WEEK 1 - KIMIA PANGAN - AIR DALAM PANGAN.pptx

Water in food

1. WEEK 1 – KIMIA PANGAN WATER IN FOOD Learn More Andriana Kusuma Pertiwi, M.Si

2. LEARNING OBJECTIVES Mahasiswa mampu menjelaskan sifat fisik dan kimia air dalam pangan Mahasiswa mampu menjelaskan jenis-jenis air dalam pangan dan mengevaluasi peranannya terhadap kestabilan pangan Mahasiswa mampu mengidentifikasi metode analisis kadar air dan aktivitas air melalui kegiatan diskusi dan penugasan .

3. FOOD CHEMISTRY Food Chemistry is the study of chemical processes and interactions of all biological and non-biological components of foods It covers the basic composition, structure and properties of foods and the chemistry changes occurring during processing and utilization

4. MAJOR CONSTITUENTS WATER CARBOHYDRATES FATS PROTEIN MINOR CONSTITUENTS VITAMINS MINERALS ENZYMES FOOD ADDITIVES BASIC CONSTITUENTS OF FOOD Food is any substance usually composed of carbohydrates, fats, proteins, water, etc that can be eaten or drunk by human for nutrition The constituents of foods are divided into two

5. z WATER IN FOOD Water is a chemical compound composed of two hydrogen atoms and one oxygen atom Intracellular and extracellular components in vegetables, fruits, and animal products Minor components of some foods Dispersing medium or solvent in food

6. Covalent Bond Oxygen is more electronegative than hydrogen, meaning it pulls the shared electrons in the covalent bonds closer to itself. region of relatively high negative charge Stronger Weaker The angel between two hydrogen atoms STRUCTURE OF WATER

7. Chemically, each form of water is the same (H 2 O), but differences exist in the physical and chemical conditions in which water exist The form where water occurs in food determines the physical properties of the food Water content : 87-90% Water content : 85-86% Same amount of water, but different physical structure TYPES OF WATER FREE WATER BOUND WATER ADSORBED WATER TYPES OF WATER

8. Most water in foods is called by free water "Free water" : water that is not chemically bound to other components (like proteins or carbohydrates) and can move freely within the food matrix Free water is lightly entrapped and therefore easily pressed from food IMPACT IN FOOD QUALITY AND PRESERVATION Reducing the amount of free water --> inhibit the growth of microorganisms. Foods with less free water, have a longer shelf life. FREE WATER

9. "Bound water" in food refers to water molecules that are closely associated with food components, such as proteins, carbohydrates, or minerals BOUND WATER Food components CHARACTERISTICS Tightly Associated Not Free to Evaporate or Freeze Easily Low Mobility Food with more bound water --> less water activity (aw) --> less prone to spoilage Bound to protein Bound to carbohydrates Bound to lipid

10. Adsorbed water refers to water molecules that are attached to the surface of food particles or other materials through physical or chemical forces CHARACTERISTICS Surface Binding: Adsorbed water is held on the surface of food components --> less mobile than free water but more mobile than chemically bound water. Lower Mobility: Because it is attached to surfaces, adsorbed water is less likely to participate in chemical reactions or support microbial growth compared to free water. ADSORBED WATER

11. Water activity (aw) is a measure of the availability of water in a food product for microbial growth, chemical reactions, and physical processes. If pure water is stored in a closed room, it will form equilibrium with the surrounding air. aw: water activity p: water vapor pressure in food materials po: pure water vapor pressure R : gas constant ; T: temperature It ranges from 0 (completely dry) to 1.0 (pure water) High aw = the water content is higher Low aw = the water content is lower WATER ACTIVITY (a w )

12. Importance in Food Science: Microbial Growth: Microorganisms, such as bacteria, yeasts, and molds, require a certain water activity level to grow. Bacteria (aw ≈ 0.90); Molds and yeasts (aw ≈ 0.60-0.80). Shelf Life and Safety: Lowering the water activity in food helps to inhibit microbial growth, extending shelf life and improving food safety. WATER ACTIVITY (a w ) Bread (aw ≈ 0.95): Has a high water activity; prone to mold growth. Dried Fruit (aw ≈ 0.60 - 0.70): Lower water activity prevents bacteria growth but allows some molds. Honey (aw ≈ 0.60): Low water activity prevents microbial growth, making it shelf-stable.

13. The sample is placed in a sealed measurement chamber inside the water activity meter. The chamber is designed to ensure that no external moisture or air affects the sample's water vapor. WATER ACTIVITY MEASUREMENT

14. DRYING OVEN METHOD The determination of water content that based on the weight difference before and after drying The sample is usually weighed into a float bottom shallow dish made up of aluminium or similar material which will not react with the food Weighed samples are placed in an oven for a specified time and temperature The sample is dried until it reaches constant mass DETERMINATION OF WATER CONTENT

15. DRYING OVEN METHOD DETERMINATION OF WATER CONTENT Advantages Disadvantages Simple ( metodenya sederhana ) Potential for thermal degradation (sampel bisa rusak karena panas) Cost-effective ( biaya relatif murah ) Slower analysis time (waktu analisis lebih lama) Accurate for a wide range of foods ( akurasi baik untuk banyak jenis pangan) High energy consumption (butuh energi tinggi) Requires minimal sample preparation (tidak perlu banyak persiapan sampel) Possible inaccuracies with foods containing volatile compounds ( hasil bisa kurang tepat jika pangan mengandung senyawa mudah menguap )

16. 2. DISTILLATION METHOD ANALYZING STEPS: Preparation of apparatus Weighing the sample Addition of solvent: usually an immiscible organic solvent like xylene or toluene, is added to the distillation flask. Note: The solvent should have a boiling point higher than that of water (100°C) but should not react with the sample. Heating and Distillation: The mixture of the sample and the solvent is then heated --> water in samples evaporates along with the solvent vapors --> pass through a condenser --> cooling down and condense back into a liquid. Collection of Water in the Receiver Dean-Stark Apparatus DETERMINATION OF WATER CONTENT

17. 2. DISTILLATION METHOD DETERMINATION OF WATER CONTENT Advantages Disadvantages Suitable for oily samples : ideal for samples containing volatile oils or substances that do not dry well using oven drying Time-consuming: the process can be slow, especially for samples with low moisture content Direct measurement : moisture content is directly measured as water, providing accurate results Handling volatile solvents: the use of organic solvents such as xylene or toluene requires careful handling due to their toxicity and flammability No need for complex calibration : the method is straightforward and does not require extensive calibration like Karl Fischer titration Not suitable for all samples: some samples may degrade or react with the solvent or heat, affecting accuracy

18. 3. KARL FISCHER TITRATION Karl Fischer Titration is a widely used analytical technique for determining the moisture content (water content) in various samples, including food, pharmaceuticals, chemicals, and more This remains one of the most reliable methods for moisture analysis in sensitive or highly precise environments PRINCIPLE: Volumetric Method Involves adding a KF reagent containing iodine to the sample. The titration is done until all water in the sample has reacted with iodine, as indicated by a change in the electrical conductivity of the solution (end-point detection). The amount of iodine consumed is directly proportional to the amount of water present. DETERMINATION OF WATER CONTENT

19. 3. KARL FISCHER TITRATION Hydranal composite 5 --> containing iodine Dry methanol https://www.youtube.com/watch?v=W7wxPpADsRw DETERMINATION OF WATER CONTENT

20. 3. KARL FISCHER TITRATION DETERMINATION OF WATER CONTENT Advantages Disadvantages High precision: capable of detecting very low levels of water content, down to parts per million (ppm) Reagent toxicity: Karl Fischer reagents contain iodine, sulfur dioxide, and methanol, which are toxic and require careful handling and disposal Versatility: applicable to a variety of samples and adaptable to different industries Reagent stability: reagents can degrade over time when exposed to moisture or light, requiring frequent standardization and replacement Speed: provides quick results, advantageous in high-throughput environments like quality control labs Cost: high initial setup cost for Karl Fischer equipment and relatively expensive reagents

21. WEEK 1 – KIMIA PANGAN SUMMARY? Learn More Andriana Kusuma Pertiwi, M.Si