Humid Air Pasteurization of Low-Moisture Foods
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Solution Overview
Problem
Conventional steam pasteurization systems for low-moisture foods like nuts and seeds are ineffective in achieving a 5 log reduction of pathogenic microorganisms without causing quality degradation, as they require short treatment durations to prevent moisture uptake and flavor alteration, and often necessitate vacuum conditions that increase operational costs.
Innovation Solution
Using humid air with a relative humidity exceeding 60% to pasteurize or sterilize low-moisture foods, pre-heating them above the condensation temperature of the water vapor, and maintaining the process at atmospheric pressure to avoid condensation and reduce moisture absorption, thereby allowing longer treatment times and energy savings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional steam pasteurization is applied at normal pressure and temperature (1 bar and 100°C) for sufficient duration to achieve 5 log reduction, then pathogenic microorganisms are effectively inactivated, but moisture uptake increases significantly causing quality degradation
Solution Approach 1:
The patent changes the parameters of the pasteurization medium from steam to humid air, adjusting relative humidity to 60-99% and temperature to 80-95°C. This parameter change allows achieving 5 log reduction while limiting moisture uptake to less than 1%, resolving the contradiction between microbial inactivation effectiveness and moisture control.
Solution Approach 2:
The patent applies different humidity levels at different stages of the process: higher relative humidity (60-99%) during pasteurization to prevent surface drying and maintain effectiveness, then reduced humidity during cooling to prevent condensation. This local quality adjustment optimizes both microbial inactivation and moisture control.
2Reliability
If steam pasteurization is applied for longer duration to increase log reduction, then pathogenic microorganisms are more effectively inactivated, but treatment duration must be limited to prevent moisture uptake
Solution Approach 1:
By changing from steam to humid air with controlled relative humidity (60-99%) and temperature (80-95°C), the patent achieves faster microbial inactivation rates. This allows achieving 5 log reduction in 30-120 seconds with minimal moisture uptake, effectively resolving the time-quality trade-off.
3Use of energy by moving object
If steam pasteurization is applied, then effective heat inactivation is achieved through high heat capacity and condensation, but condensation on product surface causes moisture uptake and quality degradation
Solution Approach 1:
The patent uses humid air as an intermediary medium instead of direct steam contact. The humid air provides heat transfer through convection and conduction without phase change condensation on the product surface, maintaining heat inactivation efficiency while preventing surface moisture accumulation and quality degradation.
Solution Approach 2:
The patent controls relative humidity at 60-99% and temperature at 80-95°C, ensuring the air remains in gaseous phase during contact with products. This parameter control prevents condensation while maintaining effective heat transfer for microbial inactivation.
4Adaptability or versatility
If vacuum conditions are used in steam pasteurization systems, then operational flexibility is improved, but operational costs increase due to vacuum system requirements
Solution Approach 1:
The patent extracts the vacuum system requirement from the pasteurization process by using humid air instead of steam. This allows atmospheric pressure operation, eliminating expensive vacuum equipment while maintaining operational flexibility through controlled humidity and temperature parameters.
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
This method achieves effective pasteurization or sterilization with reduced moisture absorption and energy consumption, preserving food quality and eliminating the need for vacuum systems, while maintaining the effectiveness of heat inactivation without significant drying requirements.
Implementation Method 1
the foods are pre-heated, pasteurized or sterilized in a gas, optionally dried, and cooled
Implementation Method 2
humid air does not require a reduction of operating pressure to reach an acceptable temperature
Implementation Method 3
Absorption of water from the pasteurizing or sterilizing gas into the foods effectively constitutes a phase transition (from gas to liquid) and generates latent heat sufficient for inactivation
Implementation Method 4
the foods are pre-heated to a temperature higher than the condensation temperature of the water vapor in the gas
Data Source
AI summary
A method of and a system for surface pasteurizing or sterilizing low-moisture particulate foods, such as nuts, oats, and spices, is disclosed wherein the foods are pre-heated, pasteurized or sterilized in a gas, optionally dried, and cooled. The gas pasteurizing or sterilizing the foods contains water vapor and one or more further gasses, preferably air.