Fruit Quality, Antioxidant Contents and Activity, and Antiproliferative Activity of Strawberry Fruit Stored in Elevated CO2 Atmospheres

ABSTRACT:  The effects of CO₂ in the storage atmosphere on color, firmness, ascorbic acid (AA), anthocyanins, flavonoids, phenolics, total antioxidant activity, and antiproliferative activity of strawberry fruit have been investigated. "Northeaster" and "Earliglow" strawberries were stored in air or in 20% CO₂ (in air) at 3 °C for 20 d. Color changes in Northeaster were delayed more by CO₂ treatment than in Earliglow. Firmness of CO₂-stored fruit increased slightly compared with those stored in air. The increases in total and reduced AA concentrations during air storage were usually prevented by CO₂ storage in both cultivars. Dehydroascorbic acid (DHA) concentrations increased during CO₂ storage. Anthocyanins and flavonoids, and total antioxidant activity of both cultivars were higher in air-stored fruit than in CO₂-stored fruit. The total phenolic concentration was lower in CO₂-stored Earliglow fruit than in air, but storage treatment did not affect that of Northeaster. A 40 mg/mL concentration of Northeaster strawberry extract inhibited about 80% of HepG₂ human liver cancer cell proliferation. CO₂ treatment did not affect the antiproliferative activity of strawberry fruits, but antiproliferative activity was greater at harvest than after storage.     

Antioxidant activity versus cytotoxic and nuclear factor kappa B regulatory activities on HT-29 cells by natural fruit juices

The antioxidant activity (free radical scavenging ability and lipid oxidation inhibitory activity) and the activity in cell culture [influence on HT-29 human colon cancer cell viability and nuclear factor kappa B (NF-κB) activation] of natural fruit juices from red grape, strawberry, cherry and sour cherry were investigated in vitro. Analysis of polyphenolic composition of fruit juices showed the dominant presence of anthocyanins (cyanidin-3-glucoside, cyanidin-3-rutinoside, peonidin-3-rutinoside, pelargonidin-3-glucoside), anthocyanidins (procyanidins B1, B2 and B3), flavonoids (glucosides of myricetin, quercetin and kaempferol), and phenolic acids (neochlorogenic acid, chlorogenic acid, ellagic acid, p-coumaroylquinic acid) in juices. DPPH test and β-carotene bleaching method indicated that grape, strawberry, cherry and sour cherry natural juices (at the concentration of 2.5%) showed very strong free radical scavenging (75–92%) and antioxidant activity (71–94%). In addition, at the concentration of 0.01% they showed complete inhibition of copper-induced oxidation of human LDL (low density lipoprotein). In contrast, selected fruit juices did not show cytotoxic effects on HT-29 cells and NF-κB inhibitory activity (at the concentrations of 0.5 and 2%). Results of this study showed no correlation between the antioxidant activity of natural fruit juices from red grape, strawberry, cherry and sour cherry and their effect on HT-29 cell viability and NF-κB inhibitory activity.     

Changes in Phenolic Compounds During Storage of Pasteurized Strawberry

This study aimed to establish mathematical models to describe changes in phenolics of pasteurized strawberry (Fragaria?×?ananassa Duch.) during storage at 23 °C for 90 days. Freshly cut strawberries cubes were pasteurized for 5 min in a water bath at 90 °C following a heating time of 15 min. Antioxidant activity, total phenolics, total anthocyanins, and individual phenolic compounds were assessed immediately before or after pasteurization and at regular time intervals during storage. The results indicated that (1) pasteurization did not affect (P?<?0.05) the concentrations of total phenolics or total anthocyanins, but significantly reduced the concentrations of quercetin-3-rutinoside, kaempferol, and cyanidin-3-glucoside, and increased the concentrations of (+)-catechin, (?)-epicatechin, epigallocatechin gallate, quercetin-3-galactoside, and ellagic acid; (2) changes in antioxidant capacity, total anthocyanin, and individual compounds during storage were described by a pseudo-first-order model with the exception of total phenolic and specifically kaempferol and ellagic acid which followed zero-order kinetic models. Pelargonidin-3-glucoside degraded at the highest rate (k?=?0.07 day^?1), followed by ellagic acid (k?=?0.004 day^?1) and kaempferol (k?=?0.003 day^?1). The rate constants can be used to predict phytochemical changes in strawberry products during storage.     

A Comparative Study of Phenolic Antioxidant Activity and Flavonoid Biosynthesis‐Related Gene Expression Between Summer and Winter Strawberry Cultivars

Strawberry (Fragaria ananassa Duch.) possesses good antioxidant properties. Phenolic compounds in strawberries, such as anthocyanins and ellagic acid, mainly act as antioxidants. This study aimed to compare the phenolic content and expression patterns of genes involved in flavonoid biosynthesis between summer and winter strawberry cultivars affected by seasonal variation, degree of ripeness, and genotype. Antioxidant activity and the total content of phenols and flavonoids decreased with fruit ripening. Most notably, summer strawberry cultivars showed higher antioxidant activity than winter cultivars. The expression patterns of flavonoid biosynthetic genes tested were cultivar‐dependent and were also affected by ripening. These results help us understand the nutritional and physiological characteristics of selected cultivars and provide a range of information for strawberry consumption.     

Effect of Nanochitosan-Based Coating With and Without Copper Loaded on Physicochemical and Bioactive Components of Fresh Strawberry Fruit (Fragaria x ananassa Duchesne) During Storage

Edible coatings based on nanochitosan (50–110 nm) with and without copper loaded were evaluated on physicochemical and bioactive components of strawberry. Fresh fruits were coated with copper-free and copper-loaded nanochitosans and stored at 4?±?1 °C with 70 % relative humidity for 20 days. Both nanochitosan coatings provided an effective control in reducing weight loss and firmness as well as delayed changes in the respiration rate during 3 weeks. The antioxidant activity declined throughout the storage period of strawberries, although the decrease in antioxidant activity showed a slower rate in the strawberries coated with copper-free nanochitosan followed by copper-loaded nanochitosan compared with the control. Anthocyanin concentrations increased in fruits coated with copper free as well as copper-loaded nonochitosan at the first 12 days of storage followed by reduction in slow rates. However, no increase of anthocyanin was recorded for uncoated samples. Intensive reduction was recorded in ascorbic acid content of strawberries coated with copper-loaded nanochitosan, while the minimum loss of the ascorbic acid content was related to the copper-free nanochitosan. Also, both nanochitosans showed a significant suppression on the polyphenol oxidase and peroxidase activity, whereas a high rate of increase was recorded in control strawberry. The nanochitosan coatings with or without copper loaded significantly suppressed the visual loss and fungal decay of the strawberries during the storage compared with the control. The sensory evaluation of coated strawberries revealed that no effect on the consumer acceptability was detected as well as that copper-free nanochitosan showed better results in the point of preserving the overall flavor and appearance compared with the copper-loaded one.     

Strawberry As a Functional Food: An Evidence-Based Review

Emerging research provides substantial evidence to classify strawberries as a functional food with several preventive and therapeutic health benefits. Strawberries, a rich source of phytochemicals (ellagic acid, anthocyanins, quercetin, and catechin) and vitamins (ascorbic acid and folic acid), have been highly ranked among dietary sources of polyphenols and antioxidant capacity. It should however be noted that these bioactive factors can be significantly affected by differences in strawberry cultivars, agricultural practices, storage, and processing methods: freezing versus dry heat has been associated with maximum retention of strawberry bioactives in several studies. Nutritional epidemiology shows inverse association between strawberry consumption and incidence of hypertension or serum C-reactive protein; controlled feeding studies have identified the ability of strawberries to attenuate high-fat diet induced postprandial oxidative stress and inflammation, or postprandial hyperglycemia, or hyperlipidemia in subjects with cardiovascular risk factors. Mechanistic studies have elucidated specific biochemical pathways that might confer these protective effects of strawberries: upregulation of endothelial nitric oxide synthase (eNOS) activity, downregulation of NF-kB activity and subsequent inflammation, or inhibitions of carbohydrate digestive enzymes. These health effects may be attributed to the synergistic effects of nutrients and phytochemicals in strawberries. Further studies are needed to define the optimal dose and duration of strawberry intake in affecting levels of biomarkers or pathways related to chronic diseases.     

Profiling ellagic acid content: The importance of form and ascorbic acid levels

As the importance of plant-based antioxidants to human health becomes clearer there is a rapidly expanding search for rich sources of these compounds. Much attention is currently focussed on the antioxidant potential of ellagic acid (EA). Making assessment difficult is that EA occurs in different forms: free EA, EA glycosides and polymeric ellagitannins. The overall structure of these forms has a pronounced effect on their antioxidant efficiency and is responsible for widely differing reactivity, solubility and hence bioavailability properties. Often associated with EA is vitamin C which also contributes to the plant foods total antioxidant activity. Previous studies have suggested that ascorbic acid may have protective effects on the polyphenol content of plants. With a view to gaining evidence that the bioactive forms of vitamin C influence EA content, several fruits with a range of EA and vitamin C contents were examined. To facilitate a more detailed assessment of the selected fruits antioxidant potential the relative proportions of EA forms were also determined. In strawberries and boysenberries EA content was predominantly in the polymeric form (21% and 12% free EA plus EA glycoside vs total EA levels for strawberry and boysenberry respectively), while in Kakadu plum it was mainly in the free form (70% of total EA). An increasing percentage of dehydroascorbic acid (9 to 14% of total vitamin C) indicating enhanced transformation of ascorbic acid to its oxidative degradation product together with stable free EA levels (≈ 950 mg/100 g DW) over the 4 month frozen storage period for the Kakadu plum samples are consistent with a possible protective effect of EA by ascorbic acid.     

Cultivars, culture conditions, and harvest time influence phenolic and ascorbic acid contents and antioxidant capacity of strawberry (Fragaria x ananassa)

Strawberries are a good source of micronutrients, especially antioxidant phenolics. More information is needed to better exploit the health-promoting effect of such fruits. Several studies focused on the effects of genotype, cultural practices, and seasonal variation on the antioxidant potential of strawberries, but often yielding contradictory results and/or focusing on only 1 source of variability. In the present study, we showed that total phenolic compounds, ascorbic acid, and antioxidant capacity strongly differed between genotypes of strawberry. The precise results revealed the importance of genetic background for the antioxidant capacity and for the content of total phenolics (with up to 3.3-fold variations). Other parameters may also influence the antioxidant capacity in strawberry such as harvest time, culture conditions, and environmental factors. Moreover, in this study, the harvesting time (at the same ripening stage) appeared to be very important, more important than genotype. Variations of the antioxidant capacity of up to 4.1-folds were observed following the harvesting time of "Elsanta" cultivar. PRACTICAL APPLICATION: This article compares the antioxidant capacity and the content in ascorbic acid and phenolic compounds of strawberries of different varieties and of fruits harvested from April to December at the same ripening stage. The importance of strawberry antioxidant capacity resides in its benefits for human health.     

Influence of alcoholic fermentation process on antioxidant activity and phenolic levels from mulberries (Morus nigra L.)

The aim of the present study was to evaluate the profile of the phenolic constituents of Morus nigra fruits and their antioxidant activity (DPPH) and to compare their contents before and after fermentation. Antioxidant phenolics of black mulberry (M. nigra L.) samples grown in Galicia (NW Spain) were extracted with methanol/formic acid/water (MFW) and determined by high performance liquid chromatography (HPLC). Two major anthocyanins (cyanidin 3-glucoside and cyanidin 3-rutinoside) and two flavonols (quercetin 3-glucoside and rutin) were isolated, together with caffeic acid and other hydroxycinnamic and ellagic acid derivatives. Their chemical structures were identified by spectral analyses with diode array detection (DAD), but also with alkaline saponification and acid hydrolysis of the mulberry phenolics. Good correlations (r² = 0.6229) were observed among total flavonols contents and the IC₅₀ radical scavenging capacities of mulberry fruits. Anthocyanins are the major flavonoids present in mulberry. It would be expected that anthocyanins contribute significantly to their antioxidant activity; nevertheless, alcohol generated during fermentation may also contribute to antioxidant activity. Our results provide useful antioxidant nutritional information of fresh and fermented mulberry fruits.     

Bioactive compounds and quantification of total ellagic acid in strawberries (Fragaria x ananassa Duch.)

Strawberries are one of the most popular edible fruits in Brazil and their consumption has increased with the development of new varieties available at almost all seasons. Fruit of seven full-ripened strawberry cultivars (Dover, Camp Dover, Camarosa, Sweet Charlie, Toyonoka, Oso Grande and Piedade) were characterized in relation to the total phenolics, vitamin C, flavonoids, free and total ellagic acid contents and antioxidant capacity. Camp Dover had the lowest values for anthocyanins and total phenolics but the highest total flavonoid content. Dover presented the highest anthocyanin, total phenolics and ellagic acid contents and also elevated antioxidant capacity. The best conditions for the determination of the total ellagic acid content in strawberries were also optimized and the results showed that the extraction with 80% acetone, and hydrolysis using 2 N TFA at 120 °C for 60 min allowed a 99% recovery.     

The effect of addition of chokeberry, flowering quince fruits and rhubarb juice to strawberry jams on their polyphenol content, antioxidant activity and colour

The aim of the study was to establish whether the addition of berries (flowering quince, chokeberry) and rhubarb juice during jam processing improves its colour and enriches jams in polyphenol compounds other than those found in strawberries. The sum of phenolic compounds determined by HPLC was distributed in a wide concentration range depending on the cultivar. Jams prepared from Elkat cultivar had 27% more total phenolic compounds than jams prepared from Senga Sengana. The following compounds were identified in jams prepared from strawberries: p-coumaric, ferulic and ellagic acids, quercetin, kaempferol, anthocyanins, (+)-catechin, (−)-epicatechin and proanthocyanidins. Proanthocyanidins and ellagic acid are the major polyphenol compounds of all strawberries jams. The Elkat cultivar (47.34 mg/100 g) contained higher amounts of proanthocyanidins compared to Senga Sengana (29.95 mg/100 g). The addition of 10% of flowering quince and chokeberry to jams during their preparation resulted in the increase in the content of phenolic components in final products, especially for proanthocyanidins. The highest level of total polyphenols (P < 0.05) was found in strawberry mixed with chokeberry, 237.82 mg/100 g for Senga Sengana and 260.61 mg/100 g for Elkat. There has been a marked increase of proanthocyanidins content (5.4 and 4.0 times) in jams made from Senga Sengana and Elkat cultivars mixed with chokeberry. However, the addition of rhubarb juice did not increase the content of polyphenol in Senga Sengana jam (not statistically significant). Antioxidant activity of strawberry jam was determined by 2,2′azinobis-(3-ethylbenzthiazoline-6-sulphonic acid (ABTS), 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH) and ferric reducing/antioxidant power methods (FRAP). The antioxidant activity of this mixed jam was more than two times higher (P < 0.05) than control sample of strawberry jam. Rhubarb juice had high effect on L* (lightness) value in case of all strawberry varieties. The redness (a*), and yellowness (b*) were significantly different in jams with supplement. Strawberry jam with chokeberries had smaller L* value than control and other samples, and the lowest a* and b* values. This variation could be due to the nature of the pigments in these fruit cultivars and the content of anthocyanins which resulted in more reddish colour.     

Comparison of phenolic composition and antioxidant properties of two native Chilean and one domestic strawberry genotypes

The phenolic composition of extracts from the forms chiloensis and patagonica of Fragaria chiloensis were compared with that of the commercial strawberry Fragaria × ananassa cv. Chandler by high performance liquid chromatography with diode-array detector (HPLC–DAD) and high performance liquid chromatography with electrospray ionization mass spectroscopy detector (HPLC–ESI–MS). The phenolic constituents in the three species were mainly proanthocyanidins, hydrolysable tannins, anthocyanins and flavonol glycosides. In both native strawberry species the main flavonol glycoside was quercetin 3-O-glucuronide and the minor anthocyanins identified were cyanidin-malonyl-glucoside and pelargonidin-malonyl-glucoside. The highest anthocyanin content was found in the commercial red strawberry while ellagic acid was the main phenolic in the native white strawberry. From the methanolic fruit extract of the native Chilean strawberry Fragaria chiloensis ssp. chiloensis f. chiloensis four known antioxidants were isolated by selective fractionation using the bleaching of the free radical scavenger 1,1-diphenyl-2-picrylhydrazyl (DPPH) as the guiding assay. The antioxidant properties (measured as the bleaching of the DPPH radical) were determined for methanol extracts of the three fruits, for fractions of F. chiloensis ssp. chiloensis f. chiloensis, and for the isolated compounds cyanidin-3-glucoside, pelargonidin-3-glucoside, quercetin-3-glucuronide and ellagic acid. This study allows a clear chemical differentiation between the commercial strawberry and the Chilean white strawberry.     

Potential impact of strawberries on human health: a review of the science

Epidemiological studies have noted a consistent association between the consumption of diets rich in fruits and vegetables and a lower risk for chronic diseases including cancer and cardiovascular disease. There is accumulating evidence that much of the health-promoting potential of these plant foods may come from phytochemicals, bioactive compounds not designated as traditional nutrients. In strawberries, the most abundant of these are ellagic acid, and certain flavonoids: anthocyanin, catechin, quercetin and kaempferol. These compounds in strawberries have potent antioxidant power. Antioxidants help lower risk of cardiovascular events by inhibition of LDL-cholesterol oxidation, promotion of plaque stability, improved vascular endothelial function, and decreased tendency for thrombosis. Furthermore, strawberry extracts have been shown to inhibit COX enzymes in vitro, which would modulate the inflammatory process. Individual compounds in strawberries have demonstrated anticancer activity in several different experimental systems, blocking initiation of carcinogenesis, and suppressing progression and proliferation of tumors. Preliminary animal studies have indicated that diets rich in strawberries may also have the potential to provide benefits to the aging brain.     

Identification of bioactive response in traditional cherries from Portugal

In recent years many studies on cherries have revealed that they are rich sources of bioactive compounds with potential human health benefits. In this work, we evaluated the antioxidant activity and antiproliferative effect in human cancer cells of nine sweet cherries, including two traditional cultivars from Portugal (Saco and Morangão). Results obtained in biological assays, together with the phenolic composition of cherries, were submitted to principal component analysis (PCA) which allowed samples to be grouped in terms of their bioactivity. Saco cherry and two exotic cultivars (Ulster and Lapin) proved to have higher contents of phenolic compounds, highest antioxidant activity and were the most effective in inhibiting human cancer cells derived from colon (HT29) and stomach (MKN45). Correlation of the data obtained showed that anthocyanins were the major contributors to the antioxidant capacity and antiproliferative effect of cherries. Additionally, hydroxycinnamic acids (neochlorogenic acid, chlorogenic acid and p-coumaroylquinic acid), flavan-3-ols (catechin and epicatechin) and flavonols (rutin and quercetin-3-glucoside) also play important roles in protection against oxidative stress.     

Impact of postharvest methyl jasmonate treatment on the volatile composition and flavonol content of strawberries

BACKGROUND: Although strawberry aroma is very complex, certain compounds have been described as main contributors, i.e. furanones, aldehydes, alcohols, sulfur compounds and particularly methyl and ethyl esters. In addition, strawberries possess potent antioxidant activity because of their high content of phenolic compounds. Among them, flavonols are highlighted as important antioxidant compounds in strawberry. The objective of this study was to assess the effect of methyl jasmonate (MJ) on the composition of the major contributors to aroma and on the content of certain flavonols in strawberry fruits. RESULTS: The levels of all studied volatile compounds were significantly affected by MJ treatment, though the individual effect differed according to the specific compound considered. Most of them increased significantly (P < 0.05), except methyl butanoate, which always showed higher levels in untreated strawberries. In contrast to aroma compounds, the change in the concentration of flavonols (i.e. myricetin, quercetin and kaempferol) was not significant in MJ‐treated strawberries. Considering the health‐promoting activity of these compounds, further investigations on the experimental conditions related to the treatment are required to control flavonol bioformation by means of MJ. CONCLUSION: The exogenous application of MJ vapour to strawberry enhances, in general, the production of the most relevant aroma‐active compounds. On the contrary, MJ treatment does not appear to influence the levels of myricetin, quercetin and kaempferol. Thus postharvest MJ treatment is proposed as an approach to obtain improved strawberry fruits in terms of sensory quality and health‐promoting properties. Copyright © 2010 Society of Chemical Industry     

Antioxidant compounds and antioxidant capacity of Peruvian camu camu (Myrciaria dubia (H.B.K.) McVaugh) fruit at different maturity stages

The antioxidant capacities of ascorbic acid and phenolic compounds present in camu camu fruit were screened during ripening. Ascorbic acid decreased, and anthocyanin, flavonol and flavanol contents, and DPPH antioxidant capacity increased during ripening. Antioxidant compounds from camu camu were fractionated in two fractions: an ascorbic acid-rich fraction (F-I) and a phenolics-rich fraction (F-II). F-I was the major contributor to the DPPH antioxidant capacity (67.5–79.3%) and F-II played a minor role (20.7–32.5%). A total of 30 different phenolic compounds were detected by HPLC-PAD. The presence of catechin, delphinidin 3-glucoside, cyanidin 3-glucoside, ellagic acid and rutin was elucidated. Other phenolic compounds, such as flavan-3-ol, flavonol, flavanone and ellagic acid derivatives, were also present. For the three ripening stages the flavan-3-ols and ellagic acid group were the most representative phenolic compounds in this fruit. Acid hydrolysis of F-II revealed the presence mainly of gallic and ellagic acids, suggesting that camu camu fruit possesses important quantities of hydrolysed tannins (gallo- and/or ellagitannins). These results confirm that camu camu fruit is a promising source of antioxidant phenolics.     

Impact of high pressure processing on total antioxidant activity,phenolic, ascorbic acid,anthocyanin content and colour of strawberry and blackberry purées

The present study was undertaken to assess the effect of high pressure treatments and conventional thermal processing on antioxidant activity, levels of key antioxidant groups (polyphenols, ascorbic acid and anthocyanins) and the colour of strawberry and blackberry purées. Bioactive compounds (cyanidin-3-glycoside, pelargonidin-3-glucoside, ascorbic acid) and antioxidant activity were measured in strawberry and blackberry purées subjected to high pressure treatment (400, 500, 600 MPa/15 min/10–30 °C) and thermal treatments (70 °C/2 min). Samples were assessed immediately after processing. Different pressure treatments did not cause any significant change in ascorbic acid (p > 0.05). In contrast, following thermal processing (P₇₀ ≥ 2 min) ascorbic acid degradation was 21% (p < 0.05) as compared to unprocessed purée. However, no significant changes in anthocyanins were observed between pressure treated and unprocessed purées (p > 0.05), whereas conventional thermal treatments significantly reduced the levels (p < 0.05). In general, antioxidant activities of pressure treated strawberry and blackberry purées were significantly higher (p < 0.05) than in thermally processed samples. Colour changes were minor (ΔE) for pressurised purées but the differences were slightly higher for thermally treated samples. Redness of purées was well retained in high pressure treated samples. Therefore processing strawberry and blackberry by high pressure processing could be an efficient method to preserve these products quality. Hence high pressure processing (HPP) at moderate temperatures may be appropriate to produce nutritious and fresh like purées.Industrial relevanceThis research paper provides scientific evidence of the potential benefits of high pressure processing in comparison to thermal treatments in retaining important bioactive compounds. Antioxidant activity (ARP), ascorbic acid, and anthocyanins after exposure to high pressure treatments (400–600 MPa) were well retained. Our results also show that redness and colour intensity of strawberry and blackberry purées were better preserved by high pressure processing than conventional thermal treatment. From a nutritional perspective, high pressure processing is an attractive food preservation technology and offers opportunities for horticultural and food processing industries to meet the growing demand from consumers for healthier food products. Therefore high pressure processed foods could be sold at a premium than their thermally processed counterparts as they will have retained their fresh-like properties.     

Ellagic acid content in berries: Influence of domestic processing and storage

The content of ellagic acid was determined from the berries of the family Rosaceae (strawberry, red raspberry, cloudberry, arctic bramble). Extraction and hydrolysis procedures were optimized and analysis was done with an HPLC method and UV detection. The influence of processing on ellagic acid content was studied in strawberry jam. Strawberries, red raspberries, and strawberry jam were analyzed fresh and after 3, 6, and 9 months of storage in a domestic freezer or refrigerator. Ellagic acid contents after 3 months of storage at −20 °C varied between 31.5 (strawberry ‘Senga Sengana’) and 68.6 mg/100 g f.w. (arctic bramble). Ellagic acid content in strawberry jam (23.8 mg/100 g f.w.) was 80% of that in unprocessed strawberries. The content of ellagic acid in strawberries and red raspberries was reduced by 40% and 30%, respectively, during the 9 months of storage at −20°C. The unprocessed berries studied, together with nuts, make the main contribution to the total dietary intake of ellagic acid in Finland. Received: 7 December 1999 / Revised version: 22 February 2000     

Variations in antioxidant properties of strawberries grown in Brazilian savannah and harvested in different seasons

BACKGROUND: Strawberries are nutritive fruits and a source of antioxidants. We evaluated antioxidant properties of ‘Camino Real’ strawberries grown in the Brazilian savannah, harvested in different seasons. Analytical and meteorological data were analyzed by partial least squares regression. RESULTS: Fruits from May showed the lowest contents of total phenolics (1789.78 mg kg^?1 fresh weight (FW)), catechin (21.37 mg kg^?1 FW), quercetins (4.89 mg kg^?1 FW) and total ellagic acid (208.68 mg kg^?1 FW) and the lowest antioxidant activity by 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) (11.39 mg Butylated hydroxytoluene (BHT) eq. g^?1 FW) and ferric reducing antioxidant power (FRAP) (22.01 mg ferrous sulfate eq. g^?1 FW) assays. Strawberries harvested in July presented the lowest concentrations of total (190.61 mg kg^?1 FW) and individual anthocyanins (73.88 mg kg^?1 FW and 5.96 mg kg^?1 FW for pelargonidin‐3‐glucoside and cyanidin‐3‐glucoside, respectively), but the highest contents of vitamin C (685.47 mg kg^?1 FW), DPPH (18.87 mg BHT eq. g^?1 FW) and FRAP (39.30 mg ferrous sulfate eq. g^?1 FW). The highest contents of free ellagic acid (26.11 mg kg^?1 FW), pelargonidin‐3‐glucoside (291.82 mg kg^?1 FW) and cyanidin‐3‐glucoside (11.84 mg kg^?1 FW) were found in strawberries from September. Rain in the previous 30 days to harvest influenced negatively many phenolics and antioxidant activity of strawberries harvested in May. In July, longer photoperiod and lower temperature at 30 days previous to harvest probably led to higher antioxidant activity and vitamin C. Increased photoperiod and temperature at the final stage of maturation seem to raise pigments and free ellagic acid in strawberries. CONCLUSION: It was possible to observe significant relationships among meteorological and antioxidant variables for strawberries grown in the Brazilian savannah. Copyright © 2011 Society of Chemical Industry     

Ellagic acid content in strawberries of different cultivars and ripening stages

Ellagic acid is a phenolic compound which occurs naturally in strawberries. Interest in ellagic acid has increased during the past few years owing to its properties as a micronutrient. The objective of this study was to determine the ellagic acid content in strawberries compared with that in other common fruits and to evaluate its variability, the effects of ripening stage, and the tissue and seasonal variability in selected cultivars widely grown in Argentina. Strawberries showed significantly higher levels of ellagic acid than many other fruits of economic importance, ranging from 0.16 to 2.07 mg g^?1 dry weight. The ellagic acid content was highest in green fruit, intermediate in mid‐ripe fruit and lowest in full‐ripe fruit. Cultivars ‘Chandler’ and ‘Camarosa’ contained the highest amounts of ellagic acid in strawberries with edible value (0.78 and 0.70 mg g^?1 dry weight respectively), while ‘Oso Grande’ and ‘Milsei’ exhibited the lowest (0.35 and 0.31 mg g^?1 dry weight respectively). Moreover, the level of this phytochemical was found to be higher when considering pulp with achenes compared with pulp without achenes. Copyright © 2003 Society of Chemical Industry