Liquid Concentrated in Foods ◼ In very pure solutions, the solute concentration in unfrozen liquid may become sufficiently high to cause crystallization of the solute. This change occurs at the eutectic temp. In frozen foods, the temp. used for food freezing are typically well above the eutectic temp. for solutes found in food products. Most often, eutectic temp. are in -55 to -75℃ range. It should be recognized that all frozen foods, even at temp. as low as -40℃, will contain small fractions of unfrozen water
Liquid Concentrated in Foods ◼ In very pure solutions, the solute concentration in unfrozen liquid may become sufficiently high to cause crystallization of the solute. This change occurs at the eutectic temp. In frozen foods, the temp. used for food freezing are typically well above the eutectic temp. for solutes found in food products. Most often, eutectic temp. are in -55 to -75℃ range. It should be recognized that all frozen foods, even at temp. as low as -40℃, will contain small fractions of unfrozen water
Definition of Freezing Time ◼ time required to reduce the product temperature from the initial freezing temperature to a temperature of 5 degrees below the initial freezing temperature
Definition of Freezing Time ◼ time required to reduce the product temperature from the initial freezing temperature to a temperature of 5 degrees below the initial freezing temperature
Effect of Freezing Rate on Product Quality ◼ The formation of large ice crystals causes greater damage to the product structure and negative impact on the quality attributes of that product. As might be anticipated, more rapid freezing and formation of small ice crystals usually result in a more desirable product after freezing and frozen-food storage
Effect of Freezing Rate on Product Quality ◼ The formation of large ice crystals causes greater damage to the product structure and negative impact on the quality attributes of that product. As might be anticipated, more rapid freezing and formation of small ice crystals usually result in a more desirable product after freezing and frozen-food storage
INDIRECT CONTACT FREEZING SYSTEMS ◼ Plate freezing system ◼ Indirect-contact freezing system ◼ Cabinet freezing system ◼ Scraped surface, continuous system
INDIRECT CONTACT FREEZING SYSTEMS ◼ Plate freezing system ◼ Indirect-contact freezing system ◼ Cabinet freezing system ◼ Scraped surface, continuous system
F000 INSULATED FROM OUTSIDE WW亚' PLATE ENVIRONMENT 时 REFRIGERANT 6.2 Schematic diagram of indirect-contact freezing system. figure