Conditions for optimal shelling, microbial reduction, and kernel quality in pecans

In-shell pecans (Carya illinoinensi 'Oconee’ and ‘Desirable’) were processed in hot water (60–90 °C) or steam for up to 7 min prior to cracking and shelling. All hot-water treated samples showed greater recovery of whole halves (mean 43.3%, rang 29.5–52.8%) after cracking than the negative control (33.6%), while steam treatment diminished recovery. Water treated pecans gained up to ~4% in mass, due to moisture uptake by the nut. Mechanical studies suggest that the force or distance to crack the shell was not changed by water conditioning, but the outer layer of the kernel did become softer. The effects of hot water or steam treatment on microbial inactivation was tested using Enterococcus faecium, a micro-organism used as a surrogate for Salmonella spp. on nuts. In the time intervals considered, 4–5 log reductions could only be attained with steam or water at 85–90 °C. D-values were 51, 16, 1.5 and 0.2 min at temperatures of 70, 80, 85 and 90 °C, respectively with a z-value of 15.9 °C. When considered together, it appears that while cracking efficiency can be optimized with 60–70 °C treatments, microbial interaction will be low. Likewise, while > 5 log CFU/g can be realized at even short times (5 min). [Display omitted] •Pre-conditioning pecans in hot water improves the recovery of intact kernel pieces.•Hot water immersion inactivates the Salmonella surrogate on pecan shell surfaces.•At T > 80 °C, a greater than 5 log CFU/g reduction could be realized in 1–2 min.•Optimal conditions with T > 80 °C and hold times longer than 5 min.