Potential use of a microalga (Chlorella vulgaris) in the pigmentation of rainbow trout (Oncorhynchus mykiss) muscle

The main purpose of this work was to evaluate the colouring effect of carotenoids present in dry biomass obtained from stressed cells ofChlorella vulgaris. Total carotenoids represented only 0.2% of dry algal biomass and consisted mainly of canthaxanthin, lutein, astaxanthin and their esters. — A rainbow trout feeding trial was conducted in order to investigate the effects of dietary algal incorporation as a pigment source, in comparison to that obtained with synthetic pigments, both astaxanthin and canthaxanthin. — The colour intensities measured in muscle were compared, in each case, with those which constitute the Salmonids Roche Colour Card, and proved similar after both 3 and 6 weeks feeding, with a significant increase detected, but at the end of experiment (9 weeks) the increase was shown only in spectrophotometric (quantitative) results.Chlorella vulgaris biomass, which is storable without any special precautions, thus appears to be a promising source of carotenoids to use in commercial fish finishing diets, quite comparable in efficiency with the existing synthetic pigments. Algal biomass micronization, which was also tried out, was not found to be advantageous for the efficiency of colouring, no evidence having been found of any difference in its absorption and in the distribution of pigment through muscle, even if a 150-g rainbow trout, which has a rather short digestive tract, was used.     

通气培养对小球藻生长及生物组成的影响

采用小球藻进行了静置培养和通气培养试验,研究了通气条件对小球藻生长速度、生物量、生物组成及脂肪酸组成的影响。结果表明:相对于静置培养(不通气),通气培养条件下,小球藻在稳定期的生长速度、生物量及其单位产量上高出10倍以上,差异极显著;小球藻的蛋白质含量、总糖含量明显较高,而总脂含量、淀粉含量则较低;小球藻饱和脂肪酸含量显著降低,不饱和脂肪酸特别是多不饱和脂肪酸含量升高。不同通气量对小球藻的生长也存在差异,其较适宜的通气条件为1L/min。在小球藻的培养过程中,可通过适宜的通气措施来改善培养效果和获得较高的目标产物。     

共培养微藻Monoraphidium sp. FXY-10 与Chlorella sp. U4341提高油脂产率与沉降率

采用共培养技术,在异养条件下培养微藻Chlorella sp.U4341和Monoraphidium sp.FXY-10,提高两株微藻共培养的油脂产率;通过共培养方式促进微藻细胞的自絮凝,加速微藻细胞的沉降,以期降低微藻生物量的采收成本。结果表明:微藻Chlorella sp.U4341与Monoraphidium sp.FXY-10单独培养的油脂产率分别为272.07、268.54 mg/(L·d),而两株微藻共培养的油脂产率提高到315.60 mg/(L·d);两株微藻共培养后,自然沉降5 h,微藻细胞沉降率高于90%,远高于单独培养条件下的沉降率。因此,微藻的共培养技术有望成为解决微藻油脂产率低、采收成本高两大瓶颈问题的解决方案。     

Potential of some volatile oils in protecting packages of irradiated wheat flour against Ephestia kuehniella and Tribolium castaneum

Six essential oils of Citrus reticulate (mandarin peel), Pimpinella anisum (anise), Anethum graveolens (dill), Allium sativum (garlic), Ocimum basilicum (basil) and Zingiber officinale (ginger), were evaluated for fumigant toxicity against Ephestia kuehniella and Tribolium castaneum and for contact toxicity against larvae of both species. The major compounds in these volatile oils were identified using gas chromatography- mass spectrometry. Both O. basilicum and Z. officinale oils gave 100% mortality within 24 h with doses of 32 μl/l air for E. kuehniella adults, and 128 μl/l air for T. castaneum adults. The oil of A. graveolens was the most effective against larvae of both species; treated filter papers giving 100% mortality of T. castaneum and E. kuehniella larvae with exposure periods of 24 h and 96 h, respectively. The persistence of toxicity of the six tested oils varied according to their chemical components with A. graveolens and O. basilicum proving the most persistent, and C. reticulate and P. anisum the least. The possible use of the oils applied as a 30% aqueous solution for protection of wheat flour irradiated with gamma radiation (1.5 KGy) from infestation by the test insect species during a 60-day storage period in damour and gunny plastic pouches was investigated. The effect of these oils on acetylcholinesterase activity also was examined to explore their possible mode of toxic action. Dill oil was the most active against E. kuehniella larvae while ginger oil had the greatest depressive action against T. castaneum larvae.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Frequency of DLK1 c.639C>T polymorphism and the analysis of MEG3/DLK1/PEG11 cluster expression in muscle of swine raised in Poland

DLK1 — (Drosophila like element 1) is a paternally expressed gene, associated with the callipyge phenotype in sheep. In a present study we designed a new real-time PCR alleleic discrimination assay for genotyping of a silent C/T mutation (c.639C>T) in DLK1 gene in swine. The DLK1 c.639C>T mutation was highly polymorphic in all breeds analyzed and C allele was predominant in Landrace and Duroc while T allele was more frequent in Pietrain and Pu?awska breed. Moreover, we analyzed mRNA expression of DLK1 and adjacent genes — MEG3 and PEG11 in muscles of swines of different breeds raised in Poland. We did not observe significantly different expression of DLK1, MEG3 or PEG11 mRNA in any of analyzed breeds. We also attempted to assess the effect of DLK1 (c.639C>T) on the expression of genes in callipyge locus but did not find significant differences between animals with alternate genotypes (C/C and T/T homozygotes).     

Sprout inhibition of potatoes with soft‐electron (low‐energy electron beams)

The surfaces of potatoes were irradiated with electrons of different energy levels, and the effects on sprouting were investigated. Electrons at 270 keV or higher effectively inhibited sprouting of four cultivars of potatoes, cvs Danshaku, Hokkaikogane, Toyoshiro and May Queen, even after storage at 23 °C for 4 months. Sugar contents in tubers treated with 270‐keV electrons were lower after storage for 3 months than their levels before electron treatment. The levels of glucose, fructose and sucrose were significantly lower in the tubers treated with 270‐keV electrons than in low temperature (5 °C)‐stored tubers. The results indicate the potential of low energy electron treatment for the shelf‐life extension of potatoes as an alternative to treatments with gamma‐rays or chemicals. Copyright © 2004 Society of Chemical Industry     

Thermal inactivation of Bacillus cereus and Clostridium perfringens vegetative cells and spores in pork luncheon roll

The aim of this study was to design a thermal treatment(s) for pork luncheon roll, which would destroy Bacillus cereus and Clostridium perfringens vegetative cells and spores. B. cereus and C. perfringens vegetative and spore cocktails were used to inoculate luncheon meat. Samples were subjected to different temperatures and removal times. The decimal-reduction times (D-values) were calculated by linear regression analysis (D = -1/slope of a plot of log surviving cells versus time). The log(10) of the resulting D-values were plotted against their corresponding temperatures to calculate (-1/slope of the curve) the thermal resistance (z-values) of each cocktail. The D-values for vegetative cells ranged from 1 min (60 degrees C) to 33.2 min (50 degrees C) for B. cereus and from 0.9 min (65 degrees C) to 16.3 min (55 degrees C) for C. perfringens. The D-values for B. cereus spores ranged from 2.0 min (95 degrees C) to 32.1 min (85 degrees C) and from 2.2 min (100 degrees C) to 34.2 min (90 degrees C) for C. perfringens. The z-values were calculated to be 6.6 and 8.5 degrees C for B. cereus vegetative and spores, respectively, and 7.8 and 8.4 degrees C for C. perfringens vegetative cells and spores, respectively. The D-values of B. cereus and C. perfringens suggest that a mild cook of 70 degrees C for 12s and 1.3 min would achieve a 6 log reduction of B. cereus and C. perfringens vegetative cells, respectively. The equivalent reduction of B. cereus and C. perfringens spores would require the pork luncheon meat to be heated for 36 s at 105 and 110 degrees C, respectively. The results of this study provide the thermal inactivation data necessary to design a cooking protocol for pork luncheon roll that would inactivate B. cereus and C. perfringens vegetative cells and spores. The data may also be used in future risk assessment studies.     

Chlorella vulgaris and Haematococcus pluvialis biomass as colouring and antioxidant in food emulsions

The use of microalgal biomass, a natural ingredient, to colour oil-in-water pea protein stabilised emulsions was studied. Various levels of incorporation of Chlorella vulgaris green, Chlorella vulgaris orange (after carotenogenesis), and Haematococcus pluvialis (red, after carotenogenesis) were used, resulting in a wide range of appealing colours from green to orange and pink. The colour stability of the emulsions was evaluated, through the evolution of the L^*a^*b^* parameters (CIELAB system) along 6 weeks. The primary and secondary oxidation products of the emulsions were also determined, and an enhanced resistance to oxidation was evidenced by emulsions containing microalgae. Therefore antioxidant functionality was another positive aspect of its use as an ingredient. Colour stability, a variety of attractive hues, and added resistance to oxidation ensure an adequate compromise of sensory and functional properties for these novel emulsions.     

电子束辐照降解玉米中黄曲霉毒素B1及对玉米品质的影响

为考察电子束辐照对玉米中黄曲霉毒素B_1(aflatoxin B_1,AFB_1)的降解效果及对玉米品质的影响,试验选取AFB_1污染的玉米为原料,研究0~50kGy剂量辐照下玉米中AFB_1的降解效果,并考察电子束辐照对玉米理化性质,包括脂肪酸值、黏度值和色度的影响。结果表明,随着电子束辐照剂量的升高(5~50kGy),玉米中AFB_1含量显著降低(P0.05);当电子束辐照剂量大于15kGy时,玉米理化性质变化较明显,其中脂肪酸值显著升高(P0.05),黏度值显著下降(P0.05),L*值无显著变化(P0.05),a*,b*值显著下降(P0.05)。     

Rational selection of non-Saccharomyces wine yeasts for mixed starters based on ester formation and enological traits

Thirty-eight yeast strains belonging to the genera Candida, Hanseniaspora, Pichia, Torulaspora and Zygosaccharomyces were screened for ester formation on synthetic microbiological medium. The genera Hanseniaspora and Pichia stood out as the best acetate ester producers. Based on the ester profile Hanseniaspora guilliermondii 11027 and 11102, Hanseniaspora osmophila 1471 and Pichia membranifaciens 10113 and 10550 were selected for further characterization of enological traits. When growing on must H. osmophila 1471, which displayed a glucophilic nature and was able to consume more than 90% of initial must sugars, produced levels of acetic acid, medium chain fatty acids and ethyl acetate, within the ranges described for wine. On the other hand, it was found to be a strong producer of 2-phenylethyl acetate. Our data suggest that H. osmophila 1471 is a good candidate for mixed starters, although the possible interactions with S. cerevisiae deserve further research.     

Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom

The purpose of this study was to establish the microbiological safety of salad vegetables and sauces served in kebab take-away restaurants. Comparison with published microbiological guidelines revealed that 4.7% of 1213 salad vegetable samples were of unsatisfactory microbiological quality due to Escherichia coli and/or Staphylococcus aureus levels at ≥10² cfu g⁻¹. Another 0.3% of salad samples were of unacceptable quality due to S. aureus at ≥10⁴ cfu g⁻¹ (2 samples) or the presence of Salmonella Kentucky (1 sample). Cucumber was the most contaminated salad vegetable with regards to unsatisfactory levels of E. coli (6.0%) or S. aureus (4.5%). Five percent of 1208 sauce samples were of unsatisfactory microbiological quality due to E. coli, S. aureus at ≥10² cfu g⁻¹ and/or Bacillus cereus and other Bacillus spp. at ≥10⁴ cfu g⁻¹. A further 0.6% of sauce samples were of unacceptable quality due to Bacillus spp. (Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis) at ≥10⁵ cfu g⁻¹ or the presence of Salmonella Agbeni (1 sample). More samples of chilli sauce (8.7%) were of unsatisfactory or unacceptable microbiological quality than any other sauce types. The results emphasize the need for good hygiene practices in kebab take-away restaurants handling these types of ready-to-eat products.     

In vivo immunomodulatory activity of polysaccharides derived from Chlorella pyrenoidosa

The effects of polysaccharides from Chlorella pyrenoidosa on immunomodulatory activity were investigated in this paper. Phagocytosis of peritoneal macrophages was detected through ingesting chicken red blood cells (CRBC) test to evaluate nonspecific immune response. The cellular immune response was measured using the delayed-type hypersensitivity response to sheep red blood cells (SRBC) in terms of antibody titration level. Oral administration of C. pyrenoidosa polysaccharides, 1 g and 2 g kg⁻¹ body weight significantly enhanced phagocytic rate (23.00 and 26.25%, respectively) and phagocytic index (0.30 and 0.36, respectively) compared with saline-treated control (P<0.05). The value of ear thickness rate was greatly elevated from 10.09% in saline-treated control to 16.22 and 19.48%, respectively in group treated with 1 g and 2 g kg⁻¹ body weight polysaccharides (P<0.05). There was a significant correlation between the dosage of C. pyrenoidosa polysaccharides and antibody titre (r=0.99, P=0.019) and the antibody titre was significantly increased by 11.80, 21.90 as well as 39.80 in 2 g kg⁻¹ bw compared to 10.30 in the control. Dietary supplementation with C. pyrenoidosa polysaccharides did not affect the growth of the mice during the experiment. These results indicated that immunomodulatory activities in mice were enhanced by administration of polysaccharides derived from C. pyrenoidosa.     

Treating lamb’s lettuce with a cold plasma – Influence of atmospheric pressure Ar plasma immanent species on the phenolic profile of Valerianella locusta

The antimicrobial effectiveness of non-thermal plasma is scientifically accepted. Applications can be found in medicinal sterilisation processes. However, the effects of plasma treatments on plant food with regard to nutritional value are not yet sufficiently investigated. To study the interactions of plasma immanent reactive species with secondary plant metabolites, lamb’s lettuce (Valerianella locusta) was exposed to an atmospheric pressure plasma jet. Changes in the phenolic profile were compared to experiments with pure substances to determine the influence of the food matrix. Whereas pure flavonoids showed a strong time-dependent decrease, not originating from photo- or thermodesorption processes, the content of diosmetin in lamb’s lettuce significantly increased. Regarding phenolic acids, plasma exposure led to a strong reduction in lamb’s lettuce, while the concentration of pure monophenols changed little within the same period of time. Treatments with plasma-similar temperatures and UV radiation suggest that due to plasma-reactive species concomitant disintegration of cell membranes and oxidation of released cellular compounds are taking place. Time-dependent changes of the leaf surface morphology due to plasma-induced erosion have been observed by scanning electron microscopy.     

Variations of internal pH in typical Italian sourdough yeasts during co-fermentation with lactobacilli

The effects of organic acids (lactic and acetic) and extracellular pH (pHex) on the intracellular pH (pHi) of Saccharomyces cerevisiae and Candida milleri during co-fermentation with lactobacilli were investigated by using Fluorescence-Ratio-Imaging-Microscopy (FRIM). Yeasts were grown in a system that partially mimics sourdough composition, using individual fermentation and combinations with lactic acid bacteria. Fermentations were carried out at 25 °C for 22 h at an initial pH of 5.3. The two yeast species grew equally well during the co-fermentations with lactobacilli. Our results reveal large differences in pHi values between the two yeast species, primarily in relation with pHex changes, while the concentration of organic acids did not seem to affect the pHi. Moreover, the pHi of S. cerevisiae seemed to be affected by maltose consumption. The pH gradient (difference between internal and external pH) of S. cerevisiae remained rather constant, ranging from 2.0 to 2.5. C. milleri instead exhibited a higher pHi, that remained constant throughout the experiments and was unaffected by pHex and/or sugar consumption. Thus, the pH gradient of C. milleri varied much more than that of S. cerevisiae, ranging from 2.3 to 3.8. Our results suggest that the two yeast species have different pHi regulation mechanisms.     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Feeding deterrent activity of terpenoid lactones with a p-menthane system against stored-product pests

Feeding deterrent activity of eight enantiomeric pairs and one optically inactive terpenoid lactone with a p-menthane system against three storage pests was determined. The lactones were tested on adults of Sitophilus granarius, adults and larvae of Tribolium confusum and larvae of Trogoderma granarium. The isomeric starting natural compounds, (+) and (−) pulegones and (+) and (−) isopulegols, were also tested. The results showed that the introduction of the lactone moiety into the p-menthane system produced antifeedant activity in the lactones obtained. The lactones with a spiro arrangement of lactone and cyclohexane rings were more active than those with condensed rings. The configuration of chiral centres present in the molecule significantly influenced the activity of the compounds studied. In most cases, lactones obtained from R-(+)-pulegone were more active antifeedants than those obtained from S-(−)-pulegone.     

Transformation of cellobiose to 3-ketocellobiose by the EDTA-treated Agrobacterium tumefaciens cells

Agrobacterium tumefaciens cells treated with EDTA were used as a biocatalyst for the transformation of cellobiose to 3-ketocellobiose. The effects of pH of the reaction medium and temperature on the reaction rate and the selectivity during the transformation by the cells were examined, and it was found that the optimum reaction conditions were pH 6 and 15 degrees C. The selectivity was about 0.8 under these conditions. The substrate concentration had no significant effect on the selectivity up to 300 mmol/I.