulfur and phosphorus.  Theyare present in all living organisms and their products. 2  Protein  It literally means "the most important" and is really very important for the life of the living thing.  They are dissolved in the cytoplasm of all living cells.  About 80-90% of muscle and liver is protein. 3  What are the proteins used for in the body?  Used in the construction and repair of body tissues  Present in the structures of enzymes and hormones.  It plays a role in buffering the acid-base balance in the body.  Present in the structure of chromosomes and genes  Takes part in muscle contraction  Present in the composition of milk 4  Building blocks of proteins  They are compounds with high molecular weight.  The building blocks are AMINO ACIDS, proteins are the polymers of them. 5  Aminoacids They are hydrocarbons chains. 6 Classifi cation of amino acids: According to the physical and chemical properties of their side chains  Aliphatic  Acidic  Alchalic  Alcohol or sulphure containing  Amite  Aromatic  Cyclic 7  Classifi cation of amino acids: According to their relationship with water  Non polar (hydrofobic)  Polar (hydrophillic) 8  Aminoacids  Plants synthesize the necessary amino acids from carbon dioxide, water and nitrogenous compounds which they get from the soil.  On the other hand animals and humans, must first obtain vegetable proteins in order to obtain the amino acids they need. 9  Supply of amino acids Amino acids that can be synthesized by the organism  Endogenous amino acids: Non-essential amino acids.  Glycine,alanine, neuroleucine, cysteine, serine, aspartic acid, glutamic acid, hydroxyglutamic acid, tyrosine and pyrosine 10  Supply of amino acids Amino acids that cannot be synthesized by the organism and must be taken externally  Exogenous amino acids: Essential amino acids.  Valine,leucine, isoleucine, methionine, threonine, lysine, phenylalanine, tryptophan.  Arginine and Histidine are essential only for children 11 Use of Essential Amino Acids in body  Leucine: Necessary for albumin formation in tissues  Isoleucine: Necessary for the use of animo acids in the organism  Lysine: Effective on the body height growth  Methionine: Effective in the development of body and hair  Phenylalanine: Necessary for the production of thyroxine and adrenaline besides pigment and blood formation  Valine: Necessary for nervous system function  Threonine: Necessary for the use of amino acids in the organism  Tryptophan: Necessary for growth and milk production 12  Use of Essential Amino Acids in body  These amino acids must be taken externally  Inthe absence of Essential Amino Acids, significant deficiencies in protein synthesis will occur. 13  Protein Structure  Proteins are formed as a result of the reaction of amino acids with each other.  There are 20 alpha amino acids joined the structure of proteins.  These amino acids are linked to each other by peptide bonds.  The α carboxyl carbon of one amino acid and the α amino nitrogen of another amino acid are connected by a C-N bond. PETIT bounds. 14  Aminoacid chains  Amino acids are linked together in various combinations to form proteins.  However, this binding is not random, each protein has a specific amino acid sequence. 15  Bounding of amino acids by peptide bonds  Dipeptide chain: formed by the bonding of two amino acids  Tripeptide chain: formed by linking three amino acids  Oligopeptide to the chain: formed by the attachment of 4-9 amino acids  Polypeptide chain: formed by the attachment of 10- 100 amino acids  The chain formed by linking more than 100 amino acids is called a macropeptide or protein. 16 Classifi cation of proteins: by origin  Plant proteins  Animal proteins 17  Classifi cation of proteins: by origin Homo proteins: Formed by aminoacids only Heteroproteins: It is formed by the binding of non-protein chemicals to amino acids. 18  Classifi cation of proteins Homo proteins Heteroproteins Albumins Phospholipids Globulins Nucleoproteins Prolamins collogen Glycoproteins Scleroproteids Chromoproteids Histones Histones Lipoproteins Protamines 19  Classification of proteins  Enzymes: protease, lipase, catalase  Transport and storage proteins: Transferrin:carries iron in the blood, Hemoglobin: carries oxygen in the blood, Myoglobin: stores oxygen in the muscle 20  Classification of proteins  Structural and contractile proteins: Collagen: in skin and tendons, Ceratin: in nails and hair, Actin and myosin; in muscle contraction  Regulatoryproteins: control the expression of genes, the growth of the body and organs, regulate metabolic reactions eg. hormones – insulin 21  Classification of proteins  Immune defense antibodies (immunoglobulins): antibiotics, allergens, toxin (snake venom) 22  Classification of proteins: In respect to their chemichal structure Soluble simple proteins Albumin:  It is found in animal and plant tissues.  It is soluble in water, diluted salt and acid/alcalic solution.  Coagulates with heat  Serum albumin in blood, lactalbumin in milk, ovalbumin in eggs and plant albumins are in this group. 23  Classification of proteins: In respect to their chemichal structure Soluble simple proteins Globulin:  It is most commonly present in animal tissues. Although some are soluble in water, many are insoluble.  They are soluble only in alkalic solutions  It coagulates with heat and precipitates with acids  Serum globulin in blood, myosin in muscle, lactoglobulin in milk and vegetable globulins are in this group. 24  Classification of proteins: In respect to their chemichal structure Soluble simple proteins Gluteins:  They are present in plant tissues.  They are insoluble in pure water and salt solutions.  They are soluble in dilute alcohols and acids.  They coagulates with heat. 25  Classification of proteins: In respect to their chemichal structure Soluble simple proteins Prolamins:  They are plant gobulins.  They are soluble in 70-80% alcohol.  Gliadin in wheat and zein in maize belong to this group. 26  Classification of proteins: In respect to their chemichal structure Soluble simple proteins Protamines:  They are the simplest natural proteins.  They are strong alcalic because they contain a high percentage of arginine.  They are soluble in water and dilute acids.  Salmin in salmon and clupein in herring are among them. 27  Classification of proteins: In respect to their chemichal structure Soluble simple proteins Histones:  They are only found in some animal tissues. They contain arginine and histidine.  They are soluble in water and very dilute acid solutions.  Examples include globulin of hemoglobin and histones of leukocyte. 28  Classification of proteins: In respect to their chemichal structure Insoluble simple proteins  They are resistant to chemical reagents and are insoluble in water, dilute acid, alkali and salt solutions.  These proteins are also called albuminoids.  Enzymes are usually inactive with these proteins.  They are not found in plants, they are found in the mechanically functioning parts of the animal organism. 29  Classification of proteins: In respect to their chemichal structure Insoluble simple proteins  Proteins of wool, silk, hair, nails, horns, hides and feathers are in this class.  They are not nutritionally valuable.  Collagen only has comparatively nutritional value.  Collagen, keratin, fibroin, spongin, glutin and elastin are in this group. 30  Classification of proteins: In respect to their chemichal structure Conjugated proteins They are proteins formed by the binding of a non- protein compound to a protein. The non-protein group is called the prosthetic group. Prosthetic group can be; phosphoric acid, pigment, sugar, oil or nucleic acid. They are classified according to the attached group. 31  Classification of proteins: In respect to their chemichal structure Conjugated proteins Phosphoproteins:  They contain phosphoric acid.  They are distinctly acidic, slightly soluble in water and easily soluble in alcalic solutions.  Milk protein casein, vitelline in egg yolk can be given as examples of this group. 32  Classification of proteins: In respect to their chemichal structure Conjugated proteins Glycoproteins:  They contain 10-30% carbohydrates in their composition.  Egg proteins, ovomucoid, salivary mucin are in this group. 33  Classification of proteins: In respect to their chemichal structure Conjugated proteins Nucleoproteins:  They form the basic part of the nuclei of animal or plant cells.  They are salt-type compounds composed from baunding of simple proteins such as histones and protamines with nucleic acids.  Since they contain a large number of phosphoric acids, they show acidic properties.  They dissolve in weak alcaline solutions. 34  Classification of proteins: In respect to their chemichal structure Conjugated proteins Chromoproteins:  They are the comjugation of proteins with dyes.  They often contain a metal substance such as iron or magnesium.  Hemoglobin is in this group.  In this compound, globin is a histone and is combined with the dye heme. 35  Classification of proteins: In respect to their chemichal structure Conjugated proteins Lecytoproteins:  They are compounds that proteins make with lecithin.  Fibrin and yolk proteins are in this group. 36 Properties of Proteins 37  Hydrolysis:  Proteins, like carbohydrates and fats, have the ability to break down hydrolytically.  This degradation occurs via enzymes (proteases). Simple proteins amino acids Conjugated Protein aminoacid prostatic group 38  Hydrolysis:  Proteins need this breakdown in order to be digested.  Because in order to be absorbed, they must first be broken down into peptones and amino acids.  This is due to this hydrolysis by which proteases are carried out.  Proteases are produced in the stomach, pancreas, and intestine.  Proteins that are completely broken down in the intestine pass into the blood strem as amino acids. 39  Solubility:  The solubility for proteins is very variable.  Many proteins are soluble in many different solutions and water.  In colloidal solutions** of proteins, the protein molecules are surrounded by water molecules.  This reaction is also called Hydrotation.  This reaction is important in terms of food processing techniques such as meat processing and pastries. **The solution formed by the dispersion of a substance at 10 -10 cm size in an −5 −7 environment that does not have a solvent for itself is called colloidal solution. 40  Isoelectric point:  Proteins are molecules with an electrical charge.  These electrical charges of proteins are closely related to the pH value of their environment.  Depending on the pH value of the environment, this electrical charge can be negative or positive.  At a certain pH value, electrical charges become neutral.  This value is different for all of them and this pH point where they have a neutral charge is called the Iso electric point.  At pH values above the iso electric point, its surfaces are negatively charged, while values below, at a positive charge. it takes 41  Isoelectric point:  When proteins have an electrical charge, they are dissolved in solution.  However, when they lose their electrical charge at the isoelectric point, they precipitate because the repulsive electrical forces disappear.  The isoelectric point is indicated by the sign pI.  Although it is different for all depending on the different amino acid structures of proteins, it varies between; pH 4.8-6.3 for neutral amino acids, pH 2.7-3.2 of acidic amino acids, pH 7.6-10.8 of basic amino acids. 42 Why is Isoelectric point important:  Separation of proteins: Only the desired protein will be precipitated in a solution adjusted to the pH value of the isoelectric point of the protein to be separated. Precipitation of milk: With the breakdown of lactose, which is the sugar of milk, the pH value of milk decreases and casein precipitates at pH 4.9 (in some sources pH 4.6)., the isoelectric point of casein. 43  Denaturation: It is the change of the biological structure of the protein molecule due to temperature, acid, heavy metals, etc. The polypeptide chains are stretched, forming a random and irregular structure. It is an irreversible change. 44 The causing factors of Denaturation: Physical Chemical Heat Acids UV Alcalies Ultrasou Alcohols nd Salts 45  Denaturation: Denatured proteins are better broken down by enzymes Denatured proteins; coagulated, agglomerated or precipitated. 46 The diff erence between hydrolisis and denaturation: Denatured proteins only undergo structural change. Protein degradation products are formed during hydrolysis. Denaturation is a required in food technology, and the occurrence of denaturation with various technologies increases the digestibility of the protein. 47  Examples of denaturation: The temperature that denatures proteins is different for proteins, but is usually in the range of 55-75°C. Gelatin and casein resistant to higher temperatures Although casein is resistant to high temperatures, it is denaturated at freezing temperatures (Precipitation of frozen milk). 48  Denaturation temperatures of proteins: Protein Denaturation temp. Egg albumin 56°C Laktalbumin 72°C Bovine serum albumin 67°C Myosin 47-56°C B-lactoglobulin 70-75°C Casein 160-200°C 49  The improtance of denaturation in food technology: Meat and fish: In denaturation caused by temperature, proteins coagulate, pores are closed, cell sap is preserved, brownend and edibility increases. Milk: During boiling, a coagulated protein layer is formed at the bottom of the pot. But it is quite limited. Because only the serum proteins of milk are denatured. Casein, which makes up most of the protein in milk, is very stable to heat and is not denatured by boiling. Prof.Dr.Özge ÖZGEN ARUN  50  The improtance of denaturation in food technology: Pastries Gluten in flour coagulates at 72°C and above, which contributes to the formation of structure in cakes and other pastries.  51  Maillard reaction:  The Maillard reaction is a chemical reaction that occurs between reduced sugars and protein in amino acids when food is heated.  Color darkening occurs as a result of the reaction. While it is desired in some products (such as bread), it is not preferred in others (milk).  Lysine is most affected by the Maillar reaction and the biological value of the protein decreases.  In addition, undesirable color formation and aroma disorders may occur. 52  The factors causes Maillard reaction  Temperature: 2-3 times faster with every 10ºC rise in temperature. It accelerates 4-5 times in those containing fructose. Darker pigments may form as temperature increases  Humidity: As humidity increases, the maillard effect increases.  pH: The higher the pH, the greater the mailard eradication. 53  The biological value of proteins  The biological value of proteins is related to the diversity and adequacy of the essential amino acids they contain.  A protein rich in essential amino acids is called a high-value protein. For example: egg protein 54  The biological value of proteins  Proteinscontaining all essential amino acids are called complete proteins.  Calculation of biological value is done by the following formula: Nitrogen retained in the organism  Bological value= Nitrogen absorbed from the digestive tract 55 The biological value of some proteins Food Protein Biological value (BV) Egg Protein 100 Milk protein 92 Swiss chese 83 Soya 85 Rice 81 Beef 78 Rye flour 76 Casein 72 Potato 69 Dry yeast 48 gelatin 0 56 The biological value of food mixtures Food Mixtures Biological Value (BV) 36% Egg+64% potato 136 70% lactalbumin+30% potato 134 75% milk+25% wheat flour 125 60% egg+40% soya 124 68% egg+32% wheat 123 76% egg+24% milk 119 51% milk+49% potato 114 88% egg+12% maize 114 78% beef+22% potato 114 35% egg+65% bean 109 52% bean+48% maize 99 57  Factors aff ecting protein digestibility and biological value  Some proteins cannot be broken down and released during digestion. This is especially true when some vegetable proteins are tightly coated with cellulose.  Deficiency of some vitamins and minerals in the diet (for example; B6, B12 and Magnesium) reduces the digestion of proteins.  Normally, the body uses carbohydrates first and then fats as an energy source. If the intake of fat and carbohydrates in the diet is not sufficient to meet the energy requirement, proteins are used as an energy source.  In this case, proteins cannot be used for essential functions such as vital events and construction and repair. 58  Factors aff ecting protein digestibility and biological value  Since the protein composition in many foodstuffs is different, taking it from one type of source (such as only legumes or only vegetables) causes nutritional deficiency.  High temperature sometimes has a negative effect on the digestibility of proteins. E.g: High heat causes damage to some essential amino acids. The Maillard reaction impairs the digestibility of lysine. However, for some proteins, heating has a positive effect on digestibility. For example, trypsin enzyme in legumes negatively affects protein digestion. However, this enzyme is destroyed during boiling with water. 59  Protein need The generalization of protein needs is not a very correct approach, and it is more accurate to evaluate it individually, taking into account the living conditions of the person. 60 Factors eff ective on protein need Age and gender: In infants, children and adolescents, the amount required per kg is higher to support growth. Gender has no significant effect Muscle activity: The requirement for muscle development increases after sports activities. Again, the requirement is higher for those who work in heavy jobs. More protein is required for febrile illness, widespread wounds and burns, and post-operative cell and tissue formation. Pregnancy and lactation period: A sufficient amount of milk must be obtained for milk production. 15 g during pregnancy in a healthy woman. It is recommended to increase 30g in lactation. 61 Factors eff ective on protein need Protein biological value and essential amino acids: Not only the amount of protein ingested, but also its digestibility rate and its biological value, which is an assessment of essential amino acid content, are also important factors. 62  Protein defi ciency Insufficient protein intake: Inadequate protein intake due to economic reasons, poor nutritional profile, anorexia Low carbohydrate intake: When carbohydrate intake is insufficient in the diet, the taken proteins are used to meet glycosynthesis and energy needs. Protein absorption disorder: Malabsorption due to reasons such as celiac Increased protein loss: Increased urinary protein loss due to kidney disease 63  Protein defi ciency Conditions that cause protein loss: Ulcerative colitis, chronic bleeding, etc. Hepatic failure: Both albumin production decreases and protein leakage into the peritoneal cavity occurs. Large burns and wounds: protein leaks out of the body 64  Adaptation to protein defi ciency As long as fat and carbohydrates are consumed for energy needs, the body tries to adapt to protein deficiency. For this; Enzymes that activate amino acids in the liver increase The amino acids produced by protein breakdown in tissues are reused. 65  Adaptation to protein defi ciency But adaptation is to some extent. Finally;  Weakness,  Anemia  Edema  Liver lipidosis  Insufficient pancreas and deficiencies of soluble vitamins occur. 66 Aminoacid metabolism defi ciencies It indicates the problems experienced in the metabolism of some amino acids due to genetic reasons. These problems are;  Homocystinuria  Maple Syrup Urine Disease  Phenyl Ketonuria  Trocinemia 67  Homocystinuria It is a disorder in methionine metabolism. Homocysteine and methionine increase in the blood as a result of insufficiency of an enzyme (cytacynin beta synthase) due to hereditary reasons. 68  Maple Syrup Urine Disease Valine is associated with the metabolism of leucine and isolosine. By-products of the metabolism of these amino acids accumulated in the blood cause neurological disorders. It gets its name because bodily fluids such as urine, sweat, and earwax smell like maple syrup. 69  Phenyl Ketonuria It is a disorder of phenylalanine metabolism. Phenylalanine does not convert to tyrosine in infants with insufficient phenylalanine hydrooxylase enzyme due to genetic reasons. It causes neurological symptoms. 70  Trocinemia It is a tyrosine metabolism disorder. It occurs in the deficiency of the enzyme required for tyrosine metabolism. Effective on liver and kidneys 71 Some protein sources 72  Meat and products Animal proteins are generally more biologically valuable than plant proteins. They are rich in essential amino acids. In addition, they have a high rate of metabolism (65-75% in vegetable proteins, 95% in animal proteins) 73  Meat and products The presence of amino acids in the protein molecule in a position where enzymes can easily act, the presence of vitamin B12 together with animal proteins, the presence of many minerals such as potassium, phosphorus, sodium, magnesium, iron, zinc in digestible form are other superior features of animal proteins. Protein is the second highest ingredient in meat after water. Most of the dry matter consists of protein. 74  Meat and products Muscle proteins are divided into 3 main groups; myofibrillary sarcoplasmic connective tissue p r o t e i n s 75  Meat protein Muscle protein (%80) Connective tissue Protein (%20) Sarcoplasma Miofibryl Collogen Reticulin Elastine Proteins (%40) Proteins (%40) Actin Albumin Globulin (%20) (%20) (%20) Miosin Myogen A Globulin (%20) X Myogen B Myoglobin Tropomyszin ve troponin (%10) 76  Sarcoplasmic proteins  They dissolve easily in water  The presence of 10 different proteins is reported They surround the myofibrils and fill their gaps  They named as; – Mitocondrial – Citocrome – Myglobine – Heamoglobin in respcet to their location. 77  Miofibrillary proteins  They are involved in muscle contraction and in the formation of rigor mortis after death.  They are divided into three according to their functions; – Contractile – Regulator – Cytoskeletal  Most are actin and myosin. 78  Connective tissue proteins  It contains three proteins; – Collagen – Reticillin – Elastin  Collagen is the protein that gives the texture of raw meat.  It is a glycoprotein.  It is high in tendons and ligaments.  It gives the main structure of bone and cartilage. 79  Milk proteins  Contains all essential amino acids  The protein rate in cow's milk is 3.6% and this rate may differ according to animal species.  Casein constitutes a significant portion of milk protein (approximately 83.3%)  Apart from casein, low amounts of lactalbumin (15.3%) and lactoglobulin (1.4%) are found. There are traces of other serum proteins 80  Casein  Casein is a glucoprotein which contains – Glucose – Galactose – Mannose  It’s isoelectric point is 4.6  It is heat resistant 81  Serum proteins  Lactalbumin  Lactoglobulin  Protease peptone  Glicomacroppetid  Membrane peptides  Red proteins  Milk antibodies They are not heat stable and coagulates at 60°C 82  Resources Prof. Dr. Hilal Çolak Food hygine lecture notes Prof.Dr. Barış Bingöl Meat and Milk technology lecture notes 83