In dairy processing, effective cleaning of process equipment is essential for efficient plant operation and for the production of safe, quality dairy products. Such cleaning is generally achieved using sodium hydroxide, caustic formulated detergents and acid at temperatures of up to 70-80°C. As such, cleaning has a negative impact on the environment. Cleaning has been reported to account for 30% of the energy use in dairy processing (Eide et al., 2003) and is the largest contributor to overall wastewater volume in many plants (Danalewich et al., 1998). Detergents represent the greatest proportion of chemicals used in dairy plants (Wildbrett, 2003) and some of the chemicals used have adverse effects on human and ecosystem health and on the environment (Fryer et al., 2006). Enzymes, which are biodegradable, have been exploited for cleaning in various other sectors, most notably in laundry and automatic dishwash detergents. Reported benefits include reduced usage of chemicals, reduced energy consumption due to milder operating conditions and reduced rinsing volumes resulting in reduced water consumption and reduced generation of waste. Similar benefits could potentially be achieved by using enzymes for cleaning-in-place (CIP) in dairy processing. However, with the exception of cleaning membranes and cold milk areas of dairy plants little attention has been given to the widespread application of enzymes for this purpose, particularly for cleaning heated components where significant and problematic fouling occurs. The main objective of this study was to determine if enzymes display realistic potential to replace (either partially or entirely) currently used environmentally significant CIP chemicals and hence reduce the overall environmental impact of CIP in dairy processing.

Contact was established with several dairy co-ops and companies supplying cleaning chemicals to the dairy industry in order to establish details of how CIP is currently undertaken. Eight commercial protease products were evaluated on a lab-scale by quantitatively assessing their ability to remove a milk fouling deposit, representative of that occurring on heated components, from stainless steel. Cleaning was carried out at 40, 50 and 60°C for 1 hour at the optimum pH determined for each enzyme under application relevant conditions and compared with the cleaning performance of currently used CIP procedures. While satisfactory enzyme cleaning was observed at all 3 temperatures, cleaning at 40°C was most favourable in terms of enzyme stability and energy use. Following cleaning at 40°C, visibly clean surfaces were observed for 6 of the 8 enzymes tested and the cleaning performance of 4 of the proteases (as judged by detection of residual organic matter and protein after cleaning) was comparable to that of 1% sodium hydroxide, the most commonly used CIP agent, at 60°C. The optimum product concentration for cleaning was determined for each enzyme and the 3 most suitable products for potential CIP application were identified based on cleaning performance, enzyme stability and cost. Further assessments of these 3 products were undertaken, including confirmation of cleaning by confocal laser scanning microscopy. Initial cost analysis indicates that the cost of these enzyme cleaning solutions is unlikely to prohibit their use in CIP applications as the cost of 2 of these enzyme-based cleaning solutions is comparable to the average costs of cleaning solutions based on 1.5% NaOH and formulated detergents and in addition, enzyme-based cleaning is likely to reduce energy costs. Lab-based studies undertaken confirmed that all enzyme activity is removed/inactivated by procedures normally undertaken after cleaning. The inclusion of lipase activity in the protease cleaning solution was also investigated with no improvement in cleaning performance observed under the conditions used. Screening of our in-house collection of microorganisms was undertaken with the aim of identifying proteases of potential use in CIP operations. Of 35 microorganisms screened, 14 were found to produce extracellular proteases with activity on denatured whey protein. Based on ability to remove milk fouling deposit from stainless steel, the crude activity produced by the fungus DSM 1024 Schizophyllum commune was found to be most suitable for CIP application.

Based on the results of this study it can be concluded that proteases, and in particular the 3 commercial products identified, are of potential use for CIP in dairy processing. While the lab-scale studies undertaken are a useful indicator of potential suitability, pilot and industrial scale studies are necessary to fully determine actual industrial applicability and confirm economic feasibility. If similar results are observed on this scale in terms of cleaning performance and cost then enzyme-based cleaning offers several advantages over the currently used CIP procedures. These include reduced environmental impact as the enzymes operate at lower temperatures resulting in reduced energy consumption and are biodegradable in contrast to many of the products currently used for cleaning which have adverse effects on human and ecosystem health and on the environment. Enzyme based cleaning is also more compatible with subsequent waste water treatment and would create safer working conditions for plant operators. The 3 commercial proteases assessed in the study are already produced and sold in bulk by global enzyme manufacturers and could be readily incorporated in CIP operations if found to be suitable for this application.

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Boyce, A.   "Minimization of hazardous waste generated by CIP operations in the dairy processing industry - State of Knowledge Report". Associated datasets and digitial information objects connected to this resource are available at: Secure Archive For Environmental Research Data (SAFER) managed by Environmental Protection Agency Ireland https://eparesearch.epa.ie/safer/resource?id=d56ca8cc-6ec3-102d-b891-8d8f2407b579 (Last Accessed: 2025-01-22)

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SAFER-Data Display URL	https://eparesearch.epa.ie/safer/iso19115/display?isoID=148
Resource Keywords	cleaning, dairy, enzymes
EPA/ERTDI/STRIVE Project Code	2007-FS-ET-2-M5
EPA/ERTDI/STRIVE Project Theme	Environmental Technologies
Resource Availability:	Public-Open
Limitations on the use of this Resource
Number of Attached Files (Publicly and Openly Available for Download):	1
Project Start Date	Saturday 1st September 2007 (01-09-2007)
Earliest Recorded Date within any attached datasets or digital objects	Saturday 1st September 2007 (01-09-2007)
Most Recent Recorded Date within any attached datasets or digital objects	Monday 31st August 2009 (31-08-2009)
Published on SAFER	Friday 19th February 2010 (19-02-2010)
Date of Last Edit	Friday 19th February 2010 at 16:29:14 (19-02-2010)
Datasets or Files Updated On	Friday 19th February 2010 at 16:29:14 (19-02-2010)

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