Retention of Thiamine and Other Water Soluble Vitamins in a Wet Pet Food Application

Since 2008, there have been several recalls due to insufficient thiamine levels in canned cat food. Cats have a high requirement of thiamine and deficiencies can lead to death within a month if not treated. Limited studies have been published regarding the impact of processing on thiamine loss. Therefore, it was our objective to determine the effect of container size and type on thiamine retention during processing of cat food. A model canned cat food was produced and placed in two container sizes (small; 89-104 mL vs medium; 163 – 207 mL) and three container types (can, pouch, and tray). Within each replicate batch (64 containers per replicate, two replicates), thermocouple probes were inserted into 14 separate containers. The retort time was determined by thermocouple heat penetration to meet the F_o=8 min at 121^◦C and 21 psi. The three sampling points for vitamin analysis were 1) batter without vitamins, 2) batter with vitamins, and 3) post retort loaf product. Samples from 1 and 2 were stored in the freezer (-20^◦C), and from 3 were stored at room temperature. Composite samples were analyzed for proximates (moisture, crude protein, crude fat, ash), pH, and B-vitamin (thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, biotin, folic acid, cobalamin) concentrations. Results were analyzed using the GLM procedure in SAS (v. 9.4) with means and interactions separated using Fischer LSD method by significant F values and an α of 5%. The proximate composition and pH were similar (P>0.10) among treatments. Neither container size nor container type had an effect on riboflavin, pyridoxine, or cobalamin concentrations (average 87.0, 179.0, 0.41 mg/kg, respectively). Small containers retained more (P<0.05) thiamine than medium (3,209 and 2,513 mg/kg), niacin (909 and 861 mg/kg), and folic acid (22 vs 15 mg/kg), while pantothenic acid retention in small containers was lower (P<0.05) than medium (273 and 324 mg/kg, respectively). The main effect means for container type only influenced thiamine concentration; wherein, retention was greater for pouches than for trays with cans intermediate to both (2,540, vs 2,359, and 2,274 mg/kg). This work suggests that thermal processing of B-vitamins can be influenced by container size and type, which likely relate to the controls over the heating and cooling cycle.