Stability Of Phenolic Compounds Research Articles

Choline chloride-based natural deep eutectic solvents for the extraction and stability of phenolic compounds, ascorbic acid, and antioxidant capacity from Citrus sinensis peel

Orange peel is a great source of bioactive compounds like phenolic compounds and ascorbic acid (AA), which have high antioxidant capacity. New methodologies have called attention for their extraction employing greener solvents, as natural deep eutectic solvents (NADES). There is a lack of information about the protective role and stability of bioactive compounds in NADES. This study aims to find the most suitable NADES for the extraction of bioactive compounds from orange peel. The first step was screening eight NADES, determining its antioxidant capacity (AC), AA, total phenolic content (TPC) and total flavonoids (TFC). The extract stability was monitored during storage for twelve days, determining phenolic compounds, AA, and AC. The results showed that choline chloride:malic acid (ChChl:MA) (TPC: 1053 mgGAE/100 g. TFC: 94.7 mg/100 g. AA: 430 mg/100 g), and choline chloride:glycerol (TPC: 903 mgGAE/100 g. TFC: 169 mg/100 g. AA:416 mg/100 g) were the most suitable NADES for the extraction of bioactive compounds. AA and phenolic compounds are more stable in ChChl:MA. The capacity of NADES to improve the stability and enhance the AC of the extracts makes these formulations suitable for their application in the food formulations avoiding the solvent elimination process.

Hydroxypropyl methylcellulose orally disintegration films produced by tape casting with the incorporation of green propolis ethanolic extract using the printing technique

Green propolis ethanol extract (GPEE) is one of the most used compounds in folk medicine. Alternative dosage forms, such as orally disintegrating films (ODFs) and forms of incorporation of active principles, such as the printing technique, are arousing interest due to the possibility of producing personalized dosages and possible reduction of the degradation of compounds. The aim of this study was to evaluate the effect of green propolis ethanol extract (GPEE) incorporation on hydroxypropyl methylcellulose (HPMC) using the printing technique (1–4 print layers). GPEE was characterized by apparent viscosity, density, and surface tension. The ODFs with different numbers of printed layers were characterized in relation to color, moisture content, mechanical properties, structure, disintegration time, surface pH, stability, cytotoxicity, and anti-inflammatory activity tests. GPEE showed properties similar to those observed for commercial inks. The number of printed layers affected film properties. ODFs with GPEE showed anti-inflammatory activity, where a reduction of about 40% NO 2 − concentration against macrophage cells was found after adding one GPEE layer. As such, printing on hydroxypropyl methylcellulose oral films as a vehicle for green propolis ethanolic extract represents an interesting alternative to produce materials with controlled anti-inflammatory activity. • Viscosity, density and surface tension values of GPEE are similar to commercial inks. • Oral films of HPMC-based printed are a promising way to deliver active compounds. • HPMS-based printed films maintain the stability of phenolic compounds. • Films printed with green propolis ethanol extract have anti-inflammatory activity.

The Influence of the Use of Different Polysaccharide Coatings on the Stability of Phenolic Compounds and Antioxidant Capacity of Chokeberry Hydrogel Microcapsules Obtained by Indirect Extrusion.

The aim of the study was to evaluate the effect of the use of different polysaccharides and their mixtures on the structure of chokeberry hydrogel microcapsules and the stability of polyphenolic compounds and antioxidant capacity during one month of refrigerated storage. As a coating material, alginate and its mixtures with pectin, carrageenan, and chitosan were used, while chokeberry juice and preparation of polyphenolic compounds were used as a core. In non-stored capsules, the addition of carrageenan, pectin, and chitosan to alginate increased the content of total polyphenolic compounds and antioxidant capacity. When compared to non-encapsulated juice, the capsules had a greater decrease in antioxidant capacity during storage. The coating variant composed of alginate and carrageenan was found to be the most beneficial for the preservation of the capsules' phenolic compounds. The findings revealed that proper polysaccharide coating selection is critical for the proper course of the microencapsulation process, the polyphenolic content of chokeberry capsules, and their antioxidant properties.

Evaluation of the release, stability and antioxidant activity of Brazilian red propolis extract encapsulated by spray-drying, spray-chilling and using the combination of both techniques

Red propolis, originary from Northeast Brazil, has a unique composition and a great commercial interest. However, due to the presence of ethanol and its remarkable sensory characteristic, its application in food products is challenging. Thus, the aim of this work was to microencapsulate the red propolis extract by spray-drying, spray-chilling, and combining both techniques. The particles loaded with propolis extracts were characterised and evaluated according to the stability of phenolic compounds, flavonoids and formononetin, during 60 days of storage. In addition, the formononetin release was also monitored during the oral, gastric, and intestinal phases in the in vitro digestion process. All produced particles presented matrix-type with size, distribution, shape, hygroscopicity, and dispersibility parameters that varied according to the carrier and encapsulation process applied. The techniques used to fabricate the particles efficiently obtained powdered propolis extract and protected the extract's bioactive compounds, total flavonoids and formononetin throughout the analysed period. The gastrointestinal release study presented distinctive releases in all phases (oral, gastric, and intestinal). The spray-dried particles, for example, released formononetin mainly in the oral stage. While the spray-chilled particles were primarily released in the intestinal phase, and coated particles were released gradually throughout the assay, reaching maximum relief in the intestinal phase. In conclusion, using microencapsulation techniques by spray-drying, spray-chilling, and their combination developed particles with different levels of protection during storage, releases and characteristics, which resulted in a range of possible applications in the food, feed, cosmetic, and pharmaceutical industries.

Red-skinned onion phenolic compounds stability and bioaccessibility: A comparative study between deep-frying and air-frying

In this study, the effect of deep-frying and air-frying on the stability and gastro-intestinal release of red-skinned onion phenolic compounds have been assessed by high-resolution mass spectrometry. Forty-four phenolic compounds were identified and quantified in raw onion. Both the frying treatments caused an increase in total phenolic compounds, which was more evident after air-frying (47.4% vs 18.6% increase). This increase was mainly a consequence of the water loss observed during frying. Quercetin was the most important phenolic compound detected both in raw and air-fried samples (99.5 ± 1.7 and 133 ± 2 μmol/100 g, respectively) while deep-fried onion was richer in quercetin-4’-O-glucoside and quercetin-3-O-glucoside-4'-O-glucoside (48.7 ± 0.9 and 41.8 ± 0.3 μmol/100 g, respectively). After digestion, 38.6%, 60.5% and 89.6% of total phenolic compounds were bioaccessible in raw, deep-fried and air-fried onion. Air-fried onion exhibited the highest concentration of bioaccessible phenolic compounds (206 ± 1 μmol/100 g). Oxidative degradation and hydrolysis reactions of quercetin-hexosides occurred during in vitro digestion. Hence, air-frying can be considered a healthy cooking method able to preserve and release after digestion most of the health-promoting compounds found in raw onion and with a lower amount of fats and polar toxic compounds compared to deep-frying.

Temperature and light conditions affect stability of phenolic compounds of stored grape cane extracts

This study aimed to determine the stability of PCs in grape canes extracts stored at different temperatures and light conditions. The PCs composition was monitored every-two weeks during three months by liquid chromatography coupled to diode array and fluorescence detectors (LC-DAD-FLD). Initially, stilbenes represented 87 % of total PCs. Storage at −20 and 5 °C reduced PCs 8 and 6 %, respectively. When extracts were exposed to 25 and 40 °C, the degradation of (+)-catechin and (-)-epicatechin was faster than under lower temperatures, and light accelerated the degradation kinetics. trans-piceatannol showed particularly sensitive to temperature increase, being mostly degraded after two weeks stored at 40 °C. Conversely, degradation of trans-resveratrol and ε-viniferin was mostly catalyzed by light, since nearly 70 % of them were degraded at 40 °C under light, in comparison with a 23 % reduction of trans-resveratrol and no changes of ε-viniferin at 40 °C in darkness.

Mate tea with Lactobacillus probiotics: viability, chemical characterization and in vitro resistance to the gastrointestinal tract

To meet the consumer demand for functional drinks with bioactive compounds, this study aimed to evaluate the addition of Lactiplantibacillus plantarum LP299V, Lacticaseibacillus rhamnosus GG and Lactobacillus acidophilus in mate tea. The viability of the probiotic bacteria, microbiological and physicochemical characteristics, the in vitro resistance to the gastrointestinal tract and the antioxidant capacity of the mate teas were evaluated during 28 days. Unlike L. plantarum and L. rhamnosus, L. acidophilus did not remain viable in the product. The physicochemical characteristics of the teas with L. plantarum and L. rhamnosus were maintained over time. Phenolic compounds of mate tea containing L. plantarum were identified by HPLC. There was stability of phenolic compounds and flavonoid content in teas over time. At the end of the gastrointestinal assay, there was 4.52 Log CFU/mL of L. plantarum, suggesting that consumption of 100 mL of tea may provide > 6.0 Log CFU/mL of the probiotic. Mate tea can carrier L. rhamnosus and L. plantarum. There is an increase in the search by consumers for health drinks and at the same time, there is a growing demand for alternatives carriers of probiotics, due to individuals with intolerance and allergy to dairy products, vegetarians and others. This study confirms the possibility of using mate tea, widely consumed in Brazil, as a positive carrier of of L. plantarum and L. rhamnosus, making it an attractive alternative beverage to the dairy matrix.

Stability of phenolic compounds in apple and strawberry: Effect of different processing techniques in industrial set up

Different technologies commonly employed by the fruit processing industry affect the phenolic content. This study aimed to establish the extent to which different processing techniques and conditions, tested at an industrial scale, affect phenolics, color, and sensory attributes of fresh strawberries and apples. The effects of freezing, thermal treatments, and high-pressure processing were investigated. In strawberries, mild and standard thermal treatments showed similar patterns for most phenolic groups; an increase in proanthocyanidins, no change in ellagic acid conjugates, and a major decrease in flavonols and anthocyanins. In apples, mild treatments and high-pressure processing had similar effects in all phenolic groups, with increases in dihydrochalcones, hydroxycinnamics, and proanthocyanidins and decreases in flavonols. However, the standard thermal treatment increased flavonols and dihydrochalcones concentrations. This study shows that each fruit behaves differently, and both technology and processing conditions should be customized accordingly to preserve or even increase the phenolic content.

Jatobá (Hymenaea stigonocarpa) pulp films: Properties, antioxidant potential and biodegradability

This study aimed to use jatobá pulp in the production of biodegradable and active films for food packaging. The films were obtained by the casting technique, through a factorial experimental design (23), analyzing concentration of jatobá pulp, glycerol, and temperature. Increasing the jatobá concentration to the maximum studied level (+1) resulted in a 4-fold increase in tensile strength than the lowest level and 1.7-fold greater elongation. The differential scanning calorimetry and contact angle results indicated that the temperature of 80 °C favored the formation of films with interesting mechanical properties of 0.81 MPa of tensile strength and 55 % of elongation, and barrier properties that reduced the water vapor permeability in 28.8 %, without affecting the stability of phenolic compounds and antioxidant activity. In addition, the films showed fast degradation in seawater, soil and beach sand, being completely degraded in 7 days.

Red Wine and Health: Approaches to Improve the Phenolic Content During Winemaking.

There is ample evidence regarding the health benefits of red wine consumption due to its content of phenolic compounds, as an alternative to improve the state of health and prevent various diseases, being the implementation of procedures that allow a greater extraction and stability of phenolic compounds during the elaboration a key aspect. The first part of this review summarizes some studies, mostly at the preclinical level, on the mechanisms by which phenolic compounds act in the human organism, taking advantage of their antioxidant, anti-inflammatory, antitumor, antithrombotic, antiatherogenic, antimicrobial, antiviral, and other activities. Although the migration of grape components into the must/wine occurs during the winemaking process, the application of new technologies may contribute to increasing the content of phenolic compounds in the finished wine. Some of these technologies have been evaluated on an industrial scale, and in some cases, they have been included in the International Code of Oenological Practice by the International Organization of Vine and Wine (OIV). In this sense, the second part of this review deals with the use of these novel technologies that can increase, or at least maintain, the polyphenol content. For example, in the pre-fermentative stage, phenolic extraction can be increased by treating the berries or must with high pressures, pulsed electric fields (PEF), ultrasound (US), e-beam radiation or ozone. At fermentative level, yeasts with high production of pyranoanthocyanins and/or their precursor molecules, low polyphenol absorption, and low anthocyanin-β-glucosidase activity can be used. Whereas, at the post-fermentative level, aging-on-lees (AOL) can contribute to maintaining polyphenol levels, and therefore transmitting health benefits to the consumer.

Cápsulas de polvo de arándano como propuesta nutracéutica para mejorar la bioaccesibilidad de compuestos fenólicos

Blueberry (Vaccinium corymbosum L.) has a high content of phenolic compounds which have been studied mainly for their antioxidant, antiobesogenic, anti-inflammatory activity, among others. Objetive. The objective of the present study was to evaluate the effect of in vitro gastrointestinal digestion on the bioaccessibility of phenolic compounds and antioxidant activity of a nutraceutical formulation of blueberry (capsule), compared to fresh and powder blueberry. Materials and methods. Methanolic extracts of fresh and lyophilized blueberry were obtained and determined its total phenols, flavonoids, anthocyanins content, as well as antioxidant activity. A gastrointestinal digestion simulation test also was carried out to assess the bioaccessibility of the phenolic compounds found in samples. Results. The results showed that gastric digestion of powder and capsule blueberry promoted greater bioaccessibility of phenols (42% and 40%), flavonoids (52% and 33%) and anthocyanins (45% and 40%), compared to fresh blueberry digests. After intestinal digestion, the bioaccessibility of phenols (63%) and flavonoids (67%) was higher in the blueberry capsule compared to its powdered blueberry counterpart. The intestinal digestion conditions negatively affected the bioaccessibility of anthocyanins regardless of the type of sample evaluated. Conclusion. Gastric digestion conditions promote greater stability of phenolic compounds in powdered and capsule blueberries, which could be relevant for the maintenance of an antioxidant environment at this level. The intestinal digestion conditions particularly affected the phenolic compounds of fresh and lyophilized blueberry, but not the capsule, which may suggest that encapsulation protected the phenols present from alkaline conditions. Further studies on in vitro absorption of the remaining components in the intestine and their possible effects on oxidative stress biomarkers in in vivo models are suggested.

Effect of glandless cottonseed meal protein and maltodextrin as microencapsulating agents on spray-drying of sugarcane bagasse phenolic compounds.

This study examines the effect of different concentrations of glandless cottonseed meal protein (GCSMP) and maltodextrin (MD) as microencapsulating agents on the shelf life stability of phenolic compounds extracted from sugarcane bagasse (SCB). Sugarcane bagasse showed high antioxidant activity, which remained stable after 30 days of storage at 4°C. The best microencapsulation process was obtained with an MD and GCSMP ratio of 63.6% and 36.4%, respectively. The encapsulating agents' ratio affected the encapsulation efficiency (EE) (p<0.05), while the spray-drying temperature did not show an effect on the EE of the SCB phenolic compounds (p>0.05). The antioxidant activity of the microencapsulated phenolic compounds was affected by the MD/GCSMP ratio (p<0.05). The combination of MD and GCSM showed a higher EE than MD (p<0.05), while the EE was lower when the ratio of encapsulating agents consisted of either MD or GCSMP alone (p<0.05). The total phenolic content (TPC) in the microcapsules was not affected by the GCSMP ratio (p<0.05). The TPC of microencapsulated phenolic compounds was stable up to 100°C for 14 days. GCSMP containing microcapsules showed a corrugated surface compared to a more homogenized surface of MD. The resulting corrugated structure explains the higher EE showed by the GCSMP. PRACTICAL APPLICATION: The use of sugarcane bagasse has been shown to add value to waste from agricultural and industrial sources. Glandless cottonseed meal protein is an excellent protective agent of antioxidants and can be extracted from agricultural waste. The encapsulated antioxidants can be used for the development of healthy, functional foods.

Physical and chemical properties of roselle extract nanocapsule with inulin, chitosan and maltodextrin as encapsulant

Roselle contains high phenolic compounds, mainly anthocyanins that are not stable with pH, metal ions, light exposure, temperature, oxygen, and enzymatic activity. The stability of phenolic compounds can be improved by nanoencapsulation. This research was aimed to evaluate the effect of inulin, inulin-chitosan and inulin-chitosan-maltodextrin with varying concentrations as encapsulants towards the physicochemical properties and encapsulation efficiency of nanocapsules product by spray drying. Roselle extract nanocapsules were prepared using various types and concentrations of encapsulants (inulin, inulin-chitosan and inulin-chitosan-maltodextrin). The solubility of nanocapsules ranged from 69.31 - 83.2%, while the hygroscopicity of nanocapsules was varied, approximately 17.89 - 23.79%. Nanocapsules moisture content was approximately 2.83 - 4.27%, while the total phenolic content of nanocapsules ranged from 6.74 - 13.41 mg GAE/g DW. The total anthocyanin of roselle extract nanocapsules was approximately 2.25 - 4.82 mg/g DW. The encapsulation efficiency of phenolic compounds in this study were approximately 60.31 - 77.13%. Nanocapsules with inulin-chitosan-maltodextrin (2.4%-2.4%-0.2%) had good properties of nanocapsules such as good solubility, high total phenolic content and total anthocyanin content. Nanocapsules with 5% inulin and inulinchitosan-maltodextrin (2.4%-2.4%-0.2%) had particle size of 641.4 and 411.1 nm respectively. The nanocapsules had a spherical shape, smooth surfaces but also a few had indentations.

Fortification of yoghurt drink with microcapsules loaded with Lacticaseibacillus paracasei BGP-1 and guaraná seed extract

The influence of co-encapsulation of guaraná seed extract (GSE) and Lacticaseibacillus paracasei BGP-1 on the viability of the bacteria and stability of phenolic compounds during storage of microcapsules and after their application in a yoghurt drink was studied. Co-encapsulation of the potential probiotic and GSE protected the phenolic compounds, with final retention of around 88%, and enhanced the viability of L. paracasei BGP-1 during storage. Concerning the yoghurt formulations, microencapsulation prevented post-fermentation and masked the bitter taste of GSE. As a result, the overall acceptability of yoghurt containing microcapsules was higher than that containing free GSE. In addition, encapsulation and association of GSE allowed for maintenance of L. paracasei counts of about 7 log cfu g−1 in yoghurt formulations stored at 7 °C for up 28 days. Therefore, co-encapsulation represents a valuable tool for the application and protection of functional ingredients in yoghurt drinks.

Olive Pomace Phenolic Compounds Stability and Safety Evaluation: From Raw Material to Future Ophthalmic Applications.

Nowadays, increasing interest in olive pomace (OP) valorization aims to improve olive’s industry sustainability. Interestingly, several studies propose a high-value application for OP extracts containing its main phenolic compounds, hydroxytyrosol and oleuropein, as therapy for ocular surface diseases. In this work, the stability and accessibility of OP total phenolic and flavonoid content, main representative compounds, and antioxidant activity were assessed under different pretreatment conditions. Among them, lyophilization and supercritical CO2 extraction were found to increase significantly most responses measured in the produced extracts. Two selected extracts (CONV and OPT3) were obtained by different techniques (conventional and pressurized liquid extraction); Their aqueous solutions were characterized by HPLC-DAD-MS/MS. Additionally, their safety and stability were evaluated according to EMA requirements towards their approval as ophthalmic products: their genotoxic effect on ocular surface cells and their 6-months storage stability at 4 different temperature/moisture conditions (CPMP/ICH/2736/99), together with pure hydroxytyrosol and oleuropein solutions. The concentration of hydroxytyrosol and oleuropein in pure or extract solutions was tracked, and possible degradation products were putatively identified by HPLC-DAD-MS/MS. Hydroxytyrosol and oleuropein had different stability as standard or extract solutions, with oleuropein also showing different degradation profile. All compounds/extracts were safe for ophthalmic use at the concentrations tested.

Bioaccessibility of Antioxidants in Prickly Pear Fruits Treated with High Hydrostatic Pressure: An Application for Healthier Foods.

High hydrostatic pressure (HHP) is a commercial processing technology which can enhance the health potential of foods by improving the bioaccessibility of their bioactive compounds. Our aim was to study the bioaccessibility and digestive stability of phenolic compounds and betalains in prickly pear fruits (Opuntia ficus-indica L. Mill. var. Pelota and Sanguinos) treated with HHP (100, 350, and 600 MPa; come-up time and 5 min). The effects of HHP on pulps (edible fraction) and peels (sources of potential healthy ingredients) were assessed. In pulps, betanin bioaccessibility increased (+47% to +64%) when treated at 350 MPa/5 min. In HHP-treated pulps, increases in the bioaccessibility of piscidic acid (+67% to +176%) and 4-hydroxybenzoic acid glycoside (+126% to 136%) were also observed. Isorhamnetin glycosides in peels treated at 600 MPa/CUT had higher bioaccessibility (+17% to +126%) than their controls. The effects of HHP on the bioaccessibility of health-promoting compounds are not exclusively governed by extractability increases of antioxidants in the food matrix (direct effects). In this work we found evidence that indirect effects (effects on the food matrix) could also play a role in the increased bioaccessibility of antioxidants in fruits treated with HHP.

Evaluation of bioactive compounds in an infused drink prepared from the powder of jaboticaba (Myrciaria cauliflora) peels

The aim of this work was to evaluate the bioactive compounds in a drink-type infusion prepared from the powder of the jaboticaba peels (Myrciaria cauliflora). The powder obtained from drying jaboticaba peels at the three different temperature ranges was analyzed for physical parameters and bioactive compounds. The results obtained from the analysis of the total phenolic compounds indicated that the powder was selected and stored for a period of 180 days. An experimental factorial design 23 was carried out to identify the best condition for the extraction of bioactive compounds in the infusion prepared from jaboticaba peel powder. The best condition to prepare the infused drink is with a mass of 2 g, extraction time of 3 min, and at a temperature of 100℃, thus achieving the highest content of bioactive compounds (47.16 mg/L). Thirteen phenolic substances were identified in the infusion from jaboticaba peel powder, especially gallic acid and hesperidin. Novelty impact statement The drying conditions were determined to obtain the dried jaboticaba peels with a high content of bioactive compounds, mainly anthocyanins and flavonoids. For infusion, the extraction capacity of phytochemicals is important, that is why a functional tea with the powder of the peels of jaboticaba was formulated and optimized for its nutraceutical properties. In addition, the results indicated the stability of phenolic compounds and physical parameters after 180 days of storage. Thus, this scientific study has practical relevance in the selection of the best extraction condition for bioactive compounds for the preparation of the infused drink (tea) using the powder of the jaboticaba peels.

Natural deep eutectic solvent (NADES): A strategy to improve the bioavailability of blueberry phenolic compounds in a ready-to-use extract

This study investigated whether a ready-to-use extract obtained using a natural deep eutectic solvent (NADES) affects the pharmacokinetic profile of blueberry phenolic compounds compared to organic solvent (SORG)-extracted compounds. SORG extract was administered as an aqueous solution after solvent removal. Wistar rats received a single dose of crude extract of blueberry obtained using NADES (CE-NADES) or SORG (CE-SORG), followed by LC-DAD-MS/MS analysis of blood and cecal feces. Non-compartmental pharmacokinetic analysis revealed that CE-NADES increased the bioavailability of anthocyanins by 140% compared to CE-SORG. CE-NADES increased the stability of phenolic compounds during in vitro digestion by delaying gastric chyme neutralization. These results suggest that besides being an eco-friendly solvent for the extraction of phytochemicals, choline chloride:glycerol:citric acid-based NADES can be used as a ready-to-use vehicle for increasing oral absorption of bioactive compounds such as anthocyanins.

A by‐product from virgin olive oil production (pâté) encapsulated by fluid bed coating: evaluation of the phenolic profile after shelf‐life test and invitro gastrointestinal digestion

AbstractPâté is a by‐product of virgin olive oil production presenting a high phenolic content and beneficial health effects. This research aims to evaluate the storage stability of phenolic compounds of pâté and a coated formulation, and to verify the bioaccessibility of the phenolic compounds. An accelerated shelf‐life test at 40 °C/75% relative humidity was carried out for 75 days. Different combinations of degradative and hydrolytic reactions impacted the results. Indeed, at the end of the storage period, 84% of phenols was recovered in pâté with free tyrosol and hydroxytyrosol showing an increase due to secoiridoids hydrolysis. The total phenolic content of coated pâté did not significantly decrease, showing a higher increment of free tyrosol and hydroxytyrosol. Simulated digestion led to the liberation of 15% of phenols by both samples. In conclusion, the coating process improved the stability of pâté phenolic compounds without affecting their bioaccessibility.

Stability of phenolic compounds and drying characteristics of apple peel as affected by three drying treatments

To realize high-value utilization of discarded apple peel, this study investigated the effects of three selected commercial drying methods on drying kinetics, microstructure, color, phenolic stability and antioxidant capacity of apple peel. Apple peel was dehydrated by hot air drying (AD) at 75, 65 and 55°C, heat pump drying (HP) at 65, 55 and 45°C, and vacuum freeze-drying (FD), respectively. The results showed that HP was superior to AD and FD in terms of drying rate. In addition, HP at 65°C provided high-quality dried apple peel due to less browning and brighter appearance, the highest retention of total phenolics (29.35mg/g) and the strongest antioxidant activities, with the highest ABTS and FRAP value of 127.15 and 219.57μmol TE/g, respectively. The content of the six major individual phenolics, i.e. caffeic acid, (-)-epicatechin, hyperoside, rutin, phlorizin and quercitrin, were found to be the highest in HP dried samples. Interestingly, the content of rutin was even increased after HP compared to the fresh sample. Considering drying efficiency, organoleptic quality and phenolic stability of the products, HP at 65°C is suggested for drying of apple peel.