Mycotoxins in botanicals and dried fruits: A review

Botanicals are used in many countries for medicinal and general health-promoting purposes. Numerous natural occurrences of mycotoxins in botanicals and dried fruits have been reported. Aflatoxins or ochratoxin A (OTA) have been found in botanicals such as ginseng, ginger, liquorice, turmeric, and kava-kava in the USA, Spain, Argentina, India, and some other countries, while fumonisins have been found in medicinal wild plants in South Africa and in herbal tea and medicinal plants in Turkey. Zearalenone was identified in ginseng root. Dried fruits can be contaminated with aflatoxins, OTA, kojic acid, and, occasionally, with patulin or zearalenone. One main area of concern is aflatoxins in dried figs; bright greenish yellow fluorescence under ultraviolet light is associated with aflatoxin contamination. OTA in dried vine fruits (raisins, sultanas, and currants) is another concern. There are also reports of aflatoxins in raisins and OTA in dried figs, apricots, dried plums (prunes), dates, and quince. Maximum permitted levels in the European Union include 4 µg kg^-1 for total aflatoxins in dried fruit intended for direct consumption and 10 µg kg^-1 for OTA in dried vine fruit. This review discusses the occurrence of mycotoxins in botanicals and dried fruits and analytical issues such as sampling, sample preparation, and methods for analysis. Fungal contamination of these products, the influence of sorting, storage, and processing, and prevention are also considered.     

Water Sorption Isotherms of Raisins, Currants, Figs, Prunes and Apricots

Moisture sorption isotherms of dried fruits [Sultana raisins, Corinthian (black) currants, figs, prunes, and apricots] were determined at 15, 30, 45, and 60°C, using the standard static gravimetric method developed by the European Cooperation Project COST 90. Experimental curves showed an inverse effect of temperature at high moisture content due to high sugar content of dried fruits. The hysteresis between adsorption and desorption was verified experimentally. The GAB equation was used to predict experimental data for water activity range 0–0.95.     

Ochratoxin A in dried vine fruit: method development and survey

A method is described for the determination of concentrations of the mycotoxin ochratoxin A in dried vine fruits (currants, raisins and sultanas) using acidic methanolic extraction,immunoaffinity chromatography clean-up and HPLC determination. The limit of detection was estimated as 0.2mug/kg, and recoveries of 63-77% were achieved at 5mug/kg. HPLC-mass spectrometric confirmation of the identity of ochratoxin was obtained. Ochratoxin A and aflatoxins were determined in 60 samples of retail dried vine fruits purchased in the United Kingdom. Ochratoxin A was found in excess of 0.2mug/kg in 19 of 20 currant, 17 of 20 sultana and 17 of 20 raisin samples examined, an overall incidence of 88% . The maximum level found was 53.6mug/kg. No aflatoxin was found in any sample analysed, using a method with a detection limit of 0.2mug/kg for each of aflatoxin B1, B2, G1 and G2.     

Ochratoxin A concentrations in Greek domestic wines and dried vine fruits.

A survey for the presence of ochratoxin A (OTA) was conducted from 1995 to 1999 on 268 locally produced commercial wines, and on 81 samples of domestic dried vine fruits (currants and sultanas) collected between 1998 and 2000 from sites of primary storage and processing. The OTA concentration in red dry wines (n = 104, median = 0.09 microgram l(-1)) was not significantly different from that for white (n = 118, median = 0.06 microgram l(-1)) and rosé (n = 20, median = 0.08 microgram l(-1)) wines. Eighteen samples of dessert wines (sweet, semi-sweet, semi-dry) and eight samples of retsina wine showed larger OTA concentrations with medians of 0.33 and 0.27 microgram l(-1), respectively. Our data indicate that the geographic region of origin influences OTA contamination for the red dry wines. In fact, a trend of increasing OTA contamination was observed for red wines from northern to southern Greece. Regarding the OTA levels in dried vine fruits, sultanas (n = 27, median = 0.6 microgram kg(-1)) were less contaminated than currants (n = 54, median = 1.3 microgram kg(-1)). Also, sultanas produced in 2000 and currants produced in 1999 showed the lowest incidence of OTA contamination, with medians of 0.3 and 0.9 microgram kg(-1), respectively.     

Dried fruits: phytochemicals and their fate during in vitro digestion

Mediterranean dried fruits that are cultivated and produced in Greece; that is, Corinthian currants, figs, prunes, cherries, apricots and peaches were evaluated in terms of total polar phenols, individual simple phenolics, anthocyanins and antioxidant capacity in vitro. The potential release of dried fruit polar phenols among the different fractions of an in vitro digestion model was also determined. Total polar phenol, flavanol, flavone/flavonol content and antioxidant capacity was in the range 86–551 mg GAE/100g, 0.2–57 mg CE/100g, 9–71 mg RE/100g and 6–47 mg AAE/100g, respectively. A 12–82% release of total phenolics was observed post-mastication, which further increased post-gastric digestion. The same trend was also followed in the case of total flavanols and flavones/flavonols. Total polar phenols and flavones/flavonols were found to enter the simulated epithelial cell wall. Simple polar phenolics and anthocyanins were identified and quantified in all dried fruit extracts and in some of the digestion fractions.     

Incidence of toxigenic fungi and ochratoxin A in dried fruits sold in Brazil

A total of 117 dried fruit samples (black sultanas, white sultanas, dates, dried plums, dried figs and apricots) from different origins were analysed both for toxigenic fungi and for the presence of ochratoxin A. Amongst the fungi found, Aspergillus niger was predominant, with 406 isolates, of which 15% were ochratoxin A producers. They were followed by A. ochraceus, with 15 isolates and 87% ochratoxigenics, and A. carbonarius, with only five isolates of which 60% were ochratoxin A producers. The average infection rates for A. niger in black sultanas, plums, figs, dates and white sultanas were 22.0, 8.0, 4.0, 1.5 and 0.5%, respectively. The apricot samples were not contaminated by any fungi or ochratoxin A. Black sultana and dried figs contained the highest contamination with ochratoxin A, with 33 and 26.3% of the samples containing more than 5 µg kg^-1 respectively, while all the white sultanas, dates and plums had no sample that exceeded this limit.     

Heat of sorption of water in dried fruits

The heats of moisture adsorption and desorption in four dried fruits (sultana raisins, figs, prunes and apricots) were estimated from equilibrium sorption data, using the Clausius-Clapeyron equation in the temperature range 15–60°C. The net isosteric heat of sorption ( q st) decreased sharply from about 20 kJ mol⁻¹ water to near zero when the moisture content was increased from 0.05 to 0.50kg water kg⁻¹ dry matter. An exponential function was fitted to the experimental q st values at various moisture contents (X) , yielding two characteristic constants ( q 0 and X 0) for each fruit. Mean and total heats of sorption were calculated from the proposed empirical equation, which are useful for enthalpy prediction in food dehydration. The heats of desorption were higher than the heats of adsorption, indicating significant hysteresis in the sorption of water, especially in dried apricots.     

The phenolics of fruits. VI. The phenolics of currants, gooseberries and blueberries. Changes in phenolic acids and catechins during development of black currants (author's transl)]

Black, red, and white currants, gooseberries and cultivated blueberries contained only small amounts of catechins (total up to 30 mg per kg). Hydroxycinnamic acid derivatives, especially of caffeic and p-coumaric acid, occured mostly in higher concentrations. Furthermore, 4-hydroxygenzoic acid, protocatechuic acid and gallic acid were found after hydrolysis in currants and only protocatechuic acid in gooseberries in different levels. Salicyclic and gentisic acid were found in traces up to 2 mg per kg, occassionally vanillic acid, syringic acid or isoferulic acid. The concentrations of the examined phenolic acids in black currants related to the whole fruit (mg per fruit) increased, and related to fresh weight (mg per 1000 g) decreased during the growth of the fruits with the exception of protocatechuic acid, which appeared mostly in a last stage of the fruit.     

Volatile compounds in dried grapes

Volatile compounds were isolated from fresh Sultana grapes, from pale golden-brown sultanas prepared by drying on racks after treatment with a commercial dipping solution, and from dark brown sultanas dried in sunlight without dipping. The fresh grape yolatiles were found in the dipped sultanas but not in the undipped sultanas. Undipped sultanas contained considerable amounts of furfural and related compounds which were present in relatively small amounts in the dipped sultanas. It is suggested that these compounds, commonly associated with non-enzymic browning, may account for the malty, caramel-like aroma of the undipped sultanas and that their production is inhibited by the drying conditions given to the dipped sultanas. The dipped sultanas contained several carbonyl compounds which were not observed in the undipped sultanas.     

Phenolic profile,antioxidant and antiproliferative activity of black and red currants (Ribes spp.) from organic and conventional cultivation

The effect of cultivation system on phenolic profile, antioxidant capacity and antiproliferation activity in black and red currants was evaluated. Results from this study showed that Ribes fruit grown in organic system posses significantly higher total phenolics, especially anthocyanins, and antioxidant activity (DPPH and FRAP) than fruit grown in conventional system. Phenolic compounds were systematically identified and characterised by UPLC/MS Q‐TOF. The mean value of total polyphenol content in organically grown currants was similar but statistically higher compared with the conventional cultivation (11831.0 and 1543.0 mg/kg of d.m., respectively). The total values of the anthocyanins in ‘Ben Hope’, ‘Ben Alder’, ‘Titania’ and ‘Rondom’ from organic and conventional farms were 1044.5 vs. 1012.4; 1568.3 vs. 1260.4; 1417.2 vs. 1382.2; and 51.8 vs. 57.9 mg kg^?1 of d.m., respectively. Conventionally grown red currant had higher anthocyanin content than organically grown red currant (11.8%) but, however, organic fruits of red currant had 2.7 times higher content of oligomeric procyanidins than fruits coming from conventional cultivation. DPPH radical scavenging activity of currant varied from 28.29 to 37.08 mmol Trolox kg^?1 (mean 31.20) for organic fruits and from 12.67 to 31.18 mmol Trolox kg^?1 (mean 25.76) for conventional fruits. Moreover, all currants from organic cultivation possess higher ferric reducing capacity than conventionally grown fruits. It appeared that extracts of red Ribes cv. ‘Rondom’ coming from organic cultivation revealed stronger antiproliferative effect in comparison with conventional cultivation. However, a similar profile of activity was observed for ‘Ben Hope’, ‘Ben Alder’ and ‘Titania’ independently of the type of cultivation. These results indicate that the cultivation technique had important effect on the ranking of the cultivar systems.     

Perceptions of the health and convenience characteristics of fresh and dried fruits

Dried fruits consumption has not received much research attention, although these foods are associated with potential health benefits. Therefore, the aim of this study was to compare fresh fruits and dried fruits on measures of health, convenience and consumer feelings.An on-line questionnaire that measured consumers' perceptions of the health benefits and convenience characteristics and their feelings about the consumption of both fresh fruits (apples and plums) and dried fruits (e.g., raisins, dates, and apricots) was completed by 693 respondents (Polish, French, and Dutch).Generally, fresh fruits were perceived to be healthier and less convenient than dried fruits. Consumers also reported more positive feelings about the consumption of fresh fruits compared to dried fruits. The more that the respondents were willing to sacrifice for their health, the more positively they rated the health aspects of both fresh and dried fruits, as well as several perceptions of convenience of both fresh and dried fruits. Health preoccupation was unrelated to most of the convenience perceptions and was associated with lower scores on several perceptions of healthiness. Recommendations for the consumer-oriented development of dried fruits are also provided.     

Phenolic profile and antioxidant capacities of dried red currant from Serbia, extracted with different solvent

The antioxidant capacity and the phenolic content of 3 dried red currant samples from different geographical regions were studied. Three solvent systems were used (methanol, ethanol, and acetone) at the same concentrations (70%) and with 100% deionized water in presence 0.1% HCl. The antioxidant capacity of the dried fruit extracts was evaluated using DPPH radical scavenging assays. The efficiency of the solvents used to extract phenols from the 3 dried red currant samples varied considerably. The polyphenol content of the dried red currant samples was 3.26 to 12.68 mg gallic acid equivalent/g dried fruit. The high phenolic content was significantly correlated with the high antioxidant capacity. The following compounds were identified and quantified using HPLC with photodiode-array detection: 3 anthocyanins, 2 flavonols, 2 flavan-3-ols, and 3 hydroxycinnamic acids in all samples. Generally, red currant fruits are a rich source of phenolics, which shows an evident antioxidant capacity.     

Chemical Composition and Potential Health Effects of Prunes: A Functional Food?

Prunes are dried plums, fruits of Prunus domestica L., cultivated and propagated since ancient times. Most dried prunes are produced from cultivar d'Agen, especially in California and France, where the cultivar originated. After harvest, prune-making plums are dehydrated in hot air at 85 to 90 degrees C for 18 h, then further processed into prune juice, puree, or other prune products. This extensive literature review summarizes the current knowledge of chemical composition of prunes and their biological effects on human health. Because of their sweet flavor and well-known mild laxative effect, prunes are considered to be an epitome of functional foods, but the understanding of their mode of action is still unclear. Dried prunes contain approximately 6.1 g of dietary fiber per 100 g, while prune juice is devoid of fiber due to filtration before bottling. The laxative action of both prune and prune juice could be explained by their high sorbitol content (14.7 and 6.1 g/100 g, respectively). Prunes are good source of energy in the form of simple sugars, but do not mediate a rapid rise in blood sugar concentration, possibly because of high fiber, fructose, and sorbitol content. Prunes contain large amounts of phenolic compounds (184 mg/100 g), mainly as neochlorogenic and chlorogenic acids, which may aid in the laxative action and delay glucose absorption. Phenolic compounds in prunes had been found to inhibit human LDL oxidation in vitro, and thus might serve as preventive agents against chronic diseases, such as heart disease and cancer. Additionally, high potassium content of prunes (745 mg/100 g) might be beneficial for cardiovascular health. Dried prunes are an important source of boron, which is postulated to play a role in prevention of osteoporosis. A serving of prunes (100 g) fulfills the daily requirement for boron (2 to 3 mg). More research is needed to assess the levels of carotenoids and other phytochemicals present in prunes to ensure correct labeling and accuracy of food composition tables in order to support dietary recommendations or health claims.     

Aspergillus carbonarius as the main source of ochratoxin A contamination in dried vine fruits from the Spanish market

Ochratoxin A (OTA) can occur in a wide range of foods, but unexpectedly high concentrations have been detected in dried vine fruits of various origins. The European Union has recently established a maximum OTA limit of 10 microg/kg for these foodstuffs. In order to determine the likely origin of OTA, a mycological study of 50 dried fruit samples (currants, raisins, and sultanas) representative of the Spanish market was conducted. Fungal contamination was detected in 49 of 50 (98%) samples. Black aspergilli were isolated from all of the positive samples. Aspergillus niger var. niger was isolated from 98% of the samples, and Aspergillus carbonarius was found in 58% of the samples. One hundred sixty-eight A. niger var. niger isolates and 91 A. carbonarius isolates were screened for their ability to produce OTA. Eighty-eight (96.7%) A. carbonarius isolates and one (0.6%) A. niger var. niger isolate were found to be OTA producers. Black aspergilli were the dominant fungi. Among black aspergilli, A. carbonarius has shown a consistent ability to produce OTA and is the most probable source of this mycotoxin in these substrates.     

A vegetable oiling agent for dried fruits

The suitability of an exceptionally stable vegetable oil blend, Durkex 500, for coating sultanas (at a level of 0.5%) was examined over a storage period of 1 month at 25°C and of 16 weeks at 37°C. During the early stages of storage at 25°C, the flavour of sultanas, either uncoated or coated with food grade paraffin, was slightly superior to that of sultanas coated with Durkex 500, or with a 50:50 blend of it with paraffin. Flavours such as musty, cardboardy, stale, etc. were reported in the coated sultanas, while sharp and acidic flavours were described in the non-oiled control sultanas. After 8 months at 25°C the uncoated sultanas appeared dull and dried up, and started clumping. However, the average flavour score of all the samples of sultanas were not significantly different (at a 5% level) from the acceptable flavour score of 5 at the end of the 25°C storage tests. The accelerated storage test study on the sultanas at 37°C gave generally similar, but somewhat erratic results.
Induction period data at 100°C were found to correlate well with the organoleptic acceptance of Durkex 500 and its 50:50 blend with paraffin in the sultanas evaluated in this work. The results show that stable oils such as Durkex 500 are acceptable vegetable coating oils for dried fruits, enabling manufacturers to conform with the Food Additives and Contaminants Committee recommendation that reduced levels of mineral oil should be used in fruit coatings.     

甘肃省市售杏仁和扁桃仁及其制品中氰化物含量状况调查

目的 调查甘肃省内市场上常见的杏仁和扁桃仁及其制品中氰化物含量,为保障人群的健康和国家制定相关标准提供科学依据。方法 从甘肃省14个地市采集样品323份,采用气相色谱-顶空法测定氰化物含量,用秩和检验分析。结果 不同产品中氰化物含量范围为干果类0.098 0～720 mg/kg,固体饮料类0.015 1～151 mg/kg,液体饮料类0.015 1～7.15 mg/kg,糕点类0.184～5.88 mg/kg,糖果类0.083 2～5.11 mg/kg,腌渍类0.702～17.3 mg/kg;不同品种中氰化物含量范围为苦杏仁及其制品0.015 1～720 mg/kg,甜杏仁及其制品0.015 1～151 mg/kg,扁桃仁及其制品0.098 0～12.0 mg/kg;不同种类中氰化物含量范围为熟(干)甜杏仁0.482～20.9 mg/kg,生(干)甜杏仁1.05～151 mg/kg,鲜甜杏仁2.32～184 mg/kg,熟(干)苦杏仁359～597 mg/kg,生(干)苦杏仁359～720 mg/kg,鲜苦杏仁634～733 mg/kg。结论 氰化物在杏仁及其制品中普遍存在,尤其是鲜苦...     

促干剂对热风条件下西梅品质的影响

本研究以西梅为试材，通过自配促干剂（88%碳酸钾、8%乙醇、3%油酸乙酯、1%氢氧化钾）与市售促干剂（绿珠牌、伊兹木牌、新兴牌、翠绿牌促干剂）处理西梅，探究促干剂对果干失水率、果干产品质量、理化特征等的影响。结果表明，自配促干剂与市售促干剂相比，在果干脱水方面具有明显优势，相同条件下自配促干剂处理的果实失水最快，最高可达26.25%；此外，不同促干剂处理西梅后果实的可溶性固形物和可滴定酸含量均有明显增加，自配促干剂处理的效果优于翠绿促干剂；在质构特征方面，干制后的西梅硬度和咀嚼性均有增加，但是自配促干剂处理的西梅干硬度最小，为1034.62 g，弹性和咀嚼性居中，可以给消费者带来较佳的口感；利用自配促干剂处理的西梅干，抗坏血酸、总酚、总黄酮损失最小，分别为25.48 mg/100 g DW、358.54 mg GAE/g、3.61 mg/g；同时DPPH自由基、ABTS+自由基清除能力较高，分别为79.75%、66.79%。综上所述，自配促干剂可以加速西梅的脱水，同时对西梅干的品质具有一定的有保护作用，该研究成果将为西梅干的生产提供指导。     

Effect of deficit irrigation on apricot fruit quality at harvest and during storage

The effect of different irrigation strategies on the fruit quality at harvest and during storage at 1 °C of 'Búlida' apricots (Prunus armeniaca L.) was studied. Irrigation treatments consisted of a control irrigated at 100% of crop evapotranspiration (ETc) throughout the season, and two deficit irrigation treatments consisting of continuous irrigation at 50% of control, and regulated deficit irrigation (RDI) at 100% of ETc during the critical periods (second rapid fruit growth and early post‐harvest) and at 25% during the rest of the season. Fruits at harvest from both deficit irrigation treatments showed higher values of total soluble solids (TSS), titratable acidity and hue angle (h°) than control fruits, whereas their diameter, fresh weight, firmness and maturity index values were similar to those in the control. During the first 10 days of the 30‐day chilling storage period, higher TSS and h° values were found in deficit irrigated fruits, whilst the other parameters were similar for all treatments. Weight loss and fungal attacks (mainly Rhizopus sp. and Monilinia sp.) during a subsequent retail sale period of 4 days at 13 °C were the lowest in RDI. Deficit irrigation was demonstrated to be commercially advantageous for keeping fruit quality, saving considerable amounts of water. Copyright © 2007 Society of Chemical Industry     

Application of the GAB model to the moisture sorption isotherms for dried fruits

The moisture adsorption isotherms for dried raisins, figs, prunes, and apricots were determined at 15, 30, 45 and 60°C, using the gravimetric static equilibrium method. The applicability of the GAB (Guggenheim-Anderson-de Boer) model to the experimental results was found to depend on the regression method employed. So, using direct non-linear regression analysis, five constants of the GAB model were estimated which enables the equilibrium moisture content of each dried fruit in the temperature range 15–60°C to be predicted with reasonable accuracy. The indirect (successive) non-linear regression method is not recommended since the basic three constants of the GAB equation are interrelated.     

Chemical composition of currant seed extracts and their protective effect on human lymphocytes DNA

On the basis of LC/UV/MS analysis, 35 compounds from the extracts of seeds of black, red, and white currants (2 cultivars of each) were identified. Black currants cultivars contained protocatechuic acid and p-hydroxybenzoic acid, and traces of nitril containing phenolic acids. The presence of synapoyl glucoside was characteristic for cv. Malling Jewel. Sesquiterpenoid glycosides and carboxymethylindol glycosides were present mainly in white and red currant cultivars. Blackcurrant seeds contained higher amounts of flavonoids, especially rutin, isoquercetin, and taxifolin. The currant seed extracts were tested for in vitro protective effect on chromosome aberrations in peripheral human lymphocytes using cytochalasin-B blocked micronucleus (CBMN) assay. The frequency of MN was scored in binucleated cells, and the cultivars of black currants showed the best antioxidant potential. At a concentration of only 0.17 mg/mL, extract of the seed cv. Malling Jewel effected a decrease in the frequency of MN of 60% compared with control cell cultures. PRACTICAL APPLICATION: Our results provide evidence of protective effects of currant seed extracts and isolated pure compounds on cytogenetic damages in human lymphocytes. Thus, currant seed extracts could exert beneficial effects in quite a few diseases, for many of the biological actions have been attributed to their antioxidant properties.