Traditional methods of preservation - DR KG/KCET

Unit 1 Topic of OBT554 Principle of Food Preservation, Open elective paper from Anna University R2017

1. OBT554 UNIT 1 Traditional Methods of Preservation

2. Hazard Analysis and Critical Control Point * *

3. Traditional preservation technologies The control of pH The control of water activity Heat treatment Freezing Fermentation Natural Antimicrobials Antioxidants Nitrites Drying

4. The control of pH The pH is the negative logarithm of the hydrogen ion activity. pH is an important factor affecting growth of micro-organisms in food because it affects ( i ) microbial energy metabolism (ii) microbial enzyme activity and (iii) stability of cellular macromolecules like carbohydrates pH also affects the sensory properties of many foodstuffs like taste. For example, lowering the pH causes coagulation of milk casein and meat proteins.

5. pH can be controlled by the choice of raw material (e.g., plant varieties, animal tissues) and by the addition or in situ formation of acidic or alkaline low molecular weight compounds. Hence, organic acids are most important in food preservation.

6. Control of Water Activity Water activity : Water activity or a w  is the partial vapor pressure of water in a substance divided by the standard state partial vapor pressure of water. Pure distilled water has a water activity of exactly one . As temperature increases, a w typically increases, except in some products with crystalline salt or sugar. Higher a w  substances tend to support more microorganisms. Bacteria usually require at least 0.91, and fungi at least 0.7.

7. Water migrates from areas of high a w  to areas of low a w .

8. Heat treatment Food preservation by application of heat is achieved by the inactivation of viable micro-organisms. Clostridium botulinum is considered to be the most heat resistant food poisoning organism. Food industry cookers – typically 121°C requires an atmosphere of about 1bar above atmospheric pressure (1bg). Pasteurisation - the partial sterilization of  packaged and non-packaged foods (such as milk and fruit juice) treated with mild heat, usually less than 100 °C (212 °F), to eliminate pathogens and extend shelf life.

9. Food industry cookers Milk Pasteurisation RETORT SYSTEM

10. Freezing Provides extended shelf life Employed for long-term preservation. Freezing changes the physical state of a substance by changing water into ice when energy is removed in the form of cooling below freezing temperature. The maximum recommended storage temperature at which microbiological Spoilage ceases is registered between 9°C and 12°C. Microorganisms commonly encountered in frozen Food include Pseudomonas, Achromobacter , Flavobacter , Micrococcus, Lactobacillus etc.

11. Fermentation Definition : Process in which microorganisms change the sensory (flavor, odor, etc.) and functional properties of a food to produce an end product that is desirable to the consumer.

12. Principle of Fermentation 1. Minimize the level of microbial contamination onto the food 2. Inhibit the growth of the contaminating microflora 3. Kill the contaminating microorganisms

13. Classification of Fermented Foods Campbell-Platt (1987) identified seven groups for classification, namely, beverages, cereal products, dairy products, fish products, fruit and vegetable products, legumes, and meat products

14. Natural Antimicrobials Definition : Chemical compounds having pharmacological and biological activity and produced by living organisms. Secondary metabolites possessing antimicrobial activity are called the natural antimicrobials and could be extracted from different sources like plants (fruits, vegetables, seeds, herb, and spices), animals (eggs, milk, and tissues), and microorganisms (fungi and bacteria) Commonly used: Secondary metabolites like terpenoid or phenolic biosynthetic origin; hydrolytic enzymes ( glucanases and chitinases ) and proteins

15. Examples Phytoalexins - broad-spectrum antibiotics, generally active against phytopathogenic fungi. Organic Acids - Citric, succinic , malic , and tartaric acids found in fruits. Phenolic Compounds - flavons , flavonols , and tannins. Essential Oils and Their Components - derived from spices and herbs eg: cinnamaldehyde from cinnamon, and eugenol from clove. Bacteriocins - Produced by Lactic Acid Bacteria

16. Antioxidants Rancidity : degradation due to changes in lipid constituents is considered the main feature of rancidification .

17. Antioxidants : a substance that inhibits oxidation, especially one used to counteract the deterioration of stored food products.

18. Lemon Juice as Antioxidant

19. Nitrites A salt or ester of nitrous acid, containing the anion NO 2 −  or the group —NO 2 . Nitrites are white-to-pale-yellow hygroscopic crystals. Examples: Sodium nitrite (NaNO 2 ), Potassium nitrite (KNO 2 ). Sodium nitrite plays an important role in inhibiting the growth and toxin production of Clostridium botulinum in cured products. Application: Nitrites and nitrates inhibit dairy microorganisms by their effect on the activity of a number of oxido -reduction enzymes, preventing natural ripening of milk and undesirable microflora forming.

20. Drying Drying reduces the water activity, thus preserving foods by avoiding microbial growth and deteriorative chemical reactions. Heating air using either an electric heater or flue gas is the conventional heating method used for drying foods. Microwave, infrared, radio frequency, refractance window, and dielectric heating use electromagnetic wavelength spectrum as a form of energy, which interacts with the materials, thus generating heat and increasing the drying rate.

21. Drying processes Can be broadly classified, based on the water-removing method applied, as (a) thermal drying, (b) osmotic dehydration, and (c) mechanical dewatering

22. Dried fish Dried chilli Dried safron flowers Dried tamarind

23. ROOT CELLAR for Storage 1950's Root Cellar

24. "Home Demonstration of Canning, Mrs. Jane McKimmon , ca. 1908-1917 "

25. Canning Tomatoes

26. SUMMARY The control of pH The control of water activity Heat treatment Freezing Fermentation Natural Antimicrobials Antioxidants Nitrites Drying

27. Thank you