Evaluation of Composite Sterility Testing Procedures for Ready-to-Eat Pudding Products

Introduction:  Sterility testing is a common practice in the manufacturing of aseptically processed products to verify that upstream preventive controls are effective. The current testing protocol for ready-to-eat (RTE) pudding products at Conagra Brands requires a minimum of 275 pudding samples (per lot) to be tested using a bioluminescence-based screening method. However, given manufacturing practices, product formulations and lot size the required testing per lot may exceed 500 samples. Compositing of pudding samples provide manufacturing facilities a feasible way to conduct sterility testing and maintain a high level of statistical confidence without increasing testing costs. Currently, there is limited scientific basis to support composite testing.

Purpose:  The purpose of this study was to develop a scientifically valid composite testing protocol per FSMA to perform sterility testing of RTE pudding products.

Methods:  Two pudding formulations (vanilla and chocolate) were used for the study. Pudding samples were individually inoculated with a three strain gram-negative cocktail and a four strain gram-positive cocktail at target levels of 1.0 to 2.0 log cfu/pudding cup and incubated three days at 35°C. Samples were analyzed using Celsis^® RapidScreen^® per manufacturer’s instructions and confirmed with FDA-approved methods. Samples were then composited in levels of one to five samples (one part inoculated positive sample combined with zero to four parts uninoculated negative samples). Alpha-amylase as a process aid (should the enzyme be added before or after incubation) was also evaluated as part of the study. The study constituted three replicates.

Results:  This study indicated that compositing of pudding samples (levels one to five) regardless of the addition of alpha-amylase before or after incubation resulted in 100% detection of the all the organisms evaluated in this study. However, samples where amylase was added post-incubation resulted in bioluminescence values significantly (P<0.05) lower compared to their counter parts.

Significance:  These findings provide scientific basis for composite testing protocols utilized by Conagra Brands for sterility testing of RTE pudding products.