Allergens are usually harmless substances. However, in susceptible individuals, they can trigger an adverse immune response, which can result in death. Consequently, individuals with food allergies need to be extremely careful of what they consume. Food labelling helps these individuals avoid the potentially serious consequences from consumption of foods they are allergic to.
Cleaning regimes have been developed to monitor soil and allergen removal, and understand the impact of varying cleaning regimes on their removal. A test section in a pilot scale cleaning rig is fouled with allergenic material, and cleaned at varying flow rates, temperatures, detergent concentrations, and cleaning times. Pressure, conductivity and electrical resistance tomography are used to monitor the dynamic process, and the cleaning fluid assessed at regular intervals to quantify the allergenic material present. By monitoring allergen levels, food manufacturers can increase the safety of products to allergenic individuals.
Bovine milk is used as the allergenic material, as it is easily available and cheap to obtain. Granulated milk is mixed with water to form a paste which is rolled to a controlled volume onto the test section, and inserted into the cleaning rig. The test section has a viewing section, enabling the volume of the fouling material to be observed during cleaning. This enables determination of when the test section is visually clean and consequently, measurements can be taken to determine if it is then also allergenically clean. An alternative test section also exists. This electrical resistance tomography test system provides a non-intrusive and non-invasive way to image the conductivity distribution within a vessel or pipeline through a number of measurements made from surrounding sensing elements.
Different sized areas of the test section were fouled and cleaning was conducted at different temperatures for the pre-rinse. During the pre-rinse, water is flushed through the test section until it is visibly clean. When the test section is visibly clean, a swab test is conducted on the test section to determine if more than 20 µg of milk protein is present in the swabbed area. An increase in temperature was found to reduce the cleaning time. However, higher temperatures increased the quantity of milk that would not remove from the test section during the pre-rinse phase. The volume of milk in the test section does not appear to affect the cleaning time. Cleaning time is determined by the area of milk covering the test section, as removal of small areas of milk are responsible for a significant quantity of the cleaning time. The results suggest that cleaning time is also determined by the adhesiveness of the milk paste to the test section. It was found that the conductivity of the pre-rinse water increased during cleaning. Conductivity measurements have also been used to determine the levels of cleanliness through calculations of the natural log of the root mean squared of conductivity.
In this study, an alkaline clean is conducted using a caustic based solution as the detergent. In this detergent phase, diluted detergent is circulated around the cleaning rig at a range of temperatures and flow rates. Samples of the cleaning fluid are removed from an outlet of the test section at regular intervals to quantify the allergenic material present using enzyme linked immunosorbent assay and bicinchoninic acid protein assay. The measured allergenic material in the fluid increases with cleaning time. The contaminated water is then drained from the rig and the rig filled with clean water again, for the final rinse.
Frequently, cleaning in place systems over clean food processing equipment and food manufacturers add precautionary labelling to their products. This study has deepened the understanding of the impact of various cleaning regimes on soil and allergen removal, preventing the need to over clean, therefore saving energy, time and money, and increasing process efficiency and ultimately eliminating the need for precautionary allergenic labelling.