Ohmic Heating for Produce Sterilization
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Solution Overview
Problem
Conventional retort processing methods for sterilizing and packaging fruits and vegetables result in undesirable physical and chemical changes, such as color degradation, texture loss, and reduced shelf life, due to excessive heat, and require large amounts of packaging materials.
Innovation Solution
Ohmic heating techniques are used to minimize exposure to excessive heat, with optimized heating time and temperature, and the use of additives like citric acid and ascorbic acid to balance ionic conductivity and reduce oxidative browning, allowing for more efficient and uniform heating, and aseptic packaging in larger volumes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional retort processing is used for sterilization, then sterilization effectiveness is improved, but product quality deteriorates due to excessive heat causing color degradation, texture loss, and nutrient destruction
Solution Approach 1:
The patent changes the heating parameters from conventional retort conditions (typically above 240°F for extended periods) to ohmic heating conditions (160-210°F for shorter periods). This parameter change allows achieving sterilization effectiveness while minimizing thermal damage to color, texture, and nutrients. The controlled temperature and time parameters in ohmic heating resolve the contradiction between adequate sterilization and quality preservation.
Solution Approach 2:
The patent replaces the conventional thermal conduction-based retort system with an ohmic heating system that uses electrical current to generate heat directly within the product. This substitution of the heating mechanism enables more uniform and controlled heating, achieving sterilization with less thermal stress on the product, thereby resolving the contradiction between sterilization effectiveness and quality maintenance.
2Reliability
If conventional retort processing is used, then sterilization is achieved, but Maillard browning reactions occur between sugars and proteins, further degrading product quality
Solution Approach 1:
The patent changes the temperature parameter to stay below the threshold that triggers significant Maillard reactions (typically above 212°F). By maintaining temperatures in the 160-210°F range during ohmic heating, the process achieves sterilization while minimizing the formation of brown pigments and preserving the natural color of fruits and vegetables, thus resolving the contradiction between sterilization and preventing harmful browning reactions.
3Reliability
If conventional retort processing is used, then sterilization is achieved, but excessive heat caramelizes sugars, degrading product quality and shelf life
Solution Approach 1:
The patent controls the temperature parameter to remain below the caramelization point of sugars (typically above 320°F). Ohmic heating at 160-210°F achieves sterilization without causing sugar caramelization, thereby preserving flavor, color, and overall product quality while maintaining shelf life, resolving the contradiction between sterilization and quality preservation.
4Reliability
If conventional retort processing is used, then sterilization is achieved, but large amounts of packing medium are required, increasing packaging and storage costs
Solution Approach 1:
The patent employs flexible packaging films or containers that can be sealed aseptically after ohmic heating. This eliminates the need for traditional rigid cans and large amounts of packing medium, as the flexible packaging provides adequate protection while minimizing material usage. The process achieves sterilization without requiring excessive packaging materials, resolving the contradiction between sterilization and packaging efficiency.
5Reliability
If conventional retort processing is used, then sterilization is achieved, but the process is time-consuming, reducing productivity
Solution Approach 1:
The patent replaces the slow thermal conduction-based retort system with ohmic heating that generates heat internally and uniformly throughout the product. This substitution enables rapid heating and sterilization, significantly reducing processing time while maintaining sterilization effectiveness, thus resolving the contradiction between reliable sterilization and high productivity.
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
Ohmic heating preserves the quality and freshness of fruits and vegetables, extending shelf life to at least 18 months, reducing packaging needs, and lowering operational and environmental costs by minimizing the use of metal cans and energy consumption.
Implementation Method 1
Ohmic heating techniques are used to minimize exposure to excessive heat, with optimized heating time and temperature
Implementation Method 2
additives like citric acid and ascorbic acid to balance ionic conductivity and reduce oxidative browning
Implementation Method 3
aseptic packaging in larger volumes
Data Source
AI summary
Disclosed are methods for processing harvested produce such as fruits and vegetables, where the sterilization, stabilization and packaging is done in such a manner that it allows for longer retention of freshness, texture, flavor and overall quality than is possible with conventional retort processes and packaging. One specific embodiment discusses sterilizing and packaging harvested produce into a bulk storage container, comprising the steps of cleaning, dicing and blanching said produce, thereby creating pre-processed produce; adding water, at least one acid or salt, and at least one carbohydrate, to said pre-processed produce to form a mixture of pre-processed produce and a liquid packing medium; processing said mixture in an ohmic processing vessel to form a sterilized mixture suitable for aseptic packaging in said container, without first packaging said mixture.