Czapek Casein 50% Glucose (CZC50G): a new medium for the identification of foodborne Chrysosporium spp.

A new medium Czapek Casein 50% Glucose agar (CZC50G) has been developed, on which the four foodborne Chrysosporium spp., C. xerophilum, C. inops, C. farinicola and C. fastidium can be distinguished by differences in growth rates and colony morphology. Chrysosporium xerophilum and C. inops both produced dense white colonies, but C. xerophilum grew faster than C. inops , 22 mm in 14 d compared to 9–12 mm in 14 d at 25°C. Some isolates produced a yellow or red reverse due to the reaction of ferric ammonium citrate incorporated in the medium with a fungal metabolite. Chrysosporium farinicola and C. fastidium both grew poorly on this medium and produced sparse colonies: C. farinicola grew faster. Electron micrographs of arthroconidia with a cryo-scanning electron microscope showed thickening of the spore walls in C. inops but not in C. xerophilum . The aleurioconidia of C. farinicola and C. fastidium were different in shape. The differences in colony morphology and growth rate on CZC50G reflected these differences and demonstrated that these four species could be distinguished easily on CZC50G.     

Chrysosporium species, potential spoilage organisms of chocolate

Standard methods of analysing foods for the presence of moulds are inadequate for thedetection of genera such as Chrysosporium which do not grow at the high wateractivities of most mycological media. The use of malt, yeast, 50% glucose agar (MY50G) insealed containers as an enrichment medium allowed time for germination and growth ofheat-stressed spores. Three Chrysosporium spp., C. xerophilum Pitt, C. inops (Carmichael) and C. farinicola (Burnside) Skou, were isolated fromcommercial chocolate bars with a water activity (a _w ) of approximately0·28. Chrysosporium inops was isolated from commercial milk crumb and anew Chrysosporium sp. was isolated from Ghanaian cocoa beans. In chocolates madeby coating MY50G agar (a_w = 0·89) with chocolate (a_w = 0·27) containing C. inops arthroconidia, two types of deterioration were seenafter storage. The first was fat bloom due to recrystallization of the cocoa butter on the outer andinner chocolate surface. The second was growth of C. inops which occurred on theinside chocolate surface adjacent to the MY50G agar filling and on the outside surface afterholding at 92% equilibrium relative humidity (erh) for 12 d. There was some evidence that C. inops could grow on the outside of chocolates held at 5·7% erh after 4months' storage at 25 °C. The appearance of the white fungal growth was not unlikefat bloom to the naked eye but was clearly different with the electron microscope.     

Mycoflora of camel and goat hairs from Al-Arish,Egypt

The frequency of occurrence of fungi in 120 hair samples of camel and goat from four different localities of Al-Arish governorate was determined.Twenty-six genera and 54 species were collected from the two substrates and the most common genera were Chrysosporium and Aspergillus, followed by Cladosporium. From the preceding genera Chrysosporium keratinophilum, C. tropicum, C. indicum, Aspergillus flavus, A. niger and Cladosporium cladosporioides. Also, other keratinophilic fungi were isolated such as C. luteum, C. pannorum, C. parvum, C. dermatitidis, C. inops, Arthroderma tuberculatum, Histoplasma capsulatum and Myceliophthora vellerea.     

The effect of age on the thermal resistance of arthroconidia from Chrysosporium inops

J. L. KINDERLERER. 1996. Food-borne members of the genus Chrysosporium have been isolated relatively infrequently. The heat resistance of arthroconidia of the xerophilic fungus, Chrysosporium inops Carmichael, was determined in 0.1% peptone at 66C. The survival curve was sigmoid in shape. The initial lag period was due to the chains of arthroconidia. Thermal inactivation occurred when one viable conidium was left per chain. The presence of chains of arthroconidia was confirmed with the cryo scanning electron microscope. The decimal reduction times were obtained from the regression line of the linear death phase for the heat-sensitive spores. The decimal reduction time (D₆₆) increased with increasing spore age. It was 1.67 min for 3-week-old spores, 1.95 min for 4-week-old spores and 5.49 min for 6-week-old spores. The older spores could recover from thermal death if they were given sufficient time. There was a significant increase in D₆₆ value for 6-week-old spores from 3.97 min to 5.49 when the counts were obtained after 14 d incubation (compared to counts after incubation for 10 d). This effect was not seen for the 3- and 4-week-old spores. There was a small population of heat-resistant spores. The initial population of arthroconidia was greater than log 7 cfu ml^-1. After heating for 1 h at 66C approximately log 2.2 cfu ml^-1 survived. These survivors represented approximately 0.001% of the original population.     

Influence of pectinase treatment on fruit spirits from apple mash, juice and pomace

The current investigation was conducted to determine the influence of pectinase treatment on fruit spirits produced from apple mash, juice, and pomace. Crispin apples were processed into apple mash, juice, and pomace in our pilot-plant, and fermented with a commercial Red Star wine yeast (Sachharomyces cerevisiae Davis 904). After fermentation, the samples of fermented apple mash, juice, and pomace were distilled, and the distillates were analyzed by HPLC with a Bio-Rad Aminex HPX 87H column and a refractive index detector. Methanol, ethanol, n-propanol, iso-butanol, and iso-amyl alcohol were identified as the major alcohols in all the apple spirits. Student's t-test results indicate that there are significant differences between the methanol concentrations of pectinase treated and non-pectinase treated apple spirits. Duncan's multiple range tests show significant differences in the concentrations of methanol of the fruit spirits made from apple mash, juice, and pomace. Apple pomace yielded significantly higher methanol concentrations than apple mash and juice. Pectinase treatment had little effect on the concentrations of n-propanol, iso-butanol, and iso-amyl alcohol. It is concluded that fruit spirits made from the pectinase treated mash, juice, and pomace of Crispin apples had methanol concentrations significantly above the United States FDA guidance of 0.35% by volume or 280 mg/100 mL of fruit brandy containing 40% ethanol.     

Effect of storage time and temperature on the survival of Clostridium botulinum spores in acid media.

Clostridium-botulinum type A and type B spores were stored in tomato juice (pH 4.2) and citric acid-phosphate buffer (pH 4.2) at 4, 22, and 32 degrees C for 180 days. The spore count was determined at different intervals over the 180-day storage period. There was no significant decrease in the number of type A spores in either the tomato juice or citric acid-phosphate buffer stored for 180 days at 4, 22, and 32 degrees C. The number of type B spores did not decrease when storage was at 4 degrees C, but there was an approximately 30% decrease in the number of spores after 180 days of storage at 22 and 32 degrees C.     

Effect of storage time and temperature on the survival of Clostridium botulinum spores in acid media.

Clostridium-botulinum type A and type B spores were stored in tomato juice (pH 4.2) and citric acid-phosphate buffer (pH 4.2) at 4, 22, and 32 degrees C for 180 days. The spore count was determined at different intervals over the 180-day storage period. There was no significant decrease in the number of type A spores in either the tomato juice or citric acid-phosphate buffer stored for 180 days at 4, 22, and 32 degrees C. The number of type B spores did not decrease when storage was at 4 degrees C, but there was an approximately 30% decrease in the number of spores after 180 days of storage at 22 and 32 degrees C.     

Storage of Resting Spores of the Gypsy Moth Fungal Pathogen, Entomophaga maimaiga

The fungal pathogen, Entomophaga maimaiga causes epizootics in populations of the important North American forest defoliator gypsy moth ( Lymantria dispar ). Increasing use of this fungus for biological control is dependent on our ability to produce and manipulate the long-lived overwintering resting spores (azygospores). E. maimaiga resting spores undergo obligate dormancy before germination so we investigated conditions required for survival during dormancy as well as the dynamics of subsequent germination. After formation in the field during summer, resting spores were stored under various moisture levels, temperatures, and with and without soil in the laboratory and field. The following spring, for samples maintained in the field, germination was greatest among resting spores stored in plastic bags containing either moistened paper towels or sterile soil. Resting spores did not require light during storage to subsequently germinate. In the laboratory, only resting spores maintained with either sterile or unsterilized soil at 4°C (but not at 20 or -20°C) germinated the following spring, but at a much lower percentage than most field treatments. To further investigate the effects of relative humidity (RH) during storage, field-collected resting spores were placed at a range of humidities at 4°C. After 9.5 months, resting spore germination was highest at 58% RH and no resting spores stored at 88 or 100% RH germinated. To evaluate the dynamics of infections initiated by resting spores after storage, gypsy moth larvae were exposed to soil containing resting spores that had been collected in the field and stored at 4°C for varying lengths of time. No differences in infection occurred among larvae exposed to fall-collected soil samples stored at 4oC over the winter, versus soil samples collected from the same location the following spring. Springcollected resting spores stored at 4°C did not go into secondary dormancy. At the time that cold storage of soil containing resting spores began in spring, infection among exposed larvae was initiated within a few days after bringing the soil to 15°C. This same pattern was also found for spring-collected resting spore-bearing soil that was assayed after cold storage for 2-7 months. However, after 31-32 months in cold storage, infections started 14-18 days after soil was brought to 15°C, indicating a delay in resting spore activity after prolonged cold storage.     

采后光照条件对白凤桃果实品质和挥发性香气物质形成的影响

研究了白凤桃果实贮藏过程中光照条件对果实成熟的影响。在7月12日(未熟期)和7月16日(硬熟期)采收果实,分别贮藏在光条件(白色荧光灯照明,果顶部光强为80μmol m~(-2)s~(-1))和暗条件中,室温均为25℃。硬熟期采收果实贮藏在光条件下,达到完熟期时,乙烯生成量较低。果肉的硬度在各个采收期,各种贮藏条件下均没有差别。光条件贮藏果实中花青苷含量较高。未熟期采收果实贮藏在光条件下时,可溶性固形物含量增加较多。光条件贮藏果实中天冬酰胺的下降比暗贮藏果实中更多。各时期采收的果实中,在光下贮藏时,果肉和果皮γ-癸内酯和γ-十二内酯的含量都明显增加。以上结果表明,白凤桃果实采收后在光下贮藏,可以明显改善果实的品质。     

Control of Postharvest Diseases of Sweet Cherry with Ethanol and Hot Water

Complete inhibition of the germination of spores of Penicillium expansum occurred after 10 s exposure to 40% ethanol or more at ambient temperature, while spores of Botrytis cinerea were completely inhibited by 30% ethanol or more. Mortality of the spores of P. expansum and B. cinerea in heated 10% ethanol was higher than in water at the same temperatures. Immersion of naturally inoculated fruit in 20, 30, 40, or 50% ethanol reduced the decay present after storage for 10 days at 20°C similarly and by approximately 60–85%. Immersion of fruit that had been inoculated with the spores of P. expansum and B. cinerea reduced decay by both pathogens after storage for 30 days at 0°C and 5 days at 20°C when 30% or higher concentrations of ethanol were used. The incidence of decay after immersion in water alone for 30 s at 24, 50, 55, or 60°C was 57.7, 44.7, 46.2, and 35.7%, respectively, while 10% ethanol at these temperatures the decay incidence to 52.2, 33.9, 32.8, or 14.7%, respectively. Water treatments at 50, 55, or 60°C alone were not effective against P. expansum, while their efficacies were significantly increased by the addition of 10% ethanol. The most effective treatment was immersion in 10% ethanol at 60°C. Ethanol treatments at 20, 30, 40, or 50% and water treatments at 55 or 60°C significantly reduced natural fungal populations on the surfaces of fruit in all of the experiments. Addition of 10% ethanol to water significantly increased the efficacy of water in reducing the fungal populations at elevated temperatures. None of these treatments caused surface injuries to the fruit or adversely affected stem colour.     

A reversed-phase HPLC method for measurement of 5-hydroxymethyl furfuraldehyde and furfuraldehyde in processed juices.

An HPLC method using a reversed-phase macroreticular PLRP-S column and phosphate buffer as eluent is described for the analysis of L-ascorbic acid degradation products, 5-hydroxymethyl furfuraldehyde and furfuraldehyde, in processed fruit juices. Measurement of the levels of 5-HMF and furfuraldehyde in citrus juices against time showed the presence of 5-HMF (0.45 mg l-1) even at zero time. An assessment on the effect of the additives on the formation of 5-HMF of reconstituted single-strength orange juice showed virtually the same results for all the samples stored at 4 degrees C and 20 degrees C, irrespective of the additive. For citrus juice samples which had been subjected to accelerated degradation, those that showed the highest decomposition of L-ascorbic acid, produced the highest level of 5-HMF. The presence of furfuraldehyde in any of the samples was not detected, probably due to the fact that furfuraldehyde was formed in such small amounts which are below the minimum detectability limit of the method (0.050 mg l-1).     

Alicyclobacillus Contamination in the Production Line of Kiwi Products in China

Alicyclobacillus are spoilage microbes of many juice products, but contamination of kiwi products by Alicyclobacillus is seldom reported. This study aims to investigate the whole production line of kiwi products in China to assess the potential risk of their contamination. A total of 401 samples from 18 commercial products, 1 processing plant and 16 raw material orchards were tested, and 76 samples were positive, from which 76 strains of microbes were isolated and identified as 4 species of Alicyclobacillus, including Alicyclobacillus acidoterrestris, Alicyclobacillus contaminans, Alicyclobacillus herbarius and Alicyclobacillus cycloheptanicus, and another 9 strains as 3 species of Bacillus by sequencing of their 16S rDNA. Through phylogenetic tree construction and RAPD-PCR amplification, it was found that there exist genotypic diversities to some extent among these isolates. Four test strains (each from one species of the 4 Alicyclobacillus species isolated in this study) could spoil pH adjusted kiwi fruit juice and some commercial kiwi fruit products with producing guaiacol (11–34 ppb).     

Efficacy of long-term coral tissue storage in ethanol for genotyping studies

With climate change threatening the future of coral reefs, there is an urgent need for effective coral tissue preservation and repositories from which DNA can be extracted. Most collections use 95 % ethanol as the storage medium, but its efficacy for long-term storage for short-fragment DNA use remains poorly documented. We conducted an accelerated DNA aging trial on three species of coral to ascertain whether ethanol-stored tissue and skeleton samples could yield fit-for-purpose DNA at time scales of 100+ yrs. We conclude that even using a crude DNA extraction technique, samples kept at 40 °C for 20 months yielded DNA of sufficient quality for Symbiodinium and coral host genotyping. If stored at ?20 °C, these samples are likely to still yield useable DNA after 100 yrs. Ethanol-stored samples compared favorably in terms of DNA quality, quantity and sample integrity with those stored in an analogue of the commercial storage buffer RNAlater ^®.     

Celery leaf spot: sources of inoculum

The relative importance of infected celery seed, infected leaf debris in the soil, and infected wild celery, in the incidence of Septoria leaf spot in cultivated celery has been investigated. Infection can be caused when the sole source of inoculum is viable spores on the seed surface; such spores are considered to be the main cause of disease outbreaks. Of all the seed samples examined, 93% were infected by Septoria spp. In untreated seed samples, 40% carried viable spores which survived for up to 15 months on seed stored in the laboratory, and for longer periods on seed stored at -20d? C. However, ageing of seed is not recommended as a commercial control measure. The fungus was not found in seed embryos or endosperms but mycelium was present in pericarps and testas. Unconfirmed evidence suggests that in favourable circumstances new spores might be produced in old seed-borne pycnidia.     

超低氧处理对贮藏期间甜橙果实挥发性物质含量的影响

本文主要探讨甜橙［(Citrus sinensis (L.) Osb.］果实在短期超低氧贮藏条件下,果皮和果汁中乙醇和乙醛等挥发性物质的含量,以及它们在不同贮藏温度和货架存放期间的变化和对果实风味品质的影响。在普通冷藏条件下,随着贮藏期的延长,甜橙果实中挥发性物质的含量虽呈上升趋势,但超低氧贮藏更明显地刺激果实中乙醇和乙醛含量的迅速增加。甜橙果实在0.3% O2的超低氧条件下贮藏30 d,果皮中乙醇的含量为519.8　μg/kg,果汁中达1547.1　μg/kg,比普通冷藏的果实高83倍,乙醛的含量较对照果实高6～7倍。低氧处理对果实可溶性固形物,可滴定酸和pH值的影响不大。甜橙果汁中乙醇含量在1000 μg/kg以下时果实的风味品质仍在正常范围之内。结果表明对甜橙果实进行短期（<20 d）的超低氧处理是可行的。     

Inhibition of Bacillus licheniformis LMG 19409 from ropy cider by enterocin AS-48

AIMS: To determine the activity of enterocin AS-48 against ropy-forming Bacillus licheniformis from cider. METHODS AND RESULTS: Enterocin AS-48 was tested on B. licheniformis LMG 19409 from ropy cider in MRS-G broth, fresh-made apple juice and in two commercial apple ciders (A and B). Bacillus licheniformis was rapidly inactivated in MRS-G by 0.5 microg ml(-1)AS-48 and in fresh-made apple juice by 3 microg ml(-1). Concentration-dependent inactivation of this bacterium in two commercial apple ciders (A and B) stored at 4, 15 and 30 degrees C for 15 days was also demonstrated. Counts from heat-activated endospores in cider A plus AS-48 decreased very slowly. Application of combined treatments of heat (95 degrees C) and enterocin AS-48 reduced the time required to achieved complete inactivation of intact spores in cider A to 4 min for 6 microg ml(-1) and to 1 min for 12 microg ml(-1). D and z values also decreased as the bacteriocin concentration increased. CONCLUSION: Enterocin AS-48 can inhibit ropy-forming B. licheniformis in apple cider and increase the heat sensitivity of spores. SIGNIFICANCE AND IMPACT OF THE STUDY: Results from this study support the potential use of enterocin AS-48 to control B. licheniformis in apple cider.     

Acid tolerance of Shigella sonnei and Shigella flexneri

AIMS: Determination of the behaviour of Shigella sonnei and Sh. flexneri under acid conditions. METHODS AND RESULTS: The growth and survival of Shigella spp. (9 isolates) in acidified Brain Heart Infusion (BHI) (pH 5.0-3.25 with pH intervals of 0.25) was determined after 6, 24 and 30 h incubation at 37 degrees C. Subsequently, survival of shigellae was studied in apple juice and tomato juice stored at 7 degrees C and 22 degrees C for up to 14 days and in strawberries and a fresh fruit salad, kept at 4 degrees C for 4 and 48 h. CONCLUSIONS: The minimum pH for growth in acidified BHI for Sh. flexneri and Sh. sonnei was, respectively, pH 4.75 and pH 4.50. Survival in fruit juices and fresh fruits depended upon their pH, the type of strain and the incubation temperature. Shigella spp. Survived for up to 14 days in tomato juice and apple juice stored at 7 degrees C. The shortest survival time (2-8 d) was observed in apple juice at 22 degrees C. Sh. sonnei but not Sh. flexneri was recovered after 48 h from strawberries and fruit salad kept at 4 degrees C. SIGNIFICANCE AND IMPACT OF THE STUDY: Acid foods, especially if kept at refrigeration temperatures, support survival of Shigella spp. and may cause Shigella food poisoning.     

Effects of temperature and desiccation on ex situ conservation of nongreen fern spores

? Premise of the study: Fern spores are unicellular and haploid, making them a potential model system to study factors that regulate lifespan and mechanisms of aging. Aging rates of nongreen spores were measured to compare longevity characteristics among diverse fern species and test for orthodox response to storage temperature and moisture. ? Methods: Aging of spores from 10 fern species was quantified by changes in germination and growth parameters. Storage temperature ranged from ambient room to -196°C (liquid nitrogen); spores were dried to ambient relative humidity (RH) or using silica gel. ? Key results: Survival of spores varied under ambient storage conditions, with one species dying within a year and two species having greater than 50% survival after 3 years. Few changes in germination or growth were observed in spores stored at either -80°C or -196°C over the same 3-yr study period. Spores stored at -25°C aged anomalously quickly, especially those dried to ambient RH or subjected to repeated freeze-thaw cycles. ? Conclusions: Spore longevity is comparable to orthodox seed longevity under ambient storage conditions, with wide variation among species and shelflife extended by drying or cooling. However, faster aging during freezer storage may indicate a similar syndrome of damage experienced by seeds categorized as "intermediate". The damage is avoided by storage at -80°C or liquid nitrogen temperatures, making cryoconservation an effective and broadly applicable tool to extend fern spore longevity. The study demonstrates that spore banks are a feasible approach for ex situ conservation of this important plant group.     

Stability ofAlternaria toxins in fruit juices and wine

Alternaria alternata is a common fungal parasite on fruits and other plants and produces a number of mycotoxins, including alternariol (3,7,9-trihydroxy-1-methyl-6H-dibenzo [b,d]pyran-6-one), alternariol monomethyl ether (3,7-dihydroxy-9-methoxy-1-methyl-6H-dibenzo[b,d]pyran-6-one), and the mutagen altertoxin I {[1S-(1α,12aβ,12bα)] 1,2,11,12,12a, 12b-hexahydro-1,4,9,12a-tetrahydroxy-3,10-perylenedione}. Alternariol and alternariol monomethyl ether have previously been detected in some samples of fruit beverages. Stability studies of these toxins as well as altertoxin I added to fruit juices and wine (10–100 ng/mL) were carried out. To include altertoxin I in the analysis, cleanup with a polymer-based Varian Abselut solid phase extraction column was used, as recoveries from C-18 columns were low. The stabilities of alternariol and alternariol monomethyl ether in a low acid apple juice containing no declared vitamin C were compared with those in the same juice containing added vitamin C (60 mg/175 ml); there were no apparent losses at room temperature over 20 days or at 80°C after 20 min. in either juice. Altertoxin I was moderately stable in pH 3 buffer (75% remaining after a two week period). Furthermore, altertoxin I was stable or moderately stable in three brands of apple juice tested over 1–27 day periods and in a sample of red grape juice over 7 days. It is concluded that altertoxin I is sufficiently stable to be found in fruit juices and should be included in methods for alternariol and alternariol monomethyl ether.     

Isolation and Identification of Psychrophilic Species of Clostridium from Milk

Four of 48 raw milk samples contained catalase-negative, gram-positive, motile, sporeforming, rod-shaped bacteria that grew optimally at 22 to 30 C and slowly at low temperatures. Isolates from two samples had a minimal growth temperature of 4 C, were anaerobic, and had characteristics similar to Clostridium hastiforme; those from the other two samples had a minimal growth temperature of 0 +/- 1 C, were anaerobic, aerotolerant, and had characteristics similar to C. carnis. Specific growth rates, doubling times, ability to grow in pasteurized milk stored in commercial cartons, and resistance of spores to heating were determined for one strain of C. hastiforme.