Low-Germ Milk Production via Direct Steam Injection and Microfiltration
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Solution Overview
Problem
Conventional pasteurization methods fail to effectively eliminate heat-resistant bacterial spores and germs in milk products, leading to potential contamination and quality issues during cheese production, as these germs can grow rapidly in plate heat exchangers and survive the moderate heat treatment.
Innovation Solution
A method involving a first heat pre-treatment of milk to 25-30°C, followed by direct steam injection to 50-60°C, cream separation, a second steam injection to 50-75°C for pasteurization, and flash cooling to rapidly reduce germ growth conditions, significantly shortening the critical temperature dwell time and enhancing germ load reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pasteurization is used to heat milk to 72-75°C for 15-30 seconds, then most food spoilage bacteria are killed, but heat-resistant bacterial spores and mold spores survive and can grow rapidly in heat exchangers
Solution Approach 1:
The patent applies preliminary action by performing microfiltration before pasteurization to remove spores and germs from the milk. This pre-treatment reduces the initial germ load to below 10^3 CFU/ml, preventing subsequent rapid multiplication during heat exchanger operation. The filtration step (10-60 bar pressure, 0.1-0.4 µm pores) removes spores before they can survive pasteurization and cause contamination.
Solution Approach 2:
The patent changes physical parameters by using high-pressure microfiltration (10-60 bar) through narrow-pored membranes (0.1-0.4 µm) to physically separate spores from milk. This parameter change enables removal of heat-resistant spores that would otherwise survive conventional thermal pasteurization temperatures and continue to multiply.
2Ease of manufacture
If the milk is kept in the critical temperature window of 35-55°C for a long period during conventional pasteurization, then cream separation can be performed, but germ growth takes place rapidly with doubling every 20 minutes
Solution Approach 1:
The patent performs cream separation before the pasteurization step, rather than during or after. By separating cream from skimmed milk first (at lower temperatures), the subsequent pasteurization process handles only skimmed milk, which can be rapidly heated and cooled without prolonged exposure to the critical 35-55°C growth window for spores.
Solution Approach 2:
The patent implements continuous high-speed processing where skimmed milk is rapidly heated through the heat exchanger and immediately cooled, minimizing dwell time in the critical temperature window. The continuous flow system prevents stagnation and rapid spore multiplication while maintaining efficient cream separation in a separate preceding step.
3Object-affected harmful factors
If ultra-high heating is used to kill heat-resistant spores, then germ load is reduced, but whey proteins are denatured
Solution Approach 1:
The patent extracts and removes heat-resistant spores and germs from the milk through microfiltration before pasteurization. By physically separating these harmful organisms using narrow-pored membranes under high pressure, the subsequent mild pasteurization (72-75°C) can effectively kill remaining vegetative cells without requiring ultra-high temperatures that would denature whey proteins.
Solution Approach 2:
The patent introduces microfiltration as an intermediary step between raw milk reception and pasteurization. This intermediate physical separation process removes spores that are resistant to thermal treatment, allowing conventional pasteurization temperatures to achieve sufficient sterilization without needing to raise temperatures to levels that would damage protein structure.
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 reduces the germ load in dairy products by shortening the critical temperature dwell time by a factor of 2 to 4, making it more effective than conventional pasteurization in eliminating mesophilic and thermophilic spores, thereby improving the hygiene and quality of milk products.
Implementation Method 1
heating it to temperatures in the range of 25 to 30°C, (b2) the pre-treated milk product by a first direct injection of highly heated steam ('direct steam injection', DSI) heated to temperatures of 50 to 60°C, and (b4) heating the skimmed milk product to temperatures of 50 to 75°C by a second direct injection of high-temperature steam
Implementation Method 2
pasteurizing the milk product, and (b5) the milk product cools down by flash cooling
Data Source
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AI summary
A process for producing low-germ whole milk products is proposed, in which (a1) the milk product to be sterilized is optionally subjected to a first heat pretreatment in a heat exchanger and heated to temperatures in the range of 25 to 30 °C, (a2) the optionally pretreated milk product is heated to temperatures of 50 to 75 °C by direct steam injection (DSI) and thereby pasteurized, and (a3) the pasteurized product is cooled by flash cooling. An analogous process for producing low-germ skimmed milk products is also disclosed, which additionally includes the separation of the cream as a key intermediate step.