Comparison of antioxidant capacity and phenolic composition of peel and flesh of some apple varieties

BACKGROUND: Apples contain a large concentration of phenolic compounds, dependent on factors such as cultivar, harvest, storage conditions, and processing. This study aims to identify the essential phenolic compounds present in various apple varieties, to measure their total antioxidant capacity (TAC) with the CUPRAC (cupric ion reducing antioxidant capacity) and ABTS (2,2′‐azino‐bis(3‐ethylbenzothiazoline‐6‐sulfonate)) methods, and to correlate their TAC values with HPLC findings. RESULTS: The order of TAC (mmol Trolox g^?1 fresh weight) of apple peels determined with the CUPRAC method was: Granny Smith > Amasya > Sky Spur > Ervin Spur > King Luscious ≥ Arap Kizi ≥ Lutz Golden. The theoretically calculated TAC values of HPLC‐quantified compounds, with the aid of the combined HPLC‐CUPRAC method, accounted for 18.4–33.5% of the experimentally observed CUPRAC capacity of peel extracts and 19.5–56.3% of flesh extracts, depending on apple variety. CONCLUSION: In synthetic samples of apple antioxidants, the CUPRAC‐TAC values of constituents, identified and analyzed by HPLC, proved to be additive, enabling measurement of the cooperative action of antioxidants using the proposed methodology. Apple peel showed higher contents of phenolics and therefore higher TAC than apple flesh, confirming the health benefit of the consumption of apples together with peel. © 2012 Society of Chemical Industry     

Recovery and evaluation of aroma development in apple peels

Aroma in Delicious apple peels was generated by conditioning peels at ambient temperature (19–23°c) for 24 h. The conditioned peels were processed, and the developed aroma was recovered in a pilot-scale apparatus. The recovered aroma was evaluated for intensity and quality against standard apple essences derived from whole apples and unconditioned or no-delay peels. The strength or ‘flavouring capacity’ of the concentrated aroma solution was estimated by threshold analysis and by a matching standard procedure at single-strength juice equivalence. The aroma recovered from conditioned peels was 2–7 times stronger than that from similar no-delay peels. Quality of the aroma solution from conditioned peels was statistically (P > 0.05), indistinguishable from standard aroma solutions prepared from whole apples or no-delay peels. Thus, the conditioned peels gave aroma solutions with 2–7 times more ‘flavouring capacity’ than no-delay peels, without significant sacrifice in quality.     

Detection of fruit juice adulteration in apple and pear juice

A method has been developed to detect the adulteration of pear juice with apples and apple juice with pears. In different varieties of apples and pears and in several commercial juices the flavonoids were examined by HPLC with respect to their quality and quantity. The chalcones phloretin glucoside and phloretin xyloglucoside are typical compounds found in apples (detection limit 7 ng). They are suitable indicators for detecting adulteration of pear juice with apples. Isohamnetin glucoside cannot be detected in apples (detection limit 10 ng), but can be used to detect pears in apple juice. The extract or juice was purified with the aid of a polyamide column. The evaporated eluate of methanol was analysed by HPLC (gradient: acetonitrile/1% acetic acid). An RP-18 column and a UV-detector were used. Additionally, the UV spectra of the compounds indicating an adulteration were recorded by a diode array detector.     

Relationships of Objective Measurements to Sensory Components Of Canned Applesauce and Apple Slices

Six cultivars of apples with different processing characteristics were studied in the form of applesauce and apple slices. Newly determined sensory components, developed to account for cultivar to cultivar variations, were used in this study of the relationships between them and various objective measurements. A total of nine models were generated for each of the two products, applesauce and apple slices, based upon stepwise regression analysis.     

PHENOLIC COMPOUNDS IN THE FLESH OF KOREAN APPLE CULTIVAR, BUSA

Phenolic compounds were purified from Busa, the most widely cultivated apple cultivar in Korea, by a sequential separation employing PVPP, Ambertite XAD‐2 and Sephadex LH‐20 column chromatography. Phenolic compounds in some fractions were farther identified by directly comparing with corresponding phenolic standards after separation on HPLC and GC‐MS. The phenolic compounds identified were p‐hydoxybenzoic, protocatechuic, 4‐hydroxymetyl‐benzonic, caffeic, p‐coumaric, o‐coumaric, ferulic, sinapic and chlorogenic acids and (±)‐catechin. Among them, 4‐hydroxymethylbenzoic, protocatechuic, o‐coumaric and sinapic acids were ascertained as new members of a family of phenolic acids present‐in apples. Also the presence of rutin, quercetin and phlorizin in apples were demonstrated using HPLC.     

低温和气调对不同色泽‘红富士’苹果贮藏期间果皮褪色现象的影响

研究低温和气调对不同色泽‘红富士’苹果贮藏期间果实理化指标的影响。以采收时2种不同色泽的‘红富士’苹果为试材,分别测定贮藏期间果实硬度、可溶性固形物含量、p H值,果皮花青苷含量、多酚含量、9种单体酚分含量和多酚氧化酶(PPO)、过氧化氢酶(POD)活性的变化。采收时,着色差的‘红富士’苹果果皮花青苷和多酚含量显著低于着色好的苹果,但其PPO、POD活性显著高于着色好的苹果;贮藏过程中,着色差的苹果果皮花青苷和多酚降解速度显著高于着色好的苹果。与冷藏相比,气调贮藏能有效地抑制花青苷和多酚的降解,延缓PPO、POD活性的上升,维持果实的品质指标。贮藏方式相同时,着色差的‘红富士’苹果比着色好的苹果更易发生果皮褪色现象;采收时色泽相同,则冷藏的‘红富士’苹果比气调贮藏的苹果更易发生果皮褪色现象。     

Characterisation of Asturian cider apples on the basis of their aromatic profile by high-speed gas chromatography and solid-phase microextraction

Headspace solid-phase microextraction (SPME) coupled to high-speed gas chromatography with FID detector (HSGC-FID) and with quadrupole mass spectrometric detector (GC–MS) was employed to study the volatile compounds in Asturian cider apples. The optimised conditions used for characterisation of cider apple were: sample equilibration at 25 °C for 12 h, followed by PDMS–DVB fibre exposure to the headspace above the sample for 5 min and finally thermal desorption of the adsorbed substances in the injector port for GC analysis. The use of high-speed gas chromatography allowed the separation of 27 compounds in less than 8 min, reducing the analysis time in 80% compared to conventional gas chromatography. A simple, rapid and reliable method to analyze volatile compounds in cider apples has been developed. The aromatic profile of 59 apple samples included in eight apple varieties was analysed. The different apples were obtained from two consecutive harvests (2005 and 2006). The apples volatile compounds together with chemometric techniques such as principal components analysis (PCA), Bayesian analysis and linear discriminant analysis (LDA), allowed us to differentiate apples on the basis of the sweet or sharp category to which the cider apple variety belongs. Volatile compounds such as ethyl heptanoate, E-farnesene, ethyl butyrate and hexyl caprylate are closely related to cider apple cultivars of the sweet category, while propyl butyrate and butyl acetate are related to the sharp class.     

Alginate coating as carrier of oligofructose and inulin and to maintain the quality of fresh-cut apples

The aim of this study was to apply an edible coating containing prebiotics such as oligofructose and inulin to fresh-cut apple wedges. An assessment of the quality, sensory, polyphenol, and volatile attributes of coated and uncoated fresh-cut apple wedges was also undertaken. Fructan analysis showed that all prebiotics remained stable over the 14-d storage period and an intake of 100 g of apple supplies 1 to 3 g of prebiotics. Browning index, firmness, acidity remained stable throughout the 14 d compared to the control while applying prebiotic coatings resulted in an increase in soluble solids. Sensory and visual assessment indicated acceptable quality of apple wedges coated with prebiotics. HPLC analysis showed that levels of polyphenolic compounds were more stable in coated apple wedges (without prebiotic inclusions) than in uncoated control apples. No difference was found between O(2) and CO(2) headspace concentration of coated and uncoated samples. Significant differences (P < 0.001) were found for headspace volatile production between the samples. Most coated samples showed lower volatile production in the headspace than uncoated samples.     

苹果酒中酚酸、黄烷-3-醇的检测

以小国光(Ralls)和富士(Fuji)及其所酿制的新鲜苹果酒为试验材料,采用反相高效液相色谱法测定分析苹果原汁、发酵中酒样和苹果成品酒中11种酚酸、5种黄烷-3-醇的含量。结果表明:苹果和苹果酒中存在4种酚酸(原儿茶酸、绿原酸、咖啡酸、对-香豆酸)、2种黄烷-3-醇(儿茶素和表儿茶素);不同品种的苹果原汁和苹果成品酒中酚类物质的含量都存在显著差异。其中,小国光苹果和小国光苹果酒中的酚类物质总含量较高;对于每个品种,绿原酸都是最主要的酚酸类物质,含量最高的黄烷-3-醇类物质都是表儿茶素。随着发酵过程的进行,苹果酒中酚类物质的含量有不同程度的增加。其增加趋势为S型曲线,即先平缓再较快再平缓。     

Detection of Pesticide (Chlorpyrifos) Residues on Fruit Peels Through Spectra of Volatiles by FTIR

The fast measurement of pesticide residues on fruits peels is crucial, for it is harmful for both human health and environment. In this study, we used apples and chlorpyrifos as the research materials and analyzed the volatiles from apples via its infrared spectra. As the low concentration of the volatiles, multi-reflecting mirrors were used to enhance the sensitivity of the spectroscopy system. From the experiment, two obvious spectral characteristics from chlorpyrifos, 990–2830 and 1259–1227 cm^?1, has been observed. By analyzing the infrared spectra of the volatiles released from chlorpyrifos with different dilution ratios on the apple peels, we found the spectral intensities increased with the chlorpyrifos concentrations. The results were further analyzed using chemometrics, it is demonstrated that there are obvious spectral differences among the apples sprayed with 1:20, 1:100, and 1:1000 chlorpyrifos and clean apples. The above four groups of the samples can be classified using principal component analysis (PCA). This study demonstrated that gas-phase long-path infrared spectroscopy is an effective method to detect the pesticide residues on fruits peels, with the advantages of no sample treatment and fast. To the best of our knowledge, this is the first study to detect pesticide residues on fresh and untreated apples using infrared spectroscopy via its volatiles.     

Factors influencing the development of aroma in apple peels

The rate and extent of apple volatile production were several times greater in peels than in flesh or whole apples. Volatile production in apples after peeling increased rapidly at 22°c, reached a maximum in 1–2 days and then gradually declined. Harvest maturity, variety, cold storage history, room temperature ripening and storage temperature of peels greatly affected the rate and extent of volatile production; the optimum peel temperature appeared to be 20–30°c. The greatest increases in volatile components from peels were due to the production of esters, primarily ethyl butyrate, butyl acetate, ethyl 2 methylbutyrate and 2-methylbutyl acetate. Controlled atmosphere storage appeared to arrest the ability of peels to produce the usual components. Under certain conditions, the components associated with apple aroma increased 10- to 30-fold in peels held at room temperature for 1–2 days.     

Phenolic composition and free radical scavenging activity of different apple varieties in relation to the cultivar,tissue type and storage

The aim of this research was to evaluate the influence of genotype, tissue type and cold storage on the bioactive compounds content and on the antiradical activity (AA) of different apple cultivars (Golden cl. B, Fuji cl. Kiku8, Braeburn cl. Hillwell). The content of analysed phyto-compounds depended on the clone, on the part of fruit, and to a minor extent, on the storage. For EC₅₀ data, the cultivar represented the main source of variation and the interaction with the type of tissue, was significant. The AA of apples, measured by means of the DPPH test, was highly correlated to the flavan-3-ols content, which represents a good predictor of the apple antiradical power. The new Braeburn’s clone, the Hillwell, had the worst AA related to a minor phyto-chemical content. Also, its phenolic content was dramatically reduced after cold storage (flesh: −50%; peels: −20%; p < 0.05). Obtained results underlined the key role of the genotype on the content of the nutraceutical power of apples, which is important to improve their quality and consumption benefits, suggesting to the breeders to pay more attention to the potential healthy compounds in the development of new hybrids.     

苹果中多酚类物质HPLC检测方法的建立

以小国光苹果为试材,建立苹果中多酚类物质的测定方法。通过对色谱条件的摸索和优化,确定以反相C18柱为固定相,以2mmol/L磷酸缓冲液和甲醇为流动相梯度洗脱分离中性酚,以80%甲醇-20%水为流动相分离酸性酚,建立苹果多酚类物质HPLC测定方法;根据食用习惯将苹果果实分为果皮、果核、果肉3个部分,用乙酸乙酯提取干粉中的酚类物质,在pH2.0条件下分离提取酸性酚,在pH7.0下分离提取中性酚,分析小国光苹果不同部位的多酚类物质含量。结果显示:各物质分离效果较好;经方法学验证,各物质线性关系良好,回收率在86.6%～101.8%之间,精密度、稳定性、重复性RSD均小于10%;苹果中不同部位的多酚类物质的种类和含量各不相同。该方法的灵敏度高,准确性和重现性良好。     

A New Analytical Method to Volatile Compounds in Cider Apples: Application to Evaluate the Starch Index

Headspace solid-phase microextraction coupled to Fast gas chromatography (GC) with flame ionization detector and with quadrupole mass spectrometric detector was employed to study the volatile compounds in Asturian cider apples. The best conditions used for volatile analysis of apple were: sample equilibration at 25 °C for 60 min, followed by polydimethylsiloxane-divinylbenzene fiber exposure to the headspace above the sample for 5 min, and finally thermal desorption of the adsorbed substances in the injector port for GC analysis. The use of Fast gas chromatography allowed the separation of 24 compounds in less than 8 min, reducing the analysis time in 80% compared with conventional gas chromatography. The aromatic profile of 26 crushed apple samples included in Designation of Origin Cider from Asturias was analyzed. The chemometric technique named multiple linear regression allowed us to establish a relationship between apple volatile compounds and the starch index. The results obtained are consistent with the known apple ripening model.     

Infectivity of Cryptosporidium parvum oocysts after storage of experimentally contaminated apples

Irrigation water and washing water have been inferred to be associated with contamination of fresh fruits and vegetables with pathogenic microorganisms infectious for humans. The objective of the present study was to determine whether apples experimentally contaminated with Cryptosporidium oocysts represent a food safety concern. Laser scanning confocal microscopy revealed no morphological changes in Cryptosporidium parvum oocysts attached to apples after 6 weeks of cold storage, suggesting that oocysts might remain viable and possibly infectious during prolonged storage. Mice were fed apple peels from experimentally contaminated apples to determine whether oocysts had remained infectious on apples stored for 4 weeks. All mice developed cryptosporidiosis. To evaluate the strength of oocyst attachment to apples, washing methods that have been reported to be helpful for recovery of oocysts from various foodstuffs were evaluated, except that the intensity of washing was increased in the present study. None of the tested washing methods succeeded in completely removing oocysts from the apple peel. The most efficient removal (37.5%) was achieved by rigorous manual washing in water with a detergent and by agitation in an orbital shaker with Tris-sodium dodecyl sulfate buffer. Glycine and phosphate-buffered saline buffers had no effect on oocyst removal. Scanning electron microscopy revealed that some oocysts were attached in deep natural crevices in the apple exocarp and others were attached to the smooth surface of the peel. Some oocysts were closely associated with what appeared to be an amorphous substance with which they might have been attached to the apple surface.     

1-Methylcyclopropene postharvest treatment and their effect on apple quality during long-term storage time

The aim of this study was to evaluate the effect of the postharvest treatment by 1-methylcyclopropene (1-MCP) and storage time on the apple physicochemically quality. The effects of apple storage during 6 months on basic parameters such as dry weight, total soluble solids and titratable acidity, composition of phenolics, antioxidant activity and sensory evaluation were studied to evaluate the potential applicability of long-time stored apples for consumption and processing. Long-time storage of apples resulted in a higher dry matter but decreases total soluble solids and titratable acidity in all examined cultivars (cv.) of apples. The total phenolics determined by HPLC in fresh apples ranged from 1,243 mg in ‘Idared’ cv. to 1,435 mg/kg in ‘Shampion’ cv. During storage, the decrease of polyphenolic content has been observed, in ‘Shampion’ cv., it was higher than in ‘Idared’ cv. Similar effects were observed for antioxidant activity. Comparing quality of fruits just after harvest, it was found that cultivar affects most of the investigated sensory attributes with the exception of ripe apple smell, crispness, crunchiness and the overall texture score. In general, ‘Shampion’ cv. apples got higher ranks for sweetness, taste and the overall quality, whereas ‘Idared’ cv. were perceived as sourer, which is in arrangement with instrumental measurements. The results of presented study demonstrate that apples after storage, especially ‘Shampion’ cv., can be a valuable sensory attributes for food product and consumption. This study indicates that the use of 1-MCP treatment in long-term storage of apples is promising for maintaining the eating quality of fruits, however, in some extent may affect their antioxidant compounds content.     

Nachweis von Fruchtsaftmanipulationen bei Apfel- und Birnensaft

Zusammenfassung Es wird eine Methode für den Nachweis von Apfelzusatz in Birnensaft und von Birnenzusatz in Apfelsaft beschrieben. Das Flavonoid-muster wurde in Apfel- und Birnensorten und in Handelssäften qualitativ und quantitativ mit HPLC unter-sucht. Als charakteristische Apfelinhaltsstoffe eignen sich die Chalcone Phloretinglucosid und -xyloglucosid als Indikatoren eines Apfelzusatzes in Birnensaft (Nachweisgrenze 7 ng). Isorhamnetinglucosid konnte nur in Birnen, nicht aber in Äpfeln nachgewiesen werden (Nachweisgrenze 10 ng). Diese Verbindung wird deshalb als Indikator eines Birnenzusatzes zu Apfelsaft verwendet. Der Extrakt bzw. Saft wird an einer Polyamidsäule gereinigt. Im eingeengten Methanoleluat werden die Flavonoide mit der HPLC im Gradientenbetrieb (Acetonitril/1%ige Essigsäure) auf RP-18 Phase mit UV-Detection bestimmt. Zur Absicherung der Befunde wird das UV-Spektrum der Leitsubstanzen mit einem Dioden-Array-Detektor aufgenommen.

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Detection of adulteration of apple juice and pear juice

Summary A method has been developed to detect the adulteration of pear juice with apples and apple juice with pears. In different varieties of apples and pears and in several commercial juices the flavonoids were examined by HPLC with respect to their quality and quantity. The chalcones phloretin glucoside and phloretin xyloglucoside are typical compounds found in apples (detection limit 7 ng). They are suitable indicators for detecting adulteration of pear juice with apples. Isohamnetin glucoside cannot be detected in apples (detection limit 10 ng), but can be used to detect pears in apple juice. The extract or juice was purified with the aid of a polyamide column. The evaporated eluate of methanol was analysed by HPLC (gradient: acetonitrile/1% acetic acid). An RP-18 column and a UV-detector were used. Additionally, the UV spectra of the compounds indicating an adulteration were recorded by a diode array detector.

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Herrn Prof. Dr. K. Herrmann zum 70. Geburtstag gewidmet     

Effect of high-pressure processing on flavonoids,hydroxycinnamic acids,dihydrochalcones and antioxidant activity of apple ‘Golden Delicious’ from different geographical origin

The influence of high-pressure processing (HPP) (400, 500 and 600 MPa at 35 °C for 5 min) on different classes of phenolic compounds and antioxidant activity (AA) of ‘Golden Delicious’ apple from two different growing regions, northeastern of Spain (lowland climate) (S-apples) and north of Italy (mid-mountain climate) (I-apples) was investigated. Total hydroxycinnamic acids, total dihydrochalcones and total flavan-3-ols content were higher in S-apple (untreated and HPP-treated) than in I-apples and total flavonols content was higher in I-apples. HPP affected phenolic compounds and AA depending on the apple geographical origin. 400 MPa/35 °C/5 min increased total flavonols (30%) and maintained total phenolic compounds determined by HPLC (TP-HPLC) in S-apples. The higher increase of TP-HPLC (54%) was achieved when I-apple was treated at 600 MPa. Untreated and HPP-treated I-apples displayed higher AA than S-apples. HPP (400 and 600 MPa) increased AA in I-apple. Positive correlations were found between TP-HPLC and AA (TP-FC, DPPH^·, ABTS^·+ and FRAP) in both Italian and Spanish apples.Industrial relevanceThe apples of cultivar ‘Golden Delicious’ are one of the most consumed fruits in the UE. High-pressure processing (HPP) of these fruits acquires great importance to obtain ingredients and apple functional foods highly demanded by consumers. For this, it is necessary to know the process variables and plant material that favor greater extraction of phenolic compounds and antioxidant activity characteristics. This paper provides useful results to help fruit processor to select the appropriate HPP conditions and the geographical origin of ‘Golden Delicious’ apple to obtain apple-based products with high content on different classes of phenolic compounds with beneficial health effects.     

NONDESTRUCTIVE CHARACTERIZATION OF APPLE FIRMNESS BY QUANTITATION OF LASER SCATTER

A laser technique for characterization of apple firmness was developed on the assumption that laser scatter was affected by firmness. Saturated area ratios and relative areas, defined as laser scatter parameters, were measured for Tsugaru and Fuji apples and the effects of laser wavelengths and optical power levels on the parameters were investigated. When a laser beam with longer wavelength, 632.8 nm, and lower power, 1.7 mW was used, the laser parameters showed significant correlation with firmness parameters. Varietal difference had significant effects on the correlation between different compressive properties and laser scatter parameters. For Tsugaru apple, bio-yield force and rupture force showed high correlation with laser features, while for Fuji apple, bio-yield deformation and rupture deformation were more significant than the bio-yield and rupture forces. The initial slope and secant slope showed high correlation with laser features regardless of cultivar.