Drying and decontamination of raw pistachios with sequential infrared drying, tempering and hot air drying

Abstract

Pistachio nuts have been associated with outbreaks of foodborne disease and the industry has been impacted by numerous product recalls due to contamination with Salmonella enterica. The current hot air drying of pistachios has low energy efficiency and drying rates, and also does not guarantee the microbial safety of products. In the study described herein, dehulled and water-sorted pistachios with a moisture content (MC) of 38.14% (wet basis) were dried in a sequential infrared and hot air (SIRHA) drier to <9% MC. The decontamination efficacy was assessed by inoculating pistachios with Enterococcus faecium, a surrogate of Salmonella enterica used for quality control in the almond industry. Drying with IR alone saved 105min (34.4%) of drying time compared with hot air drying. SIRHA drying of pistachios for 2h with infrared (IR) heat followed by tempering at a product temperature of 70°C for 2h and then by hot air drying shortened the drying time by 40min (9.1%) compared with drying by hot air only. This SIRHA method also reduced the E. faecium cell population by 6.1-logCFU/g kernel and 5.41-logCFU/g shell of pistachios. The free fatty acid contents of SIRHA dried pistachios were on par with that of hot air dried samples. Despite significant differences in peroxide values (PV) of pistachio kernels dried with the SIRHA method compared with hot air drying at 70°C, the PV were within the permissible limit of 5Meq/kg for edible oils. Our findings demonstrate the efficacy of SIRHA drying in achieving simultaneous drying and decontamination of pistachios.

Effect of drying methods on nut quality of hazelnuts (Corylus avellana L.)

“…In our study, the highest IV values were found for Ordu Levant hazelnuts (94.69-94.91) while the lowest values were recorded for Tombul cultivar (92.96-93.96), and also, in generally, it is known that IV value varies according to cultivars. Our study demonstrated that the effect of the four drying methods on IV value was statistically significant (p \ 0.001; Tavakolipour et al (2010) and Venkitasamy et al (2017), the rise in drying temperature was observed to lead to an increase in FFA values. However, Kashaninejad et al (2003) reported that drying methods did not affect FFA values in pistachios.…”

“…Fu et al (2016) and Qu et al (2016) also reported that PV increased due to the extended time of sun-drying. Furthermore, Venkitasamy et al (2017) reported that the PV in Kerman pistachio increased in parallel to the increase in drying temperature (0.80-1.87 meq O 2 kg -1 ). In general, decreases RV and increases of FFA, PV and IV values and corresponding decreases of O/L values were recorded.…”

Assessment of Drying Kinetics, Textural and Aroma Attributes of Mentha haplocalyx Leaves during the Hot Air Thin-Layer Drying Process

“…The impact of hot air-drying technology on quality attributes of foods has been studied in recent years. For instance, the changes of lipid composition and oxidation in pistachios, the effect of volatile components of the enoki mushroom as well as the physicochemical properties and biological activity of mushroom polysaccharides induced by hot air drying have been studied [16][17][18].…”

Effects of infrared radiation drying and heat pump drying combined with tempering on the quality of long‐grain paddy rice

“…Intermittent drying is a process by which drying conditions are changed with time (Kingsly, 2007;Kumar et al, 2014) by performing drying and tempering stages sequentially. For all drying methods, tempering is widely considered a significant procedure and has been proven to have positive effects on paddy rice drying (Sacchetti et al, 2005;Igathinathane et al, 2008;Venkitasamy et al, 2017;Wang et al, 2017). Studies have shown that temperature, time and the intermittent ratio all affect the tempering effects of paddy rice drying (Shei & Chen, 1998;Cnossen et al, 2003;Ng et al, 2005).…”