Intraspecific variability of growth and patulin production of 79 Penicillium expansum isolates at two temperatures

Penicillium expansum is the main species responsible for patulin production in apples and pears. Generally, fruit is stored at suboptimal conditions for mould growth and this situation could influence on the intra-species variability in both capability for growth and mycotoxin production. The aim of this research was to assess the impact of suboptimal environmental conditions on the intra-specific variability of P. expansum growth and patulin production using seventy nine isolates of this mould. Petri dishes with Apple Concentrate Agar Medium (ACAM) were inoculated centrally and incubated at two temperatures, one near optimal (20 °C) and the other representative of suboptimal cold storage (1 °C). For each condition, 10 Petri dishes were inoculated, and colony growth and patulin production was measured over time. The Kruskal-Wallis test revealed significant differences among growth rate (μ) and lag phase (λ) within the seventy nine assayed isolates. Coefficients of variation revealed a wider dispersion of μ (mm/day) and λ (days) at 1 °C compared with 20 °C. There were significant differences (p < 0.05) among patulin levels (ng/mm²) for the different conditions, values being lower at the lower temperature. Coefficients of variation revealed a wider dispersion of mycotoxin production at 1 °C. In order to address the strain variability in growth initiation and prove the well-established notion of reducing patulin production in foods by preventing fungal growth, a greater number of strains should be included.     

Sensitivity of Penicillium expansum field isolates to tebuconazole, iprodione, fludioxonil and cyprodinil and characterization of fitness parameters and patulin production

A total of 236 Penicillium expansum field isolates from decayed apple fruit collected from packinghouses and processing industries located in the region of Imathia, Northern Greece were tested for their sensitivity to tebuconazole, fludioxonil, iprodione and cyprodinil. Preliminary fungitoxicity tests on the response of the isolates showed several phenotypes, distinguished according to their sensitivity to fungicides tested. The EC₅₀ values ranged from 0.64 to 5 (average = 0.98) μg/ml for iprodione, 0.9 to 7.3 (average = 2.66) μg/ml for tebuconazole, 0.008 to 1.28 (average = 0.55) μg/ml for cyprodinil and from 0.013 to 0.47 (average = 0.08) μg/ml for fludioxonil. A bimodal distribution of the EC₅₀ values of isolates with distinct sensitive and resistant populations to fludioxonil and tebuconazole were observed. In the case of cyprodinil, a much broader, hundred-fold, range of sensitivity was found, probably indicating that some isolates are relatively insensitive to cyprodinil compared to the most sensitive ones. Isolates exhibiting simultaneously reduced sensitivity to tebuconazole and fludioxonil or tebuconazole and iprodione or to tebuconazole and cyprodinil were also observed at low frequencies. A small portion of the population (7.5%) showed multiple resistance to tebuconazole, fludioxonil and iprodione. Study of fitness determining parameters showed that the resistance to tebuconazole, fludioxonil and iprodione had a significant adverse effect on mycelial growth rate and pathogenicity. Contrary to that, these fitness parameters were not affected in the isolates showing reduced sensitivity to cyprodinil. Analysis of patulin production on YES-agar growth medium and on artificially inoculated apple fruit showed that all isolates were mycotoxigenic. Most of the cyprodinil-insensitive isolates produced patulin at concentrations similar to or relatively higher (up to 1.5-fold on growth medium) than the sensitive ones. In contrast, a significant reduction (up to 98% of multiple resistant isolates) in patulin production was observed in all other phenotypes, indicating an adverse effect of fitness penalties on the mycotoxigenic ability of resistant isolates. The above mentioned data clearly show a considerable risk for the selection of P. expansum isolates resistant to fludioxonil, iprodione, tebuconazole and cyprodinil. The potential risk of increased patulin contamination of apples and their byproducts by the appearance and predominance of highly mycotoxigenic isolates of P. expansum resistant to the anilinopyrimidines is discussed.     

Determination of patulin in apple and quince products by GC–MS using C5–7 patulin as internal standard

A reliable gas chromatographic mass spectrometric method has been validated for the determination of trace levels (<10 μgL⁻¹) of patulin in apple products and quince jam. The method was based on extraction of patulin with ethyl acetate-hexane, alkalinisation and silylation with N,O-bis-trimethylsilyltrifluoroacetamide with 1% of trimethylchloro-silane. The accurate determination of patulin was achieved by employing commercial ¹³C_5–7 patulin labelled as an internal standard, which allowed compensating target analyte losses and enhancement or suppression matrix effects. Limits of detection and quantification of method using real samples were 0.4 and 1.6 μgkg⁻¹, respectively. Recoveries of patulin from samples spiked at 8–50 μgkg⁻¹ levels ranged between 71% and 89%. The repeatability of measurements (expressed as relative standard deviation) was lower than 16%. The method was successfully applied to the determination of patulin in apple fruit and apple products including juice, cider and baby food, and also in quince fruit and quince jam. A new PCR system for the detection of Penicillium expansum in samples containing highly degraded DNA was developed which permitted the detection of the mould in 2/3 of the samples containing patulin, including juices and jams.     

Some factors influencing patulin production by Penicillium expansum in pome fruits

BACKGROUND: The objective of our study was to examine the effects of Penicillium expansum on patulin production in relation to isolates, species and cultivar type, incidence and severity of decay. In addition, patulin production at different incubation times and its diffusion were also investigated. These factors were evaluated in pome fruits inoculated with P. expansum and kept at 20 °C for short periods of time. RESULTS: The ability of five P. expansum isolates to grow and produce patulin in inoculated Golden Delicious apples varied among the strains from below the limit of quantification to 662 µg kg^?1. Variety and species of pome fruits influenced patulin production. P. expansum isolate PE97.IT produced a higher patulin content in apples than in pears. The highest patulin production was 386 µg kg^?1 in Golden Delicious. No blue mould symptom appeared in pears inoculated with P. expansum and no patulin was detected after 3 days at 20 °C. However, patulin increased with incubation time after 6 and 8 days. No patulin was detected in healthy pear tissue but it was high in the decayed area. CONCLUSION: Since patulin production is associated primarily with infected rotten tissue, patulin control is possible by using healthy fruits, sorting damaged and rotten fruits before processing. Copyright © 2010 Society of Chemical Industry     

Biocontrol of postharvest gray and blue mold decay of apples with Rhodotorula mucilaginosa and possible mechanisms of action

The efficacy of Rhodotorula mucilaginosa against postharvest gray mold, blue mold and natural decay development of apples and the possible mechanisms involved were investigated. The decay incidence and lesion diameter of gray mold and blue mold of apples treated by R. mucilaginosa were significantly reduced compared with the control fruits, and the higher concentration of R. mucilaginosa, the better the efficacy of the biocontrol. R. mucilaginosa also significantly reduced the natural decay development of apples following storage at 20 °C for 35 days or at 4 °C for 45 days followed by 20 °C for 15 days. Germination and survival of spores of Penicillium expansum and Botrytis cinerea were markedly inhibited by R. mucilaginosa in an in vitro test. Rapid colonization of the yeast in apple wounds was observed whether stored at 20 °C or 4 °C. In apples, the activities of peroxidase (POD) and polyphenoloxidase (PPO) were significantly induced and lipid peroxidation (malondialdehyde (MDA) content) was highly inhibited by R. mucilaginosa treatment compared with those of the control fruits. All these results indicated that R. mucilaginosa has great potential for development of commercial formulations to control postharvest pathogens on fruits. Its modes of action were based on competition for space and nutrients with pathogens, inducement of activities of defense-related enzymes such as POD, PPO and inhibition of lipid peroxidation (MDA content) of apples, so as to enhance the resistance and delay the ripening and senescence of apples.     

Browning characteristics of fresh-cut ‘Tsugaru’ apples as affected by pre-slicing storage atmospheres

The change in browning characteristics of the slices processed from ‘Tsugaru’ apples stored at 0 °C for 5 months under controlled atmosphere (CA, 1 kPa O₂ + 1 kPa CO₂, 3 kPa O₂ + 3 kPa CO₂) or air has been investigated for 5 days at 20 °C. Respiration and ethylene production of the slices from apples stored in CA were retarded. Electrolyte leakage and browning index were lower in the slices from apples stored under CA than air. Vitamin C and phenolic contents in the slices from apples stored under air were maintained at higher level compared to the slices from apples stored under CA. Polyphenol oxidase activity in the slices was not affected by pre-slicing storage atmospheres. Therefore, the atmospheres of pre-slicing storage affected browning development in fresh-cut products of ‘Tsugaru’ apples and browning was found to be correlated with the levels of electrolyte leakage and phenolic compounds.     

Saccharomyces cerevisiae YE‐7 reduces the risk of apple blue mold disease by inhibiting the fungal incidence and patulin biosynthesis

The yeast strain, Saccharomyces cerevisiae YE‐7, was tested to control the apple blue mold disease caused by Penicillium expansum and the accumulation of patulin mycotoxin. Compared with control, pre‐treatment of pathogen‐infected apples with YE‐7 significantly reduced the incidence of blue mold diseases and patulin accumulation in rotten apple tissue by 48% and 42.6%, respectively. Interestingly, late treatment of pathogen‐infected apples with YE‐7 did not decrease patulin accumulation in the rotten tissue compared with pre‐treatment or simultaneous‐treatment. Independently, patulin amount and gene expression of isoepoxydon dehydrogenase were also measured. YE‐7 pre‐treated apples showed 75% and four times reduction in patulin accumulation and IDH gene expression, respectively. The results indicated that YE‐7 directly affected patulin biosynthesis and did not affect accumulated patulin. On the other hand, cold storage enhanced the effect of YE‐7 on apple blue mold disease incidence.

Practical applications

Postharvest blue mold decay caused by Penicillium expansum was important postharvest disease of apples. In addition, under favorable conditions, P. expansum can cause severe losses in apple fruits due to the production of patulin. In this study, a strain of S. cerevisiae (YE‐7) was assessed for its efficacy not only in controlling apple blue mold diseases, but also in reducing patulin accumulation in fruit tissue. The research will give a practical way to control the decay in a bio‐control way instead of the chemical.     

Flavonoid constituents and their contribution to antioxidant activity in cultivars and hybrids of rabbiteye blueberry (Vaccinium ashei Reade)

Fruit from 42 blueberry (Vaccinium spp.) cultivars, including 36 rabbiteye cultivars (Vaccinium ashei Reade), three V. ashei hybrid derivatives, and three northern highbush (Vaccinium corymbosum L.) standards were evaluated for antioxidant capacity, individual flavonoid content, and the contribution of each identified phenolic compound to total antioxidant activity. Considerable variation was found in flavonoid content, antioxidant activity, and their contribution to total antioxidant activity among cultivars. Among 42 blueberry cultivars, the rabbiteye ‘Early May’ contained the highest amount of chlorogenic acid, myricetin 3-arabinoside, quercetin derivatives, and delphinidin-, cyanidin-, petunidin-, and malvidin-basis anthocyanins. ‘Early May’ cultivar also had the highest antioxidant activity (88.2 μmol TE/g fw). ‘Owen’, ‘Bluegem’, ‘Clara’, Climax’, and ‘Centurion’ were among the other rabbiteye cultivars that also had high levels of flavonoids and antioxidant activities. In contrast, the pink-fruited V. ashei hybrid, ‘Pink Lemonade’, had the lowest content of flavonoids and lowest antioxidant activity. The mean flavonoid content and antioxidant activity of rabbiteye cultivars was higher than those among northern highbush and V. ashei hybrids. The antioxidant activity of V. ashei hybrid derivatives was derived mainly from chlorogenic acid, myricetin, and quercetin, which contributed 62.5% of total antioxidant activity, whereas anthocyanins (malvidin, petunidin, delphinidin, and cyanidin) were the main contributors to the antioxidant activity of rabbiteye cultivars (76.2%) and northern highbush standards (76.8%). Blueberry cultivars identified to have high phenolic content and high antioxidant activity could be used as parents for future blueberry breeding programmes to develop new blueberry cultivars with higher antioxidant activity and further improve human health.     

Analysis of grape polyamines from Grapevine leafroll associated viruses (GLRaV-2 and -3) infected vines

This is the first report comparing the free polyamine content of ‘Pinot noir’ grapes from vines infected with Grapevine leafroll associated viruses (GLRaV)-2 or -3, with samples taken from healthy vines. Berries were collected from three different rootstock/scion combinations, and all samples were from commercial vineyards in Oregon. Three free polyamines (putrescine, cadaverine, and spermidine) were found in all ‘Pinot noir’ grapes analysed in this study. Berries from healthy Vitis riparia rootstock/‘Pinot noir’ clone 114 were significantly higher in putrescine (28.6 μmol/l) and total polyamines (41.9 μmol/l), compared to their GLRaV-3 infected samples (20.7 and 33.0 μmol/l, respectively). Vine virus status did not alter total or individual polyamines in berries from the other two rootstock/scion combinations (unknown rootstock/‘Chardonnay’ interstock/‘Pinot noir’ scion [clone unknown] and self-rooted/‘Pinot noir’ clone Pommard). Levels of putrescine, spermidine, and total polyamines varied between berries taken from the healthy vines of the three different rootstock/scion combinations.     

Yeast biocontrol of fungal spoilage of pears stored at low temperature

To reduce the use of fungicides, biological control with yeasts has been proposed in postharvest pears. Most studies of antagonists selection have been carried out at room temperature. However, in regions like North Patagonia where fruits are stored at − 1/0 °C during 5-7 months the selection of potential antagonist agents must be carried out at low temperature. In this study, 75 yeast cultures were isolated from healthy pears from two Patagonian cold-storage packinghouses. Aureobasidium pullulans, Cryptococcus albidus, Cryptococcus difluens, Pichia membranifaciens, Pichia philogaea, Rhodotorula mucilaginosa and Saccharomyces cerevisiae yeast species were identified. Additionally, 13 indigenous isolates of Penicillium expansum and 10 isolates of Botrytis cinerea were obtained from diseased pears, characterized by aggressiveness and tested for sensitivity to postharvest fungicides. The yeasts were pre-selected for their ability to grow at low temperature. In a first biocontrol assay using the most aggressive and the most sensitive isolate of each pathogen, two epiphytic isolates of A. pullulans and R. mucilaginosa were the most promising isolates to be used as biocontrol agents. They reduced the decay incidence by P. expansum to 33% and the lesion diameter in 88% after 60 days of incubation in cold. Foreign commercial yeast used as a reference in assays, only reduced 30% of lesion diameter in the same conditions. Yeasts were not able to reduce the incidence of B. cinerea decay. The control activity of the best two yeasts was compared with the control caused by the fungicides in a second bioassay, obtaining higher levels of protection against P. expansum by the yeasts. These two regional yeasts isolates could be promising tools for the future development of commercial products for biological control.     

Study on the role of patulin on pathogenicity and virulence of Penicillium expansum

Although the antibacterial activity and toxicity to humans and animals of the mycotoxin patulin are well known, its role in the postharvest decay of apples by Penicillium expansum has never been investigated. In the present study the gene disruption technique was used to alter the sequence of 6-methyl-salicylic acid synthase, an enzyme involved in the first committed step of patulin biosynthesis. Thirty-nine mutants were obtained, however only two of them (M5 and M21) passed the sub-cultural and molecular confirmation tests. They proved to produce 33-41% less patulin than their wild-type (WT) strain, although no difference in the growth and morphology of the colony was observed. Moreover, the mutants showed a significantly reduced pathogenicity and virulence on artificially inoculated apples. In particular, a 33-34% and 47-54% reduction of disease incidence and severity were recorded for M5 and M21, respectively. As confirmation, when the biomass of the mutants was quantified in vivo by Real-time PCR, a significant difference was recorded as compared to the WT and even between mutants. Moreover, when patulin production potential of mutants was restored by exogenous application of the mycotoxin, their ability to cause the disease was not significantly different from that of WT. Finally, mutants showed an increased susceptibility to the application of the antioxidant quercetin, their pathogenicity and virulence being significantly reduced at only 1/100 of the concentration needed for the WT. Based on these findings, patulin seems to have a role in the development of blue mold decay on apples.     

Effects of apple and pear varieties and pH on patulin accumulation by Penicillium expansum

BACKGROUND: Accumulation of patulin in apples and pears and subsequently in their by‐products is caused mostly by Penicillium expansum which causes blue mould. Fruit pH and other parameters are sometimes characteristic of a certain variety and thus the use of particular varieties might affect patulin content in the final products. The aim of this study was to evaluate the influence of fruit variety and pH on patulin accumulation. Patulin accumulation in both apple and pear juices at different pH and also in different apple varieties (Golden, Gala and Fuji) and pear varieties (Blanquilla and Conference) was assessed. RESULTS: The pH of juices significantly influenced patulin accumulation, especially in apple juice in which the highest amounts of patulin were detected at pH 3.5. In fruits, the pH values of the substrate were determinant only under cold storage. Thus, Golden apples, which presented a lower pH, accumulated more patulin at 1 °C. However, this trend was not observed at other temperatures in which varieties with higher amounts of organic acids (Golden and Fuji apples) accumulated most patulin. In the pear varieties, significant differences in pH did not lead to significant differences in patulin accumulation. CONCLUSION: Although pH influences patulin accumulation, other factors such as organic acid content may play an important role. Concerning the apple and pear varieties we studied, it seems that rather than variety, other parameters like pH or acidic content may be more important. These parameters vary significantly depending on the degree of ripeness of the fruit. Gala apple, which is used in Spanish juice production, was the only variety that accumulated dramatically higher amounts of patulin. Copyright © 2008 Society of Chemical Industry     

In vitro binding of bile acids by bananas,peaches, pineapple,grapes, pears,apricots and nectarines

The in vitro binding of bile acids by bananas (Musa × paradisiaca), peaches (Prunus persica), pineapple (Ananus comosus), grapes (Vitis spp.), pears (Pyrus communis), apricots (Prunus armeniaca) and nectarines (Prunus persica, nectarina) was determined using a mixture of bile acids secreted in human bile at a duodenal physiological pH of 6.3. Six treatments and two blank incubations were conducted, testing various fresh fruits on an equal dry matter basis. Considering cholestyramine (bile acid binding, cholesterol lowering drug) as 100% bound, the relative in vitro bile acid binding percentages on dry matter (DM), total dietary fibre and total polysaccharides basis were 2–9%, 15–101% and 10–101%, respectively. Bile acid binding, on a DM basis, for bananas was significantly (P ? 0.05) higher and that for nectarines significantly lower than those for peaches, pineapple, grapes, pears and apricots. The bile acid bindings for peaches and pineapple were similar and significantly higher than those for grapes, pears and apricots. Binding values for grapes and pears were significantly higher than apricots. These results point to the relative health promoting potential of bananas > peaches = pineapple > grapes = pears > apricots > nectarines, as indicated by their bile acid binding on a DM basis. The variability in bile acid binding between the fruits tested maybe related to their phytonutrients, antioxidants, polyphenols, flavonoids (anthocyanins, flavonols, and proanthocyanidins), structure, hydrophobicity of undigested fractions, anionic or cationic nature of the metabolites produced during digestion or their interaction with active binding sites. Animal studies are planned to validate in vitro bile acid binding of fruits, observed herein, to their healthful potential, atherosclerosis amelioration and cancer prevention.     

New vitamin E isomers (gamma-tocomonoenol and alpha-tocomonoenol) in seeds,roasted seeds and roasted seed oil from the Slovenian pumpkin variety ‘Slovenska golica’

The Štajerska region in north-eastern Slovenia and the Styria region in southern Austria have a long tradition of growing pumpkins (Cucurbita pepo L.) as an oil crop. GC-MS determination of the free and esterified minor compounds in oil of roasted pumpkin seeds from the Slovenian C. pepo L. variety ‘Slovenska golica’ revealed the presence of two previously unreported compounds: alpha-tocomonoenol and gamma-tocomonoenol. Using the GC-MS data, reference samples (Crude Palm Oil) and tocopherol and tocotrienol standards it was possible to assign and quantify alpha-tocomonoenol (17.6 ± 0.6 μg/g) and gamma-tocomonoenol (118.7 ± 1.0 μg/g) compounds in roasted ‘S. golica’ seed oil using HPLC. The concentrations of alpha-tocopherol and gamma-tocopherol were 77.9 ± 1.9 μg/g and 586.0 ± 4.6 μg/g, respectively. Surprisingly the gamma-tocotrienol concentration found was only 6.9 ± 0.2 μg/g. Analysis of the seeds from which the oil was pressed showed the initial gamma-tocotrienol amount was even lower (1.6 ± 0.1 and 2.2 ± 0.1 μg/g in the ground and roasted seeds, respectively) than in the roasted seed oil.     

Control of <Emphasis Type="Italic">Penicillium expansum</Emphasis> and patulin accumulation on apples by quercetin and umbelliferone

The effectiveness of seven phenolic compounds (esculetin, ferulic acid, quercetin, resveratrol, scopoletin, scoparone and umbelliferone) in controlling Penicillium expansum growth and patulin accumulation was evaluated by both in vitro and in vivo studies. The in vitro screening showed that quercetin and umbelliferone were the most effective compounds in controlling Penicillium growth and patulin accumulation, respectively. Quercetin and umbelliferone, resulted to be effective also in the in vivo screening, were further tested (alone and in combination) on Granny Smith and Golden Delicious apples. The efficacy in controlling Penicillium growth was better expressed on Golden Delicious than on Granny Smith apples, with quercetin providing a better control of both incidence of decay and disease severity as compared to umbelliferone. Both compounds exerted a considerable control of patulin accumulation on the two apple cultivars. Quercetin and umbelliferone can be considered as natural compounds to be used as alternative strategy to chemical fungicides in postharvest control of P. expansum infections on apples.     

Survival of Penicillium expansum and Patulin Production on Stored Apples after Wash Treatments

ABSTRACT: Penicillium expansum is a widespread fungus found on apples that causes fruit decay and may lead to production of a toxic secondary metabolite, patulin. This study was undertaken to evaluate the effectiveness of several chemical sanitizers against P. expansum NRRL 2304 and to establish sanitizing wash treatments that would inhibit P. expansum growth and subsequent patulin production on Empire apples destined for cider. Wash treatments included 200 ppm NaOCl, 1% StorOx®, 0.5% potassium sorbate, 300 ppm SO₂, and 0% to 5% acetic acid. Spores of P. expansum or inoculated apple slices were dipped in sanitizing wash solution for 5 min, and mold growth and patulin production was monitored on subsequent storage. It was found that 0.5% potassium sorbate and 300 ppm SO₂ did not affect mold survival or patulin production; 1% StorOx® was effective against mold spores in solution (4 log Most Probable Number destruction of spores), but there was no significant reduction in spore count when the same solution was used to sanitize mold‐inoculated apple discs. Washing with 200 ppm NaOCl delayed growth of P. expansum on inoculated apple discs but failed to completely inhibit patulin production. Acetic acid solution (2% to 5%) was the most efficient chemical against P. expansum. A wash treatment with ≥2% acetic acid for more than 1 min is recommended to completely inhibit growth of P. expansum and subsequent patulin production on apples destined for cider.     

Effect of damaged starch on acrylamide formation in whole wheat flour based Indian traditional staples, chapattis and pooris

Variation in acrylamide content of two Indian traditional products, chapatti and poori was observed with respect to the damaged starch content in whole wheat flour of different wheat varieties from which these products were prepared. Wheat cultivar ‘lokwan’ was milled by altering mill aperture, feed rate and moisture content to obtain whole wheat flour with damaged starch contents ranging from 6.23% to 28.12%. Acrylamide content of the chapatti and pooris prepared from such flours ranged from 12.5 to 65.5 μg/kg in chapatti, and 25.5 to 130.5 μg/kg in pooris. Impact of several additives showed 10 μmol/g flour citric acid, and 100 μmol/g flour calcium chloride to reduce acrylamide in pooris by approximately 54% and 72%, respectively, without altering the sensory analysis of the products.     

Chitin content of cultivated mushrooms Agaricus bisporus, Pleurotus ostreatus and Lentinula edodes

The chitin contents of pileus and stipes of fruit bodies of Agaricus bisporus, Pleurotus ostreatus and Lentinula edodes (shii take) were determined and compared. The fruit bodies of different, common varieties of the cultivated mushroom species were taken from Hungarian and German large-scale farming. The analytical procedure was carried out on the powder of cleaned, dried and milled pileus and stipes. The pileus of A. bisporus variety ‘K-23’ showed a significant decrease (p < 0.05) during the cultivation’s flushes (breaks), 1–3, while the chitin level of stipes seemed to be constant. The other analysed A. bisporus varieties (var. ‘158’, ‘K-7’, ‘Sylvan A-15’, ‘Sylvan 608’, and Le Lion C-9) had practically the same chitin levels. This indicates that the chitin content is a stable characteristic of the species and there are no significant differences between the different varieties. The chitin levels of pileus and stipes were not significantly different (for A. bisporus, 6.68 and 7.25) but showed significant differences for P. ostreatus (p < 0.05) and L. edodes (p < 0.001). In the case of the latter two species, the pileus had the higher and the stipe the lower chitin content. The presented data confirm that a mushroom saprotrophic (A. bisporus) had higher chitin level than had the wood-rotting ones (P. ostreatus, L. edodes).     

Interactions between dietary fibre-rich preparations and glycoconjugated bile acids in vitro

Binding in small intestine and excretion of bile acids constitute a major hypocholesterolemic pathway. Interactions between different types of commercial and laboratory-made dietary fibres and glycoconjugated bile acids were investigated in vitro at pH 5.0 and 6.5. The interactions were greater at the lower pH and with dihydroxy-bile acids. Digested cereal products (barley, oat, rye and wheat flour; oat bran), alcohol-insoluble substances from apples, strawberries, rowan berries, carrots, white cabbage, red beets and sugar beet pulp, as well as arabinoxylan, bound 1.21–1.77 μmol bile acids/100 mg of preparation at pH 5.0. Novelose bound approximately 0.65 μmol bile acids/100 mg. Carob fibre had the highest binding capacity (1.83–1.96 μmol bile acids/100 mg) whereas cellulose had no effect. Besides the source and chemical composition, the bile acid binding correlated especially well with the presence of three-dimensional cell wall structures of the tested preparations but less well with the proportions of soluble and insoluble dietary fibre.