Frozen Fruit Dehydration and Rapid Convection Freezing
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Solution Overview
Problem
Existing methods for freezing fruits and vegetables fail to preserve their original structure, appearance, taste, and texture upon thawing due to issues with water content and freezing processes, leading to texture changes, liquid release, and damage from ice crystal formation.
Innovation Solution
A process involving a slow and slight dehydration treatment to reduce water content by 2-10% followed by rapid convection freezing, using a stream of humid air or an aqueous solution with organic salts like betaine or potassium acetate to maintain water in a liquid state at low temperatures, ensuring microscopic ice crystal formation without structural damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If convection freezing is used to freeze fruits, then the freezing speed increases, but large ice crystals form that break the fruit structure
Solution Approach 1:
The invention changes the temperature parameter of the freezing medium to between -30°C and -50°C, which is colder than conventional convection freezing but not as extreme as liquid nitrogen. This intermediate temperature range allows for faster freezing than air convection while preventing the formation of large destructive ice crystals, thus preserving fruit structure.
Solution Approach 2:
The invention utilizes the phase transition of water to ice at controlled temperatures. By maintaining the freezing medium in the liquid phase at sub-zero temperatures (between -30°C and -50°C), the fruit surface freezes rapidly forming a protective layer, while the interior freezes more slowly, allowing water to redistribute and form smaller crystals that preserve structure.
2Speed
If liquid nitrogen or liquid carbon dioxide is used for freezing, then the freezing speed increases and microscopic crystals form, but the cost increases significantly
Solution Approach 1:
The invention replaces expensive cryogenic liquids (liquid nitrogen at -196°C or liquid CO2 at -80°C) with a more economical aqueous solution that can be maintained at less extreme temperatures (-30°C to -50°C). This aqueous medium is cheaper and easier to handle while still achieving rapid freezing and microscopic crystal formation that preserves food quality.
Solution Approach 2:
The invention changes the temperature parameter from extreme cryogenic temperatures (-196°C for liquid nitrogen) to a more moderate range (-30°C to -50°C) using an aqueous solution. This parameter change reduces the cost of the freezing medium while maintaining effective freezing speed and quality preservation through controlled ice crystal formation.
3Strength
If slow convection freezing is used, then the fruit structure is preserved, but the freezing time increases and water comes out upon thawing
Solution Approach 1:
The invention utilizes phase transition of the aqueous freezing medium and controlled ice crystal formation. The medium remains liquid at sub-zero temperatures until contact with fruit, then freezes rapidly at the fruit surface forming a protective layer. This controlled phase transition enables faster freezing than air convection while preserving structure through microscopic crystal formation.
Solution Approach 2:
The invention changes the temperature parameter to an optimized range between -30°C and -50°C, which is colder than air convection freezing (typically -18°C) but not as extreme as liquid nitrogen. This parameter optimization achieves a balance between freezing speed and structure preservation, reducing freezing time while preventing large crystal formation that would damage the fruit.
4Strength
If water content is reduced by dehydration before freezing, then ice crystal damage is reduced, but the appearance and taste are significantly altered
Solution Approach 1:
The invention applies a preliminary action by immersing fruit in an aqueous solution before freezing to pre-form a protective ice layer on the surface. This preliminary step protects the fruit during subsequent freezing, reducing internal ice crystal damage without requiring significant water removal that would alter appearance and taste. The solution may contain protective agents that further preserve organoleptic properties.
Solution Approach 2:
The invention changes the water content parameter only slightly (2-10% reduction) compared to extensive dehydration methods, maintaining most of the fruit's original water content and organoleptic properties. This moderate parameter change is sufficient to reduce free water available for large crystal formation while preserving the fruit's natural appearance, taste, and texture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The process allows for the continuous production of frozen fruits that maintain their original texture, appearance, taste, and odor upon thawing, preventing structural damage and liquid release, while being cost-effective and preserving nutritional properties.
Implementation Method 1
immersing the product inside a bath with liquid nitrogen (at about −200° C.), liquid carbonic anhydride (at about −80° C.) or an aqueous solution optionally stirred at a very low temperature (between −50° and −35° C.)
Implementation Method 2
the freezing speed of the products is much quicker and the water freezes in the form of microscopic crystals which do not come out of the cells
Data Source
AI summary
A process for the production of frozen foods, particularly vegetables or fruits, including the stages of subjecting the food to a slight and slow dehydration, preferably by air convection, to partially eliminate its water content by between approximately 2 and 10% by weight, especially its outermost layer; allowing the food to rest to favor the redistribution of the free water contained therein and subjecting the food, after its packaging, to a rapid convection freezing treatment, either by immersion in an aqueous solution of salts or by the use of liquid nitrogen. In the case of chopped fruits, before the dehydration stage the portions are sprayed with an antioxidant product.