Semester of Graduation

Fall 2017


Master of Science (MS)


School of Nutrition and Food Sciences

Document Type



Hot water conditioning of in-shell pecans is one common practice followed by industries to facilitate shelling. It also acts as a preventive control for potential microbiological contamination that might occur during pre- and post-harvest processes. However, heat treatment may have an effect on the eating quality of nuts. The main objectives of the study were to develop a post-harvest hot water treatment intervention as a kill step to destroy foodborne pathogens on in-shell pecans and evaluate the effect of treatments on physicochemical properties, consumer acceptance and purchase intent of dehulled and roasted pecans. The time (1-5 min) and temperature (70, 80, and 90 ºC) treatments to achieve a 5-log reduction of Salmonella enterica, E. coli O157:H7 and Listeria monocytogenes as well as non-pathogenic Enterococcus faecium were studied. The D-value of organisms showed that Salmonella and Listeria were the most and least resistant pathogens, respectively, and Enterococcus faecium was found to be the suitable surrogate for Salmonella enterica. As calculated from the D-value, hot water treatment for 8.6, 6.6 and 4.6 min at 70, 80 and 90°C, respectively, gave 5 log CFU/g reduction of the most heat resistant pathogen. In-shell nuts were subjected to these treatments, shelled and roasted at 160°C for 10 mins. The effect of hot water treatment on the physicochemical properties (% moisture content, water activity, color, and texture) of the roasted pecans was determined. Sensory evaluation studies using a 9-point hedonic scale were performed by serving the samples of roasted pecans to consumers (N=112). Hot water treatment alone had no significant effect on the physicochemical properties of shelled pecans. However, roasting the treated pecans decreased the moisture content (P<0.05), water activity (P<0.05) and hardness values (P>0.05). Hot water treated pecans became darker on roasting which was liked by consumers; pecan hot water treated at 90°C was the darkest with lowest L* value (P<0.05). Pecans hot water treated at 70°C for 8.6 min followed by roasting were most liked by the consumers (liking >6.3 for all attributes). Thus, hot water conditioning of pecans is an effective method as it improves its microbial safety, quality and sensory liking.



Committee Chair

Adhikari, Achyut