Influence of chlorine concentration on the effectiveness of Cleaning-in-Place agents

Effectiveness of Cleaning-in-Place (CIP) agents for cleaning food-contact surfaces in food manufacturing facilities continues to be a topic of interest. Sodium hydroxide (NaOH) is used to remove the organic matter attached on a food surface. Sodium hypochlorite (NaClO) is a common additive used in conjunction with NaOH in cleaning solutions. Although NaClO is added to improve the effectiveness of the cleaning, NaClO is viewed as potentially harmful to the environment. The overall objective of this investigation was to reduce the environmental impact of NaOH-based cleaning solutions through minimization of NaClO usage while ensuring no loss in cleaning efficacy.

A deposit of non-fat dry milk solution was placed on the surface of stainless-steel coupons and held at 75oC for one hour. The coupons were cleaned with cleaning solutions with varying concentration of NaOH, NaClO, and water in an agitated temperature-controlled container. Cleaning efficiency was monitored by rate of decrease in fraction of residual film (RF). A 5-by-5 full factorial design was used to evaluate the effectiveness of NaClO, NaOH, and their interactions during cleaning.

With the dry mass difference method, NaOH concentration was shown to be significant (p-value < 0.0001) factor for cleaning, while NaClO concentration was not at α = 0.05. Local maxima in NaOH concentration by itself was found at 7.5 kg/m3 of solution.

Higher NaOH and NaClO concentration is shown to not always be better for cleaning efficiency. By understanding the interaction between the two in cleaning food film, amount of chlorine in waste streams can be minimized.