Effectiveness of Dry Cleaning Treatments for Removing Milk Chocolate from Valve/Pipe Assemblies and Pilot-scale Chocolate Processing Equipment

Dark chocolate produced on equipment used to manufacture milk chocolate can contain milk due to cross- contact. This study evaluated the use of dry cleaning methods for removing milk chocolate residue from a butterfly or ball valve attached to a stainless steel pipe and from pilot-scale equipment used in chocolate manufacture. Milk-free dark chocolate (40 degree celsius) was pumped through a milk chocolate-contaminated valve/pipe assembly after no cleaning, use of a pig purging treatment, or a 40 degree celsius cocoa butter flush. Dark chocolate samples were collected at 7-sec intervals. Treatments investigated for the removal of residual milk chocolate from a conche and a ball mill included no cleaning, a 40 degree celsius cocoa butter rinse, and wet cleaning. After cleaning, three batches of dark chocolate (40 degree celsius) were processed in the ball mill and conche, and each batch was collected. Milk chocolate was processed on a 3-roll refiner, followed by push-through with dark chocolate (similar to 9 kg) with 0.3 kg samples collected at 5-min intervals. Dark chocolate samples were analyzed for milk concentrations by ELISA. Trials and analyses were completed in triplicate. Dark chocolate push-through alone resulted in milk concentrations >= 4,500 mu g/g in samples obtained from the contaminated valve/pipe combinations within the first few seconds of collection, and >= 16.2 kg of dark chocolate was needed to obtain milk concentrations below the ELISA LOQ (2.5 mu g/g). A pig purging treatment of the ball valve/pipe assembly resulted in milk concentrations below the ELISA LOQ. A cocoa butter flush of the butterfly valve/pipe decreased initial milk concentrations, but milk was detected until >= 18.7 kg dark chocolate purge. Milk concentrations in first batches of dark chocolate processed in a ball mill and conche without cleaning were >= 17,000 mu g/g while the use of a cocoa butter rinse reduced milk levels in dark chocolate by >= 89%. Some dry cleaning treatments were effective at reducing levels of milk in dark chocolate due to cross-contact.