Food Preservation Fish The preservation of fish is a difficult challenge because of three main factors Psychrophilic bacteria may be present o Many fish oils are unsaturated and are easily oxidized Typical fish proteins are not as stable as red meat proteins Chilling does not affect the activity of psychrophilic bacteria. Frozen fish is typically kept at much lower temperatures (-300Cl)than other frozen foods in order to ensure the control of psychrophilic bacteria
Food Preservation ⚫ Fish ⚫ - The preservation of fish is a difficult challenge because of three main factors: • Psychrophilic bacteria may be present. • Many fish oils are unsaturated and are easily oxidized. • Typical fish proteins are not as stable as red meat proteins. ⚫ - Chilling does not affect the activity of psychrophilic bacteria. Frozen fish is typically kept at much lower temperatures (-300C/) than other frozen foods in order to ensure the control of psychrophilic bacteria
Food Preservation ● Produce Harvested fruits and vegetables continue to respire and mature They contain large amounts of water and will wither if water loss is excessive Peas, green beans, and leafy vegetables have high respiration rates compared with those of apples oranges, and pears Potatoes, turnips and pumpkins respire slowly and are easy to store. Moisture loss is more rapid with lettuce than with a turnip because of the large available surface area
Food Preservation ⚫ Produce ⚫ - Harvested fruits and vegetables continue to respire and mature. ⚫ - They contain large amounts of water and will wither if water loss is excessive. ⚫ - Peas, green beans, and leafy vegetables have high respiration rates compared with those of apples oranges, and pears. ⚫ - Potatoes, turnips and pumpkins respire slowly and are easy to store. Moisture loss is more rapid with lettuce than with a turnip because of the large available surface area
Food Preservation Most fruits have an optimum ripenin temperature, usually about 200C. Few fruits w ripen below 50C .-Freezing of many produce items will damage cell structure, and breakdown is very rapid after thawing Modified atmosphere packaging used(CO2, 02) Bananas can remain in a mature but green state for up to six months in atmos pheres of 92% nitrogen, 5% oXygen, 3% carbon dioxide and no ethylene
Food Preservation ⚫ - Most fruits have an optimum ripening temperature, usually about 200C. Few fruits will ripen below 50C. ⚫ - Freezing of many produce items will damage cell structure, and breakdown is very rapid after thawing. ⚫ - Modified atmosphere packaging used(CO2 , O2 ) ⚫ - Bananas can remain in a mature but green state for up to six months in atmospheres of 92% nitrogen, 5% oxygen, 3% carbon dioxide and no ethylene
Food Preservation o- Atmosphere and temperature control are key requirements for extending the shelf life of fresh produce Trade-offs for many produce items 90%RH+perforated plastic wrap; or Selecting packaging films with high gas transmission rates i.e. precut salad bags(the shelf life of about ten days) excellent moisture barrier and very low oXygen barrier
Food Preservation ⚫ - Atmosphere and temperature control are key requirements for extending the shelf life of fresh produce. Trade-offs for many produce items: 90%RH+perforated plastic wrap; or Selecting packaging films with high gastransmission rates. i.e. precut salad bags(the shelf life of about ten days): excellent moisture barrier and very low oxygen barrier
Food Preservation o Barrier Packaging Solvent Stray odors Water vapor vapor R Essential oils Other gases Water Oxygen and volatiles vapor Figure 2.2 a barrier packaging material is one that slows down or stops the movement of selected gaseous substances into or out of a package
Food Preservation ⚫ Barrier Packaging Figure 2.2 A barrier packaging material is one that slows down or stops the movement of selected gaseous substances into or out of a package