Water Chemistry PDF

Water Chemistry Water Water makes up about ~60 percent of the human body In just one day, 200 million work hours for collecting water Unsafe water kills 200 children every hour 80% of all illness in the developing world is water related https://www.youtube.com/watch?v=1...

Water Chemistry Water Water makes up about ~60 percent of the human body In just one day, 200 million work hours for collecting water Unsafe water kills 200 children every hour 80% of all illness in the developing world is water related https://www.youtube.com/watch?v=1hSLL_lRNE8 http://fieldnotes.unicefusa.org/infographic-world-water-crisis Water In Canada Water-borne infections in First Nations communities is 26 times higher than the national average, and “about 30% of reserved-based community water systems are classified as posing a high risk to water quality” Water in Nutrition Daily intake - about 1.5-2.5 L Required for hydrolysis of large molecules Some produced by oxidation of small molecules AND water found in foods Water is lost from the body by evaporation/ perspiration, urine and feces Water in Nutrition Biological function of water Hydrolysis Cellular structure (e.g., muscle, membranes, skin) - healthy, turgid cells Carbohydrates Nutrient transport - throughout the body Lubrication – saliva, tears, hip and other joints Metabolism - for reactions, e.g., digestion Protein Lipids Water in Nutrition WITHOUT WATER, DEATH IN FOUR DAYS!!! [Without Oxygen, death in 4 minutes – without food, death in 2-4 months] [Water can also be toxic in excess, too low solute conc. in blood] 60% of adult body weight is water (80% of birth weight) Extracellular (12 L) Blood (90% water), lymph, digesta, interstitial fluid Osmotic balance and blood pressure Intracellular (30 L) - inside the cells Muscle (75% water) Adipose (12% water) Water in Nutrition Urine production Kidneys filter blood and reabsorb ~99% of water passing through them Osmotic (blood pressure) and hormonal (vasopressin, aka anti-diuretic hormone-ADH) control ~ 1200 mol/L maximum solute concentration – up to 4x plasma concentration Obligatory water loss: amount needed to dilute the solutes from the diet Primarily salt and urea Note effect urea (high protein diet)! Water in Nutrition Biological function of water Importance of the molecular mobility of water Glucose Transport Cellular structure (e.g., muscle, membranes, skin) - healthy, turgid cells Nutrient transport - throughout the body NaCl Transport Remember Salt and Glucose Remember why glucose is important Remember why salt is important http://www.macmillanhighered.com/BrainHoney/Resource/6716/digital_first_content/trunk/test/hillis2e/ https://rockland-inc.com/glucose-and-energy-metabolism.aspx asset/img_ch25/c25_fig10.html Water in Agriculture 1 pound of beef requires 1,799 gallons 1 gallon of wine requires 1,008 gallons A 0.3 pound burger requires 660 gallons 1 slice of bread requires 11 gallons 1 apple requires 18 gallons 1 pound of chocolate requires 3,170 gallons https://io9.gizmodo.com/a-chart-showing-you-how-much-water-it-takes-to-grow-all-1696247343 Water in Agriculture Importance of the molecular mobility Muscle Structure Biological function of water Cellular structure (e.g., muscle, membranes, skin) - healthy, turgid cells Water in Agriculture Importance of the molecular mobility of water Muscle Structure Biological function of water  Cellular structure (e.g., muscle, membranes, skin) - healthy, turgid cells Meat Quality  Remarkable Science of Water Water can dissolve more substances than any other liquid The freezing point of water lowers as the amount of salt dissolved increases Water expands by 9% when it freezes If you pour salt into a full glass of water, the volume will decrease Water boils at 100 oC (212 oF) Extremely high surface tension Image source: Huffington Post Tetrahedral Molecular Geometry column contains four valence electrons NO DIPOLE MOMENT Methane + 4 Hydrogen https://opentextbc.ca/chemistry/chapter/8-2-hybrid-atomic-orbitals/  +2e- Tetrahedral Molecular Geometry LARGE DIPOLE MOMENT Water  Cohesion is the action or property of like molecules sticking together, being mutually attractive. All because of asymmetry Adhesion is the tendency of dissimilar particles or surfaces to cling to one another Nanostructure Attributes Strong Cohesion Strong Adhesion High Boiling and melting points High latent heat of vaporization  Agriculture Food Science Nutrition How an application of a How foods hydrate  Water is the transport molecule of the blood pesticide / herbicide coats a Why we add surfactants to  Allows NaCl and sugars to be soluble leaf emulsions  Due of small size O2 is soluble Water is used to transport Why gels and dough exist  Solubilization of proteins and carbohydrates nutrients Hydration of proteins and carbohydrates Adhesion and Cohesion All Because of Asymmetry! Water Methane Bent configuration (asymmetry) of water (bond angle 104.5) Tetrahedral (bond angle 109.5) Water has no net electric charge, one side is No dipole moment positive and the other is negative Intermolecular interactions Strong dipole moment (Van der Walls) (0.4-4.0 kJ/mol) Hydrogen Bonds (12-30 kJ/mol) Property Methane Water Melting Point -182 oC 0 oC Specific Heat Capacity 2.20 J g-1 oC-1 4.18 J g-1 oC-1 Latent Heat 760 kJ/kg 2257 kJ/kg Vaporization Boiling Point -160 oC 100 oC High Boiling and melting points Agriculture Why life on earth exists Nutrition  Why life on earth exists Food Science Structuring of foods Glasses, gels, liquids, solids High latent heat of vaporization and fusion & Heat Capacity Food Science Nutrition Agriculture Evaporative cooling to protect Why we use steam as a heating  When water evaporates it removes a enzymes in plants medium in processing plants lot of heat energy Why it is an energy intensive process to heat and cool foods  Skin is cooled  Temperature and The Dipole Moment Changing the temperature of water modifies the dipole moment of the molecule which changes the hydrogen bond length which is correlated with the hydrogen bond strength An increase in the hydrogen bonding leads to increased cohesion, density (down to 4oC) and viscosity; while the adhesion, density (from 4 to 0 oC), and thermal conductivity all decrease https://www.sciencenews.org/article/warming-could-disrupt-atlantic-ocean-current http://www.meteor.iastate.edu/gccourse/ocean/vertical.html  Cohesion is the action or property of like molecules sticking together, being mutually attractive. Adhesion is the tendency of dissimilar particles or surfaces to cling to one another Remember! -- All because of asymmetry Water nanostructure Strong Cohesion Strong Adhesion High Boiling and melting points High latent heat of vaporization Water Activity Water activity is a measure of the availability of water molecules to enter into microbial, enzymatic and chemical reactions Bound water is unavailable for reactions Capillary water is somewhat available for chemical reactions Free water is available for chemical reactions More predictive of shelf-life than simply measuring total water content of a food Types of Water Water binding-bound water Refers to the molecular interaction of water with solutes (sugars) and ions (salts). Also referred to as “hydration”. Water bound to solutes behave differently than “bulk” water. The water is molecularly immobile or unavailable. Water holding-entrapped water Refers to the entrapment of water in a gel by high-MW molecules such as proteins and polysaccharides in a way that prevents water from flowing and from being “exudated”. Entrapped water, often termed free or capillary water behaves like pure water and maintains its molecular availability and mobility. 24 Water Activity The activity of a substance as defined from thermodynamic principles is its “fugacity” or its tendency to escape from the substance. For water, this is quantified as the vapor pressure of the substance. Every liquid will exhibit a vapor phase which is in equilibrium with the liquid phase. The vapor has a characteristic pressure which is dependent on the temperature of the system. The addition of a solute to water will decrease the vapor pressure of the solution. 25 Determining water activity Aw is calculated as follows, where, P = vapour pressure of the food and Po is the vapour pressure of pure water at the same temperature Aw is normally measured (instrumentally) by determining the Equilibrium Relative Humidity (ERH) where, Aw = ERH(%)/100 Water Activity Water’s large dipole moment disrupt electrostatic interactions between ions dissolving them. The presence of ions in water will affect or disrupt the water structure.  Negative ends of the water dipole (oxygen free electron pairs) will orient themselves towards cations and positive ends of the same dipole (hydrogen atoms) will orient themselves towards anions.  This forms a “hydration sphere” about one layer deep around the ion. The water in this hydration sphere is typically called “bound water”.  Bound water can still form hydrogen bonds and this “structures” the water several layers removed from the hydration sphere. 27 Mobility of Water in Foods 1) Hydration (Bound, Visceral) Water water molecules associated directly with the food macromolecules (exchangeable, not covalently or H- bonded) gives macromolecules their structure not available for microbial growth nor chemical reactions it does not contribute to product deterioration present even in dry foods, e.g., powders Mobility of Water in Foods 2) Trapped (Capillary) water ~ 5% of the total water in a food, may be much more in tissue products like leaves associated with cellular and tissue structures - not easily pressed out can be removed by drying does not support microbial growth but provides a“moist” texture, e.g., dried fruits or capillary water in vegetables, meats 3) Free Water can be 90% + of the water in a food (e.g. orange juice) available for both microbial growth & chemical reactions easy to remove (just squeeze or press) out of product Water Activity Typical aw values Free water aw = 1.0 (lots of water available) 0.9 some water immobilized (“bound”), below this value the bacteria stop growing 0.8 more water immobilized, the yeasts and bacteria stop growing 0.7 even more water immobilized, the molds, yeasts and bacteria stop growing 0.5 enzymatic reactions are very slow or stopped 0.3 chemical reactions are very slow or stopped Hysteresis Desorption (drying or freezing) and sorption (wetting) isotherms are typically non-superimposable in a phenomenon termed hysteresis. Hysteresis in foods is the phenomenon by which at constant water activity (Aw) and temperature, a food adsorbs a smaller amount of water during adsorption than during a subsequent desorption process. Water Content Vs. Water Activity Food Moisture (%) Water activity Ice (0oC) 100 1.0 Ice (-50oC) 100.62 Fresh Meat 70.985 Bread 40.96 Raisins 27.60 Skim Milk powder 11.60 Macaroni 10.45 Potato Chips 1.5.08 http://tbn3.google.com/images?q=tbn:btUjXHYwEgQovM:http://www.allbestmilk.com/MyImages/Skim%2520milk%2520powder.jpg Mainly salts and sugars Mainly protein Interact strongly with lots Does not interact as strongly of water with water Phase Diagram of Water Can exist in three physical states (very unique) Gaseous, Liquid and Solid Both pressure and temperature may be manipulated to change the physical state of water Used in evaporative drying, freeze drying, boiling,  Supercritical Fluids SCF can effuse through solids like a gas, and dissolve materials like a liquid CO2 and water are most used supercritical fluids, for decaffeination Supercritical Fluids At specific temperature / pressure combinations THC and CBD become soluble Once extracted, drop pressure, CO2 becomes gas and CBD and TCH become insoluble Frozen Foods: Purposes: to stop microbial growth (but not kill) (preservatives are typically not added) to slow chemical and physical reactions Freezing does not degrade nutrients Target temperature less than -10 oC optimal is ~ -25 oC Frozen Food Stability Freezing - Microbial - some survival - Physical - ice formation - Chemical - cryo-concentration Storage - Microbial - no growth - Physical - recrystallization, sublimation - Chemical - slow reactions Thawing - Microbial - growth possible - Physical - drip loss - Chemical - decompartmentalization  Water to Ice Most compounds, as the temperature of the liquid increases, the density decreases Liquid water each molecule H-bonds ~3.4 other water molecules. In ice each water is hydrogen bonded to 4 other molecules. Water to Ice Water can undergo liquid to solid state transitions. The melting point of pure water (at 1.00 atm) is 273.16 K. Unit Cell of Hexagonal Ice When water crystallizes, it preserves the tetrahedral “structure” of liquid water. Water crystallizes into an “open structure” that is less dense (91 %) than the liquid state. Ice will float instead of sink. Ice formation can disrupt tissue structure. When ice melts, only 15 % of hydrogen bonds are broken which explains why the latent heat of fusion (333kJ/kg) is small compared to the latent heat of vaporization (2230 kJ/kg). This means water is a highly structured liquid. 39 How do foods freeze? Bottle is supercooled (oC below melting point) To form a new surface between ice(crystal) and water there is an energy impeding crystallization By introducing a surface (dust, surface the freezer/container, bubble) water can turn to ice with less energy Slower freeze, less nuclei and more crystal growth Fast freezing more nuclei and less crystal grow (ideal 10 monosaccharide units covalently bonded together) Monosaccharides--Configuration Fischer Projections for Linear Sugars Rules: Draw the carbon chain vertically (carbonyl group at the top) Aldehyde Ketone Vertical lines are below the plane Horizontal lines are above the plane Carbon numbering of the sugar always starts at the most oxidized group (i.e. the carbonyl group) Aldose sugar Ketose sugar Glucose Fructose Monosaccharides-- Configuration Chirality Enantiomers Enantiomers are isomers that are related by a reflection operation/mirror plane.  Monosaccharides-- Configuration Stereoisomers are isomers that differ in the 3-dimensional arrangement of atoms (from a molecule) in space. Stereoisomers  Configuration vs Conformation CONFIGURATION CONFORMATION Conformation refers to its The configuration arrangement in space is arrangement of stereogenic how the sugar orients centers itself due to the rotation of single bonds configuration is set at synthesis and is Conformational change is a changed during physical phenomenon chemical reactions Temperature, pH dependent The conformation dictates the physical properties of sugars and the reactions they partake in. Monosaccharides-conformation The formation of a ring structure introduces a new chiral center. The previously achiral carbonyl carbon is now chiral and can assume two configurations (α- and β-) The process of interconversion between the α- and β- forms is called mutarotation. α- and β- are called anomers. As long as this hemiketal or hemiacetal group remains, cyclization remains reversible (this is called a reducing sugar) Anomeric carbon DISACCHARIDES Mono and disaccharides Sweetness varies with different sugars all compared to sucrose sucrose 1.00 fructose 1.7 glucose 0.70 maltose 0.50 lactose 0.40 Artificial sweeteners - Cyclamates 30X, Aspartame 200X, Saccharin 300X, Sucralose 800X  FOOD QUALITY Saccharides are not just sweet Saccharides are not just sweet SWEET PRECEPTION Reducing & Non-reducing Sugars Lactose Sucrose Reducing Sugar Non-Reducing Sugar Preserves the hemiacetal No hemiacetal group group sucrose is NOT a reducing sugar Glucose, galactose, fructose, Does not undergo Maillard reaction and lactose are reducing sugars Undergoes caramelization Undergoes Maillard reaction Undergoes caramelization reducing sugar act as a reducing agent because it has an aldehyde or free ketone group Maillard Reaction Things to know Reducing Sugar + Protein (free amine) form Schiff base A series of molecular rearrangements Degradation productions Important end products include: Melanoidins (pigment) Flavours (breakdown products) http://www.compoundchem.com/2015/01/27/maillardreaction/ Trending Science--Maillard Reaction Fennema, Food Chemistry, 5th ed. Trending Science--Maillard Reaction Acrylamide in Diet Swedish food consumption data to study the dietary intake of acrylamide Based on foodstuffs with low to high levels of acrylamide (10 monosaccharide units covalently bonded together) The structural diversity in polysaccharides is limitless. 87 88 Starch Linked together by (1→4) bonds Amylose Starch content is typically 15 to 25 % Degree of polymerization can be anywhere from 100 to 10,000 Has one reducing end and one non-reducing end The unbranched nature of amylose, the –OH groups can form intermolecular hydrogen bonds with other –OH groups Amylose-amylose interaction reduce solubility Starch Amylopectin Highly branched polymer of (1→4) bonds and branched by non-random, evenly spaced α-(1→6) bonds Branch points occur every 20 to 25 glucose residues Mol weight between 1 million to 1 billion g/mol Branched nature makes intermolecular hydrogen bonding difficult. A Chains = No branch points, non-reducing ends. B Chains = Branch points, non-reducing ends. C Chains = Parent chain holding the reducing end  Starch exists as large particles called Starch granules (~2 μm to 100 μm) Starch granules are predominantly composed of amylose and amylopectin Figure Starch multiscale structure: (a) starch granules (30 μm), (b) amorphous and semicrystalline growth rings (120-500 nm), (c) amorphous and crystalline lamellae (9 nm), magnified details of the semicrystalline growth ring, (d) blocklets (20-50 nm) constituting a unit of the growth rings, (e) amylopectin double helixes forming the crystalline lamellae of the blocklets, (f) nanocrystals: other representation of the crystalline lamellae called starch nanocrystals when separated by acid hydrolysis, (g) amylopectin’s molecular structure, and (h) amylose’s molecular structure (0.1-1 nm) Starch Gelatinization Starch functionality is attributable to three basic behaviors. Gelatinization loss of molecular order Pasting disruption of the starch granule Retrogradation starch polymers (amylose) forms intermolecular hydrogen bonds and may recrystallize Potato Wheat Gelatinization Starch https://www.youtube.com/user/GuelphCerealLab Corn Tapioca Starch-Modifications Starch is an important food polysaccharides Digestible by humans (source of energy) Starch contributes to the texture of foods (puddings, candies, desserts, baked products) Certain indigestible starches behave like fiber (resistant starches) and fermented by gut bacteria as a prebiotic 94  Pectin Pectin is hemicelluloses found in the middle lamella of plant cell walls. Found in fruits (peels) and vegetables. Pectin is obtained from apple pulp, citrus peels, sugarbeet pulp. The most complex hemicellulose polysaccharides. Consists of two main polymers covalently linked together “smooth” galacturonans and “hairy” rhamnogalacturonans (Type I and Type II) 95  Pectin Methoxylated Pectin - Ionization of acids pKa ~3.5 Me--OCH3 Low-methoxy pectin (LMP) = Less than 50 % of High-methoxy pectin (HMP) = More than 50 % of galacturonic acid –COOH groups methoxylated. galacturonic acid –COOH groups methoxylated. Most pectin when extracted has a degree of Pectin are “graded” according to the esterification between 50-80% degree of methoxylation/esterification 96  High Methoxy Pectin - pKa ~3.5 >50% High-methoxy pectin (HMP) = More than 50 % of galacturonic acid –COOH groups methoxylated. LOW pH ideally between 2.8 and 3.2 65-70% sugar to bind water so it will not interfere with hydrogen bonding Attractive H-bonds 97  Low methoxy Pectin