Water in Foods Food Chemistry Lecture Notes

TPN1211 Food Chemistry, 3(3-0) Coordinator: Prof.Dr. C. Hanny Wijaya Food Technology Study Program Department of Food Science and Technology IPB University http://fst.ipb.ac.id Internationally...

TPN1211 Food Chemistry, 3(3-0) Coordinator: Prof.Dr. C. Hanny Wijaya Food Technology Study Program Department of Food Science and Technology IPB University http://fst.ipb.ac.id Internationally Approved Food Technology Program by IFT and IUFoST Course 2 Water in Foods Feri Kusnandar, Slamet Budijanto English translation: Hanifah Nuryani Lioe Food Technology Study Program Department of Food Science and Technology, FATETA-IPB Recommended References Jilid 1 & 2 Penerbit Bumi Aksara Open Access : patpi.or.id Titi Rahayu (+62 819-0875-0205) Recommended References Kimia & Teknologi Pati IPB Press Feri Kusnandar Dian Herawati Hanifah N. Lioe Nurheni Sri Palupi Slamet Budijanto Kontak Admin WA: 081319298713 Course Learning Outcomes After completing the topics, students will be able to: ▪ describe chemical structures, physicochemical properties of water and its role in food. ▪ explain the concept of water activity (aw) in food system. ▪ describe the role of water in food characteristics, chemical reactions, and microbial growths. Sub-topics 1.1 Chemical structures and physicochemical properties 1.2 Water activity and its importance in food system 1.3 Role of water in chemical reaction and microbial growth Water in Foods Go to fullsize image Determine the quality of food Preserve the freshness of food Go to fullsize image Determine shelf life and stability during food storage Roles of Water in Food ▪ Affecting texture, freshness and preservation of foods ▪ Universal solvent (salt, vitamins, sugars, pigments) ▪ Ionizable (H3O+, OH-) ▪ For chemical reactions (example: protein hydrolysis = n amino acids) ▪ Affecting enzyme activities ▪ Important for microbial growth→ determine safety and stability of food ▪ As a heat transfer medium Water/Moisture Content in Foods Moisture Moisture Food Food content (%) content (%) Tomato 94 Dried fish 38 Watermelon 93 Meat 66 Cabbage 92 Bread 36 Pineapple 85 Dried fruit 28 Mung bean 88 Milk powder 14 Cow milk 90 Wheat flour 12 Wet weight (g) : Dry weight (g) + Moisture weight (g) % Wet basis = Moisture weight/Wet weight * 100 % Dry basis = Moisture weight/Dry weight * 100 Food Categories by Perishability ▪ Highly perishable: beef, chicken, fish, milk, eggs ▪ Moderately perishable: vegetables, fruits, bread, cake ▪ Non-perishable: seeds, sugars, dried spices, legumes Water as a Solvent Salt dissolution in water Glucose solubility in water Water Involvement in Chemical Reaction Synthesis of a Polymer Hydrolysis of a Polymer Role of Water in Amylose and Peptide Synthesis Polysaccharide synthesis Peptide synthesis Water Involvement in Lipid Synthesis Lipid synthesis Physicochemical Properties of Water pH (pure water) 7.0 Molecular weight 18.0153 Melting point at 1 atm 0.0oC Boiling point at 1 atm 100oC Heat of fusion at 0oC 6.012 kJ (1.436 kcal)/mol Density 1 g/ml Heat of vaporization at 100oC 40.657 kJ (9.711 kcal)/mol Heat of sublimation at 0oC 50.91 kJ (12.16 kcal)/mol Water activity (aw) 1.00 Molecule of Water ▪ Molecular structure: H2O ▪ Atom H and O linked with covalent bond ▪ Polar properties: ▪ H tend to have positive charge (+) ▪ O tend to have negative charge (-) Hydrogen Bond in Water Molecule ▪ Hydrogen bond formed due to the electropositive nature of the H atom and the electronegative nature of O atom ▪ The amount of hydrogen bond energy is 10% of the energy of covalent bonds (10 kcal/mol) ▪ The existence of H bonds causes water to have a high boiling point (100oC, at 1 atm) and is flowing Water/Solute Interactions Hydrogen Bonds Involving Water Physical Properties: Water vs Other Chemicals Water Phase Diagram (Liquid – Vapor – Solid) 375oC 218 atm Heat of fusion Boiling Freezing point Condensation 1 atm Liquid Heat of vaporization Pressure Solid Gas Triple 0.0098oC point 4.6 Torr Sublimation deposition 0 Temperature (oC) 100 (Tb) (Td) Latent and Sensible Heating and Cooling Curves for Water Heating Steam direction Temperature (oC) V 100 Liquid H2O C M 0 Ice F Cooling 63 397 816 3076 direction Zone I Zone II Zone III Zone IV Zone V Heat energy (joules) Sensible heat : Heat energy due to temperature change Latent energy : heat energy due to change of state Application: Drying Process in Food Industry 1 atm = 760 Torr Hot air dryer : evaporate water from liquid to vapor at normal pressure Vacuum dryer : evaporate water from liquid to vapor at lowered pressure Freezer dryer: evaporate water from solid phase to vapor at very lowered pressure Sub-topics 1.1 Chemical structures and physicochemical properties 1.2 Water activity and its importance in food system 1.3 Role of water in chemical reaction and microbial growth Definition ▪ Moisture content (MC): Describe the water contained in food (in percent). Does not describe biological activity. ▪ Relative humidity (RH): Describe water vapour content in the air (in percent). ▪ Water activity (aw): Describe the degree of moisture activity in food, both in chemical and biological reactions. Value: 0 - 1 (without units). aw = 1 → for pure water Degree of Water Binding ▪ Physically bound water ▪ Capillary water: held within the small pores or capillaries of the food matrix, usually in spaces between cells or in fibrous structures. ▪ Trapped water: physically enclosed within the structure of the food matrix, such as within the gel network of proteins or polysaccharides. This water is not freely mobile but is held in place by the physical structure of the food. ▪ Absorbed water: physically bound to the surface of food particles or macromolecules, such as proteins and carbohydrates. This water forms a thin layer over the surface of these components through hydrogen bonding or van der Waals forces. Degree of Water Binding ▪ Chemically bound water ▪ Integral part of constituents: Binds to other compounds as part of other compounds, such as proteins, carbohydrates. When decomposed, water will come out (hydrolysis process) ▪ Hydrates: water is bound as a molecule in the form of H2O. Example CaSO4.5H2O ▪ Mobile or free water (“Air bebas”): Not bound to any other molecules and is freely available. Type of Water in Foods Type 1: ▪ The actual bound water ▪ Water molecules are chemically bound to other molecules through hydrogen bonds. ▪ Water molecules form hydrates with other molecules containing O and N atoms, such as carbohydrates, proteins and salts. ▪ Can not freeze, some can be removed by drying. Type of Water in Foods Type 2: ▪ Water molecules form hydrogen bonds with other water molecules, found in micro capillaries. ▪ Its nature is different from pure water. ▪ More difficult to remove than free water. ▪ If removed, the moisture content of the food will reach 3-7% Type of Water in Foods Type 3: ▪ Water that is physically bound in a matrix of food system, such as membranes, capillaries, fibers, etc. ▪ Characterized as free water. ▪ Easily evaporated and can be used for microbial growth and media for chemical reactions. ▪ If removed, the moisture content of the ingredients will reach 12-25% with aw ~ 0.8 Type of Water in Foods Type 4: ▪ Unbounded water in a tissue of a material. ▪ Are pure water (ordinary water) with full activity. ▪ Food with this type of water can have aw > 0.9 Water Classification in Foods H2 O Other compound Capillary water Dissolved water Absorbed water Constitution water / (ERH>98% or (ERH:24-100% or (ERH:15-68% or Crystal water aw>0.98) aw=0.24-1.00) aw=0.15-0.68) (ERH: