Effects of infrared heating as an emerging thermal technology on physicochemical properties of foods.

Infrared (IR) radiation is part of an electromagnetic spectrum between the ultraviolet and microwave regions. IR radiation impacts the surface of the food, generating heat that can be used as an efficient drying technique. Apart from drying, IR heating is an emerging food processing technology with applications in baking, roasting, microbial inactivation, insect control, extraction for antioxidant recovery, peeling, and blanching. Physicochemical properties such as texture, color, hardness, total phenols, and antioxidants capability of foods are essential quality attributes that affect the food quality. In this regard, the main objective of this review study was to highlight and discuss the effects of IR heating on food quality to expand its food applications and commercial adoption. The fundamental mechanisms, type of emitters, and IR processing parameters are discussed in this review to explore their impacts on food quality. Infrared heating has been shown that the appropriate operating conditions (distance, exposure time, IR power, and temperature) with high heat transfer, thus leading to a shorter drying time. Besides, IR heating used in food processing to improve food-surface color and flavor, it also enhances hardness, firmness, shrinkage, crispiness, and viscosity. Meanwhile, antioxidant activity is enhanced, and some nutrients are retained.

Optimization of Infrared Heating Conditions for Precooked Cowpea Production Using Response Surface Methodology.

The infrared heating of preconditioned cowpea improves its utilization and potential application in food systems. This study investigated the effect of optimizing preconditioning and infrared heating parameters of temperature and time on cooking characteristics of precooked cowpeas using response surface methodology (RSM). The moisture level (32-57%), infrared heating temperature (114-185 °C), and time of processing the seeds (2-18 min) were optimized using a randomized central composite design to achieve optimal characteristics for bulk density and water absorption. A second-order polynomial regression model was fitted to the obtained data, and the fitted model was used to compute the multi-response optimum processing conditions, which were the moisture of 45%, the heating temperature of 185 °C, and time of 5 min. Precooked cowpea seeds from optimized conditions had a 19% increase in pectin solubility. The total phenolic and total flavonoid contents were significantly reduced through complexation of the seeds' phenolic compounds with other macromolecules but nonetheless exhibited antioxidant properties capable of scavenging free radicals. There was also a significant reduction in phytate and oxalates by 24% and 42%, respectively, which was due to the heat causing the inactivation of these antinutrients. The obtained optimized conditions are adequate in the production of precooked cowpea seeds with improved quality.

Influence of infrared heating processing technology on the cooking characteristics and functionality of African legumes: a review.

African legumes are an important protein source in the human diet. However, a long and often extended cooking process has been identified as a major challenge in the consumption and utilisation of these legumes. The application of infrared heating as a method of shortening the cooking-time of African legume seeds and flour, by increasing their water absorption rates and pasting viscosity is emphasised in literature. Structural changes caused by infrared heating of moisture-conditioned African legumes include microstructural, molecular and interaction of the biomolecules in the seeds. However, to the best of the authors' our knowledge, no overview on elucidated mechanisms surrounding the microstructural and molecular changes of infrared heated African legumes has been done. The authors' therefore, present current knowledge of these mechanisms including certain highlighted factors such as seed sizes, moisture, surface temperature and time, affecting the efficacy of the application of infrared heating to African legumes. In conclusion, infrared heating is a promising technology that provides a potential solution to the consumption and utilisation challenges of African legumes and flour from these legumes, to enhance their consumption in the food industry.

Fully automated focused infrared microashing combined with use of ICP-based instruments for rapid analysis of multiple elements in biological samples.

A fully automated focused infrared microashing sample preparation system was proposed for preparation of biological samples with high organic matter content for the determination of multiple elements combined with inductively coupled plasma optical emission spectroscopy and inductively coupled plasma mass spectrometry. The whole ashing procedure, including sample transfer, carbonization and oxidation of the sample, dissolution of ash, constant volume control, and homogenization of the solution, was automatically controlled. Gold-plated infrared tubes were used to produce and focus infrared radiation to heat the sample. Ozone was used to accelerate the carbonization of samples at a lower temperature to avoid the production of large amounts of empyreumatic oil. In addition, the self-designed double-layer tube serves as a site for ashing and carbonization of the sample and as a container for dissolving ash, as well as for holding the solution. This is the only container in the entire system to reduce the risk of pollution. Eight biological certified reference materials were used as examples to evaluate the performance of the proposed device. A sample ashing pretreatment cycle, from solid sample to liquid solution, took only 40 min and simultaneously treated 12 samples. Except for individual results, the relative errors between the certified values and recorded values for 38 micro and trace elements, including Ca, Mg, Na, P, Li, Be, Sc, Ti, V, Mn, Co, Ni, Cu, Zn, Rb, Sr, Y, Mo, Ag, Cs, Ba, Tl, Th, U, and rare earth elements, were typically less than 30%. The relative standard deviations for five determinations were typically less than 15%. Graphical abstract Automated dry ashing sample preparation system. ICP inductively coupled plasma.

Influence of electrical and hybrid heating on bread quality during baking.

Energy efficiency and product quality are the key factors for any food processing industry. The aim of the study was to develop energy and time efficient baking process. The hybrid heating (Infrared + Electrical) oven was designed and fabricated using two infrared lamps and electric heating coils. The developed oven can be operated in serial or combined heating modes. The standardized baking conditions were 18 min at 220°C to produce the bread from hybrid heating oven. Effect of baking with hybrid heating mode (H-1 and H-2, hybrid oven) on the quality characteristics of bread as against conventional heating mode (C-1, pilot scale oven; C-2, hybrid oven) was studied. The results showed that breads baked in hybrid heating mode (H-2) had higher moisture content (28.87%), higher volume (670 cm(3)), lower crumb firmness value (374.6 g), and overall quality score (67.0) comparable to conventional baking process (68.5). Moreover, bread baked in hybrid heating mode showed 28% reduction in baking time.

Application of Infrared Pyrolysis and Chemical Post-Activation in the Conversion of Polyethylene Terephthalate Waste into Porous Carbons for Water Purification.

In this study, we compared the conversion of polyethylene terephthalate (PET) into porous carbons for water purification using pyrolysis and post-activation with KOH. Pyrolysis was conducted at 400-850 °C, followed by KOH activation at 850 °C for samples pyrolyzed at 400, 650, and 850 °C. Both pyrolyzed and post-activated carbons showed high specific surface areas, up to 504.2 and 617.7 m2 g-1, respectively. As the pyrolysis temperature increases, the crystallite size of the graphite phase rises simultaneously with a decrease in specific surface area. This phenomenon significantly influences the final specific surface area values of the activated samples. Despite their relatively high specific surface areas, pyrolyzed PET-derived carbons prove unsuitable as adsorbents for purifying aqueous media from methylene blue dye. A sample pyrolyzed at 650 °C, with a surface area of 504.2 m2 g-1, exhibited a maximum adsorption value of only 20.4 mg g-1. We propose that the pyrolyzed samples have a surface coating of amorphous carbon poor in oxygen groups, impeding the diffusion of dye molecules. Conversely, post-activated samples emerge as promising adsorbents, exhibiting a maximum adsorption capacity of up to 127.7 mg g-1. This suggests their potential for efficient dye removal in water purification applications.

Optimizing niger seed (Guizotia abyssinica) oil quality: A comprehensive analysis of infrared-heat induced changes in bioactive profile, physiochemical attributes, and oxidative stability.

Infrared heating (IRH) at 140, 160, and 180°C for varying durations (5, 10, and 15 min) was employed for improving the niger (Guizotia abyssinica) seed oil (NSO) quality for diverse food applications. The study explored changes in phenolic profile, oxidative stability index (OSI), tocopherols, phytosterols, fatty acid profiles, and physicochemical attributes of NSO. Upon IRH at 180°C for 10 min, the oil yield, total phenolic, and flavonoid contents increased from 33.09% to 40.56%, 6.67 to 173.62 mg GAE/kg, and 24.76 to 120.64 mg QE/kg, respectively. The viscosity, chlorophylls, carotenoids, radical scavenging activity, OSI, caffeic, protocatechuic, vanillic, and syringic acids were highest upon IRH at 180°C for 15 min. The tocopherols and phytosterols initially augmented while decremented upon raising IRH conditions. The infrared spectra indicated no adverse impact of IRH on NSO quality. The appropriate IRH conditions can be considered for improving NSO quality and making it valuable for various edible products.

Fast co-pyrolysis behaviors and synergistic effects of corn stover and polyethylene via rapid infrared heating.

Rapid infrared heating with fast heating rates and the capacity to load materials on the gram scale help investigate the co-pyrolysis behaviors, minimizing the gap of materials' pyrolysis temperature and volatile release during the co-pyrolysis. This work explored the effects of temperature and heating rate on the co-pyrolysis product s behaviors and synergistic interactions of corn stove and polyethylene. Initial increases in oil yield were followed by decreases when the heating rate rose, and when the temperature increased from 500 °C to 600 °C, the oil yield rose from 17.91 wt% to 20.58 wt% before falling to 14.75 wt% at 800 °C. High heating rate promoted the oil generation, and the maximum oil yield was at 25 °C/s with varying heating rates from 15 °C/s to 35 °C/s. The pyrolysis gas produced at 25 °C/s exhibited the highest LHV (Low heating value) and lowest CO2 yield, which were 17.23 MJ/nm3 and 39.29 vol%, respectively. The suitability of heating rate and temperature may improve the interaction between H-radicals of PE and oxygenated groups of CS to generate stable macromolecular compound and enhance oil production. GC-MS studies of the oil products demonstrated that oxygenated compounds such as furans, phenols and acids from lignocellulosic depolymerization had been converted to high molecular weight long chain alcohols (mostly C26, C20 and C14 alcohols) via stronger interactions during fast infrared-heated co-pyrolysis. The alcohols increased from 32.29 % to 65.06 % as temperatures rose from 500 °C to 800 °C. Few furan heterocycles, acids and phenols were detected, suggesting that the oil presented higher quality and stronger synergistic effects. Rapid infrared heating accelerated the synergistic effects between volatile-volatile interactions during co-pyrolysis of corn stover and polyethylene, and the increases in temperature and heating rates further enhanced the release of many volatile substances and the formation of fine pores. Raman results showed char of 600 °C deposited more pure aromatic structures, the influence of temperature on aromatization was stronger than that of heating rate.

Cross-interaction of volatiles in fast co-pyrolysis of waste tyre and corn stover via TG-FTIR and rapid infrared heating techniques.

Using fast infrared heating technology to minimize the pyrolysis temperature differential and optimizing secondary reactions is advantageous for studying co-pyrolysis behaviors. In this study, the co-pyrolysis behaviors of waste tyres (WT) and corn stover (CS), including product distribution, pyrolysis kinetics, and thermodynamics, were studied using TGA-FTIR analysis and fast infrared heating reactor. The DTG curves for the co-pyrolysis of WT and CS significantly differed from the calculated values, implying that the pyrolysis intermediates produced by CS during the pyrolysis process may have synergetic effects with the pyrolysis of WT. The apparent activation energies using the Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were similar, 244.88 kJ/mol and 245.93 kJ/mol, respectively. The experiment results suggest that the bio-oil yield increased first and then decreased with a further temperature increase. The yield of bio-oil gradually increased from 35.36% to 46.06% as temperature rose from 500 °C to 700 °C; but the further increasing to 800 °C decreased the bio-oil yield to 40.72%. The aromatic compounds in tar gradually increased with increasing the temperature, while the aliphatic compounds increased initially and then reduced. Meanwhile, the oxygenated compounds first decreased and then increased with increasing the pyrolysis temperature. The yield of light oil components (C＜10) increased from 5.11% at 400 °C to 7.71% at 700 °C. A further increase in the pyrolysis temperature to 800 °C reduced the light oil content to 4.93%.

Conversion of polyethylene terephthalate waste into high-yield porous carbon adsorbent via pyrolysis of dipotassium terephthalate.

A method for conversion of polyethylene terephthalate (PET) waste into porous carbon material is proposed. The recycling of PET bottle waste includes the stages of low-temperature hydrolysis of the polymer and subsequent pyrolysis at 800 °C. To provide PET hydrolysis at âˆ¼150 °C and atmospheric pressure, the polymer was pre-dissolved in dimethyl sulfoxide and then an aqueous solution of potassium hydroxide was added. The potassium terephthalate formed as a result of the alkaline hydrolysis of PET allows the carbon-containing precursor to be preserved for further activation to temperatures beyond 600 °C. The proposed method leads to the formation of a porous carbon material, increasing the yield of carbon residue to 25 wt%, which is higher compared to the yield of carbon residue in the direct pyrolysis of PET. The obtained porous carbon is characterized by graphite-like structure and specific surface area of âˆ¼1100 m2 g-1. It has been shown that PET-derived carbon material can be used to remove pollutants from aqueous media. The adsorption properties of the carbon material were demonstrated by adsorption of methylene blue from an aqueous solution. The capacity of the carbon material was found to be 443 mg g-1.

Pyrolysis behavior of low-density polyethylene over HZSM-5 via rapid infrared heating.

Catalytic fast pyrolysis experiments of low-density polyethylene (LDPE) over HZSM-5 were carried out by using infrared heating technology. The effects of heating rate (1-30 °C/s), pyrolysis temperature (450-650 °C), and mass ratio of catalyst to LDPE (0:100 to 50:100) on product distribution and oil composition in LDPE pyrolysis were investigated, and the fast pyrolysis mechanism was explored. The results indicated that a higher heating rate, namely 20 °C/s, can remarkably enhance the liquid oil yield (93.42%), but the oil is heavy due to about 90% high­carbon n-aliphatics. The addition of HZSM-5 performed an excellent effect on obtaining high-quality liquid oils, among which the total content of monocyclic aromatic hydrocarbons (MAHs) and iso-aliphatics obviously increase from 0.68% to 70.26%. The optimal HZSM-5/LDPE ratio of 10:100 was identified by considering the cost-effective factor. Furthermore, the lower catalytic temperature is favorable to the generation of light oil components, especially MAHs. The feasible generation paths were proposed, which mainly derived from the secondary reaction of the intermediate formed by initial chain cleavage including cyclization, aromatization, Diels-Alder reaction, as well as isomerization.

Establishing Sterility Assurance for Bacillus canaveralius 29669 Spores Under High Heat Exposure.

The ever-increasing complexity in critical spacecraft hardware and materials has led to the development of new microbial reduction procedures as well as to changes in established processes such as heat microbial reduction (HMR). In the space biology field of Planetary Protection, 500°C for 0.5 s is the current HMR recommendation to reduce microorganisms from flight hardware. However, more studies are needed to effectively determine the microbial reduction capability of high-temperature (more than 200°C), short-duration (under 30 s) heat exposures. One of the many recent microbial reduction bioengineering research avenues harnesses electromagnetic energy for microbial reduction, with previous investigations demonstrating that infrared heaters are capable of the short temperature ramp time required for rapid heating investigations above 200°C. Therefore, this study employed a 6 kW infrared heater to determine the survivability of heat resistant Bacillus canaveralius 29669 to high-temperature, short-duration infrared temperatures. While B. canaveralius 29669 spores can survive microbial heat reduction processes above 200°C, we found evidence suggesting that the 500°C for 0.5 s temperature sterilization specification for Planetary Protection should be updated. This research presents spore survival data and a corresponding model pointing to a re-evaluation of the recommended HMR exposure of 500°C for 0.5 s, while simultaneously meeting requirements on the forward biological contamination of solar system bodies and opening up design possibilities for future spacecraft hardware.

Fast pyrolysis characteristics and its mechanism of corn stover over iron oxide via quick infrared heating.

The harm done to the environment by fossil fuels was serious, and it is urgent to find effective methods and adopt carbon-neutral feedstock to prevent further environmental damage. An innovative infrared heating reactor was developed for the generation of high-yield bio-oil and cleaner pyrolysis gases. This work was devoted to exploring the fast pyrolysis characteristics and its mechanism of corn stover over the iron oxide in a novel infrared heating (IH) reactor and a traditional electric heating (EH) reactor. In the IH reactor, the bio-oil yield increased initially and then decreased with increasing pyrolysis temperature, reaching a maximum yield of 29 wt% at 600 °C. The yield of pyrolysis bio-oil and water decreased as the reusability number rose, whereas the char yield increased. Bio-oil yields decreased less from R0 to R3 and the catalyst was more effective in IH. IH produced more char and gas but considerably less water than EH, and its bio-oil had fewer phenols. Raman spectroscopy demonstrated that the aromatic structure of biochar increased as the pyrolysis temperature increased. Cellulose and hemicellulose can be completely cleaved at lower temperatures in IH. In addition, Fe2O3 catalysts have shown the advantages of low cost, efficient cycling, and long action time. Infrared heating coupled with iron oxide catalyst shows the potential to increase bio-oil yield and is more promising for industrial production than EH.

Investigation of nonlinear photoacoustic microscopy using a low-cost infrared lamp.

Nonlinear photoacoustic microscopy (PAM) is a novel approach to enhance contrast and resolution. In this study, a low-cost infrared (IR) lamp as a simple approach for nonlinear PAM is demonstrated. Numerical simulations are first performed to verify the nonlinear photoacoustic effect under steady heating for two cases: (a) Differentiation of absorbers with different Grüneisen coefficients; (b) enhancement of photoacoustic amplitude. Then, sets of experiments are conducted to experimentally demonstrate our proposed approach: (a) Longitudinal monitoring of photoacoustic A-line signals from two samples, porcine tissue ex vivo and hemoglobin and indocyanine green (ICG) solutions in tubes in vitro for demonstrating the above-mentioned two cases; (b) PAM imaging of hemoglobin and ICG solutions in tubes before and after IR lamp heating. Different signal change and amplitude enhancement are observed in different demonstrations, showing the efficacy of the proposed approach. By virtue of cost-effectiveness and decent performance, our work facilitates nonlinear PAM studies.

Improvement of the nutritional quality of lentil flours by infrared heating of seeds varying in size.

The present study aimed to tackle research gaps regarding how infrared heating affected macro- and micronutrients of lentil flours from seeds varying in size. Infrared treatments reduced resistant starch contents of lentil flours from 26.1-33.6% to 6.0-17.8%, increased protein digestibility from 73.6-75.0% to 78.2-82.2%, and enhanced soluble dietary fiber contents from 6.1-7.8% to 7.4-10.3%. Infrared treatments did not alter the primary limiting amino acid of Greenstar and Imvincible lentil flours (tryptophan) but changed that of Maxim to methionine + cysteine at 150 °C heating. Regarding micronutrients, the thermal modifications decreased the levels of heat-labile B vitamins, including B1 (thiamine), B3 (niacin), and B9 (mainly 5-methylterahydrofolate), consistent with reducing α-amylase activity to an undetectable level in all the three lentil flours. The novel findings from this research will be meaningful for the agri-food industry to utilize infrared processing as an effective and clean-label approach to improving the nutritional profiles of lentil and other flours.

Infrared heating under optimized conditions enhanced the pasting and swelling behaviour of cowpea starch.

Native starches are not suitable for industrial use and must be modified for improved functionality. In this study, the effect of moisture preconditioning and infrared heating time on physicochemical properties of cowpea starch was investigated using a two-factor central composite rotatable design. Factors (moisture levels:10-40 g/100 g starch and infrared heating time:10-60 min) with their corresponding α mid-point values resulted in 13 experimental runs. Selected functional and pasting properties were determined as response variables. Starch samples produced under optimized conditions were compared with corn starch and their physicochemical properties determined. Except for pasting temperature, cowpea starch prepared using the optimal conditions (moisture: 46.21 g/100 g starch, dry basis and heating time of 32.88 min) had higher functional and pasting properties compared with the native cowpea starch. Infrared heating significantly reduced the gelatinization temperatures of cowpea starch but did not significantly change that of the corn starch. The crystallinity and double-helical order structure of moisture conditioned cowpea starch also reduced after modification. Cowpea starch showed a bigger granule size, higher swelling power but lower water absorption capacities and pasting properties compared with the control. The infrared heating process is a novel and promising modification method for improving the swelling properties of starch.

Influence of infrared heating on the functional properties of processed lentil flours: A study focusing on tempering period and seed size.

Lentils are an important member of the nutritious Leguminous crops, and the functional properties of lentil flours can be effectively improved by infrared heating, an efficient and short-time thermal processing method. This research primarily focused on the effects of tempering time (24-96 h) and seed size on the modification of lentils using infrared heating. Lentil seeds of three varieties, including CDC Greenstar (large green), CDC Imvincible (small green), and CDC Maxim (small red), were tempered at 25% moisture for 24, 48 and 96 h and then infrared heated to a surface temperature of 130 and 150 °C. Overall, under the same infrared heating treatment, a longer tempering period and a smaller seed size led to greater degrees of starch gelatinization and protein denaturation. In addition, a smaller seed size and a higher surface temperature tended to cause a higher level of photodegradation of amylose (possibly amylopectin too). Due to these physicochemical changes, the combined treatment of tempering and infrared heating noticeably reduced the average particle sizes, enhanced the water-holding capacity, diminished the peak and final viscosities, and decreased the gel hardness of the processed lentil flours. Generally, more obvious effects were found with higher levels of starch gelatinization, protein denaturation, and breakdown of amylose. The present study advanced our understanding of how extended tempering and seed size influenced the techno-functional properties of lentil flours modified using infrared heating. The new findings from the research are meaningful for the utilization of infrared heating to process lentil seeds for the development of novel food ingredients.

A New Infrared Heat Treatment on Hot Forging 7075 Aluminum Alloy: Microstructure and Mechanical Properties.

When hot forging 7075 aluminum alloy, as a military material durable enough for most of its applications, it needs to be heat-treated to ensure the target material property achieves the application requirements. However, the material properties change because of heat throughout usage. In this study, a new approach was devised to heat treat the alloy to prevent material property changes. The study further clarified the effect of rapid heat treatment on the high-temperature resistance of a hot forging 7075 aluminum alloy. Infrared (IR) heat treatment was used as a rapid heating technique to effectively replace the conventional resistance heat (RH) treatment method. Our experimental result showed that IR heat treatment resulted in better age hardening at the initial aging stage, where its tensile strength and elongation appeared like that of a resistance heat treatment. More so, based on hardness and tensile test results, the IR-heated treatment process inhibited the phase transformation of precipitations at a higher temperature, improving high-temperature softening resistance and enhancing the thermal stability of the hot forging 7075 aluminum alloy.

Fast pyrolysis behaviors of cedar in an infrared-heated fixed-bed reactor.

To explore fast pyrolysis behaviors of cedar biomass, the infrared heating technique with quick heating rate was taken in a fixed-bed reactor. The effects of heating rates (5-30 °C/s) and pyrolysis temperatures (400-600 °C) on pyrolysis products distribution and compositions were discussed, and the reaction mechanism was proposed. The results show that high heating rate can significantly suppress secondary reaction of primary volatiles. GC/FID and GC/MS analyses indicate that higher heating rate is favorable to the generation of glucose derivatives such as acids and furans. However, higher temperature can obviously promote further conversion of guaiacyl-contained structure following demethylation, demethoxylation and H/CH3 assisted demethoxylation routes, which were proposed to interpret the formation of biphenolic hydroxyl and monophenolic hydroxyl compounds such as phenol, 2-methyl-phenol and 2,4-dimethyl-phenol, respectively. Moreover, the demethylation route exhibits obvious conversion advantage at higher temperature due to lower energy barrier.

Strengthening of Reinforced Concrete Beams with Externally Mounted Sequentially Activated Iron-Based Shape Memory Alloys.

Iron based shape memory alloys (Fe-SMA) have recently been used as active flexural strengthening material for reinforced concrete (RC) beams. Fe-SMAs are characterized by a shape memory effect (SME) which allows the recovery of previously induced plastic deformations through heating. If these deformations are restrained a recovery stress is generated by the SME. This recovery stress can be used to prestress a SMA applied as a strengthening material. This paper investigates the performance and the load deformation behavior of RC beams strengthened with mechanical end anchored unbonded Fe-SMA strips activated by sequentially infrared heating. The performance of a single loop loaded and a double loop loaded SMA strengthened RC beam are compared to an un-strengthened beam and a reference beam strengthened with commercially available structural steel. In these tests the SMA strengthened beam had the highest cracking load and the highest ultimate load. It is shown that the serviceability behavior of a concrete beam can be improved by a second thermal activation. The sequential heating procedure causes different temperature and stress states during activation along the SMA strip that have not been researched previously. The possible effect of this different temperature and stress states on metal lattice phase transformation is modeled and discussed. Moreover the role of the martensitic transformation during the cooling process on leveling the inhomogeneity of phase state in the overheated section is pointed out.