Assuring water quality and safety in food processing

FoodInc: Food Industry consulting group

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Most of us take water for granted, thanks to improvements in public health over the past century.

As food producers and processors, we require good quality water for a range of operations, including washing, blending or mixing, cleaning, ice making, steam production and product transportation in-process. To assure food safety, we must operate within a framework based upon sound science that ensures water quality in process, and optimises its use.

As found in the recent water quality issue in Havelock North, drinking water provides an efficient route for the spread of pathogens. It is essential that food processors take steps to assure that water and food are completely safe and suitable.

Water as an ingredient poses the biggest challenge in terms of quality and purity. Not only must it be safe but also it must not impart off flavours, odours, colour or create product stability issues due to presence of transition metals. High levels of metallic and non-metallic compounds also pose a risk. High nitrate levels in drinking water may lead to methaemoglobinemia (blue baby syndrome) and have been implicated in an increased risk of stomach cancer (Chambers et al., 2001). Methaemoglobin (MetHb) is formed when nitrite (formed from the endogenous bacterial conversion of nitrate from drinking water) oxidizes the ferrous iron in haemoglobin (Hb) to the ferric form. Levels of nitrate in drinking water should not be greater than the WHO guideline value of 50 mg/L

The Ministry of Health, in its rationale behind the Health (Drinking Water) Amendment Act 2007 states New Zealand has relatively high rates of largely preventable enteric or gastro-intestinal disease in comparison with other countries¹. This is at least partly attributable to contamination of drinking-water. The highest rates of cryptosporidiosis occur in areas where water is either ungraded or graded as unsatisfactory².

Good Manufacturing Practices and HACCP

The Food Act 2014, and the subsequent Food Regulations 2015, specify the requirements for process water and water as an ingredient and give guidance to the food industry (including retail and food service operations) on how to ensure its safety.

Under the Food Regulations 2015, water is classed as an essential service, essential to the production or processing and handling of food. Its definition is broad and includes ice, steam and seawater.

Section 21 of the Food Regulations 2015 requires operators to ensure that any water used for producing food, processing and handling food, personal hygiene, cleaning, or any other purpose is suitable for the purpose for which it is used; and does not adversely affect the safety or suitability of food. In addition to this, the capacity of the water supply to the place of food business must be adequate for the operations of the food business.

Water source

Drinking water is supplied to the food industry either publicly, by local government authorities, or privately by the food business itself. However, the water used to supply the drinking water can come from a variety of sources including surface water (e.g. streams, rivers, and lakes), groundwater (e.g. natural springs, wells, bores), rainwater and seawater (treated at a desalination plant).

It is the source of water which generally determines the quality of the water and whether treatment of the water is necessary to ensure it meets drinking water standards and is safe to be used in food production (i.e. safe for human consumption).

The provision and treatment of private water  supplies  used  by  the food industry is the responsibility of the specific food business using the supply. Typically, private water supplies will require treatment and ongoing verification following treatment (e.g. laboratory testing) to ensure they are fit for human consumption and can be used in food production

To assist many businesses, the “Template” Food Control Plan, published by the Ministry for Primary Industries has expanded the regulations to give more guidance on the use of water within the food industry. The main area of focus of food control plans is the prevention or minimisation of contamination of food. Essential to this is the availability of suitable water, which includes water as an ingredient, as a processing aid and as hot and cold water for cleaning and hand washing.

In New Zealand, we are fortunate that systems are in place, through local councils (registered suppliers), to treat and provide safe, potable water to residential and commercial customers in their region. This makes the task of ensuring safe and suitable water consumed within the food industry much simpler. Although testing of water supply within food factories for absence of E. coli is common (and necessary to ensure the council supplied water has not been contaminated on site), the presence of a low level of residual chlorine is very effective in maintaining pathogen free water supplies.

Where water is obtained from other sources, such as surface, ground water or roof water, businesses will need to comply with the self- supplied water requirements set out in Part 2 of MPI’s Food Notice: Food Control Plans and National Programmes (15 December 2015) to operate a Food Control Plan. Refer Table 1.



Table 1: Testing requirements for self-supply water (DWSNZ)¹,²

Test                                   Criteria

E. coli                                 Less than 1 in any 100ml sample

Turbidity                             Must not exceed 5 Nephelometric Turbidity Units (NTU)



Operators of Food Control Plans are responsible for the safety of supplied water from the point at which it enters the business. This includes keeping water pipes in sound condition, flushing after repairs and maintenance and flushing to remove stagnant water if not used for more than seven days. Any water tanks must be kept clean and in good repair to prevent build-up of sediment and be covered and have screened openings to protect against access by animals, birds and debris.


Any self-supplied water must also be safe to use with food and meet the requirements for clean water. Where water supply comes from a roof collection area, it must only come from roofs and gutters made from safe substances (e.g. no lead-based paint, bitumen, exposed timber or copper guttering). Precautions such as screening guttering and removing overhanging vegetation should be done to reduce contamination potential. Also, a first flush device must be installed and used to divert the first flush of water when it rains.

A water treatment system may be necessary to ensure that self- supplied water is safe for use. Typical water treatment systems include a combination of filtration, chlorination, UV disinfection and others. Any system must be installed and maintained in accordance with the manufacturer’s instructions and be regularly checked for effective performance. This may include testing for free chlorine at levels of at least 0.2mg/L (recommended weekly testing) or regularly testing for the absence of E. coli (at least every 3 months). Guidance should be sought from equipment suppliers or your local public health unit water assessor.

Compliance with the above requirements will give any food processor confidence that any water used within their process is not a contamination source for their products. But, as with any system, its performance needs to be monitored to ensure on-going compliance.


Treatments and techniques

Most processors draw water from city water supplies or wells. The standard food manufacturing plant assumption is that these are safe sources but this needs to be verified.


Water treatment processes remove pathogens and impurities that may otherwise be harmful to human health or aesthetically unpleasant. Treatment processes vary depending on the source water. But typically, an adsorbent material is added to the water to bind dirt and form heavy particles that settle to the bottom of a water storage tank. The water is then filtered to remove even smaller particles. Finally, a small amount of disinfectant (e.g. chlorine), at a level safe for human consumption, may be added to kill any remaining microorganisms.

The use of chlorine depends very much on pH control. The optimum pH is 7.4. Above 7.8 chlorine is ineffective. Whilst the free chlorine content can be high, very little chlorine occurs as active hypochlorous acid, but rather as inactive hypochlorite Newer sanitising agents are less pH dependent, including chlorine dioxide and Anolyte (hypochlorous acid) from electrolyzed water.


Examples of specific applications

Recombining milk powders

In general, good clean safe city water with no objectionable flavours, odours or high levels of suspended solids must be the starting point for recombining or reconstituting dairy powders.

The ‘salt’ balance is most important for physical stability when UHT treating or sterilising high protein dairy products as it affects heat stability, viscosity and shelf life.

The mineral content (calcium and magnesium) needs to be limited with total hardness at a maximum of 100mg/litre as calcium carbonate, which is lower than the general domestic water supply.

Where fat is present in the product there should be no traces of copper (no brass fittings) or iron which easily trigger fat oxidation. When processing oils the water should be softened to remove calcium, magnesium and iron salts.

Chloride, sulphate and nitrate levels are also recommended to be lower than general domestic water.

Nitrate levels are particularly relevant for all water used for infant formulas and foods: these should not exceed 45mg/l as Nitrogen dioxide. This is particularly important where water is drawn from supplies affected by dairy runoff.

Canned food processors

Canned food manufacturers are required to have >5ppm free chlorine in their post-process cooling waters to prevent microbiological post- process contamination of the contents as the rigid container seams contract while cooling.

Leafy salads wash water.

Chlorination and monitoring of wash waters is essential to ensure the maintenance of free chlorine levels. pH must be monitored regularly as this affects free chlorine levels. Similarly with make-up water.


Analytical methods and kits

Your laboratory can undertake some basic tests such as pH and turbidity using test kits. Pathogens, metals and pesticides testing needs to be conducted by qualified analytical laboratories.

It is common practice to test process water, at least annually, for the presence of E. coli to ensure that no contamination has occurred in the reticulation system.

Water suppliers publish test results on a regular basis. These reports should be obtained by food processors as part of their monitoring programme:

  • Annual and monthly reports can be downloaded from some water suppliers’ websites. These reports include tests conducted on water leaving the local supply plant and within the distribution network.
  • Ministry of Health (MoH) annual compliance survey is reported publicly in July each year.
  • The MoH Annual Microbiological and Chemical Quality of Drinking-Water Supplies, is available on their website and is issued in Nov/Dec each year, covering the previous year for all water suppliers, water treatment and network results. (MoH, 20157)
  • Water Information NZ (WINZ, http://www.drinkingwater.esr.cri. nz) is a public source of information and for those managing water quality.
  • Regional Council websites also detail the location of all bores in their areas.



The rules governing food safety include requirements for adequate supplies of safe drinking water for use in food production¹,². As

such the safety of water supplies directly affects the safety of food. Therefore, food businesses should follow good-sense practices when considering the source, treatment and intended use of water in food production to ensure the quality and safety of the foods produced. All food companies should know the composition of their process and ingredient water and test it regularly.


References and sources of information

  1. drinking-water/drinking-water-legislation,
  2. NZ Government Regulatory Impact Statement regarding the adequacy of the supply of safe drinking water, Nov 2000
  3. Hrudey, S.E., and Hrudey E.J, 2004. Safe drinking Water: Lessons from Recent Outbreaks in Affluent nations. IWA Publishing, London, UK, pp.81-118
  4. Hawkes Bay District Health Board Update November 2016
  5. 1972, English, Book, Illustrated edition: Analysis of raw, potable and waste waters / Department of the Environment. Great Britain. Department of the Environment.
  6. Considering Water Quality For Use In The Food Industry for-Use.pdf
  7. Annual report on Drinking Water Quality 2014-2015 Ministry of health, New Zealand Government
  8. Chilton, J., Howard, G., Schmoli, O., 2006. Protecting Ground Water for Health. World Health Organisation. 696p
  9. He, l., Ying, G., Liu, Y., Su, H., Chen, J., Liu, S., Zhao, J., 2016. Discharge of swine wastes risks water quality and food safety: Antibiotics and antibiotic resistance genes from swine sources to the receiving environments. Environment International 92-93, pp.210-219
  10. Jong, R., Drury, C.F, Yang, J.Y., Campbell, C.A., 2009. Risk of water contamination by nitrogen in Canada as estimated by the IROWC-N model. Journal of Environmental Management 90, pp.3169-3181
  11. Lu, Y., Song, S., Wang, R., Liu, Z., Meng, J., Sweetman, A., Jenkins, A., Ferrier, C., Li, H., Luo, Wang, T., 2015. Impacts of soil and water pollution on food safety and health risks in China. Environment International 77, pp.5-15
  12. Lui,Y., Wang, C., Tyrrell, G., Li, X.F., 2010. Production of Shiga-like toxins in viable but nonculturable Escherichia coli 0157:H7. Water Research 44, pp.711-718
  13. Schreiber, C., Rechenburg, A., Rind, E., Kistemann, T., 2015. The impact of land use on microbial surface water pollution. International Journal of Hygiene and Environmental Health 218, pp.181–187