The liquid application process is the operational stage in which fats, oils, flavors, enzymes or other liquid ingredients are added to feed, either before pelleting (pre-pelleting application, typically limited to a few percent to avoid impairing pellet binding) or after pelleting and cooling (post-pelleting application, allowing for much higher total fat inclusion since it does not interfere with the pelleting process itself).

Post-pelleting liquid application is widely used where higher fat formulations are required, employing equipment ranging from simple spray or drum coating systems to vacuum coaters for more complete liquid absorption into porous products, with liquid temperature, viscosity and application rate all affecting how evenly the liquid is distributed across the product batch.

Sequencing multiple liquid ingredients during a single coating pass is a common operational requirement, particularly where a formulation calls for both a primary fat or oil coating and a smaller-quantity heat-sensitive additive (such as an enzyme or flavor) applied separately — many coating system designs allow staged application of different liquids through separate spray zones or sequential dosing within the same coating cycle to accommodate this need.

Liquid metering accuracy is typically verified through flow meter readings cross-checked against batch weight gain (the increase in product weight attributable to the liquid added), providing two independent ways of confirming the correct quantity of liquid was actually applied to a given batch, which is particularly important where the liquid being applied carries a functional or regulatory significance beyond simple energy content.

Operational control of the liquid application process includes monitoring application rate accuracy (often via flow meters or weighing systems), maintaining appropriate liquid temperature for good flow and atomization where spraying is used, and verifying coating uniformity periodically to confirm that all portions of a batch receive a consistent dose of any functional or nutritionally important liquid ingredients.

Equipment cleaning and changeover between different liquid ingredients is also an operational consideration, particularly where the same coating equipment is used for multiple liquid types across different production runs, since residual liquid from a previous formulation remaining in delivery lines, nozzles or the coating chamber itself can carry over into a subsequent batch if cleaning procedures between liquid changes are inadequate.