| Due to outbreaks of Salmonellosis which were associated with whole raw almonds, the use of infrared (IR) heating technology was investigated for improving safety of raw almonds. Pediococcus sp. NRRL B-2354 was used as a surrogate of Salmonella Enteriditis PT 30 for evaluating the pasteurization efficacy of different processing conditions. After almonds were heated to the target temperatures 100, 110 and 120°C with IR, they were cooled at ambient temperature to a holding temperature of 70, 80 or 90°C before being transferred to a custom-designed holding device for different time periods up to 60 min. Experiments revealed that heating up the almonds to 100, 110 and 120°C by IR could reduced the Pediococcus population 0.32, 0.58 and 0.62 log CFU/g, respectively. During ambient cooling of IR heated almonds to holding temperatures, 70, 80 and 90°C, an additional 0.5 to 1.0 log CFU/g reduction was obtained which summed the total Pediococcus reduction up to around 0.8 to 1.8 log CFU/g after heating-up and the subsequent cooling-down period. Holding the almonds at 70, 80 and 90°C holding temperatures provided an additional 1.4 to 7.5 log CFU/g bacterial reduction in Pediococcus population depending on the holding times. Holding almonds at 90°C for 10–15 min reduced the Pediococcus population size by more than 5-log CFU/g and holding at 80°C for longer than 22 min provided more than 4-log CFU/g reduction, thus satisfying the targeted 4-log CFU/g reduction required in the almond industry. The L*a*b* color values of whole almonds were not affected significantly (P > 0.05) by the IR process whereas the a* and b* color values of ground almonds changed significantly (P < 0.05). The sensory panel did not detect any significant difference (P > 0.01) in appearance, texture, flavor and overall quality of pasteurized almonds compared with untreated samples. It can be inferred that infrared is a promising technology for surface pasteurization of raw almonds without significantly compromising the raw quality attributes.IR heating for improving the processing efficiency was also investigated in dry roasted almonds. Almonds were roasted at 130, 140 and 150°C temperatures with three different methods: IR roasting, sequential infrared and hot air (SIRHA) roasting, and traditional hot air (HA) roasting. The value of overall color change was used as the indicator of degree of roasting. The heating rate and overall color changes of almonds under different roasting methods and temperatures were evaluated. The time required to heat almonds to the purpose temperatures 130, 140 and 150°C were 35, 43 and 53 sec using IR, compared to about 15 min with HA heating. When SIRHA roasting at 130, 140 and 150°C roasting temperatures was used to produce medium roasted almonds with roasting times of 21, 11 and 5 minutes, respectively. The SIRHA roasting process had 38%, 39% and 62% time saving compared to HA roasting at the same corresponding roasting temperatures. The overall color change followed zero-order reaction kinetics and the activation energies were 73.58, 52.15 and 67.60 kJ/mol for HA, IR and SIRHA roasting, respectively. No significant difference (p > 0.1) was observed in sensory quality of medium roasted almonds processed with different roasting methods.IR pasteurization process was more investigated for its efficacy in improving the safety of dry roasted almonds. The pasteurization efficacy of almonds under different medium roasting methods and temperatures were evaluated. Pediococcus sp. NRRL B-2354 was still used as a surrogate for Salmonella enterica Enteriditis PT 30 for evaluating the pasteurization efficacy of different processing methods and conditions. When SIRHA roasting at 130, 140 and 150°C roasting temperatures with roasting times of 21, 11 and 5 minutes was used to produce medium roasted almonds, 4.10-, 5.82- and 6.96-log CFU/g bacterial reductions were achieved, respectively. When IR heating alone was used to produce medium roasted almonds, a 4.12-log CFU/g bacterial reduction was achieved at 150°C for 4 min, but the hot air roasting at 140 and 150°C resulted in 4.62- and 5.39-log CFU/g bacterial reductions in relativity longer roasting time 18 and 13 min, compared with IR or SIRHA roasting. The decimal reduction time of the bacteria at all roasting temperatures were calculated for SIRHA roasting as 8.68, 3.72 and 1.42 min, respectively, with a correlation coefficient greater than 0.92 and the thermal resistance constant was found as 25.4°C. We conclude that the SIRHA roasting is a good new method for the production of dry-roasted pasteurized almonds with potential to reduce costs due to reduced roasting time compared to current HA roasting.The nine medium roasted almond samples produced by three different heating methods IR roasting, SIRHA roasting and regular HA roasting and processed at three different temperatures 130, 140 and 150°C were packed in paper bags and stored at 37°C for six or eight months. Shelf life of the roasted almonds was determined by measuring the changes in color, peroxide value, moisture content, water activity, flavor components and sensory quality. No significant differences were observed in color, moisture content, and water activity among the almond samples processed with different roasting methods with the same storage conditions. GC/MS analysis showed that aldehydes, alcohols, pyrazines were the main flavor components of almonds. Benzaldehyde made the largest contribution to the aroma of raw and fresh roasted almonds. Aliphatic aldehydes such as hexanal, 2-octenal, nonanal were produced as off-flavors of roasted almond during storage. The quality of roasted almonds produced with SIRHA and HA heating were similar during the first three months of storage. However, peroxide value and aliphatic aldehydes of all roasted samples increased significantly during storage and they were significantly different for different roasting methods after three months of storage. We postulate that hexanal and nonanal might be better indicators of the shelf life of roasted almonds than peroxide value.
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