ARS | Publication request: Potential of Microwave Heating as a Pasteurization Method for Almonds

Submitted to: Institute of Food Technology
Publication Type: Other
Publication Acceptance Date: June 24, 2007
Publication Date: June 28, 2007
Citation: Jennifer, R., Hendrix, K., Sanders, T.H. 2007. Potential of Microwave Heating as a Pasteurization Method for Almonds. Institute of Food Technology.

Technical Abstract: Pasteurization of almonds to reduce the risk of Salmonella contamination is an objective of the almond industry. Microwave (MW) technology may generate almond surface temperatures effective in reduction of Salmonella. This study was conducted to examine almond surface and internal temperatures generated by various MW power protocols and evaluate the shelf-life of raw and roasted MW-treated almonds. Dry and wetted Carmel almonds were subjected to 2.8, 3.4, and 4.2 kW and 4.0, 4.5, and 5.0 kW of MW energy, respectively. Infrared thermometers and fiber optic probes were used to measure external and internal temperatures. Raw and roasted samples from all treatments were stored at 35ºC for 16 weeks and at 4 week intervals shelf-life indicators and moisture were evaluated. Almond surface and internal temperatures of the dry samples in all protocols ranged from 90-110º C and 105-130º C, respectively. External and internal temperatures of the wetted samples were 85-100º C and 100-125º C, respectively. Oxidative stability index (OSI) differences among treated and control samples were generally not meaningfully different although OSI for all samples gradually decreased during storage. Peroxide value of treated and control samples followed similar increasing trends during storage except that wetted samples exposed to 5.0 kW increased more rapidly than other raw wet treated stored samples. Free fatty acids (FFA) values among the raw dry treated and control samples were not different; however the raw wet control samples had higher FFA values than the corresponding wet treated samples. All treated and control samples gradually decreased in moisture content throughout the study. The temperatures achieved with MW energy and the lack of meaningfully different oil chemistry among control and treated samples during storage suggests that MW technology has high potential for use as a pasteurization treatment for almonds.