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 ⚫ 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 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 ⚫ - 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 ⚫ - 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 ⚫ - 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 ⚫ 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
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