Investigation on the toxicity of fungi from rootstock snacks

Chicken embryo bioassay was used to monitor the toxicity of extracts from rootstock snack samples during a 210-day storage period. Results show that the relative toxicity values which were initially very low increased significantly as from 120th day (when 32% mortality was recorded) up till the last day when 73% was obtained. Toxicity of extracts from axenic cultures of 12 fungal species isolated from the snack samples was also determined. The strains of Aspergillus chevalieri, Rhizopus nigricans and Rhizopus sp investigated were nontoxic. A. niger, A. flavus, A.fumigatus, Penicillium chrysogenum, A. parasiticus, P. citrinum, A. ochraceus, Fusarium monifilorme and A. candidus were found to be toxic in decreasing order of potency as recorded after 30 days of growth at room temperature on substrate of 0.90 water activity level. Trends in the moisture content levels, pH and the incidence of fungal growth on the snack samples were also studied. Results suggest that storage for a period not exceeding 90 days and maintenance of safe moisture level would control mould growth and the associated mycotoxins in the snack.     

The fate of aflatoxins during the production of “Ogiri”, a West African fermented melon seed condiment from artificially contaminated seeds

Twenty-six market samples and four laboratory-prepared samples of “ogiri” were screened for aflatoxin contamination. Aflatoxins were not detected in any of the samples. The fermented product (ogiri) was prepared with Aspergillus flavus contaminated melon seeds. Losses of 64.7% aflatoxin B₁ and 82.9% aflatoxin G₁ were observed at the end of the third day of fermentation of the ground melon seeds. The samples were completely detoxified at the fourth day of fermentation. Increase in pH of the mash from 6.2 to 7.2 was observed during fermentation.     

Mould contamination and the influence of water activity and temperature on mycotoxin production by two aspergilli in melon seed

Both the moisture levels and the incidence of mould contamination recorded for shelled water melon seed samples (22) obtained from 9 markets were generally higher as those recorded for the unshelled seed samples. 16 fungi, mostly toxigenic, were isolated from the surface-disinfected mouldy seeds. Of these isolates, 7, 3 and 2 species belonged to Aspergillus, Penicillum and Fusarium genera, respectively, while Botryodiplodia, Rhizopus, Sclerotium and Syncephalastrum had one respresentative each. Production of aflatoxins (B₁, B₂) by 5 toxigenic strains of Aspergillus flavus and of ochratoxin A by 4 toxigenic strains of A. ochraceus in melon seed at varying water activity (a_w) and temperature levels were investigated. Of the a_w levels (0.65, 0.70, 0.80, 0.90 and 0.98) provided, toxins were detected only at and above 0.80 with the peak production recorded at either 0.90 or 0.98 a_w level. Whereas aflatoxins were produced and detected under all the test temperatures (15, 20, 25, 30, 35, and 40 °C), the elaboration of ochratoxin A was detected only as from 25 to 40 °C. Optimum temperature for toxin production by all the strains of the two fungi used was 30 °C.     

PROCESSING AND ACCEPTABILITY OF FRIED CASSAVA BALLS ("AKARA-AKPU") SUPPLEMENTED WITH MELON AND SOYBEAN FLOURS

The processing and acceptability of fried cassava balls (“Akara‐akpu”) supplemented with melon and soybean flours were studied. Cassava flour, defatted soybean flour and cassava mash were produced. Some functional and chemical properties of the flours were determined. Akara‐akpu prepared from 100% cassava mash served as control; 100% cassava flour, 80% cassava flour + 20% defatted soybean and 70% cassava flour + 30% defatted melon flour were prepared. Akara‐akpu balls were subjected to chemical and physical analyses. Akara‐akpu prepared from composite flour blends had higher protein, fat, ash and energy value than Akara‐akpu from 100% cassava mash. The cyanide content and degree of starch gelatinization of Akara‐akpu prepared from 100% cassava mash (control) were higher than Akara‐akpu prepared from cassava mash plus composite flour blends. There was a significant difference (P ≤ 0.05) in weight and yield between Akara‐akpu prepared from 100% cassava mash (control) and cassava mash plus composite flour blends. There was no significant difference (P ≤ 0.05) in volume between Akara‐akpu made from control sample and those cassava plus composite flour blends.     

Spoilage moulds and aflatoxins from poultry feeds

Aflatoxin producing strains of Aspergillus flayus Link (IMI 280819) and A. oryzae (Ahlb.) Cohn (IMI 280831) were among the eleven spoilage moulds isolated from five types of poultry feeds. The recorded pH and moisture content values of the various feeds are conducive to mould deterioration. All the four principal aflatoxins (B₁, B₂, G₁, G₂) were detected in the analysed feeds though at toxicologically ‘safe’ levels for most farm animals. Significant quantities of aflatoxin B₁ were produced by the two fungal isolates in all the five classes of poultry feeds with A. flavus yielding the larger amounts. Optimum aflatoxin B₁ production and mycelial growth in chick mash infusion medium were recorded for both species at 30 and 35 °C, respectively and similarly on the 8th and 6th day respectively when cultures were incubated at 30 °C.     

Effects of sodium chloride and relative humidity on growth and sporulation of moulds isolated from cured fish

A total of 14 moulds were isolated from 84 samples of cured fish obtained from several processing centres and retail shops in Lagos, Ogun and Oyo States, Nigeria. Aspergillus niger, A.flavus and A. chevalieri were the most prevalent. With the exception of Basipetospora sp., slight inhibition of mycelial growth and/or sporulation was recorded when isolates were cultured in basal medium containing 5% sodium chloride. The extent of inhibition increased with increasing salt concentrations, and at 25% level all the species had their growth completely inhibited. When fish substrates inoculated with test fungi were kept inside 65% relative humidity (RH) chambers for 21 days, no detectable utilization of the substrates was recorded for any of the fungal species. Whereas only A. chevalieri and A. restrictus utilized the substrates when placed inside 70% RH chambers, all the test moulds recorded detectable utilization (though at varying extents) of same at 80% and 90% RH levels. The latter RH was the most conductive and under it A. niger, Penicillium sp. and the two isolated Scopulariopsis sp. brought about the greatest loss in weight of the substrates.     

PRODUCTION AND CHARACTERISTICS OF TRADITIONAL ALCOHOLIC BEVERAGE MADE WITH SWEET POTATO AS THE SACCHARIFYING AGENT

Efforts were made to reproduce the traditional Japanese alcoholic beverage, miki using cooked rice and mashed raw sweet potato tubers as the saccharifying agent. The resulting miki-like alcoholic beverage contained 5–6% ethanol (v/v); it had a pleasant aroma but a sour taste with faint bitterness. With increased amounts of raw sweet potato added to the initial mash, the concentrations of higher alcohols, esters and bitter compounds in the miki increased. Oligosaccharides, including maltotetraose and maltopentaose, were detected in the miki made with higher concentrations of raw sweet potato mash. Miki, a previously uncharacterized, traditional, Japanese alcoholic beverage was therefore produced without the enzymic activities of germinating seeds, such as malt, or a fungal starter, such as koji .     

Assessment of the microbiological safety of edible dried seeds from retail premises in the United Kingdom with a focus on Salmonella spp.

Sesame seed products have recently been associated with a number of Salmonella outbreaks in the UK and elsewhere. Aside from sesame seeds, there is little published information on the prevalence of Salmonella spp. in edible seeds. A study of 3735 samples of retail edible dried seeds in the UK was therefore carried out between October 2007 and March 2008 to assess their microbiological safety in relation to Salmonella contamination and levels of Escherichia coli, an indicator of faecal contamination. Overall, Salmonella was detected in 23 samples (0.6%), of which over half (57%) were sesame seeds. Other seeds contaminated with Salmonella were linseed (1 sample), sunflower (1 sample), alfalfa (1 sample), melon (4 samples) and mixed seeds (3 samples). E. coli was detected in 9% of samples, with 1.5% containing unsatisfactory levels (≥10²/g). These included melon, pumpkin, sesame, hemp, poppy, linseed, sunflower and mixed seeds. The UK retailers affected by the detection of Salmonella in their products recalled the contaminated batches, and Food Standards Agency food alerts were issued to advise against the consumption of affected seed products. This study highlights the importance of good hygiene practices and effective decontamination procedures during the production of these products.     

Breaking of structural dormancy in seeds of Tetrapleura tetraptera by Aspergillus niger

Aspergillus niger (strain UUF9202) significantly reduced the dormancy period and boosted aggregate germination percentage (AGP) in seeds of Tetrapleura tetraptera. A net reduction in mean germination time (MGT) to 12 days and an increase from 0 to 42% AGP were obtained in 32 days. The optimal spore inoculum of the fungus was 8.5 × 10≥10 ml^?1 per 100 seeds in 96 h pregermination incubation. The potential of some physical factors in combination with this fungal concentration in enhancing AGP was evaluated. The treatments were as follows: (i) hot water scarification at 30°C, 50°C, 80°C and 100°C plus A niger; and (ii) nicking by decoating at either the micropylar or chalazal ends plus A niger. Micropylar scarification plus A niger gave the highest AGP (94%) followed by chalazal scarification plus A niger (86%) and hot water dip at 80°C + A niger (82%). The control seeds which were soaked in presterilised (by autoclaving at 121°C for 15 min) A niger spore suspension at 30°C gave zero germination.     

Fungal isolates and metabolites in locally processed rice from five agro-ecological zones of Nigeria

This study reports the distribution of fungal isolates and fungal metabolites that naturally contaminate locally processed rice from five agro-ecological zones of Nigeria. The fungal species were isolated by the dilution plate technique and identified by appropriate diagnostics, while metabolites were determined by a liquid chromatographic tandem mass spectrometric method. Aspergillus and Penicillium species were the predominant isolates found in the rice samples while Fusarium spp. were not isolated. The mean fungal count differed significantly (p < 0.05) across the zones and ranged from 9.98 × 10² cfu g^?1 in the Southern Guinea Savannah to 96.97 × 10² cfu g^?1 in the Derived Savannah. For 16 fungal metabolites, selected from 63 positively identified fungal metabolites based on their concentration and spread across the zones, an occurrence map was constructed. The Northern Guinea Savannah recorded the highest contamination of fungal metabolites while the Sudan Savannah zone recorded the least.     

Aspergillus species from section Flavi isolated from soil at planting and harvest time in peanut‐growing regions of Argentina

Aspergillus species from section Flavi were isolated from soil samples in three peanut‐growing regions of Córdoba Province, Argentina. The samples were collected during the planting and harvest periods. Both total fungal population and Aspergillus species from section Flavi showed no significant differences between planting and harvest time in two of the regions evaluated. Only in one region were there significant differences in cfu g^?1 of total fungal population and Aspergillus species from section Flavi. A flavus was the dominant species isolated in all three localities during the planting and harvest periods. There were significant differences (p < 0.05) in the ratio of toxigenic and atoxigenic strains dependent on the period and the region evaluated. In one region, higher frequencies of toxigenic A flavus and A parasiticus in soil were found and a high contamination level of aflatoxins was detected in peanut seeds. Copyright © 2003 Society of Chemical Industry     

Effects of oilseed substrates (ground nyjer and flax seeds) on the growth and Ochratoxin A production by Aspergillus carbonarius

Aspergillus carbonarius is one of the major Ochratoxin A (OTA) producing fungus. Nyjer and flax seeds are important oilseeds that are used for both human and animal consumption, but they are highly susceptible to fungal growth and mycotoxin contamination. The objectives of this study were to determine the growth and OTA production by A. carbonarius on ground nyjer and flax seeds with water activity levels ranging from 0.82 to 0.98 a_w at three incubation temperatures (20, 30, 37°C). It was found that A. carbonarius was not able to grow on the two types of oilseeds with 0.82 or 0.86 a_w. Also, the fungus was not able to grow on flax seeds with high water activity (0.98 a_w). The OTA was only detected on flax seed samples with 0.94 a_w at 20°C. On nyjer seeds, the highest concentration of OTA (271 μg/kg) was detected from samples with 0.98 a_w incubated at 20°C for 5 days, while on flax seeds the highest OTA (146 μg/kg) was found on the seed samples with 0.94 a_w incubated at 20°C for 15 days. Linear regression models also indicated that 0.98 a_w was optimal for both fungal growth and OTA production on nyjer seeds. Overall, ground nyjer seed is better than flax seed to support growth and OTA production by A. carbonarius.     

Novel use of Acacia senegal (Super Gum™) and Anogeisus latifolia (Gatifolia SD) as functional ingredients in extruded snack products: Their role in manipulating product characteristics and modulating the potential glycaemic response of snack foods

Acacia senegal (in the form of Super Gum™) and Anogeissus latifolia (in the form of gum Gatifolia SD) were used in the manufacture of ready to eat extruded cereal snack products. Inclusions rates were 0, 5, 10 and 15% w/w replacement levels for wheat flour from a control recipe. The inclusion of Super Gum™ and Gatifolia increased product expansion and reduced product density compared to a cereal flour based control snack product. Inclusion of the gum materials also decreased the hardness of the snack products whilst increasing the crispiness of the product (number of fracture peaks recorded during axial compression of samples). Glucose area under the curve (AUC) measurements obtained using in vitro digestion procedures illustrated that the potential glucose release of snack products was reduced by more than 30% by the inclusion of Gatifolia and Super Gum™ at 15% w/w compared to the control sample. Such a reduction in potential glucose release was not dose responsive. These results illustrate a potential nutritional benefit of the utilisation of Gatifolia and Super Gum™ in the ready to eat snack food sector of the food industry.     

The fate of aflatoxins during the production of "Ogiri", a West African fermented melon seed condiment from artificially contaminated seeds

Twenty-six market samples and four laboratory-prepared samples of "ogiri" were screened for aflatoxin contamination. Aflatoxins were not detected in any of the samples. The fermented product (ogiri) was prepared with Aspergillus flavus-contaminated melon seeds. Losses of 64.7% aflatoxin B1 and 82.9% aflatoxin G1 were observed at the end of the third day of fermentation of the ground melon seeds. The samples were completely detoxified at the fourth day of fermentation. Increase in pH of the mash from 6.2 to 7.2 was observed during fermentation.     

COMBINED EFFECTS OF ENZYME DOSAGE AND REACTION TIME ON PAPAYA JUICE EXTRACTION WITH THE AID OF PECTIC ENZYMES – A PRELIMINARY REPORT

Pectic enzymes are widely used in the food industry for fruit juice extraction as well as in the clarification of cloudy juices. Our laboratory has been using pectic enzymes produced from a strain of Saccharomyces cerevisiae (ATCC 52712) in different applications including fruit juice extraction. The enzyme was produced in the laboratory by culturing the yeast in papaya juice supplemented with 1% pectin for 6 days. Known amounts of enzyme preparation (0–40 mg protein) were added to a measured weight of papaya mash for varying reaction periods (30–90 min) and the amount of free‐run juice obtained in each treatment compared with a control sample. Treatment of 200 g of papaya mash with different dosages of the pectic enzyme extract resulted in rapid increases in flow rate of free‐run juice. Mash treated with 32 mg of total protein extract with a 30‐min reaction time was the optimum for a maximum rate of juice flow (25 mL/min) when initial rates were measured. There was no significant difference (P > 0.05) between the red‐ and yellow‐fleshed varieties of the papaya used. When juice flow was monitored over 6 min, the treated samples gave a flow rate that was more than twice those of the untreated samples. This biotechnological approach could be adopted to enhance papaya‐juice production by local fruit juice processors when parameters for scale‐up processes are established.     

EFFECTIVENESS OF CHLORINE AND NISIN‐EDTA TREATMENTS OF WHOLE MELONS AND FRESH‐CUT PIECES FOR REDUCING NATIVE MICROFLORA AND EXTENDING SHELF‐LIFE1

Efficacy of nisin‐EDTA treatments as a sanitizing treatment for reducing native microflora of whole melons and extending shelf‐life of fresh‐cut pieces was compared to chlorine treatments. Whole cantaloupe and honeydew melons were washed with water, nisin (10 μg/mL)‐EDTA (0.02 M), or 200 ppm chlorine for 5 min at ～ 20C before fresh‐cut preparation and storage at 5C for 15 days with periodic microbiological sampling. In addition, some fresh‐cut pieces were washed with 10 μg/mL nisin‐EDTA or 50 ppm chlorine for 1 min before storage. Changes in appearance, odor, overall acceptability and the shelf‐life of the minimally processed fresh‐cut melons were investigated. Preliminary studies indicated that water washes, EDTA (0.002 to 0.2 M) or nisin (5 to 10 μg/mL) were not effective in reducing the microflora of whole melon when used individually. Nisin‐EDTA and chlorine treatments were significantly (P < 0.05) more effective in reducing native microflora than water washes. Nisin‐EDTA treatments were significantly (P < 0.05) more effective than chlorine in reducing populations of yeast and mold and Pseudomonas spp. on whole melon surfaces but were not as effective as chlorine treatments for reducing aerobic mesophilic bacteria, lactic acid bacteria and total gram‐negative bacteria. Microbial contaminants on fresh‐cut pieces washed with 50 ppm chlorine or nisin‐EDTA were further reduced. However, microbial populations increased throughout refrigerated storage irrespective of treatments. Odor, appearance, and overall acceptability ratings for cantaloupe and honeydew fresh‐cut pieces treated with nisin‐EDTA or chlorine were not significantly (P > 0.05) different from each other throughout the storage period (15 to 21 days). However, both treatments led to significantly (P < 0.05) improved ratings compared to the controls for the fresh‐cut pieces at 9 to 12 days of storage and thereafter. The results of this study suggest that treatments with nisin‐EDTA before and after fresh‐cut processing would improve the quality and extend the shelf‐life of fresh‐cut melon.     

Novel alcoholic beverages: production of spirits and liqueurs using maceration of melon fruits in melon distillates

BACKGROUND: The object of this study was to macerate melon fruit (Cucumis melo, L.) in melon distillate to produce a liqueur that would possess the sensory attributes of the fruit. Chemical and sensory analysis was performed on the different spirits. RESULTS: Spirits macerated with melon pieces, seeds and placenta showed double the sugar concentration compared to spirits macerated with seeds and placenta only. Concentrations of esters and higher alcohols were also higher in the first macerated. Neither n‐butanol nor ethyl butyrate were detected in any of the batches. The sensory analysis results (rank‐order tests) did not disclose any significant differences among the spirit batches although maceration with seeds and placenta conferred a golden colour to the spirit that is popular in commercial products. All the batches can be grouped close together in the greenish yellow quadrant, though in the region closer to yellow. Liqueurs contained higher quantities of ethyl acetate than the macerated spirits. CONCLUSIONS: Macerated spirit with seeds and placenta was the most adequate for production on account of its deeper colour, its suitability for filtration, and its typical melon aroma, as well as its lower production costs. The acceptability of melon liqueur was similar to other spirits tasted. Copyright © 2009 Society of Chemical Industry     

Isolation and Identification of Representative Fungi from Shaoxing Rice Wine Wheat Qu Using a Polyphasic Approach of Culture‐Based and Molecular‐Based Methods

Ribosomal intergenic spacer analysis (RISA) and traditional culture‐based methods were employed to examine the fungal community of Shaoxing rice wine wheat Qu. Results showed that RISA profiles of total DNA exhibited nine distinguishable bands. By comparison, the RISA fingerprints recovered from enrichment media gave variable patterns containing fewer bands. Bands corresponding to five fungal species detected by RISA of total DNA were also observed in RISA fingerprints from enrichment cultures. A total of twenty‐four pure cultures were isolated with media of potato dextrose agar (PDA), Czapek (CPK) and wheat Qu extraction (WQE). A total of eight, eighteen and eleven fungal species and 7.9 × 10⁵ cfu/g Qu, 3.0 × 10⁵ cfu/g Qu, and 3.9 × 10⁶ cfu/g Qu, were isolated using PDA, CPK and WQE media, respectively. Predominance of each representative species did vary with the culture medium. Comparison of ITS sequences of excised RISA bands and recovered pure isolates with those in GenBank database revealed that the representative fungal species in wheat Qu were Absidia corymbifera, Saccharomyces cerevisiae, Rhizopus oryzae, Rhizomucor pusillus, Aspergillus oryzae, Candida tropicalis, Emericella nidulans, Clavispora lusitaniae, Aspergillus fumigatus, Aspergillus niger, Rhizopus microsporus, Pichia guilliermondii and Pichia anomala. Species of Saccharomyces cerevisiae, Candida tropicalis and Rhizopus oryzae detected in the original samples by analysis of RISA were not recovered in any of the three media. In addition, some species recovered from the enrichments were not detected by RISA analysis. Results obtained with culture‐based or molecular‐based methods clearly confirmed the importance of developing an integrated approach to gain a better understanding of the microbial community in wheat Qu.     

Chlorine dioxide treatment decreases respiration and ethylene synthesis in fresh‐cut ‘Hami’ melon fruit

The effects of chlorine dioxide (ClO₂) on respiration and ethylene synthesis of fresh‐cut melon fruit and the possible mechanisms involved were investigated. Fresh‐cut ‘Hami’ melon fruit fumigated with gas ClO₂ in sealed container for 12 h and then stored at 5 °C with 95% relative humidity (RH) for 19 days. Results showed that fruit treated with ClO₂ resulted in lower rates of the total respiration, alternative pathway respiration, cytochrome pathway respiration and ethylene production. Furthermore, the expressions of ethylene biosynthesis‐related genes, including CmACS2, CmACO1 and CmACO3 were reduced by ClO₂ treatment. Taken together, it is suggested that ClO₂ treatment might be an effective way to delay ripening of fresh‐cut ‘Hami’ melon, partially due to the reduced respiration and ethylene biosynthesis.     

PRODUCTION OF SHOCHU ON A COMMERCIAL SCALE FROM POST-DISTILLATION SLURRY BY A NEWLY DEVELOPED RECYCLING PROCESS

During commercial scale fermentation for the production of rice shochu using post-distillation slurry in place of the first-stage mash, it was difficult to stir the mash from the first to the third day because of the high viscosity of the mash. Shochu was therefore fermented with a two-step addition of cooked rice, adding rice on the first and third days, to reduce the viscosity of mash during the first few days. Even though the ethanol concentration of the mash after 9 d was 17.2 v/v% and was a little lower than that obtained in laboratory scale tests, the yield of pure ethanol was 473 ml kg^?1 of rice and this value was higher than the average value (450 ml kg^?1) when shochu is made in the standard manner on a commercial scale. The shochu produced on a commercial scale by the newly developed recycling process was very mild and smooth, and received high scores in sensory tests.