Industry sector: food industry
Company activity: cheese manufacturing
Company type: subcontractor for a major global group
Company founding period: 1930s (for the group)
Contacts: group new works and safety manager, local production site CEO, local quality manager
Company context
This company produces stretched-curd and whey-based cheeses such as mozzarella, ricotta, and fromage blanc desserts. Some of these products, like mozzarella, are packaged in pouches containing brine. The brine is prepared on-site by adding salt to water taken from the standard supply network.
Filtration challenge
The customer wanted to obtain sterile brine to improve the product’s bacteriological quality, in response to rising consumer expectations. To achieve this, they decided to implement two filtration stages at two distinct points in the brine-manufacturing process:
- the first to filter the cooled network water (6 to 8 °C) before preparing the brine
- the second on the brine itself, at the outlet of the preparation tank, just before final cheese packaging
The operating constraints for these two filtration steps were as follows:
- temperature range: 4 to 8 °C
- flow rate: 4 m³/h
- inlet/outlet: DN25 Tri-Clamp
- pressure range: 4 to 5 bar
In addition, the filtration housings had to be supplied with full manufacturing guarantees and compliance with food-industry requirements. The filters themselves had to be food-contact approved, with certificates to support it.
Pemflow filtration solution
First filtration stage (cold network-water filtration):
We selected a size 2 electropolished bag filter with a 10 µm rating. This choice was based both on our experience with this type of installation and on a water-quality analysis report for the distribution network provided by the local authorities.
Second filtration stage (sterilizing filtration of the brine before final pouch packaging):
We designed a two-step solution to obtain brine of high bacteriological quality:
- pre-filtration at 1 µm absolute
- sterilizing filtration at 0.2 µm absolute, bacterial grade
For each stage, the choice was a 316L sanitary stainless-steel housing, with a mechanically polished finish and a surface roughness below 0.8 µm. These characteristics guarantee the absence of product retention and therefore eliminate the risk of bacterial growth. The selected configuration includes three 20-inch filter cartridges per housing, providing a maximum flow rate of 6 m³/h, above the customer’s requirement of 4 m³/h.
The 1 µm pre-filtration is performed by three pleated 20-inch depth-filtration cartridges made from borosilicate fibers. This filter media provides excellent retention with extremely low pressure drop.
The sterilizing filtration is performed using a pleated PES (polyethersulfone) membrane, ensuring a bacterial reduction factor greater than 10¹¹ (bacterial challenge conducted with the microorganism Brevundimonas diminuta). Its thermally welded construction enhances cartridge integrity and ensures the lowest possible level of extractables in the filtrate.
To learn more about the bacterial challenge requirements for sterilizing filters:
Sterilizing filtration: decoding the requirements for pharma-biotech applications
Expert advice
PES is a naturally hydrophilic material. The filter membrane therefore wets quickly and completely, ensuring fast filtration with high flow rates and high efficiency. PES also has extremely low protein binding, minimizing the risk of binding and thus retention of the proteins to be filtered.
All the recommended materials are also US FDA compliant and meet food-contact requirements.
Our filtration solution fully satisfied the customer, who particularly appreciated the simple and quick installation of the filters.
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