| 1. |
- Schoug, Åsa, et al.
(författare)
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Freeze-drying of Lactobacillus coryniformis Si3--effects of sucrose concentration, cell density, and freezing rate on cell survival and thermophysical properties
- 2006
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Ingår i: Cryobiology. - Maryland Heights, USA : Elsevier BV. - 0011-2240 .- 1090-2392. ; 53:1, s. 119-127
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Tidskriftsartikel (refereegranskat)abstract
- Freeze-drying is commonly used to stabilize lactic acid bacteria. Many factors have been reported to influence freeze-drying survival, including bacterial species, cell density, lyoprotectant, freezing rate, and other process parameters. Lactobacillus coryniformis Si3 has broad antifungal activity and a potential use as a food and feed biopreservative. This strain is considered more stress sensitive, with a low freeze-drying survival, compared to other commercialized antifungal lactic acid bacterial strains. We used a response surface methodology to evaluate the effects of varying sucrose concentration, cell density and freezing rate on Lb. coryniformis Si3 freeze-drying survival. The water activity of the dry product, as well as selected thermophysical properties of importance for freeze-drying; degree of water crystallization and the glass transition temperature of the maximally freeze concentrated amorphous phase (Tg') were determined. The survival of Lb. coryniformis Si3 varied from less than 6% to over 70% between the different conditions. All the factors studied influenced freeze-drying survival and the most important factor for survival is the freezing rate, with an optimum at 2.8 degrees C/min. We found a co-dependency between freezing rate and formulation ingredients, indicating a complex system and the need to use statistical tools to detect important interactions. The degree of water crystallization decreased and the final water activity increased as a function of sucrose concentration. The degree of water crystallization and Tg' was not affected by the addition of 10(8)-10(10) CFU/mI. At 10(11) CFU/ml, these thermophysical values decreased possibly due to increased amounts of cell-associated unfrozen water.
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| 2. |
- Feng, X. M., et al.
(författare)
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Image analysis for monitoring the barley tempeh fermentation process
- 2007
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Ingår i: Journal of Applied Microbiology. - Oxon, United Kingdom : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 103:4, s. 1113-1121
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To develop a fast, accurate, objective and nondestructive method for monitoring barley tempeh fermentation. Methods and Results: Barley tempeh is a food made from pearled barley grains fermented with Rhizopus oligosporus. Rhizopus oligosporus growth is important for tempeh quality, but quantifying its growth is difficult and laborious. A system was developed for analysing digital images of fermentation stages using two image processing methods. The first employed statistical measures sensitive to image colour and surface structure, and these statistical measures were highly correlated (r = 0.92, n = 75, P < 0.001) with ergosterol content of tempeh fermented with R. oligosporus and lactic acid bacteria (LAB). In the second method, an image-processing algorithm optimized to changes in images of final tempeh products was developed to measure number of visible barley grains. A threshold of 5 visible grains per Petri dish indicated complete tempeh fermentation. When images of tempeh cakes fermented with different inoculation levels of R. oligosporus were analysed the results from the two image processing methods were in good agreement. Conclusion: Image processing proved suitable for monitoring barley tempeh fermentation. The method avoids sampling, is nonintrusive, and only requires a digital camera with good resolution and image analysis software. Significance and Impact of the Study: The system provides a rapid visualization of tempeh product maturation and qualities during fermentation. Automated online monitoring of tempeh fermentation by coupling automated image acquisition with image processing software could be further developed for process control.
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| 3. |
- Feng, X. M., et al.
(författare)
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Rhizopus oligosporus and yeast co-cultivation during barley tempeh fermentation-Nutritional impact and real-time PCR quantification of fungal growth dynamics
- 2007
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Ingår i: Food microbiology (Print). - London, United Kingdom : Elsevier BV. - 0740-0020 .- 1095-9998. ; 24:4, s. 393-402
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Tidskriftsartikel (refereegranskat)abstract
- Barley tempeh was produced by fermenting barley kernels with Rhizopus oligosporus. The potential of the yeasts Saccharomyces cerevisiae (three strains), S. boulardii (one strain), Pichia anomala (one strain) and Kluyveromyces lactis (one strain) to grow together with R. oligosporus during barley tempeh fermentation was evaluated. All yeast strains grew during the fermentation and even during cold storage of tempeh (P < 0.01). The growth of yeasts slightly increased the ergosterol contents, but did not influence amino acid contents and compositions, and did not reduce phytate contents. Slight increases of vitamins B6 and niacinamide, and slight decreases of B1 and biotin were observed. Quantification of fungal growth is difficult during mixed species fermentations because ergosterol is found in all fungal species, and colony-forming-unit (cfu) estimations are not reliable for R. oligosporus and other sporulating fungi. Therefore, we developed a quantitative real-time PCR method for individually quantifying S. cerevisiae and R. oligosporus growth in barley tempeh. The PCR results were highly correlated with the ergosterol content of R. oligosporus and with the number of cfu of S. cerevisiae. Thus, real-time PCR is a rapid and selective method to quantify yeasts and R. oligosporus during mixed species fermentation of inhomogenous substrate such as barley tempeh. © 2006 Elsevier Ltd. All rights reserved.
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| 4. |
- Jennessen, Jennifer, et al.
(författare)
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Morphological characteristics of sporangiospores of the tempe fungus Rhizopus oligosporus differentiate it from other taxa of the R-microsporus group
- 2008
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Ingår i: Mycological Research. - Oxon, United Kingdom : Elsevier BV. - 0953-7562 .- 1469-8102. ; 112, s. 547-563
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Tidskriftsartikel (refereegranskat)abstract
- The fungus Rhizopus oligosporus (R. microsporus var. oligosporus) is traditionally used to make tempe, a fermented food based on soybeans. Interest in the fungus has steadily increased, as it can also ferment other substrates, produce enzymes, and treat waste material. R. oligosporus belongs to the R. microsporus group consisting of morphologically similar taxa, which are associated with food fermentation, pathogenesis, or unwanted metabolite production (rhizonins and rhizoxins). The ornamentation pattern, shape, and size of sporangiospores of 26 R. microsporus group strains and two R. oryzae strains were studied using low-temperature SEM (LT-SEM) and LM. This study has shown that: (1) LT-SEM generates images from well-conserved sporangiophores, sporangia, and spores. (2) Robust spore ornamentation patterns can be linked to all different taxa of the R. microsporus group, some previously incorrectly characterized as smooth. Ornamentation included valleys and ridges running in parallel, granular plateaus, or smooth polar areas. Distribution of ornamentation patterns was related to spore shape, which either was regular, ranging from globose to ellipsoidal, or irregular. Specific differences in spore shape, size, and ornamentation were observed between Rhizopus taxa, and sometimes between strains. (3) R. oligosporus has a defect in the spore formation process, which may be related to the domesticated nature of this taxon. It had a high proportion, 10-31 %, of large and irregular spores, and was significantly differentiated from other, natural Rhizopus taxa as evaluated with partial least squares discriminant analysis. it is remarkable that the vehicle of distribution, the sporangiospore, is affected in the strains that are distributed by human activity. This provides information about the specificity and speed of changes that occur in fungal strains because of their use in (food) industry.
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| 5. |
- Schnürer, Anna, et al.
(författare)
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Fungal survival during anaerobic digestion of organic household waste
- 2006
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Ingår i: Waste Management. - Oxford, United Kingdom : Elsevier. - 0956-053X .- 1879-2456. ; 26:11, s. 1205-1211
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Tidskriftsartikel (refereegranskat)abstract
- Anaerobic digestion of organic waste yields energy rich biogas and retains nutrients (N, P, K, S, etc.) in a stabilised residue. For the residue to be used as a soil fertiliser, it must be free from pollutants and harmful microorganisms. Fungal survival during sanitation and anaerobic treatment of source-separated organic household waste and during aerobic storage of the residue obtained was investigated. Decimal reduction times were determined for inoculated fungi (Aspergillus flavus and Aspergillus fumigatus, Penicillium roqueforti, Rhizomucor pusillus, Thermoascus crustaceus and Thermomyces lanuginosus). Several different fungal species were found after waste sanitation treatment (70 degrees C, 1 h), with Aspergillus species dominating in non-inoculated waste. Anaerobic waste degradation decreased the diversity of fungal species for processes run at both 37 and 55 degrees C, but not total fungal colony forming units. Fungi surviving the mesophilic anaerobic digestion were mainly thermotolerant Talaromyces and Paecilomyces species. T crustaceus and T lanuginosus were the only inoculated fungi to survive the thermophilic anaerobic degradation process. Aerobic storage of both types of anaerobic residues for one month significantly decreased fungal counts.
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| 6. |
- Schnürer, Johan, 1957-, et al.
(författare)
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Antifungal lactic acid bacteria as biopreservatives
- 2005
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Ingår i: Trends in Food Science & Technology. - : Elsevier. - 0924-2244 .- 1879-3053. ; 16:1-3, s. 70-78
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Forskningsöversikt (refereegranskat)abstract
- Food-borne fungi, both yeasts and moulds, cause serious spoilage of stored food. Moulds may also produce health-damaging mycotoxins, e.g. aflatoxins, trichothecenes, fumonisin, ochratoxin A and patulin. Consumer demands for minimally processed foods and reduced use of chemical preservatives have stimulated research on antifungal lactic acid bacteria as biopreservatives. Recently, a number of antifungal metabolites, e.g. cyclic dipeptides, phenyllactic acid, proleinaceous compounds, and 3-hydroxylated fatty acids have been isolated from lactic acid bacteria. This review summarizes these findings and suggests potential applications of antifungal lactic acid bacteria in the preservation of food and feeds.
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| 7. |
- Broberg, Anders, et al.
(författare)
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Metabolite profiles of lactic acid bacteria in grass silage
- 2007
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Ingår i: Applied and Environmental Microbiology. - Washington, USA : American Society for Microbiology. - 0099-2240 .- 1098-5336. ; 73:17, s. 5547-5552
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Tidskriftsartikel (refereegranskat)abstract
- The metabolite production of lactic acid bacteria JAB) on silage was investigated. The aim was to compare the production of antifungal metabolites in silage with the production in liquid cultures previously studied in our laboratory. The following metabolites were found to be present at elevated concentrations in silos inoculated with LAB strains: 3-hydroxydecanoic acid, 2-hydroxy-4-methylpentanoic acid, benzoic acid, catechol, hydrocinnamic acid, salicylic acid, 3-phenyllactic acid, 4-hydroxybenzoic acid, (trans, trans)-3,4-dihydroxycyclohexane-1-carboxylic acid, p-hydrocoumaric acid, vanillic acid, azelaic acid, hydroferulic acid, p-coumaric acid, hydrocaffeic acid, ferulic acid, and caffeic acid. Among these metabolites, the antifungal compounds 3-phenyllactic acid and 3-hydroxydecanoic acid were previously isolated in our laboratory from liquid cultures of the same LAB strains by bioassay-guided fractionation. It was concluded that other metabolites, e.g., p-hydrocoumaric acid, hydroferulic acid, and p-coumaric acid, were released from the grass by the added LAB strains. The antifungal activities of the identified metabolites in 100 mM lactic acid were investigated. The MICs against Pichia anomala, Penicillium roqueforti, and Aspergillus fumigatus were determined, and 3-hydroxydecanoic acid showed the lowest MIC (0.1 mg ml(-1) for two of the three test organisms).
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| 8. |
- Börjesson, T., et al.
(författare)
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Near-infrared spectroscopy for estimation of ergosterol content in barley : A comparison between reflectance and transmittance techniques
- 2007
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Ingår i: Cereal Chemistry. - St. Paul, USA : AACC International. - 0009-0352 .- 1943-3638. ; 84:3, s. 231-236
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Tidskriftsartikel (refereegranskat)abstract
- The fungal-specific lipid ergosterol correlates with fungal biomass and often also with the degree of mycotoxin contamination of cereals. We compared the ability of a near-infrared reflectance (NIR) instrument with a broad wavelength range (400-2500 nm) and a near-infrared transmittance (NIT) instrument with a narrower wavelength range (850-1050 nm) to predict the ergosterol content of naturally infected barley samples. The two instruments were equally good at predicting ergosterol content in Swedish samples (r(2) = 0.81 and 0.83 for NIT and NIR, respectively). The NIT instrument was then used for samples from three countries (Sweden, Ireland, UK). This model had about the same root mean-squared error (approximate to 5 mg of ergosterol/kg, db, of grain) as the dataset with only Swedish samples, although the r(2) value was lower (0.58). The investigation has shown that it is possible to predict ergosterol content in whole barley samples using NIR or NIT instrumentation, and acceptable models can be obtained using different barley cultivars and samples from different countries and harvest years. This should make it possible to routinely predict the fungal biomass at grain terminals.
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| 9. |
- Dal Bello, F., et al.
(författare)
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Improvement of the quality and shelf life of wheat bread by fermentation with the antifungal strain Lactobacillus plantarum FST 1.7
- 2007
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Ingår i: Journal of Cereal Science. - London, United Kingdom : Elsevier. - 0733-5210 .- 1095-9963. ; 45:3, s. 309-318
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Tidskriftsartikel (refereegranskat)abstract
- Lactobacillus plantarum FST 1.7 was screened for in vitro antimicrobial activity and was shown to be active against spoilage moulds and bacteria. Isolation of antimicrobial compounds from cell-free supernatant identified lactic acid, phenyllactic acid and the two cyclic dipeptides cyclo ((L)-Leu-(L)-Pro) and cyclo ((L)-Phe-(L)-Pro) as the major components responsible for this activity. L. plantarum FST 1.7 was tested for the ability to produce the antifungal compounds during sourdough fermentation and to produce bread of good quality and increased shelf-life. A rheofermentometer was used to examine the gaseous release and development characteristics of the dough. A range of parameters was determined including pH, TTA and specific loaf volume. The results were compared with those obtained using Lactobacillus sanfranciscensis, a chemically acidified and a non-acidified dough. The quality of sourdough and bread produced using L. plantarum FST 1.7 was comparable to that obtained using common sourdough starters, e.g. L. sanfranciscensis. Sourdoughs and breads were evaluated for the ability to retard growth of Fusarium culmorum and Fusarium graminearum two fungi found on breads. Sourdough and bread produced with strain FST 1.7 showed consistent ability to retard the growth of both Fusarium species, thus indicating that L. plantarum FST 1.7 has also the potential to improve the shelf-life of wheat bread.
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| 10. |
- Druvefors, Ulrika Ädel, et al.
(författare)
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Mold-inhibitory activity of different yeast species during airtight storage of wheat grain
- 2005
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Ingår i: FEMS yeast research (Print). - : Elsevier. - 1567-1356 .- 1567-1364. ; 5:4-5, s. 373-378
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Tidskriftsartikel (refereegranskat)abstract
- The yeast Pichia anomala J121 inhibits spoilage by Penicillium roqueforti in laboratory and pilot studies with high-moisture wheat in malfunctioning airtight storage. We tested the biocontrol ability of an additional 57 yeast species in a grain mini silo system. Most yeast species grew to CFU levels comparable to that of P. anomala J121 after 14 days of incubation (> 10(6) CF U g(-1)). Of the 5 8 species, 38 (63 strains) had no mold-inhibitory effects (Pen. roqueforti levels > 10(5) CFU g(-1)). Among these were 11 species (18 strains) that did not grow on the wheat grain. Several of the non-inhibiting yeast species have previously been reported as biocontrol agents in other postharvest environments. Weak inhibitory activity, reducing Pen. roqueforti levels to between 10(4) and 10(5) CFU g(-1), was observed with 11 species (12 strains). Candida silvicola and Pichia guillermondii reduced Pen. roqueforti to <10(4) CFU g(-1). Candida fennica, Candida pelliculosa, Candida silvicultrix, P. anomala (29 strains), Pichia burtonii, Pichia farinosa and Pichia membranifaciens strongly inhibited Pen. roqueforti (< 10(3) CFU g(-1)) in the mini silos, but none had higher biocontrol activity than P. anomala strain J121. This report is the first of biocontrol activity of C fennica and C silvicultrix. The ability of 27 yeast species to grow to high CFU values without inhibiting mold growth suggests that nutrient competition may not be the main mode of action of P. anomala J121.
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