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 °C) was pumped through a milk chocolate-contaminated valve/pipe assembly after no cleaning, use of a pig purging treatment, or a 40 °C 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 °C cocoa butter rinse, and wet cleaning. After cleaning, three batches of dark chocolate (40 °C) 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 (∼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 µg/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 µg/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 µg/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.