Effect of a Modified Atmosphere on Drying and Quality Characteristics of Carrots

Comparative evaluation of physical characteristics and volatile flavor components of Bangia fusco-purpurea subjected to hot air drying and vacuum freeze-drying

Bangia fusco-purpurea is an economically important seaweed with Fujian characteristics. Given that its harvest is seasonal, drying is often used to remove moisture, extend storage time, and facilitate further processing. Hence, the current study sought to explore the impact of different drying processes on the quality and volatile fingerprints of Bangia fusco-purpurea. To this end, the effects of hot air drying (HAD) and vacuum freeze drying (VFD) on the drying characteristics, microstructure, rehydration, and volatile components of dried B. fusco-purpurea were investigated. The results showed that the water removal efficiency of HAD was significantly higher than that of VFD. However, VFD better preserved the skeletal structure of B. fusco-purpurea than HAD, with a faster rehydration rate and a more uniform cell structure after rehydration. Using electronic nose and comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC × GC-TOF MS), significant differences in the volatile profiles of fresh, HAD, and VFD B. fusco-purpurea were assessed. E-nose analysis revealed that both HAD and VFD treatments significantly reduced sulfides, aromatic compounds, and nitrogen oxides in fresh B. fusco-purpurea. However, the alcohol, aldehyde, and ketone contents were lower in the VFD samples compared with HAD and fresh samples, whereas the content of methyl flavor substances was significantly higher. GC × GC-TOF MS analysis revealed that the most abundant volatile categories in HAD and VFD were hydrocarbons, alcohols, and esters. The number of volatile components in the HAD samples was significantly lower than in the VFD and fresh samples. As drying progressed, hydrocarbons and alcohols were formed in dried B. fusco-purpurea due to the thermal degradation of carbohydrates, lipids, amino acids, and the Maillard reaction. There were also significant flavor differences between HAD and VFD B. fusco-purpurea. Thus, although HAD exhibits better drying efficiency, VFD has more significant advantages in terms of product quality.

Drying of Carrot Strips in Indirect Solar Dehydrator with Photovoltaic Cell and Thermal Energy Storage

Minimizing agricultural losses, accompanied by employing technologies capable of taking advantage of solar energy, are the current challenges of the Antofagasta region of Chile due to having an average solar irradiance of 7.2 kWh/m2 per day. With this objective, using an indirect solar dryer with storage of thermal energy in the form of sensible heat, the effect of drying on the quality of carrot strips was studied using chromatic coordinates CIEL*a*b*, the color difference (ΔE), the relationship between redness/yellowness (R = a*/b*), browning index (BI), whiteness index (WI), chroma (C), hue angle (h°) and drying kinetics. The experimental drying data were fitted to 15 typically employed nonlinear regression models. The ΔE = 14.11 ± 0.14 between the carrots in the dry and fresh conditions represented a detectable color change, the R ratio increased from 0.75 to 0.89, the BI index decreased from 209.82 ± 0.62 to 148.38 ± 0.26 and the WI index increased from 24.5 ± 0.11 to 31.8 ± 0.17, indicating color affectations due to the process. The coefficients of determination, (R2) close to 1 and the values closest to 0 of χ2, SSE and RMSE, led to the best fit corresponding to the Weibull distribution model. In addition, it was found that the operation of the drying installation in the hours without incident solar radiation maintained the drying temperature values throughout the process.

The retention and bioavailability of phytochemicals in the manufacturing of baked snacks

There is a growing body of evidence supporting the role that phytochemicals play in reducing the risk of various chronic diseases. Although there has been a rise in health products marketed as being "supergrains," "superfood," or advertising their abundance in antioxidants, these food items are often limited to powdered blends, dried fruit, nuts, or seeds, rarely intercepting the market of baked snacks. This is in part due to the still limited understanding of the impact that different industrial processes have on phytochemicals in a complex food matrix and their corresponding bioavailability. This review brings together the current data on how various industrial dehydration processes influence the retention and bioaccessibility of phytochemicals in baked snacks. It considers the interplay of molecules in an intricate snack matrix, limitations of conventional technologies, and constraints with consumer acceptance preventing wider utilization of novel technologies. Furthermore, the review takes a holistic approach, encompassing each stage of production-discussing the potential for inclusion of by-products to promote a circular economy and the proposal for a shift in agriculture toward biofortification or tailored growing of crops for their nutritional and post-harvest attributes.

Reducing atmosphere drying as a novel drying technique for preserving the sensorial and nutritional notes of foods

Reducing atmosphere drying (RAD) was assayed as a novel technique for preserving the color and the nutritional fresh notes of apricot. A freeze, hot air and vacuum drying techniques were applied for a comparison purpose. The results showed that the apricot samples dried by both RAD_MIX and RAD_NITROGEN preserved better the fresh color notes while the freeze-drying was characterized by light and dully notes compared to a fresh sample. The total phenolic content significantly differed between fresh, RAD_MIX, RAD_AIR, hot air and vacuum with the highest value observed for both vacuum and hot air with 284.8 and 259.5 mg GAE 100 g^-1 dm, respectively. DPPH inhibition activity was significantly similar for both fresh (or freeze drying) and each RAD_MIX, hot air and vacuum dried samples with 83.52, 76.3, 70.31, 67.86%, respectively, with the highest value attributed to RAD_MIX sample. The RAD-type dried samples (RAD_MIX, RAD_NITROGEN, RAD_AIR) possessed ABTS scavenging activity range of 68.74, 64.49 and 61.61 μmol TE g^-1 dm respectively, which were close to that of the fresh sample (63.36 μmol TE g^-1 dm) with the highest value attributed to RAD_MIX sample. The total flavonoid content was significantly similar between fresh (or freeze drying), vacuum, hot air and RAD_MIX samples with a range of 27.38, 24.25, 19.41 and 18.81 mg QE 100 g^-1 dm, respectively, which exhibited an advantageous role of hydrogen in RAD_MIX system over both RAD_NITROGEN and RAD_AIR. For the first time, a technique based on the use of hydrogen in the drying atmosphere of a closed system was successfully proved for drying foods. This novel technique exhibits an opportunity for the food drying processors to produce dried foodstuffs with fresh color and nutritional notes.

Effect of ultrasonic power on drying process and quality properties of far-infrared radiation drying on potato slices

The experiments of contact ultrasound-assisted far-infrared radiation (FIR) drying on potato slices were conducted to investigate the effects of ultrasonic power on drying characteristics and quality properties. The results showed that contact ultrasound was helpful for accelerating mass transfer of the samples, and the improvement of ultrasonic power could significantly shorten drying time. The ultrasonic reinforcement effect on drying rate declined along with the decrease in moisture content. D _eff values were within 1.15 × 10^-10 and 1.96 × 10^-10 m²/s, and improved with an increase in ultrasound power. Compared with FIR dried ones, more and larger pore size of microcapillaries in the samples' tissue structure could be observed with contact ultrasound application, and higher ultrasonic power produced more microtunnels. Contact ultrasound in FIR drying could reduce the color difference of dried potato slices, and decrease the hardness and brittleness values. Higher TPC and TFC could be achieved as ultrasonic power increased.

Modeling of drying and ameliorative effects of relative humidity (RH) against β-carotene degradation and color of carrot (Daucus carota var.) slices

Drying and β-carotenes retention kinetics were predicted using models in relative humidity (RH) drying condition. This was achieved by drying carrot slices using RH-convective hot-air dryer at 60, 70 and 80 °C under RH (10% 20% and 30%) conditions at 2.0 m/s air velocity. Three mathematical models describing thin layer were compared to their goodness of fit in terms of coefficient of correlation (R²), root mean square error (RMSE) and reduced Chi square ( χ 2 ). The Wang and Singh model could satisfactorily describe RH-convective drying of carrot slices with R², RMSE and χ 2 in the ranges of 0.996-0.999, 5.4 × 10^-4-9.4 × 10^-4 and 0.0150-0.03353 respectively. The results reveal that a range of 3.61-8.2% retention of β-carotene was observed for every 10% increase in RH in various drying air temperature. In summary, higher temperatures were mainly responsible for β-carotenes degradation however this can be mitigated when drying is conducted under higher RH.

Influences of convective and vacuum drying on the quality attributes of osmo-dried pequi (Caryocar brasiliense Camb.) slices

Pequi is a fruit from Brazilian Cerrado. Despite its ascorbic acid and carotenoid contents, consumption of pequi is restricted to its region of origin. The goal of this work was to study drying of pequi slices (convective or vacuum drying at 40°C and 60°C) preceded or not preceded by osmotic pretreatment (sucrose solution concentrations of 40% and 60%). It was found that osmotic dehydration pretreatment substantially decreased the moisture content, duration of the drying process, and the volumetric ratio of the dried product. However, it also promoted leaching of bioactive constituents, such as ascorbic acid and carotenoids. Vacuum and low temperature drying without osmotic pretreatment were preferable because the ascorbic acid and carotenoids were retained, rehydration coefficients were higher and there were minimal volume and color changes.

Effects of Air-Impingement Jet Drying on Drying Kinetics, Nutrient Retention and Rehydration Characteristics of Onion (Allium cepa) Slices

This study is designed to investigate drying kinetics, nutrient retention and rehydration ratio of onion slices under air-impingement jet drying (AIJD) with different drying temperatures (40, 50 and 60°C), air velocities (11, 12 and 13 m/s), and the distance between jet nozzles and material box (0, 40 and 80 mm). Additionally, the influence of AIJD and hot air drying (HAD) on drying efficiency and product quality of onion slices was comparatively investigated. It was found that the moisture effective diffusivity of onion slices under AIJD ranged from 3.51 × 10−10 to 5.51 × 10−10 m2/s, and the activation energy (E a) of onion determined from Arrhenius equation was 14.73 kJ/mol, and ascorbic acid content (AAC), total phenolic content (TPC) and DPPH (1,1-diphenyl-2-picrylhydrazyl) scavenging activity (DSA) significantly decreased in the dried onions compared to that in fresh onion. In addition, the results suggest that the Modified Page model provides the best fit for AIJD curves. Furthermore, AIJD product is better than HAD both in decreasing drying time and enhancing drying rate, AAC, TPC, DSA and rehydration ratio. Accordingly, the AIJD method has advantages in drying time and quality of products, indicating that this technology can be widely applied to food drying process.