Dehydration of red bell-pepper (Capsicum annuum L.): Change in drying behavior, colour and antioxidant content

Drying of Red Chili Pepper (Capsicum annuum L.): Process Kinetics, Color Changes, Carotenoid Content and Phenolic Profile

Studies were conducted focusing on the drying of chili pepper fruits (Capsicum annuum L.), cultivar Cyklon, using convective (AD), convective-microwave (AMD), vacuum (VD), and freeze-drying (FD) methods. The influence of the drying method and temperature on the kinetics of the process and selected quality attributes of the dried product were evaluated. It was demonstrated that the Midilli model best described the drying kinetics for all methods across the entire measurement range. FD and VD produced dried products with the highest brightness and the greatest value of the a* color parameter. The lowest b* color parameter was observed for the product dried using FD at 40 °C, while the highest b* value was noted for samples dried using AMD (100 W) at 60 °C. The highest carotenoid retention was achieved with the FD method at 40 °C, while the lowest carotenoid content was found in the product obtained using the AMD method (100 W) at 60 °C. The smallest losses of capsaicinoids were observed after FD drying at 40 °C, while the largest were found for AMD (100 W) at 60 °C. The analysis of chili pepper fruit extracts revealed the quantitative composition of 12 main phenolic compounds using the UHPLC-UV method. The highest polyphenol content was obtained with FD, while the lowest total polyphenol content was recorded after AD. Regardless of temperature, the total flavonoid content was highest in extracts from FD products, and the lowest flavonoid content was found after AMD at 100 W. For all drying methods analyzed, the total flavonoid content in the pepper extracts decreased with increasing temperature.

Cooking effect on bioactive compounds and antioxidant capacity of red pepper (Capsicum annuum L.)

The present review assessed the effect of heat processing on red peppers' (Capsicum annum L.) bioactive compounds and antioxidant capacity. The Google Scholar and Scopus databases were used to search the existing literature. Out of 422 articles accessed based on the inclusion and exclusion criterias included, only 15 studies were qualified for detailed review. The studies examined effects of processing on red hot peppers' bioactive compounds and antioxidant capacity. Information on type of heat applied for individual processes and the conditions used, countries in which the studies were carried out and effect of heat processing's were assessed. The review showed many studies were incomprehensive to details of processing condition constraining the validity of the results obtained from various cooking effects on bioactive compounds and antioxidant capacity. Further studies aimed at gaining a better understanding of the heat processing conditions and factors that influence the bioactive compounds and antioxidant capacity of red peppers are needed.

Effect of Microwave-Based Dry Blanching on Drying of Potato Slices: A Comparative Study

Microwave (MW)-based dry blanching can inactivate oxidative enzymes like peroxidase (POD) and polyphenol oxidase (PPO) rapidly and retain a higher amount of water-soluble nutrients, like ascorbic acid. This study compared the MW-based dry blanching of potato slices of various thicknesses (5, 8, and 10 mm) with conventional methods (water and steam blanching). The time required for water and steam blanching was longer than that required for MW blanching. Potato slices of 10 mm thickness required a longer blanching duration compared with slices of a lesser thickness (5 and 8 mm). The MW-blanched samples (77.37-83.5%) retained a higher content of ascorbic acid, followed by steam-blanched (69.15-74.92%) and water-blanched (67.18-71.54%) samples. The Page, modified Page, Midilli-Kucuk, and Hii, Law, and Cloke models predicted the thin layer drying of potato slices (5 mm thickness) better with a higher coefficient of determination values (0.9607-0.9976) compared to Fick's and Exponential models (0.8942-0.9444).

Effects of microwave drying on physicochemical characteristics, microstructure, and antioxidant properties of propolis extract

BACKGROUND

The heat sensitivity of phenolics and flavonoids leads to considerable losses of these compounds during conventional drying. Microwave drying has the advantage of shorter drying time and rigorous process control, minimizing damage to heat-sensitive compounds. Microwave drying kinetics and the impacts of microwave drying on physicochemical characteristics, morphological structure, antioxidant properties, total phenolics, and flavonoid content of propolis extract were investigated.

RESULTS

Increasing the microwave power output from 180 to 900 W resulted in a 67% reduction in drying time. Morphological changes were more noticeable at higher microwave power levels as shown in scanning electron microscopy images. Water activity values of microwave dried propolis extracts were below 0.4, which satisfied the requirement for shelf-stable dry products. The solubility of microwave dried propolis extract increased with increasing microwave power level, and the highest solubility was achieved for the propolis extract microwave dried at 900 W. Microwave dried propolis extracts exhibited lower total phenolic content levels than fresh propolis extract. The microwave power level did not affect the total flavonoid content but it affected 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging activity of microwave dried propolis extracts. The DPPH free-radical scavenging activity closest to the fresh propolis extract was obtained for the microwave dried propolis extract at 900 W. This also showed the highest 6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid (Trolox) equivalent antioxidant capacity.

CONCLUSION

Microwave drying of propolis extract at 900 W was found to be the most efficient drying condition because it yielded the shortest drying time, the highest effective moisture diffusivity, and phenolic and flavonoid content levels that were very similar to those in fresh propolis extract. © 2023 Society of Chemical Industry.

Effect of Antioxidant-Rich Moringa Leaves on Quality and Functional Properties of Strawberry Juice

Moringa oleifera and strawberry are cultivated extensively worldwide and are divinely blessed with an enormous amount of nutritional and medicinal constituents, such as vitamin C, vitamin E, iron, potassium, and phenolic antioxidants that play a pivotal role in treating, confining, and preventing diabetes and many kinds of cancer. The focus of the study is to develop different samples of highly acceptable ready to serve (RTS) Moringa strawberry juice blend by underutilizing Moringa and strawberry juice in different proportions. Moringa oleifera's bitter taste and green color steeply limits its acceptability and counter this drawback utilized with strawberry juice. The physicochemical analysis of blended juice was performed to investigate the suitability and keeping quality of the juice mixture. The collected data signify that pH titratable acidity (TA) and total soluble solids (TSS) the slight modification after the inclusion of Moringa juice extract and throughout the storage. The Moringa treatment positively improved the total phenolic content (TPC), antioxidant, and vitamin C from 12 to 49.17 mg GAE/100g, 61.41 to 87.69%, and 64.03 to 86.65 mg/100 mL, respectively, but there was a slight decline in antioxidant quantity while stored under refrigerated conditions for one month. An assimilative trend was noticed in TPC and vitamin C, which collapsed from 49.17-36.32 mg GAE to 86.65-79.19 mg, respectively. In accordance with sensory analysis T 2 (90% strawberry juice and 10% Moringa extract), the juice blend was rated best in context to flavor, color, and taste. This juice blend proved to be greatly effective especially for children suffering from malnutrition as well as women to counter with its appreciable number of nutritional constituents.

Effects of Hot Air Drying on Drying Kinetics and Anthocyanin Degradation of Blood-Flesh Peach

The purpose of this study was to explore the drying kinetics, effective moisture diffusivity, activation energy, color variation, and the thermal degradation properties of anthocyanins of blood-flesh peach under hot air drying for the first time. The results showed that the hot air-drying process of blood-flesh peach belongs to reduced-speed drying. The Page model could accurately predict the change of moisture ratio of blood-flesh peach. The effective moisture diffusivity during hot air drying of blood-flesh peach was in the range between 1.62 × 10⁻¹⁰ and 2.84 × 10⁻¹⁰ m²/s, and the activation energy was 25.90 kJ/mol. Fresh samples had the highest content (44.61 ± 4.76 mg/100 g) of total monomeric anthocyanins, and it decreased with the increase of drying temperature. Cyanidin-3-O-glucoside and delphinidin-3-O-galactoside were the main anthocyanins of blood-flesh peach as identified and quantified by UPLC-QqQ-MS. Interestingly, during the drying process, the content of cyanidin-3-O-glucoside increased at the beginning, and then decreased. However, the content of delphinidin-3-O-galactoside kept decreasing during the whole drying process. Considering the drying efficiency, fruit color and quality, 70 °C would be a suitable temperature for drying blood-flesh peach. This research will provide beneficial information for understanding the anthocyanin degradation of blood-flesh peach during drying, and guide the production of high-quality dried products.

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.

Effect of Thermal and Non-Thermal Technologies on Kinetics and the Main Quality Parameters of Red Bell Pepper Dried with Convective and Microwave-Convective Methods

The drying process preserves the surplus of perishable food. However, to obtain a good-quality final product, different pretreatments are conducted before drying. Thus, the aim of the study was the evaluation of the effect of thermal (blanching treatments with hot water) and non-thermal technologies (pulsed electric field (PEF) and ultrasound (US)) on the kinetics of the drying process of red bell pepper. The convective and microwave-convective drying were compared based on quality parameters, such as physical (water activity, porosity, rehydration rate, and color) and chemical properties (total phenolic content, total carotenoids content, antioxidant activity, and total sugars content). The results showed that all of the investigated methods reduced drying time. However, the most effective was blanching, followed by PEF and US treatment, regardless of the drying technique. Non-thermal methods allowed for better preservation of bioactive compounds, such as vitamin C in the range of 8.2% to 22.5% or total carotenoid content in the range of 0.4% to 48%, in comparison to untreated dried material. Moreover, PEF-treated red bell peppers exhibited superior antioxidant activity (higher of about 15.2-30.8%) when compared to untreated dried samples, whereas sonication decreased the free radical scavenging potential by ca. 10%. In most cases, the pretreatment influenced the physical properties, such as porosity, color, or rehydration properties. Samples subjected to PEF and US treatment and dried by using a microwave-assisted method exhibited a significantly higher porosity of 2-4 folds in comparison to untreated material; this result was also confirmed by visual inspection of microtomography scans. Among tested methods, blanched samples had the most similar optical properties to untreated materials; however non-thermally treated bell peppers exhibited the highest saturation of the color.

Physico-Chemical Properties of Red Pepper (Capsicum annuum L.) as Influenced by Different Drying Methods and Temperatures

An experiment was carried out in the laboratories of the Department of Food Engineering, Department of Vegetable Science, and Department of Plantation Spices Medicinal and Aromatic crops, Bidhan Chandra Krishi Viswavidyalaya (BCKV), West Bengal, India. The work was performed during 2018–2019 and 2019–2020 with different drying methods including sun drying, solar drying and oven drying. In oven drying, different temperatures such as 50, 55, 60, 65, and 70 °C were considered. A randomized complete block design (RCBD) was designed with seven treatments and three replications. Experimental results were significantly varied among the treatments as influenced by different drying methods and temperatures. Minimum time taken (480 min) to reach safe moisture content was recorded in T7 (oven drying at 70 °C), whereas maximum values in color components such as L* value (24.55), a* value (32.14), b* value (20.53), and pungency score (7.85) were recorded in T6 (oven drying at 65 °C). However, the highest texture (1180.81) was observed in T1 (sun drying). Biochemical parameters were significantly varied among the treatments. The maximum amounts of ascorbic acid (56.06 mg/100 g) and oleoresin content (10.72) were found in T3 (oven drying at 50 °C), whereas minimum values of biochemical parameters were recorded by T1 (sun drying) and T2 (solar drying) methods, respectively. Mathematical relationships were found in different drying methods and temperatures. Models such as the Lewis, Page, Modified Page, and Henderson and Pabis models were selected to fit the data. Maximum R2 value (0.9835) was found in both the Page and Modified Page models with similar values of drying method and temperature at 65 °C. This value was the highest among all models in all drying temperatures. However, the lowest χ2, and RMSE values (0.000818 and 0.027261, respectively) were recorded with the Page model.

Effects of Different Solvents Extractions on Total Polyphenol Content, HPLC Analysis, Antioxidant Capacity, and Antimicrobial Properties of Peppers (Red, Yellow, and Green (Capsicum annum L.))

Plants possessing various bioactive compounds and antioxidant components have gained enormous attention because of their efficacy in enhancing human health and nutrition. Peppers (Capsicum annuum L.), because of their color, flavor, and nutritional value, are considered as one of the most popular vegetables around the world. In the present investigation, the effect of different solvents extractions (methanol, ethanol, and water) and oven drying on the antioxidant and antimicrobial properties was studied of red, yellow, and green peppers. The green pepper water extract showed the highest total polyphenol content (30.15 mg GAE/g DW) followed by red pepper water extract (28.73 mg GAE/g DW) and yellow pepper water extract (27.68 mg GAE/g DW), respectively. The methanol extracts of all the pepper samples showed higher TPC as compared to the ethanol extract. A similar trend was observed with the total flavonoid content (TFC). The antioxidant assays (DPPH scavenging and reducing power) echoed the findings of TPC and TFC. In both antioxidant assays, the highest antioxidant activity was shown by the water extract of green pepper, which was followed by the water extract of red pepper and yellow pepper. Furthermore, all extracts were assessed for their potential antimicrobial activity against bacterial and fungal pathogens. Aqueous extracts of all three pepper samples exhibited slightly higher inhibition zones as compared to their corresponding ethanolic and methanolic extract. Minimum inhibitory concentration (MIC) values ranged from 0.5 to 8.0 mg/ml. The lowest MIC values ranging from 0.5 to 2.0 mg/ml concentration were recorded for aqueous extracts of green pepper. High-performance liquid chromatography (HPLC) analysis revealed tannic acid as the major phenolic compound in all three pepper samples. Thus, it is envisaged that the microwave drying/heating technique can improve the antioxidant and antimicrobial activity of the pepper.

Short- and Medium-Wave Infrared Drying of Cantaloupe (Cucumis melon L.) Slices: Drying Kinetics and Process Parameter Optimization

The main objective of the present work was to study the drying kinetics and obtain the optimum process parameters of cantaloupe slices using short-and medium-wave infrared radiation (SMIR) drying technology. The effect of three independent variables of infrared radiation temperature (55–65 °C), slice thickness (5–9 mm) and radiation distance (80–160 mm) on the L value, color difference (∆E), hardness and vitamin C content were investigated by using the Response Surface Methodology (RSM). The results showed that the Page model can adequately predict the moisture content between 55 and 65 °C (R2 > 0.99). The effective moisture diffusivity (Deff) varied from 5.26 × 10−10 to 2.09 × 10−9 m2/s and the activation energy (Ea) of the SMIR drying was 31.84 kJ/mol. Infrared radiation temperature and slice thickness exerted extremely significant effects on L value and color difference (ΔE) (p < 0.01), with higher infrared radiation temperature and thin slice thickness leading to a decrease in the L value and an increase in ΔE. Hardness and vitamin C content were significantly affected by infrared radiation temperature, slice thickness and radiation distance, of which the slice thickness was the most distinct factor affecting the hardness value. Higher infrared radiation temperature and larger slice thickness and radiation distance resulted in higher vitamin C degradation. For the given constraints (maximized vitamin C content and L value, minimized ΔE and hardness value), the optimum drying parameters were infrared radiation temperature 58.2 °C, slice thickness 6 mm and radiation distance 90 mm. Under the optimum drying combination conditions, the experimental values were 65.58 (L value), 8.57 (∆E), 10.49 N (hardness) and 106.58 mg/100 g (vitamin C content), respectively. This study is beneficial to the development of the cantaloupe food processing industry and provides more insights for the application of SMIR drying technology to improve the drying rate and product quality of cantaloupe.

Osmotic, osmovacuum, sonication, and osmosonication pretreatment on the infrared drying of Ginkgo seed slices: Mass transfer, mathematical modeling, drying, and rehydration kinetics and energy consumption

This study evaluated the mass transfer, drying, and rehydration kinetics (drying and rehydration curve, moisture diffusivity [D_eff ]), energy consumption (specific energy consumption [SEC], moisture extraction rate (MER), and specific moisture extraction rate [SMER]), and mathematical modeling of infrared dried Ginkgo biloba seed (GBS) using the various nonthermal pretreatments namely: osmotic (OS), osmovacuum (V + OS), ultrasound (US, ginkgo seed immersed in a distilled water with US), and osmosonication (US + OS, ginkgo seeds immersed in an OS solution with US). Results showed that various pretreatments affected mass transfer, drying, and rehydration characteristics, and energy consumption, which was confirmed by principal component analysis. In terms of mass transfer, US pretreatment recorded the highest weight loss while the osmosonication pretreatment registered the highest solid gain. The entire drying process occurred in the falling-rate period. The D_eff values were within the normal range of agroproducts (10^-11 to 10^-8 m² /s). The modified Page-I and Weibull model best fitted the drying and rehydration kinetics, respectively, with the coefficient of determination (R² ) > 0.991, root mean square error, residual sum of squares, and reduced chi-square closer to zero, compared with the other models. The untreated GBS (control) had the lowest energy efficiency (lowest SMER and MER) and the highest SEC than the pretreated GBS. Among the various pretreatments, the US pretreatment of GBS was superior, with the highest D_eff , MER, SMER, and drying rate, and lowest drying time and SEC. Based on the findings, sequential US pretreatment and infrared drying is a feasible drying technique for GBS that could be used commercially. PRACTICAL APPLICATION: Ginkgo tree cultivation in China has exceeded market needs with 60,000 tons per annum of GBS produced. Hence, there is a compelling need to explore new chances to use GBS availability irrespective of the seasonality and address the problem where GBS utilization is limited to the early phases of home-cooked dishes. Although drying increases the shelf life of ginkgo seeds, there is a higher operation cost. Thus, pretreatment can reduce energy consumption and augment the product quality is ideal. This research reported the impact of nonthermal pretreatments on ginkgo seeds' mass transfer, drying, and rehydration characteristics. The present results will provide a comprehensive understanding of the engineering application of ginkgo seed pretreatment, allowing for the best technique to be selected.

Bell Peppers (Capsicum annum L.) Losses and Wastes: Source for Food and Pharmaceutical Applications

Currently, the high added-value compounds contained in plant by-products and wastes offer a wide spectrum of opportunities for their reuse and valorization, contributing to the circular economy. The bell pepper (Capsicum annum L.) is an exotic vegetable with high nutritional value that, after processing, leaves wastes (peel, seeds, and leaves) that represent desirable raw material for obtaining phytochemical compounds. This review summarizes and discusses the relevant information on the phytochemical profile of bell peppers and their related biological properties as an alternative to revalorize losses and wastes from bell peppers for their application in the food and pharmaceutical industries. Bell pepper fruits, seeds, and leaves contain bioactive compounds (phenols, flavonoids, carotenoids, tocopherol, and pectic polysaccharides) that exhibit antioxidant, antibacterial, antifungal, immunosuppressive and immunostimulant properties, and antidiabetic, antitumoral and neuroprotective activities, and have a potential use as functional food additives. In this context, the revalorization of food waste is positioned as a technological and innovative research area with beneficial effects for the population, the economy, and the environment. Further studies are required to guarantee the safety use of these compounds and to understand their mechanisms of action.

Effect of pretreatment and temperature on the drying kinetics and physicochemical and techno-functional characteristics of pumpkin (Cucurbita maxima)

The study was carried out to assess fresh slices and thermally pretreated pumpkin (Cucurbita maxima) dried at temperatures of 55 °C, 60 °C, 65 °C, and 70 °C. The drying kinetics and quality attributes of the dried product were determined, and results indicated that the modified Page model was the best fit, with activation energies of 29.47 kJ mol-1 and 16.06 kJ mol-1 for drying fresh and thermally pretreated slices, respectively. A significant effect (p < 0.05) related to thermal pretreatment and temperature was evidenced on the physicochemical properties. The fresh pulp powders presented the following ranges of moisture and color (ΔE), 7.10%-8.31% w.b.; 21.23-25.23, respectively, and for the pretreated pulp powders, they were 8.94%-11.54% w.b., and from 19.00- 28.30, respectively. There were no significant effects on the techno-functional properties in the powders; cold water solubility was 5.36%-6.46%, water absorption capacity was 3.42-6.52 g/g, and oil absorption capacity was 1.00-1.30 g/g. The carbohydrate and fiber contents significantly decreased in the pretreated powder. An increase in antioxidant activity was found in fresh and thermally pretreated pulp powder at a temperature of 70 °C, presenting values between 2.23-2.98 μmol Trolox equivalent g-1d.b. evaluated by the DPPH method and between 40.48-45.92 μmol Trolox equivalent g-1d.b. by ABTS, and no significant differences (p > 0.05) were determined after pulp pretreatment. The total content of carotenoids presented retention percentages for fresh pulp powders of 52.09%, 41.92%, 30.55%, and 22.79%, while for pretreated pulp powders, they were 30.67%, 32.86%, 24.84%, and 14.71% when dried at temperatures of 55 °C, 60 °C, 65 °C, and 70 °C, respectively. The powders obtained from heat-pretreated pumpkin pulp showed significant differences (p < 0.05) in physicochemical characteristics and total carotenoids, but they were not found (p > 0.05) in the techno-functional properties and antioxidant activity evaluated by the DPPH and ABTS methods.

The Quality of Red Bell Pepper Subjected to Freeze-Drying Preceded by Traditional and Novel Pretreatment

It has been demonstrated previously in the literature that utilization of PEF or a combination of a pulsed electric field (PEF) and ultrasounds (US) can facilitate dehydration processes and improve the quality of dried products even better than the application of thermal methods such as blanching. The aim of the study was to evaluate the quality of red bell pepper subjected to freeze-drying preceded by blanching or PEF or US treatment applied in a single and combined mode. Furthermore, the freeze-drying was preceded by shock freezing or vacuum freezing performed inside the freeze-dryer as a result of pressure drop during the first stage of freeze-drying. All of the analyzed technological variants enhanced the drying kinetics when compared to the intact material. Freeze-dried bell pepper subjected to non-thermal pretreatment exhibited higher vitamin C, total phenolic and carotenoids content than blanched material despite the fact that blanching reduced drying time the most compared to all other analyzed methods.

Nanostructured chitosan edible coating loaded with α-pinene for the preservation of the postharvest quality of Capsicum annuum L. and Alternaria alternata control

Bell peppers are susceptible to postharvest diseases caused by the fungus Alternaria alternata that limit its commercialization. Nowadays, nanotechnology allows encapsulation of natural components such as terpenes. The objective of this work was to develop chitosan nanoparticles with α-pinene (P-CSNPs) and a nanostructured edible coating (EC-P-CSNPs). The P-CSNPs were characterized by TEM (Transmission Electron Microscopy), FTIR (Fourier-Transform Infrared Spectroscopy), DLS (Dynamic Light Scattering) and ζ potential. The P-CSNPs and the EC-P-CSNPs were applied to the bell peppers inoculated with A. alternata under cold storage for either 0, 7, 14 and 21 days at 12 ± 2 °C followed by a shelf-life period of 5 days at 20 ± 2 °C to assess their post-harvest quality. Nanoparticles size was 3.9 ± 0.5 nm and the ζ potential value was between 13.4 and 14.9 mV. The incorporation of α-pinene was corroborated by FTIR. Significant changes in weight loss were obtained for P-CSNPs and EC-P-CSNPs at percentage of 3 and 6% compared to the control. For firmness, color, total soluble solids, titratable acids, maturity index, total flavonoid content and antioxidant capacity, no differences were found. Total carotenes were higher in bell peppers without A. alternata. The chitosan nanoparticles and edible coating inhibited A. alternata during the cold storage period of bell pepper and preserved the physicochemical quality.

The effects of production methods on the color characteristics, capsaicinoid content and antioxidant capacity of pepper spices (C. annuum L.)

The effects of production methods for red pepper flakes (RPF) and traditional (TRI) and industrial (INI) isot spices were evaluated with respect to the carotenoid and capsaicinoid contents, extractable color (ASTA color), surface color parameters, nonenzymatic browning (NEB), and the DPPH free radical-scavenging capacity of fresh red Capsicum (FRC). The measured characteristics were significantly affected by the processing methods used. RPF exhibited the highest antioxidant activity and best color quality in terms of carotenoid content, which was the highest; ASTA value; surface color intensity; and NEB, which was the lowest. In contrast, INI-processing methods resulted in poor color quality, causing the maximum increase in NEB. The concentration of capsaicinoid increased at the end of TRI processing, whereas it decreased in the two other methods. These results suggest that the traditional production method for isots prevents excessive destruction of their color attributes and contributes to the desirable characteristic browning.

The Impact of Vacuum and Convective Drying Parameters on Kinetics, Total Phenolic Content, Carotenoid Content and Antioxidant Capacity of Kiwiberry (Actinidia arguta)

This study aimed to investigate the impact of convective and vacuum drying performed at different temperatures on the content of bioactive components of kiwiberry. Dried fruits obtained from Geneva and Weiki cultivars were analyzed for total carotenoid content, total phenolic content (TPC), and antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. The secondary goal was to establish drying kinetics and to find the best-fitting model for the drying process. The results showed that the highest total carotenoid content was found in Geneva fruits dried by vacuum method and was equal to 39.55–90.27 µg/g dry matter (d.m.). Considering free radical scavenging activity, the best results were also achieved for vacuum dried Geneva cultivar. These samples exhibited EC50 equal to 0.16–0.51 mg d.m./mL and 0.05–0.24 mg d.m./mL as evaluated using DPPH and ABTS assays, respectively. Vacuum drying method usually better preserved the phenolic content of kiwiberry—samples dried at 50 °C did not differ significantly from fresh material. Generally, the shortest drying time was observed for the samples dried at 70 °C regardless of the drying method. Changing the temperature during drying from 80 to 50 and 60 °C did not cause expected benefits regarding chemical property preservation. In most cases, the Midilli et al. model represented the best fit to describe obtained drying kinetics.

The Effect of Traditional and Non-Thermal Treatments on the Bioactive Compounds and Sugars Content of Red Bell Pepper

The aim of the study was an investigation of the effect of traditional and non-thermal treatment on the bioactive compounds of red bell pepper. As a thermal process, blanching in water and in steam was studied, while for non-thermal the sonication, pulsed electric field treatment and their combination were used in this experiment. The red bell peppers were evaluated based on quality attributes such as: total carotenoids content; polyphenols; vitamin C; antioxidant activity and sugars content. Vitamin C and sugar content were analyzed using liquid chromatography and other measurements were determined based on the spectrophotometric method. Results showed that the blanching in water or in steam reduced bioactive compounds concentration; whereas non-thermal treatments as pulsed electric field (PEF) applied separately or in combination with ultrasound (US + PEF) let to obtain similar or slightly lower content of bioactive compounds in comparison to untreated peppers. When sonication (US) and combined treatment as PEF + US were applied; in most cases reduction of bioactive compounds concentration occurred. This effect was probably related to the effect of relatively long (30 min) ultrasound treatment. The application of appropriate parameters of non-thermal processing is crucial for the high quality of processed material.

Mathematical Modeling, Moisture Diffusion and Color Quality in Intermittent Microwave Drying of Organic and Conventional Sweet Red Peppers

The aims of this research were to evaluate the influence of intermittent microwave drying on the moisture diffusion and color qualities of organically and conventionally grown sweet red peppers and mathematically express drying kinetic data. Pepper samples of 150 g were dried at 150, 300 and 450 W using a microwave oven. Results showed that intermittent microwave drying at 450 W occurred mainly in the falling rate period, whereas drying at lower powers resulted in relatively longer constant rate periods for both peppers types. The Midilli model provided the best fit for all data. The moisture diffusivity (Deff) values of organic and conventional samples ranged from 59.69 × 10−10 to 182.01 × 10−10 m2s−1 and from 59.11 × 10−10 to 181.01 × 10−10 m2s−1, respectively, and the difference was insignificant. The pre-exponential factor for the Arrhenius equation (D0) and activation energy (Ea) values were almost identical for both product types. Overall, organic or conventional growing did not alter the structural features related to the heat transfer properties. Intermittent microwave drying at 150 and 300 W for organic peppers and 150 W for conventional peppers gave the highest ΔL*, Δa* and a*/b* values, producing the most bright and red pepper powders. Thus, these treatments can be used to produce higher color quality powders.

Red bell pepper (Capsicum annuum L.): Optimization of drying conditions and preparation of functional bread

The aim of this study was to optimize the drying conditions (pretreatments and drying temperatures) of red bell pepper to obtain red bell pepper powder (RBP) with maximum bioactive retention and assess its potential use as a functional ingredient in bread. The RBP pretreated (blanching + dipping in ascorbic and citric acid solution) and dried at 60 °C retained the highest bioactive compounds. Wheat flour blends were prepared with RBP at 0%, 2%, 4%, 6%, 8%, and 10% level of incorporation and among hydration properties, water absorption increased with increasing levels. The prepared breads were assayed for physical, nutritional, bioactive, and sensory characteristics. Bread supplementation with RBP improves its color, mineral, fiber, and bioactive properties. However, the texture of bread becomes hard with the increased level of RBP due to a decrease in specific volume. The significant increment was recorded for bioactive compounds, such as total phenols, antioxidant activity, flavonoids, and carotenoids as the level of powder increased. Bread enriched with 6% RBP showed highest sensory scores (8.45) and index of acceptability (87.83%) as compared to other breads. Thus, RBP acts as a valuable supplement for developing bread with improved nutritional and bioactive constituents. PRACTICAL APPLICATION: This study describes the effect of different pretreatments and drying temperatures for processing of RBP as a functional ingredient in bread, being a staple food around the world. RBP powder is a novel ingredient that improved the nutritional, bioactive, and appearance of bread. Hence, it will be helpful in the utilization of perishable crops like bell pepper and will demonstrate its commercial viability to improve the nutritive value of bakery products.

The effect of different drying techniques and microwave finish drying on the powder properties of the red pepper powder (Capsicum annuum L.)

The objective of this study was to investigate the effects of different drying processes (microwave, freeze, convective hot air, and vacuum drying) and microwave finish drying (FD + MD and CD + MD) on the physical and powder properties of the red pepper powder. The effect of moisture content on the powder properties and the relationship between microwave output power or drying temperature and physical and powder properties were also determined by using most common mathematical models (linear, power, logarithmic, and quadratic). Results showed that an increase in both microwave output power and temperature (for CD and VD) generally resulted in a decrease in drying time, moisture content, and chroma and an increase in bulk and tapped density values. The drying time, moisture content, and water activity values can be significantly decreased, whereas, the color values can be significantly increased by combining FD and CD with microwave finish drying (P < 0.05). The moisture content (y = - 1.94 ln(x) + 7.6455, R² = 0.9905), bulk (y = 54.224 ln(x) + 153.71, R² = 0.9705), tapped (y = 61.7 ln(x) + 225.6, R² = 0.9994) and particle densities (y = - 327.4 ln(x) + 2260.5, R² = 0.9966), and porosity (y = - 3.778 ln(x) + 89.806, R² = 0.9586) values followed a logarithmic trend depending on the increase in the convective hot air drying temperature. The inverse relationship was observed between the moisture content, bulk and tapped densities of the red pepper powders.

Influence of Postharvest Temperatures on Carotenoid Biosynthesis and Phytochemicals in Mature Green Chili (Capsicum annuum L.)

An intense red color appearance in hot chili is what industry commonly demands. The harvested mature green “Takanotsume” chili, a popular cultivar in Japan, incubated at 20 and 30 °C is investigated. At 30 °C, the chili rapidly degraded chlorophylls and obtained an intense red color, but presented an orange–red color at 20 °C. The sample showed higher carotenoid accumulations at 30 °C, along with significantly upregulated carotenoid biosynthesis-related genes—phytoene synthase (Psy), lycopene-β-cyclase (Lcyb), β-carotene hydroxylase (CrtZ), and capsanthin/capsorubin synthase (Ccs)—during the experiment. While the expression of the Ccs gene was reduced, there was a 5.5-fold upregulation of the Psy gene at the end of incubation. At 20 °C, the Psy gene was downregulated. These observations suggest that the expression of individual genes is temperature-dependent, and these would affect specific carotenoid compounds. The antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl; DPPH and ferric-reducing antioxidant power; FRAP) values had no difference between temperatures; the higher content of total phenolics and vitamin C presented in the chili at 30 °C probably corresponds to the advanced ripening process. Thus, 30 °C is the recommended incubation temperature for mature green chili to achieve the industry-demanded intense red color and high accumulation of phytochemicals.

Color Development and Phytochemical Changes in Mature Green Chili (Capsicum annuum L.) Exposed to Red and Blue Light-Emitting Diodes

Exposure of mature green "Takanotsume" chili fruit to blue and red light-emitting diodes (LEDs) was investigated. The red LED accelerated the red color development of chili as indicated by higher a* and chroma values, as well as lower hue angle and total chlorophyll compared to the blue LED and darkness (control). These were linked to increases in β-carotene, free-capsanthin, and total carotenoids. The carotenoid biosynthesis-related genes, lycopene-β-cyclase (Lcyb), β-carotene hydroxylase (CrtZ), and capsanthin/capsolubin synthase (Ccs), were up-regulated by the red LED after 2 days of the experiment. The blue LED was more effective in increasing the expression of the phytoene synthase (Psy) gene at day 1 of experiment. The total phenolic, vitamin C content, and antioxidant capacity were also higher in the blue LED-treated chili. Results suggest that the responses of each carotenoid-related gene to the light wavelengths and the accumulation of phytochemicals are specific characteristics of this chili cultivar.

Amla fruit powder addition influences objective color and instrumental texture of pan bread

The effect of sun-dried (SD), oven-dried (OD) and freeze-dried (FD) amla fruit powders on the mixing characteristic, objective color (ICI tristimulus L* a* b* values) and instrumental texture was investigated. The addition of differently dried amla powders did not affect the mixograms significantly. The color characteristics were affected by both the levels of addition as well as by the type of powder (SD, OD and FD) incorporated into the pan bread. The L*, a*, b* values were not significantly different for the crusts of all types of the breads at varying levels. However, incorporation of SD, OD and FD powder lowered L*and b* values significantly for the crumb, making it look lesser white but browner in color. The specific loaf volume of bread made with SD and OD amla fruit powders at lower levels of addition gave compression force values and specific loaf volumes very close to the bread made with 20 ppm of potassium bromate. But higher amounts (1-3%) of amla fruit powder resulted in harder bread texture, lower specific loaf volume and also a coarser crumb grain. Therefore, amla fruit being rich in ascorbic acid seems a good choice an alternative natural dough improver in place of potassium bromate which has been regarded as a potential carcinogen and now banned in many countries of the world.

Development of a functional food (pan bread) using amla fruit powder

The amla fruit powders were analyzed for ascorbic acid, sugars, pectin, total phenolics (TPC), and total antioxidant activities (TEAC). Fresh amla was found to have 6644.305 mg/100 g ascorbic acid with sun-dried, oven-dried and freeze-dried having 748.427 mg/100 g, 641.364 mg/100 g, 791.233 mg/100 g, respectively. There were no significant differences for the TPC values which ranged from 113.1 for oven-dried (OD), 128.7 for sun-dried (SD), 161.2 mg for freeze-dried (FD) and 1410.5 GAE/g for fresh amla pulp (FA). The TEAC values ranged from 6.6 for OD, 6.8 for FD, 7.6 for SD and 116.4 mM/g for FA. The FD amla fruit powder had the highest total sugars (36.94%, db). The specific loaf volume of bread improved significantly (from 3.54 to 3.79 cc/g) as the level of SD or OD amla powder addition was raised to 0.25% but then decreased at higher level of addition (3.41 cc/g). However, in case of FD amla powder, the bread volume increased up to the addition level of 0.50% (4.09) then decreased slightly (3.95 cc/g) but was still significantly higher the SD and OD amla powders. Similarly, the TPC (from 0.32 to 1.16 mg GAE/g, db), TEAC (0.06-0.14 mM/g, db) and vitamin C (3.80-31.98 mg/100 g, db) contents also improved significantly as the level of amla powders were increased to 1%. The supplemented breads were well-accepted by the consumers. It can be concluded that amla supplemented pan bread with its superior nutritional and sensory qualities can be a possibility to improve consumer nutrition.

Progression of the Total and Individual Capsaicinoids Content in the Fruits of Three Different Cultivars of Capsicum chinense Jacq

The evolution of individual and total capsaicinoids content in three pepper varieties of Capsicum chinense Jacq. (‘Bode’ (B), ‘Habanero’ (H), and ‘Habanero Roxo’ (Hr)) during fruit ripening was studied. The five major capsaicinoids (nordihydrocapsaicin, capsaicin, dihydrocapsaicin, homocapsaicin, and homodihydrocapsaicin) were extracted using ultrasound-assisted extraction and the extracts were analysed by ultra-performance liquid chromatography with fluorescence detection (UHPLC-Fl). The plants were grown in a glasshouse and sampled every 7 days until over-ripening. As expected, the results indicated that the total capsaicinoids content increases during the ripening of pepper fruits. The maximum contents of capsaicinoids were reached at different fruit development stages depending on the cultivar. The ‘Habanero Roxo’ pepper presented the greatest total capsaicinoids content (3.86 mg g−1 fresh weigh, F.W.), followed by the ‘Habanero’ pepper (1.33 mg g−1 F.W.) and ‘Bode’ pepper (1.00 mg g−1 F.W.). In all the samples, capsaicin represented more than 80% of the total capsaicinoids content. Due to the high variability observed in the evolution of capsaicinoids content over the ripening process, this work intends to contribute to the existing knowledge on this aspect in relation to the quality of peppers.