Avocado leaves: Influence of drying process, thermal incubation, and storage conditions on preservation of polyphenolic compounds and antioxidant activity (original) (raw)
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Journal of Food and Dairy Sciences
The effect of antioxidant properties as free radical scavenging activity and phytochemical compounds of fresh and dried samples of dill, parsley, coriander, peppermint and celery leaves were studied. Moreover, the chemical constituents and the content of minerals in these medicinal and aromatic plants were also investigated. Results explained that the contents of total phenolics ranged from 1446.88 for coriander to 3128.57mg/100gm for peppermint and after the drying process decreased to 1280.10 and 2356.45mg/100gm, respectively. Also, peppermint had the highest content of flavonoids, while the lowest content was observed in coriander leaves. Otherwise, fresh coriander leaves had the highest content of carotenoids, while the lowest content was in the fresh peppermint leaves. Results explained also that the main component of phenolic compounds was protocatchuic in all fresh and dried samples under investigation. Celery leaves had the highest protocatchuic content. Concerning minerals content reveal that the parsley leaves had the highest content of calcium, potassium and magnesium, while peppermint had the highest phosphorus and iron contents. Results also show that celery leaves had the highest sodium content. Fresh dill and peppermint recorded the highest percentages of total antioxidant activity. Also, fresh celery had gradual effect on DPPH compounds being used as synthetic free radical. Coriander and parsley showed the lowest antioxidant activity. After the drying process total antioxidant activity decreased. Slight decrease was observed with dill and peppermint leaves, while celery and parsley leaves were more effective by using the air oven drier process.
Journal of Food Processing and Preservation, 2018
The purpose of this research was to study the effect of microwave drying (MD) on the major phenolic compound oleuropein, total phenolic and flavonoid contents, and antioxidant activity of the olive leaves. The results were compared to those obtained after using freeze drying (FD), vacuum drying (VD), oven drying (OD), and ambient air-drying (AAD). Response surface methodology, using a central composite face-centerd design, was used to optimize the effects of microwave irradiation power (300-500 W), solid mass (1.5-2.5 g), and drying time (4-6 min) on oleuropein and other olive leaves antioxidant compounds. The second-order models were found highly adequate with very low root mean squared deviation (RMSD) and high coeffecient of determination (R 2) values. The results of MD under optimum conditions (2.085 g sample at 459.257 W for 6 min of drying period) has demonstrated to be the best drying method followed by FD, VD, OD, and AAD. Practical applications Olive leaves are agricultural waste which contains significant amounts of valuable compounds such as oleuropein and phenolic compounds. Nowadays, application of these compounds has attracted considerable interest as food additives and/or nutraceuticals in both food and pharmaceutical industries. Several methods have been applied for the extraction of phenolic compounds from olive leaves and by-products. However, to obtain higher extraction yield, it is important to reduce the water content of the samples before extraction. This study demonstrates the feasibility of using microwave drying as a promising technique compared to other methods (e.g., freeze-, vacuum-, oven-, and ambient air-drying) for drying of olive leaves with minimum changes in total phenolic, flavonoids, antioxidant activity, and oleuropein contents. Abbreviations: AA, antioxidant activity (mg-TEAC/g-DL); AAD, ambient air-drying method; Acontrol, the absorbance of control at 517 nm; Asample, the absorbance of sample at 517 nm; b 0 , intercept; b i , linear coefficient; b ii , second-order coefficient; b ij , interaction coefficient and (I and j53); CCFD, face-centerd design; C i,experimental , the concentration of experiment i; C i,calculated , the value from the model equation; DPPH, a, a-diphenyl-b-picrylhydrazyl free radical scavenging method; FD, freeze drying method; HPLC, high performance liquid chromatography; n, the number of experiments; OD, oven drying method; R 2 , coefficient of determination; R 2 a , adjusted determination coefficient; RMSD, root mean square deviation; RSM, response surface methodology; TFC, total flavonoid contents (mg-CE/g-DL); TPC, total phenolic contents (mg-GAE/g-DL); VD, vacuum drying method; X 1 , microwave irradiation power (W); X 2 , solid mass (g); X 3 , drying time (min); X i , uncoded independent parameter and (i 5 1-3); Y, dependent parameter also known as response.
Antioxidant properties of herbs with enhancement effects of drying treatments: A synopsis
Our recent work on the antioxidant properties (AOP) of herbs showed that three species (Etlingera elatior, Morus alba, and Thunbergia laurifolia) displayed enhancement effects of microwave-, oven-, and freezedrying. AOP analysed were total phenolic content (TPC), ascorbic acid equivalent antioxidant capacity (AEAC), ferric reducing power (FRP), and chelating efficiency concentration (CEC 50 ). Microwave-and oven-drying led to drastic decline in AOP but freeze-drying resulted in significantly increase for leaves of E. elatior. Leaves of M. alba responded positively to all three drying treatments. TPC and FRP following oven-drying remained unchanged but AEAC and CEC 50 increased by 27% and 22%, respectively. Freezedrying resulted in increase in TPC (16%), AEAC (26%), FRP (20%), and CEC 50 (44%). Microwave-drying increased TPC, AEAC, and FRP by 24%, 91%, and 30%, respectively. Microwave-drying enhanced AOP of T. laurifolia leaves. TPC and AEAC increased by 34% and 67%, respectively. Results indicated that different drying treatments have variable effects on AOP of herbs. Effects include little or no change, significant losses or enhancement in phenolic content and antioxidant activity. Decline in AOP following drying treatments has been attributed to thermal degradation of phytochemicals, enzymatic degradation of phenolic compounds and loss of antioxidant enzyme activities. Reasons for the increase in AOP following drying treatments include the release of bound phenolic compounds by the breakdown of cellular constituents and the formation of new compounds with enhanced antioxidant properties.
The Efficacy of Two Drying Techniques on the Bioactive Composition and Antioxidant
Journal of the University College of Science and Technology (JUCST), 2022
Antioxidant is a substrate that stops molecules inside a cell from oxidizing. During the biological oxidation reaction, free radicals created; Also, it have the ability to stop a chain reaction by removing the free radical intermediate. The aim of the study was conducted to estimate the impact of two drying methods on phytochemical constituents of the Prickly pear fruit (Opuntia ficus indica, L.). Methods: In this work, the effects of oven-drying and freeze-drying methods have been studied in Special Units Departments-National Research Center (Cairo) in august 2021 on the chemical composition, total
Journal of Medicinal Plants Research, 2012
The effect of drying techniques (ambient-drying and oven-drying) on the total phenolic contents and antioxidant activity of selected fruits (apple (Malus pumila, var. skysuper), plum (Prunus salicina, var. Fezele manani), apricot (Prunus armeniaca L, var. Nuri), strawberry (Fragaria ananassa var. Corona) and mulberry (Morus alba L, var. serrata) were studied. The antioxidant attributes of the fruits were evaluated following different colorimetric assays, while the composition of phenolic acids of the fresh fruits was analyzed by the reverse phase high performance liquid chromatography (RP-HPLC). The amounts of total phenolics (TP) were higher in mulberry samples followed by strawberry, plum, apple and apricot. The tested fruits exhibited appreciable radical scavenging capacity ranging from 58.7 to 82.2% and inhibition of linoleic acid peroxidation activity ranging from 61.8 to 86.1%. The RP-HPLC analysis of the fresh fruits revealed the presence of vanillic-(16.9), syringic-(12.7), p-coumaric-(2.30 to 47.5), ferulic-(0.9 to 32.9), sinapic-(3.10 to23.3), caffeic-(6.70-32.8), and gallic-(2.60 to 5.60) acids mg/kg of fresh fruit; p-coumaric acid being the most prominent component detected. The results of this study revealed that the amounts of TP and antioxidant activity of all the tested fruits, except those of apricot, decreased after drying treatment; relatively more pronounced decline was observed for the ambientdried samples as against oven-drying. Therefore, it could be suggested that oven-drying at optimum temperature is comparatively a better means to dry and preserve fruits retaining maximum amounts of antioxidant compounds.
Molecules
Mexican spices are used in the supplementation of the human diet and as medicinal herbs for the particularly high amounts of compounds capable of deactivating free radicals. In addition, these spices can have beneficial effects on chronic, no-transmissible diseases such as type II diabetes and hypertension arterial. The objective of this study is to determine the content of phenolic compounds on the antioxidant activity and inhibitory enzymes of α-amylase, α-glucosidase and angiotensin-converting enzyme in melissa, peppermint, thyme and mint, which are subjected to microwave drying, conventional and freeze-drying to be used as alternative treatments. Spices were evaluated to determine total phenols, flavonoids, tannins, 2,2-Diphenyl-1-picrylhydrazyl (DPPH), (2,2′-azino-bis- (3-ethyl benzothiazolin-6-ammonium sulphonate) (ABTS) and Ferric Reducing/Antioxidant Power (FRAP), enzymatic activity. The investigation showed that conventional drying caused a decrease in antioxidant propertie...
Scientia Horticulturae, 2020
Drying of different parts of wild pomegranate fruits such as arils, flavedo (peel), albedo (inner membrane) and pomace (residue remains after juice extraction from arils) were carried out with four different methods viz. natural sun drying (D 1), solar tunnel drier (D 2), mechanical cabinet (D 3) and oven (D 4) drying. Different attributes such as yield, drying time, moisture, total phenols (TP), total flavonoids (TF) and antioxidant properties of dried samples (arils, flavedo, albedo and pomace) were evaluated separately during the study. Out of which, one drying method (D 3) with one fruit part (flavedo) was selected for comparison on the basis of highest TP, TF, DPPH antioxidant activity (AA), metal chelating activity (MA) and ferric reducing antioxidant power (FRAP). The functional groups of mechanical cabinet dried arils and flavedo were analyzed by FTIR, which indicates the presence of significant amount of phytochemicals in flavedo than arils. Further, effect of drying temperature shows that lyophilized flavedo had comparatively higher L* (33.40), a* (3.68), b* (13.78) values, TP (61.87 mg GAE/g), TF (8.48 mg QuE/g), AA (91 %), MA (63.86 %) and FRAP (3.40 μM Fe 2+ /g) as compared to mechanical cabinet dried flavedo. The study concluded that lyophilized wild pomegranate fruit flavedo could be utilized in pharmaceutical and nutraceutical industries to make various functional/nutraceutical foods.
2000
Flavonoids and other phenolic metabolites have important biological activities related to their antioxidant properties and, especially, to their free-radical scavenging ability. It has been suggested that dietary phenolics might be beneficial agents for the prevention of cardiovascular diseases and cancer, a suggestion supported by epidemiological and experimental studies. In the present review, the antioxidant activity of flavonoids and other phenolic metabolites is reviewed, as well as their bioavailability, absorption and metabolism in animals and humans. In addition, the flavonoid content and that of other phenolics in different fruits and vegetables is reviewed. The changes in flavonoids and other phenolic antioxidants during the postharvest life of fruit and vegetables are evaluated. The effect of storage, technological treatments (controlled atmospheres, UV irradiation, heat shocks, etc.), and processing (minimal processing, juice manufacturing, drying, cooking, canning, etc.) on the content of the biologically active phenolics is also reviewed.
Effect of Drying on Total Phenolic Compounds, Antioxidant Activity, and Kinetics Decay in Pears
International Journal of Fruit Science, 2015
The polyphenols have been identified as food components sensitive to high temperatures, so that the application of heat treatments can lead to a significant reduction in the phenolic content and also on antioxidant capacity. The objectives of the present work were to investigate the decrease in total phenolic compounds and antioxidant activity in pears during air drying at different temperatures and to model the kinetics of those variations. The pears (cv. D. Joaquina) were dried at 60 and 70 ºC in an electrical drying chamber with hot air at 0.5 m/s. Along drying several samples were collected for analysis, being submitted to multiple extractions with methanol and acetone solutions. The phenolic compounds were determined by the Folin-Ciocalteu method and the antioxidant activity was determined by the ABTS method.
2011
The effect of antioxidant properties as free radical scavenging activity and phytochemical compounds of fresh and dried samples of dill, parsley, coriander, peppermint and celery leaves were studied. Moreover, the chemical constituents and the content of minerals in these medicinal and aromatic plants were also investigated. Results explained that the contents of total phenolics ranged from 1446.88 for coriander to 3128.57mg/100gm for peppermint and after the drying process decreased to 1280.10 and 2356.45mg/100gm, respectively. Also, peppermint had the highest content of flavonoids, while the lowest content was observed in coriander leaves. Otherwise, fresh coriander leaves had the highest content of carotenoids, while the lowest content was in the fresh peppermint leaves. Results explained also that the main component of phenolic compounds was protocatchuic in all fresh and dried samples under investigation. Celery leaves had the highest protocatchuic content. Concerning minerals content reveal that the parsley leaves had the highest content of calcium, potassium and magnesium, while peppermint had the highest phosphorus and iron contents. Results also show that celery leaves had the highest sodium content. Fresh dill and peppermint recorded the highest percentages of total antioxidant activity. Also, fresh celery had gradual effect on DPPH compounds being used as synthetic free radical. Coriander and parsley showed the lowest antioxidant activity. After the drying process total antioxidant activity decreased. Slight decrease was observed with dill and peppermint leaves, while celery and parsley leaves were more effective by using the air oven drier process.