Degradation kinetics of total phenolic compounds, capsaicinoids and antioxidant activity in red pepper during hot air and infrared drying process

A comparative study of electrical and conventional pre-treatments for quality assessment of hot air dried green bell pepper

In this study, the effect of pretreatments (hot water blanching, microwave blanching and ohmic heating) on drying kinetics and quality characteristics of green bell pepper dried at 60, 70 and 80 °C was investigated. Four mathematical models were fitted to experimental data and Logarithmic model was found to be the best for all the samples. Rehydration ability of only ohmic heating pretreated peppers was higher than untreated ones. Total polyphenol (TP) content and antioxidant capacity (AC) of dried peppers varied between 3.21-5.08 mg gallic acid equivalent (GAE)/g dry matter (DM) and 1037.57-2407.40 mmol AAE/100 g DM, respectively. The content of ascorbic acid (AA) in dried samples was in the range of 187.25-722.55 µg/g DM. The bioaccessibility of TP after in-vitro digestion varied from 79.44 to 97.73%. Losses of chlorophyll a and b were very high in all samples compared to fresh ones but the most in control samples.

Ultrasound-assisted ascorbic acid solution pretreated hot-air drying improves drying characteristics and quality of jujube slices

BACKGROUND

The effective hot-air drying of foods such as jujube requires an effective green pretreatment alternative to chemical pretreatments. Jujube slices were pretreated using 5 and 10 mg mL^-1 ultrasound-assisted vitamin C (UVC) for 10, 20, and 30 min, followed by hot-air drying.

RESULTS

Ultrasound-assisted vitamin C pretreatment for 10, 20, and 30 min modulated the characteristics of fresh jujube slices such as water loss (from -28.25% to -25.52% after 30 min of UVC pretreatment), solid gain (from -31.68% to -26.82% after 30 min of UVC pretreatment), loss of total and reducing sugars (from 200.25 mg and 34.88 mg to 287.14 mg and 4.71 mg, respectively, after 30 min of UVC pretreatment), total soluble solids (from 76.32 ^o Brix to 82.08 ^o Brix), and water diffusivity (from 9.01 × 10^-10  m²  s^-1 to 6.71 × 10^-10  m²  s^-1 ). These characteristics were associated with altered surface morphology and improved drying characteristics. The UVC pretreatment preserved an acceptable reddish-yellow or orange-like color during hot-air drying and reduced the browning index from 26.3 optical density (OD)/g DM to 23.25 OD/g dry mass basis (DM), which was connected with reduced 5-hydroxymethylfurfural (HMF) content. On the other hand, the proportions of bioactive components such as vitamin C increased from 1.05 mg g^-1 DM to 9.02 mg g^-1 DM, phenolics increased from 12.8 mg gallic acid equivalent (GAE)/g DM to 17.5 mg GAE/g DM, flavonoids increased from 4.0 mg rutin equivalent (RE)/g DM to 4.4 mg RE/g DM, and procyanidin content increased from 2.0 mg catechin equivalents (CE)/g DM to 2.9 mg CE/g DM in UVC pretreated jujube slices, which had a positive association with increased antioxidant activity - for example, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) increased from IC₅₀ 22.5 mg DM/mL to 8.0 mg DM/mL, 2,2-diphenyl-1-picrylhydrazyl (DPPH) changed from IC₅₀ 36.5 mg DM/mL to 9.5 mg DM/mL, and ferric reducing antioxidant power (FRAP) increased from 2.0 mg vitamin C equivalent (VCE)/g DM to 11.9 mg VCE/g DM).

CONCLUSION

The data indicated that UVC can be used as a promising pretreatment method for improving the hot-air drying characteristics and the quality of jujube slices. © 2023 Society of Chemical Industry.

Kinetic Model of Moisture Loss and Polyphenol Degradation during Heat Pump Drying of Soursop Fruit (Annona muricata L.)

The aim of this study is to investigate the impact of time and temperature of the heat pump drying process of soursop slices at different levels on moisture content and total polyphenol content (TPC). Twelve types of classical kinetic models have been used in this work to describe the suitability of experimental data with models. The conformity is assessed based on statistical values (e.g., coefficient of determination (R2), Chi–square value (X2), etc.). The loss of moisture in the material is described in accordance with Fick’s diffusion law. Value of moisture rate (MR), and effective moisture diffusivities (Deff) have been identified. Experimental results show that MR value depends on the time and drying temperature, Deff increases when increasing the drying temperature from 20–50 °C with values of 1.24 × 10−9, 1.85 × 10−8, 7.69 × 10−8, and 5.54 × 10−7 m/s2. The Singh et al. model is the best option to describe the moisture of the sliced soursop drying process at 30 °C (R2 = 0.97815). The largest TPC decomposition occurs at a temperature of 50 °C. The ability to decompose TPC is proportional to the drying temperature. The TPC decomposition dynamic model follows a first–order reaction when drying at 20 °C with a determinant coefficient R2 = 0.9693.

Nutraceutical Difference between Two Popular Thai Namwa Cultivars Used for Sun Dried Banana Products

Musa (ABB group) “Kluai Namwa” bananas (Musa sp.) are widely grown throughout Thailand. Mali Ong is the most popular Kluai Namwa variety used as raw material for sun-dried banana production, especially in the Bangkratum District, Phitsanulok, Thailand. The sun-dried banana product made from Nanwa Mali Ong is well recognized as the best dried banana product of the country, with optimal taste compared to one made from other Kluai Namwa varieties. However, the production of Mali Ong has fluctuated substantially in recent years, leading to shortages. Consequently, farmers have turned to using other Kluai Namwa varieties including Nuanchan. This study investigated the nutraceutical contents of two popular Namwa varieties, Mali Ong and Nuanchan, at different ripening stages. Nutraceuticals in the dried banana products made from these two Kluai Namwa varieties and four commercial dried banana products were compared. Results indicated that the content of moisture, total sugar, and total soluble solids (TSS) (°Brix) increased, while total solids and texture values decreased during the ripening stage for both Kluai Namwa varieties. Rutin was the major flavonoid found in both Namwa Mali Ong and Nuanchan varieties ranging 136.00−204.89 mg/kg and 129.15−260.38 mg/kg, respectively. Rutin, naringenin, quercetin and catechin were abundant in both Namwa varieties. All flavonoids increased with ripening except for rutin, gallocatechin and gallocatechin gallate. There were no significant differences (p < 0.05) in flavonoid contents between both varieties. Tannic acid, ellagic acid, gallic acid, chlorogenic acid and ferulic acid were the main phenolic acids found in Mali Ong and Nuanchan varieties, ranging from 274.61−339.56 mg/kg and 293.13−372.66 mg/kg, respectively. Phenolic contents of both varieties decreased, increased and then decreased again during the development stage. Dopamine contents increased from 79.26 to 111.77 mg/kg and 60.38 to 125.07 mg/kg for Mali Ong and Nuanchan, respectively, but the amounts were not significantly different (p < 0.5) between the two Namwa varieties at each ripening stage. Inulin as fructooligosaccharide (FOS) increased with ripening steps. Production stages of sun-dried banana products showed no statistically significant differences (p < 0.05) between the two Namwa varieties. Therefore, when one variety is scarce, the other could be used as a replacement in terms of total flavonoids, phenolic acid, dopamine and FOS. In both Namwa varieties, sugar contents decreased after the drying process. Sugar contents of the dried products were 48.47 and 47.21 g/100 g. The drying process caused a reduction in total flavonoid contents and phenolic acid at 63−66% and 64−70%, respectively. No significant differences (p < 0.05) were found for total flavonoid and phenolic contents between the dried banana products made from the two Namwa varieties (178.21 vs. 182.53 mg/kg and 96.06 vs. 102.19 mg/kg, respectively). Products made from Nuanchan varieties (24.52 mg/kg) contained significantly higher dopamine than that from Mali Ong (38.52 mg/kg). The data also suggest that the banana maturity stage for production of the sun dried products was also optimum in terms of high nutraceutical level.

Effect of Combined Infrared and Hot Air Drying Strategies on the Quality of Chrysanthemum (Chrysanthemum morifolium Ramat.) Cakes: Drying Behavior, Aroma Profiles and Phenolic Compounds

Chrysanthemum (Chrysanthemum morifolium Ramat.) is a seasonal plant with high medicinal and aesthetic value, and drying is an effective practice to enhance its storability after harvesting. The effects of hot air drying (HAD), combined infrared and hot air drying (IR-HAD), and sequential IR-HAD and HAD (IR-HAD + HAD) on the drying behavior, color, shrinkage, aroma profiles, phenolic compounds, and microstructure of chrysanthemum cakes were studied. Results showed that the increasing temperature resulted in a decrease in drying time and an increase in drying rate and moisture diffusivity. The Logarithmic and Page models exhibited superior fit in describing the dehydration process. Among the three drying strategies, IR-HAD was more effective in reducing energy consumption, improving shrinkage, water holding capacity, water binding capacity and cellular microstructure, while IR-HAD + HAD showed better inhibitory effect on color deterioration. Furthermore, gas chromatography–mass spectrometry (GC-MS) analysis revealed that different drying strategies dramatically influenced the aroma profiles in samples, and IR-HAD obtained the highest concentration of volatiles. The results of ultra-performance liquid chromatography (UPLC) indicated that the introduction of infrared radiation contributed to increasing the contents of chlorogenic acid, luteolin, total phenolic and flavonoid. These suggested that IR-HAD was a promising technique for drying medicinal chrysanthemum.

Effect of Osmotic Dehydration Pretreatment on the Drying Characteristics and Quality Properties of Semi-Dried (Intermediate) Kumquat (Citrus japonica) Slices by Vacuum Dryer

The effect of osmotic dehydration (OD) pretreatments at different temperatures and immersion times on drying characteristics, total phenolic content (TPC), total antioxidant activity (TAA) (DPPH and CUPRAC methods), and color of kumquat slices dried under vacuum conditions (70 °C-100 mbar) was investigated. The OD pretreatment was performed in a sucrose solution (45 °Bx) at the temperatures of 40 and 50 °C and immersed at times of 30, 60, and 90 min. OD before vacuum drying decreased the total required drying time by up to 70 min compared to the control non-pretreated samples. Page, Modified Page, Henderson Pabis, and Two Terms Exponential models were found to satisfactorily describe the drying behavior of thin layer dried kumquat slices. The minimum and maximum values of effective moisture diffusivity (Deff) for semi-dried kumquat slices were 5.04 × 10⁻⁸ to 7.19 × 10⁻⁸, respectively. OD treatments induced a decline in TPC (5.30–33.92%) and TAA (23.63–59.34% and 4.17–31.67% for DPPH and CUPRAC assays, respectively) of kumquat slices. It was observed that OD pre-treatment can decrease the gross drying time, and make the color and sensorial attributes of dried kumquats better.

Antioxidant and Antimicrobial Activity of Rosemary (Rosmarinus officinalis) and Garlic (Allium sativum) Essential Oils and Chipotle Pepper Oleoresin (Capsicum annum) on Beef Hamburgers

The inclusion of natural ingredients to preserve meat and meat products has increased in recent years. This study evaluated rosemary (REO) and garlic essential oils (GEO) as well as chipotle pepper oleoresin (CPO), alone or in combination, as preservatives on beef hamburgers (BH). Six treatments were evaluated: T1 (control, without additives), T2 (GEO 1%), T3 (REO 1%), T4 (CPO 0.5%), T5 (GEO 1% + CPO 0.5%) and T6 (REO 1% + CPO 0.5%). The microbiological quality, physicochemical characteristics, sensory evaluation, and lipid oxidation of hamburgers were evaluated. REO, GEO and CPO limited the growth of aerobic microorganisms, S. aureus, Salmonella spp., B. thermosphacta, moulds and yeasts, lactic acid bacteria and coliforms (p < 0.05); however, this effect depended on time. Furthermore, lipid oxidation decreased significantly (p < 0.5) in all treatments, except for T5 (GEO 1% + CPO 0.5%). Regarding sensory acceptance, consumers preferred BH with GEO in terms of colour, odour, flavour and overall appearance (p < 0.05). It is concluded that REO, GEO and CPO, alone or in combination, improve microbiological quality and inhibit the lipid oxidation of BH.

Influence of hot air drying on capsaicinoids, phenolics, flavonoids and antioxidant activities of 'Super Hot' chilies

Hot air drying is an alternative technique to either maintain or increase bioactive compounds in agricultural products because temperatures can be controlled. The effects of different hot air oven drying temperatures and times on the physicochemical changes, bioactive compounds (capsaicinoids, phenolic and flavonoid profiles and contents) and antioxidant activities in dried 'Super Hot' chili fruits were evaluated. The chilies were dried in a hot air oven at low (60-100 °C) or high (120-160 °C) temperatures for 30, 60, 120 min and at 12-13% moisture content (MC). The main compounds presented in chili fruits were capsaicinoids, limonene, pinene, tocopherol and oleic acid, regardless of drying temperature and time. Although the total flavonoid contents decreased during the drying process, the total phenolic contents increased (38-51%), and capsaicinoids, the primary pungent compounds, increased six-times at 120-160 °C compared to the fresh chilies. The phenolic profiles showed that chlorogenic acid was the most stable and abundant amongst the nine quantified phenolic compounds. In the flavonoid profile, both rutin and quercetin can be detected at a high temperature of 160 °C, with a decreasing trend. The main pungent compounds, capsaicin and dihydrocapsaicin, were found to increase compared to the fresh chilies, especially at 12-13% wet basis (w.b.). Although the antioxidant activities (ABTS• + and DPPH•) of dried chilies at all temperatures decreased with increasing drying time, these activities were still detected. Therefore, drying chilies at 160 °C (120 min) can not only maintain the capsaicinoids, phenolics and flavonoids that can be utilized by the pharmaceutical and food industry, but can also reduce the production time.

Response Surface Methodology as a Tool for Optimization of Pulsed Electric Field Pretreatment and Microwave-Convective Drying of Apple

The benefits of using hybrid drying are increasingly remarked. Microwave-convective drying (MW-CD) links the advantages of both microwave and convective drying methods and allows the negative phenomena that appear when the methods are used separately to diminish. Most importantly, reduced specific energy consumption and relatively short drying time are observed, which can be additionally decreased by the application of various preliminary treatments, e.g., pulsed electric field (PEF). Thus, the purpose of this study was to determine the impact of PEF pretreatment on the MW-CD of apples and its chosen physicochemical properties. This research was designed using response surface methodology (RSM). The first variable was microwave power (100, 200, and 300 W), and the second was specific energy input (1, 3.5, and 6 kJ/kg). Optimization responses were assumed: drying time to MR = 0.02, water activity, hygroscopicity after 72 h, rehydration ratio, relative dry matter content, total phenolic content, ability to scavenge ABTS•+ radical cations, and DPPH• radicals based on the EC50 values. The most optimal parameters were comprised of specific energy intake of 3.437 kJ/kg and microwave power of 300 W (desirability equalled 0.624), which provided the most minimized drying time and obtaining of apples with the most desired properties.

Influence of sequential exogenous pretreatment and contact ultrasound-assisted air drying on the metabolic pathway of glucoraphanin in broccoli florets

In this investigation, the combinations of exogenous pretreatment (melatonin or vitamin C) and contact ultrasound-assisted air drying were utilized to dry broccoli florets. To understand the influences of the studied dehydration methods on the conversion of glucoraphanin to bioactive sulforaphane in broccoli, various components (like glucoraphanin, sulforaphane, myrosinase, etc.) and factors (temperature and moisture) involved in the metabolism pathway were analyzed. The results showed that compared with direct air drying, the sequential exogenous pretreatment and contact ultrasound drying shortened the drying time by 19.0-22.7%. Meanwhile, contact sonication could promote the degradation of glucoraphanin. Both melatonin pretreatment and vitamin C pretreatment showed protective effects on the sulforaphane content and myrosinase activity during the subsequent drying process. At the end of drying, the sulforaphane content in samples dehydrated by the sequential melatonin (or vitamin C) pretreatment and ultrasound-intensified drying was 14.4% (or 26.5%) higher than only air-dried samples. The correlation analysis revealed that the exogenous pretreatment or ultrasound could affect the enzymatic degradation of glucoraphanin and the generation of sulforaphane through weakening the connections of sulforaphane-myrosinase, sulforaphane-VC, and VC-myrosinase. Overall, the reported results can enrich the biochemistry knowledge about the transformation of glucoraphanin to sulforaphane in cruciferous vegetables during drying, and the combined VC/melatonin pretreatment and ultrasound drying is conducive to protect bioactive sulforaphane in dehydrated broccoli.

Effect of Alternative Preservation Steps and Storage on Vitamin C Stability in Fruit and Vegetable Products: Critical Review and Kinetic Modelling Approaches

Vitamin C, a water-soluble compound, is a natural antioxidant in many plant-based products, possessing important nutritional benefits for human health. During fruit and vegetable processing, this bioactive compound is prone to various modes of degradation, with temperature and oxygen being recognised as the main factors responsible for this nutritional loss. Consequently, Vitamin C is frequently used as an index of the overall quality deterioration of such products during processing and post-processing storage and handling. Traditional preservation methods, such as thermal processing, drying and freezing, are often linked to a substantial Vitamin C loss. As an alternative, novel techniques or a combination of various preservation steps ("hurdles") have been extensively investigated in the recent literature aiming at maximising Vitamin C retention throughout the whole product lifecycle, from farm to fork. In such an integrated approach, it is important to separately study the effect of each preservation step and mathematically describe the impact of the prevailing factors on Vitamin C stability, so as to be able to optimise the processing/storage phase. In this context, alternative mathematical approaches have been applied, including more sophisticated ones that incorporate parameter uncertainties, with the ultimate goal of providing more realistic predictions.

Mathematical modeling of nutritional, color, texture, and microbial activity changes in fruit and vegetables during drying: A critical review

Retention of quality attributes during drying of fruit and vegetables is a prime concern since the product's acceptability depends on the overall quality; particularly on the nutritional, color, and physical attributes. However, these quality parameters deteriorate during drying. Food quality changes are strongly related to the drying conditions and researchers have attempted to develop mathematical models to understand these relationships. A better insight toward the degradation of quality attributes is crucial for making real predictions and minimizing the quality deterioration. The previous empirical quality models employed kinetic modeling approaches to describe the quality changes and therefore, lack the realistic understanding of fundamental transport mechanisms. In order to develop a physics based mathematical model for the prediction of quality changes during drying, an in-depth understanding of research progress made toward this direction is indispensable. Therefore, the main goal of this paper is to present a critical review of the mathematical models developed and applied to describe the degradation kinetics of nutritional, color, and texture attributes during drying of fruit and vegetables and microbial growth model during storage. This review also presents the advantages and drawbacks of the existing models along with their industrial relevance. Finally, future research propositions toward developing physics-based mathematical model are presented.

Optimization of an Extraction Process to Obtain a Food-Grade Sulforaphane-Rich Extract from Broccoli (Brassica oleracea var. italica)

Sulforaphane (SFN) is a powerful health-promoting compound found in broccoli in the form of its inactive precursor, glucoraphanin (GFN). SFN formation occurs through the enzymatic hydrolysis of glucoraphanin by myrosinase under specific chemical conditions. Its incorporation in food formulations has been hindered by the thermal instability of SFN and low concentration in Brassicaceae. Then, extracting SFN from broccoli at a temperature below 40 °C appears as an option to recover and stabilize SFN, aiming at delivering it as a nutraceutical. We studied an eco-friendly extraction process to obtain an SFN-rich extract from broccoli. The effect of the broccoli mass/solvent ratio, ethanol concentration in the extractant solution, and extraction time on the recovery of SFN, GFN, phenolic compounds, and antioxidant activity were studied through a Box–Behnken design. The regression models explained more than 70% of the variability in the responses, adequately representing the system. The experimental factors differently affected the bioactive compound recovery and antioxidant activity of the extracts. The extraction conditions that allowed the highest recovery of bioactive compounds and antioxidant activity were identified and experimentally validated. The results may provide the basis for the design of a process to produce a sulforaphane-rich food supplement or nutraceutical by using a GRAS extractant.

Mitigation of relative humidity (RH) on phytochemicals and functional groups of dried pineapple (Ananas comosus) slices

As part of finding a mechanism to ameliorate the decomposition of phytochemicals and antioxidant in drying processing, this research was conducted. To achieve this, pineapple slices was dried using relative humidity (RH) dryer at varied temperature (60–80 °C) combined with RH (10–30%) conditions. The results revealed that higher RH retained with significantly difference (p <0.05) the phytochemical and antioxidant concentrations and preserved the color and functional groups of dried pineapple under varying drying temperatures. The result also shows that concentrations of these compounds may differ as a result of disparities in the chemical composition which may be worsening by drying conditions such as higher temperature and lower RH. In effect, RH could savage the intensity of losses of these compounds and could therefore play a critical role in drying technology. Practical application: The loss of phytochemicals including polyphenols and antioxidant remains one of the challenging phenomena in drying technology. This research finds ameliorative option for mitigating against the loss of polyphenols and antioxidant by exploring the use of relative humidity (RH). The result shows that RH could savage the intensity of loss of these compounds and could therefore play a critical role in drying technology.

Acoustically-aided osmo-dehydration pretreatments under pulsed vacuum dryer for apple slices: drying kinetics, thermodynamics, and quality attributes

The research work investigates the effect of different pretreatment conditions (osmotic dehydration [OD], ultrasound [US], and ultrasound-assisted osmotic dehydration [UOD]) on the drying kinetics modeling, thermodynamics, weight reduction, degradation kinetics of vitamin C, and color of apple slices under pulsed vacuum dryer (PVD). The findings showed that UOD pretreatment significantly improved drying time and increased weight reduction comparative to OD, US, and the control sample. Drying kinetics modeling revealed that the Hii model better described the drying kinetic behavior of the apple slices than the other nine mathematical models based on higher coefficient of determination (R² ), root mean square error (RMSE), and reduced chi-square (χ² ). Analysis of vitamin C content revealed a 46.05%, 31.28%, and 25.95% retention for UOD, US, and OD, respectively, after drying. Second-order kinetics could accurately predict the degradation kinetics of vitamin C compared to first-order kinetics. Vitamin C degradation kinetics showed lower k-value, higher D-value (time required for 90% degradation), and half-life indicating a higher retention of vitamin C content for UOD pretreatment compared to OD and US during drying. L*, b*, and chroma values of UOD were significantly (P < 0.05) higher compared to US, OD, and the control sample. PRACTICAL APPLICATION: The findings of this study revealed that ultrasonic-aided osmotic dehydration is a unique and novel pretreatment technique prior to drying, which significantly shortens drying time as a result of faster moisture/mass transfer, improves processing efficiency thereby reducing processing cost, improves quality parameters, and preserve phytochemicals. This makes the business operations of food processors competitive and as well provide value for customers.

Impact of production and drying methods on the volatile and phenolic characteristics of fresh and powdered sweet red peppers

Aroma, phenolic compounds and sensory properties of fresh and powdered organic and conventional sweet red peppers dried by three methods (hot air, intermittent microwave and infrared) were studied. The number of aroma compounds was higher in both fresh and powdered organic pepper samples; however, the total amount was higher in conventional samples. In both organic and conventional samples, alcohols were the dominant aroma group. (E)-β-ionone and β-ocimene, which are important compounds in peppers, were determined only in organic peppers. Among the drying methods, intermittent microwave drying was more effective in creating new aroma compounds. The liquid chromatography, coupled with tandem mass spectrometry (LC-MS/MS) revealed that luteolin derivative compounds comprised an average of 70% of the phenolics. Higher amount of phenolic were determined in organic samples. Infrared drying was more effective in retaining of phenolics than the other two methods. Sensory analysis revealed that hot air-dried samples were least preferred.

Dry pasteurization of paprika (Capsicum annuum L.) by short time intensive microwave-infrared radiation: Inactivation of Salmonella Typhimurium and Aspergillus flavus considering quality degradation kinetics

The inactivation of S. Typhimurium and A. flavus along with quality degradation kinetics was studied during combined microwave-infrared (MW-IR) heating of paprika. The spatial changes in the distribution of temperature and variation in water activity (a_w) of the paprika samples resulted in a 7.389 log reduction in S. Typhimurium, and 6.182 log reduction in A. flavus. During heating, the deterioration of red pigments was more pronounced compared to that of the yellow pigments. The alteration of color was observed to be due to the increase in a large number of brown pigments. The inhibition of DPPH radicals accelerated with an increase in the power level of MW-IR radiation; the inhibition rate increased from 0.0859 to 0.1485 s^-1. Also, the pungency of dried paprika was found to increase due to moisture reduction, inactivation of peroxidase, and the short-duration of heating.

Effect of Drum-Drying Conditions on the Content of Bioactive Compounds of Broccoli Pulp

This work studied the effect of drum-rotation frequency, drum temperature, and water-to-pulp ratio in a double-drum drier on the content of sulforaphane, glucoraphanin, total phenolic compounds, ascorbic acid, and antioxidant activity of broccoli pulp through a multilevel factorial design with one replicate. Drum-drying conditions did not significantly affect sulforaphane content, unlike glucoraphanin, however the poor adherence of broccoli pulp resulted in a final product with undefined shape and heterogeneous color. On the other hand, antioxidant activity was unevenly affected by drying conditions; however, drum-rotation frequency affected it in the same way that phenolic compounds and ascorbic acid, showing a concordant behavior. The ascorbic acid content decreased significantly after drying, and it was highly dependent on the experimental factors, resulting in a regression model that explained 90% of its variability. Drum-rotation frequency of 5 Hz, drum temperature of 125 °C, and water-to-pulp ratio of 0.25 resulted in an apparent increase of sulforaphane and phenolic compounds content of 13.7% and 47.6%, respectively. Drum drying has great potential to fabricate dehydrated broccoli-based foods with functional properties. Besides, since drum drying has low investment and operation costs, it represents a very attractive option for the industrialization of broccoli derivatives.

Immunomodulation effects of polyphenols from thinned peach treated by different drying methods on RAW264.7 cells through the NF-κB and Nrf2 pathways

Thinned peach is abundant in polyphenols, and has been shown to exhibit various bioactivities. In this study, we evaluated the underlying immunomodulatory activity of polyphenol extracts of thinned peach (PETP) via the NF-κB and Nrf2 signaling pathways in RAW264.7 macrophages. The results demonstrated that the PETP efficiently activated the nuclear translocation of NF-κB and Nrf2, as well as downstream cytokines (IL-1β, IL-6, TNF-α and IFN-γ), SOD activity and ROS levels in RAW264.7 cells. Specifically, the PETP of natural drying and hot air drying exhibited less efficacy than that of freeze drying in NF-κB pathway. Interestingly, the PETP of hot air drying at 50 °C was more effective than freeze-dried PETP in activating Nrf2 nuclear translocation. Additionally, 50 µg/mL PETP enhanced immune responses, whereas 800 µg/mL PETP inhibited inflammatory development in macrophages. These findings indicated that different PETP affected the immunomodulation effects differently, which associated with the drying methods and incubation concentrations.

Cold plasma: An emerging pretreatment technology for the drying of jujube slices

Jujube slices were pretreated by cold plasma for 15, 30, and 60 s on each side, followed by hot air drying at 50, 60, and 70 °C. Scanning electron microscopy investigation indicated that the application of cold plasma significantly changed the surface topography of jujube slice by etching larger cavities, which can facilitate moisture transfer and consequently enhance drying rate and effective diffusivity. Modified Henderson & Pabis model and Two-term model were the two most recommended models for describing the drying kinetics of jujube slices. Cold plasma pretreatment improved the contents of procyanidins, flavonoids, and phenolics by 53.81%, 33.89%, and 13.85% at most, respectively, and thereby enhanced antioxidant capacity by 36.85% at most. Besides, cold plasma pretreatment can reduce the production of 5-hydroxymethylfurfural by 52.19% at most. In summary, cold plasma can be used as a promising pretreatment tool for drying processes of jujube slices.

Physical and viscoelastic properties of carrots during drying

It is essential to understand the physical and mechanical properties of a product since these properties affect the structure, texture, and ultimately consumer acceptance. The effect of drying conditions on dynamic viscoelastic properties, stress relaxation function and creep compliance, and physical properties, such as moisture distribution, color parameters, and shrinkage, was studied. An increase in drying temperature and duration resulted in a decrease in moisture content and volume, which were highly correlated (R = .988). Water evaporation followed the falling rate period, demonstrating that the water transport was limited by internal resistances. The decomposition of carotenoids led to a decrease in magnitude of color parameters (L, a, and b), between 30.1% and 51.6% with 4 hr drying. It was observed that the material shrinkage and moisture content highly affected the mechanical properties; increased stress relaxation modulus and decreased creep compliance values of the sample. The creep behavior, expressed with Burger's model (R²  ≥ .986), was highly dependent on moisture content. The linear viscoelastic region of carrots was found to be at strains lower than 3%. The three-element Maxwell model well fitted to describe the viscoelastic behavior of carrots (R²  ≥ .999, RMSE ≤ 2.08 × 10^-4 ). The storage moduli (G') were higher than loss moduli (G″), indicating that samples presented solid-like behavior. The findings can be used to improve the textural attributes of carrots and carrot-based products.

Evaluation of capsaicinoid profile and antioxidant properties in dried Korean red pepper (Capsicum annuum L.) as affected by variable dose rates of electron beam and gamma ray irradiation

The application of food irradiation is based on the parameters including energy (MeV), dose rate (kGy/s or kGy/h), and absorbed dose (kGy). Red pepper powders were treated with different dose rates of 1, and 5 kGy/s electron beam (EB) as well as 1.8 and 9 kGy/h gamma ray (GR) in separate experiments. Constant absorbed dose (3 kGy) was maintained to observe whether different dose rates affect the product quality. Total and individual capsaicinoids increased at low EB and GR dose rates. Vitamin C content decreased at all dose rates, except at low GR dose rate, where no significant difference was observed. Low EB dose rate led to a marked increase (21%) in the total phenolics than high dose rate (13%). In contrast, high GR dose rate increased the total phenolics than low dose rate. Maximum antioxidants (1.36 mg TE/mL) were observed at high EB dose rate, although low dose rate also increased the antioxidant activity. Results indicated that different dose rates delivering the same absorbed dose had significant impact on the product quality and that the efficacy of absorbed dose is dependent on applied dose rates. In other words, a constant absorbed dose applied to the product is influenced by dose rate of the irradiation treatment.

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.