Infrared Decontamination of Oregano: Effects on Bacillus cereus Spores, Water Activity, Color, and Volatile Compounds

Abstract

Infrared (IR) heating, a novel technology for decontaminating oregano, was evaluated by investigating the reduction of inoculated Bacillus cereus spores and the effect on water activity (a(w)), color, and headspace volatile compounds after exposure to IR treatment. Conditioned oregano (a(w) 0.88) was IR-treated in a closed heating unit at 90 and 100 °C for holding times of 2 and 10 min, respectively. The most successful reduction in B. cereus spore numbers (5.6 log units) was achieved after a holding time of 10 min at 90 °C, while treatment at 100 °C for the same time resulted in a lower reduction efficiency (4.7 log units). The lower reduction at 100 °C was probably due to a reduced aw (aw 0.76) during IR treatment or possibly to the alteration or loss of volatile compounds possessing antimicrobial properties. The green color of oregano was only slightly affected, while the composition of volatile compounds was clearly altered by IR heating. However, two of the key aroma compounds, carvacrol and thymol, were only slightly affected, compared to the effect on the other studied compounds, indicating that the typical oregano aroma can likely be preserved. In conclusion, IR heating shows potential for the successful decontamination of oregano without severe alteration of its color or the key aroma compounds, carvacrol and thymol.

Effect of Infrared Blanching on Enzyme Activity and Retention of β‐Carotene and Vitamin C in Dried Mango

“…Infrared blanching was performed in a near infrared (NIR) test oven from IRCON Drying Systems AB previously described by Staack and others (, b) and Eliasson and others (). The NIR emitters (electric quartz lamps) have an emission maximum of 1.2 μm, reaching about 2100 °C within 1 s. The 300 g of sliced mango was placed in an aluminum tray at the center of the oven.…”

“…The distance between the NIR emitters and the samples was always constant, 0.5 m above and below. A temperature history similar to water blanching was achieved based on previous experience (Staack ; Eliasson and others, ) by systematically changing the IR power output between 100% and 8% along the blanching process. The power sequences selected to maintain the required temperature profile for mango slices (65 °C for 10 min or 90 °C for 2 min) are presented in Table .…”

Ultraviolet (UV‐C) radiation as a practical alternative to decontaminate thyme ( Thymus vulgaris L.)

“…Irradiation is the most used decontamination technique, which is very effective in microbial inactivation, but it has disadvantages such as oxidation of aromatic components, poor consumer acceptance, and requirement for special facility with high cost (Sadecka, 2007;Variyar, Gholap, & Thomas, 1997). Because of these limitations, many researchers have studied alternative methods such as pulsed electric field (Keith, Harris, Hudson, & Griffiths, 1997), infrared heating (Eliasson, Libander, Lövenklev, Isaksson, & Ahrné, 2014;Staack, Ahrné, Ahrné, Borch, & Knorr, 2008), remote plasma (Hertwig et al, 2015), pulsed UV light (Fine & Gervais, 2004;Nicorescu et al, 2013;Sharma & Demirci, 2003), cold plasma (Kim, Lee, & Min, 2014), and combination of far infrared and ultraviolet (UV-C) radiation (Erdoğdu & Ekiz, 2011 ), gamma irradiation under modified atmosphere packaging (Kirkin, Mitrevski, Gunes, & Marriott, 2014) and combination of UV-C radiation and mild heat treatment (Cheon, Shin, Park, Chung, & Kang, 2015).…”

A comparative study of infrared and microwave heating for microbial decontamination of paprika powder

“…However, since steam treatment has important impact on sensorial properties, there is a continuous interest to investigate other methods. Alternative thermal decontamination methods could be microwave heating ( Dehne et al, 1990 ; Dehne and Bögl, 1993 ; Emam et al, 1995 ; Legnani et al, 2001 ; Dababneh, 2012 ) or infrared (IR) heating ( Staack et al, 2008a ; Erdoğdu and Ekiz, 2011 , 2013 ; Eliasson et al, 2014 ). Both IR and microwave heating show attractive properties, above all fast direct heating of the material, which probably could be used in order to reduce processing time, compared to conventional technologies, and thereby potentially also preserve quality characteristics in a better way.…”

“…While a number of studies already investigated IR or microwave decontamination of herbs and spices ( Dehne et al, 1990 ; Dehne and Bögl, 1993 ; Emam et al, 1995 ; Legnani et al, 2001 ; Staack et al, 2008a ; Erdoğdu and Ekiz, 2011 , 2013 ; Dababneh, 2012 ; Eliasson et al, 2014 ) only a few made comparative studies where one applied technology is compared to another one. IR heating has been compared to the combined effect of IR heating followed by non-thermal ultraviolet treatment ( Erdoğdu and Ekiz, 2011 ).…”