Influence of Run Time and Aging on Fouling and Cleaning of Whey Protein Deposits on Heat Exchanger Surface

Abstract

In the cleaning operations of heat exchange surfaces in dairy processing plants, the effect of heating/run time (HT) and aging on the fouling/cleaning of heat exchangers is not well understood. Longer heating time of the same deposit is expected to result in the formation of stronger and perhaps more cleaning resistant deposit. In this study, the phenomenon of heating and aging on the formation and cleaning of dairy fouling is investigated using the heat induced whey protein gels (HIWPG) produced in laboratory. The processes were also investigated with the whey protein deposits formed in pilot-scale plant trails.The HIWPGs were produced in tubular capsules for various heating (or run) times (60, 120, 240, 1440 and 2880 min respectively) and then dissolved in aqueous sodium hydroxide (0.5 wt %). The heating process here would have been of 'pure' aging. The dissolution rate was calculated based on the previously established UV Spectrophotometer analysis. The structure and texture of the gels were analysed using Scanning Electron Microscope (SEM) and texture analyser. In the pilot-scale plant study, whey protein fouling layers were generated by recirculating whey protein solution (6 wt %) for various heating periods (30, 60, and 90 min respectively). The deposit layers were then removed by recirculating aqueous sodium hydroxide (0.5 wt %) and the cleaning efficiency was monitored in the form of the recovery of heat transfer coefficient while both fluid electric conductivity and turbidity were recorded as indications of cleaning completion. It was found that increasing the HIWPG heating time significantly increased the gel hardness and dissolution time, implicating the difficulty in cleaning. Similarly to these results on gels, increasing the pilot-scale plant heating/run time increased the extent of fouling. The fouling layer formed next to the metal surface experienced the longest period of aging and the slope of the heat transfer coefficient increase seen at the final cleaning stage is related to this aging effect. The rate of cleaning for deposits formed initially on the metal surface is lower indicating a 'pure' aging effect of the deposit near surface.

Study on the dissolution of heat-induced ovalbumin gel in alkaline solutions relevant to the removal of fouling deposits

“…Fig. 6c shows the trend of initial dissolution rate for HIOVAG with increase of heating is similar to the dissolution rate of HIWPCG previously (Fickak et al, 2012). …”

“…(Ç) Time to dissolve 90% of HIOVAG (13.8 wt.% protein content in the gel, heated at 90°C) against heating time at 60°C and 480 rpm in 1.0 wt.% NaOH solution. (d) Time to recover 90% of heat transfer coefficient (HTC) during cleaning process of whey protein concentrates fouling, reported byFickak et al (2012). ( ) Pulling energy required for partial removal of HIOVAG, reported byLiu et al (2006).…”

Whey protein fouling on polymeric heat exchangers

“…The cleaning of SS was only possible through chemical agents, such as sodium hydroxide solutions, as reported in the literature. [28][29][30][31] as plant downtime for cleaning can be reduced and no additional detergents are needed to run the polymer heat exchanger.…”