Water Properties PDF

WATER Dr. FG & Dr. DKY  nutrisi yang paling diperlukan tubuh membawa nutrisi ke seluruh bagian tubuh membantu tubuh membuang limbah melumasi dan melindungi sendi mengatur...

WATER Dr. FG & Dr. DKY  nutrisi yang paling diperlukan tubuh membawa nutrisi ke seluruh bagian tubuh membantu tubuh membuang limbah melumasi dan melindungi sendi mengatur suhu tubuh Dr. FG & Dr. DKY Water Balance in the Body Dr. FG & Dr. DKY Typical Water Content in Food and Drinks Food Water (%) Cucumber 96 Lettuce, tomato 95 Cabbage, cauliflower, eggplant 92 Beer 90 Onions, peaches 89 Fruit juices, milk 87 Potatoes, Figs 78 Chicken, liver 70 Beef 65 Cheese 37 White bread 35 Preserves 28 Honey 20 Butter and margarine 16 Wheat flour, dried pasta 12 Dried nuts, dried whey 5 Shortening 0 Dr. FG & Dr. DKY  Water Structure Water is a nonlinear, polar molecule containing an oxygen atom bonded to two hydrogen atoms by covalent bonds It is thought that in the liquid and solid states water molecules associate together in some way so that their effective molecular weight appears to be much higher dalam keadaan cair dan padat, molekul-molekul air saling berasosiasi sedemikian rupa sehingga berat Dr. FG & Dr. DKY molekul efektifnya tampak jauh lebih tinggi Water Structure and Bonding Q= Q Bonding 104.5 H-O-H (vapor) 105 H-O-H (liquid) 109.5 H-O-H (ice) 180 O..H- O Dr. FG & Dr. DKY Molecular ions of water and Ionization of water At neutral pH and 25ºC one water molecule in every 10 million becomes ionized through the bonding of one of its protons to another water molecule: Pada pH netral dan suhu 25ºC, satu molekul air dari setiap 10 juta menjadi terionisasi melalui ikatan salah satu protonnya dengan molekul air lainnya. Hydronium ion Hydroxyl ion Dr. FG & Dr. DKY Phase Transitions of Water Dr. FG & Dr. DKY  Phase Transitions of Water LIQUID GAS = Evaporation GAS LIQUID = Condensation GAS SOLID = Deposition SOLID GAS = Sublimation SOLID LIQUID = Freezing LIQUID LIQUID = Melting endapan Dr. FG & Dr. DKY  Phase Transitions of Water Ikatan hidrogen adalah ikatan elektrostatik lemah yang mudah putus, dan di dalam air ikatan tersebut terus-menerus terbentuk, putus, dan terbentuk kembali Hydrogen bonds are weak electrostatic links which are easily broken, and in water such bonds are constantly being formed, broken and re-formed. If water is heated the thermal energy of the molecules is increased, and their resulting increased motion favors the breaking rather than the formation, of hydrogen bonds. Dalam uap air, tidak ada ikatan hidrogen dan air ada sebagai unit tunggal Jika air dipanaskan, energi termal molekul meningkat, dan peningkatan gerakan yang dihasilkan lebih mendukung pemutusan daripada pembentukan ikatan hidrogen In water vapor no hydrogen bonds are present and the water exist as single units. On the other hand, if liquid water is cooled the loss of thermal energy and the resulting decreased motion of the water molecules favors the formation of hydrogen bonds. Ditermal sisi lain, jika air cair didinginkan, hilangnya energi dan gerakan molekul air yang menurun mendukung pembentukan ikatan hidrogen. In ice hydrogen bonding is so extensive that all the water molecules are linked together by hydrogen bonds so forming a rigid and regular structure. Pada es ikatan hidrogen sangat luas sehingga semua molekul air saling terhubung melalui ikatan hidrogen sehingga membentuk struktur yang kaku dan teratur. Dr. FG & Dr. DKY  Perubahan fase dan pentingnya dalam industri makanan Phase change and importance in food industry Evaporation and food processes Tomato paste production Fruit juice concentrate Evaporated milk Drying of fruits Dr. FG & Dr. DKY Freezing and food processes Fish, meat, vegetable, fruit,.. freezing Effect of freezing in foods Destabilisasi emulsi Destabilization of emulsions Flokulasi protein Flocculation of proteins Increased lipid oxidation Peningkatan oksidasi lipid Meat toughening Pengerasan daging Cellular damage Kerusakan sel Loss of water holding capacity Hilangnya kapasitas menahan air Sublimation and food processes Freeze dried coffee Freezed dried vegtables Freeze dried fruits Dr. FG & Dr. DKY  Air sebagai Pelarut Water as Solvent Karena polaritasnya, air dapat berinteraksi dan melarutkan senyawa polar lainnya dan senyawa yang terionisasi (elektrolit). Because of its polarity, water can interact with and dissolve other polar compounds and compounds that ionize (electrolytes). Substances that readily dissolve in water are said to be hydrophilic, or water loving. Zat yang mudah larut dalam air dikatakan bersifat hidrofilik, atau menyukai air. Water molecules align themselves around electrolytes so that the negative oxygen atoms of the water molecules are oriented toward the cations (the positive ions) of the electrolytes and the positive hydrogen atoms are oriented toward the anions (the negative ions). Molekul air menyelaraskan dirinya di sekitar elektrolit sehingga atom oksigen negatif dari molekul air berorientasi ke kation (ion positif) dari elektrolit dan atom hidrogen positif berorientasi ke anion (ion negatif). Dr. FG & Dr. DKY Consider the dissolution of the crystalline electrolyte sodium chloride (NaCl). The polar water molecules are attracted to the charged ions in the crystal. The attractions result in sodium and chloride ions on the surface of the crystal dissociating from one another, and the crystal begins to dissolve. Perhatikan pelarutan elektrolit kristal natrium klorida (NaCl). Molekul air polar tertarik ke ion bermuatan dalam kristal. Daya tarik tersebut mengakibatkan ion natrium dan klorida pada permukaan kristal terdisosiasi satu sama lain, dan kristal mulai larut. Salt crystal dissolving Salt after dissolving Dr. FG & Dr. DKY Interactions of Water with Food Components The interactions of water with food components are at the root of many problems/solutions with the properties of food systems. Interactions of water with carbohydrates: The binding of water to sugars and polysaccharides is an important contributor to the properties of many foodstuffs. Pengikatan air pada gula dan polisakarida merupakan kontributor penting terhadap sifat banyak bahan makanan.  retarding the formation of ice crystals (with liquid water- i.e. frozen desserts) memperlambat pembentukan kristal es (dengan air cair - misalnya makanan penutup beku)  formation of gel structure with high amount of water (binding high amount of water- i.e. agar) pembentukan struktur gel dengan jumlah air yang tinggi (mengikat jumlah air yang tinggi - yaitu agar) Dr. FG & Dr. DKY  Interactions of water with nonpolar (oil) molecules: Water and oil do not mix…. WHY? Kekuatan kolektif ikatan hidrogen air. The answer: The collective strength of hydrogen bonds of water. Oil is nonpolar, meaning its molecules do not have a charge distribution that can interact with polar molecules like water. Oil molecules are hydrophobic, meaning they do not form hydrogen bonds with water molecules. This behavior is why oil and water naturally separate, with water molecules forming a network through hydrogen bonds and excluding the nonpolar oil molecules. Dr. FG & Dr. DKY Interactions of water with proteins: pengaruh air pada struktur dan perilaku protein. Water is important for proteins because of influence of water on the structure and behaviour of proteins. A protein molecule presents three kinds of surface groups to its aqueous environment, depending on the nature of the amino acid side chain Molekul protein menyajikan tiga jenis gugus permukaan pada lingkungan berairnya, tergantung pada sifat rantai samping asam amino. Dr. FG & Dr. DKY  Asam glutamat Kelompok bermuatan polar Polar charged groups - Glutamic acid (-CH2CH2COO-) - Lysine (-CH2)4NH3+ ) Polar neutral groups Kelompok netral polar - Glutamic acid at low pH (-CH2CH2COOH) - Serine (-CH2OH) Non-polar groups - Valine (-CH(CH3)2) - Methionine (-CH2CH2-S-CH3) Metionina Non polar side chains are usually found buried in the interior of the protein and will not concern us. Rantai samping non polar biasanya ditemukan terkubur di bagian dalam protein dan tidak akan menjadi masalah bagi kita The pH value will obviously be a major influence on the properties of ionisable side chains. Nilai pH jelas akan memberikan pengaruh besar pada sifat rantai samping yang dapat terionisasi As a general rule only small proportion of the polar groups of a native protein will be unable to bind water, because of being buried in the largely hydrophobic interior of the molecule. Sebagai aturan umum, hanya sebagian kecil gugus polar dari protein asli yang tidak akan mampu mengikat air, karena terkubur di bagian dalam molekul yang sebagian besar bersifat hidrofobik. Dr. FG & Dr. DKY  Interactions of Water with Food Materials We should consider food as a whole and leave the components behind. The state of water in a food is described between the moisture content of the product and the relative humidity of air surrounding it. Keadaan air dalam makanan dijelaskan antara kadar air produk dan kelembaban relatif udara di sekitarnya. What is Water Activity? Dr. FG & Dr. DKY What is Water Activity? Water activity or the equilibrium relative humidity of a system is defined as: where aw = Water activity p = vapor pressure of water in food Po = vapor pressure of pure water (at the same temperature) ERH = Equilibrium relative humidity Dr. FG & Dr. DKY Dr. FG & Dr. DKY Dr. FG & Dr. DKY  The relationship between moisture content and relative humidity is represented by the SORPTION ISOTHERMS. Hubungan antara kadar air dan kelembaban relatif diwakili oleh ISOTERM SORPSI Types of Water? It is convenient to divide the water into three types Zone 1 Monolayer (tightly bound) water Air monolayer (terikat erat) Zone 2 Additional (loosely bound) water Air tambahan (terikat longgar) Zone 3 Free (capillary) water Air bebas (kapiler) Dr. FG & Dr. DKY Dehydrated foods are preserved because water activity is at a level where no microbiological activity can occur and where deteriorative chemical Makanan anddehidrasi biochemical reaction rates are diawetkan karena aktivitas air berada pada tingkat di mana tidak ada reduced to a minimum. aktivitas mikrobiologi yang dapat terjadi dan di mana laju reaksi kimia dan biokimia yang merusak dikurangi hingga minimum. Food Water activity Fresh fish and meat 0.99 Bread 0.95 Fresh fruits and vegetables