Biomedical subjects

M J Nout

Publications and source records attributed to M J Nout.

At least 19 recordsLinked to original sources

PubMed2001

A Chinese fermented soybean food.

Sufu or furu is a fermented soybean product originating in China. It is a cheese-like product with a spreadable creamy consistency and a pronounced flavour. Sufu is a popular side dish consumed mainly with breakfast rice or steamed bread. It has a long history and written records date back to the Wei Dynasty (220-265 AD). Sufu is made by fungal solid state fermentation of tofu (soybean curd) followed by aging in brine containing salt and alcohol. The present review is based on scientific data published in Chinese and international sources. Several types of sufu can be distinguished, according to processing method or according to colour and flavour. Choice of processing can result in mould fermented sufu, naturally fermented sufu, bacterial fermented sufu, or enzymatically ripened sufu. Depending on the choice of dressing mixture, red, white or grey sufu may be obtained. The stages of the process are discussed and include the preparation of tofu, the preparation of pehtze, salting and ripening. Fungal starters include Actinomucor spp., Mucor spp. and Rhizopus spp. The chemical composition is discussed with particular reference to the proximate composition, the amino acid content and profile, as well as the volatile flavour components of various types of sufu.

Biotechnology↗

PubMed2000

In vitro digestibility of bacillus fermented soya bean.

Bacillus fermented legume products include among others dawadawa and soumbala made from African locust bean, and natto and kinema made from soya bean. Bacillus subtilis is the dominant species involved in the fermentation. During Bacillus fermentation for 48 h of autoclaved soya bean the quantity of soluble and dialyzable matter increased from 22% and 6% up to 65% and 40%, respectively. Protein and carbohydrate degradation during fermentation of soya bean with several Bacillus spp. was investigated and appeared to be substantial during the first 18 h of fermentation resulting in the release of high levels of peptides and oligosaccharides. In vitro digestibility was increased from 29% up to 33-43% after Bacillus fermentation for 48 h. It was shown that Bacillus spp. were able to degrade soya bean macromolecules to a large extent resulting in water-soluble low molecular weight compounds. In vitro digestion of Bacillus fermented soya bean using gastrointestinal enzymes only slightly increased the amount of dialyzable matter, which clearly demonstrated the beneficial effect of Bacillus fermentation on food nutrient availability.

Absorption↗

PubMed2000

Location and limitation of cellulose production by Acetobacter xylinum established from oxygen profiles.

The static fermentation of coconut water sucrose by Acetobacter xylinum was carried out at initial pH's of 3.0, 4.0, 5.0 or 6.0. Cellulose was produced at the surface, and its production was most favourable at pH's 4.0 and 5.0. These pH values also allowed for optimal bacterial growth. Oxygen concentration profiles were measured with microelectrodes at different cultivation stages, and steep profiles were obtained with penetration depths between 50 and 100 microm. A substrate penetration depth analysis confirmed the hypothesis that the first stage of the fermentation is entirely oxygen controlled. Diffusion calculations showed, however, that at a later stage sucrose becomes a limiting substrate also, which was confirmed by the decrease in cellulose production rate over time. The effective diffusion coefficient of oxygen in deactivated cellulose pellicles was measured with microelectrodes, and a value of 1.4 x 10(-9) m2/s was obtained under all investigated conditions. The oxygen flux was 5.9 x 10(-6) mol/m2.s, while a significantly higher value of 9.1 x 10(-6) mol/m2.s was obtained at pH 4.0.

Journal Article↗

PubMed1998

Beta-glycosidase (amygdalase and linamarase) from Endomyces fibuliger (LU677): formation and crude enzyme properties.

In our previous studies, the yeast Endomyces fibuliger LU677 was found to degrade amygdalin in bitter apricot seeds. The present investigation shows that E. fibuliger LU677 produces extracellular beta-glycosidase activity when grown in malt extract broth (MEB). Growth was very good at 25 degrees C and 30 degrees C and slightly less at 35 degrees C. When grown in MEB of pH 5 and pH 6 with addition of 0, 10 or 100 ppm amygdalin, E. fibuliger produced only slightly more biomass at pH 5, and was only slightly inhibited in the presence of amygdalin. Approximately, 60% of the added amygdalin was degraded (fastest at 35 degrees C) during an incubation period of 5 days. Supernatants of cultures grown at 25 degrees C and pH 6 for 5 days were tested for the effects of pH and temperature on activity (using amygdalin, linamarin and prunasin as substrates). Prunase activity had two pH optima (pH 4 and pH 6), amygdalase and linamarase only one each at pH 6 and pH 4-5 respectively. The linamarase activity evolved earlier than amygdalase (2 days and 4 days respectively). The data thus indicate the presence of at least two different glycosidases having different pH optima and kinetics of excretion. In the presence of amygdalin, lower glycosidase activities were generally produced. However, the amygdalin was degraded from the start of the growth, strongly indicating an uptake of amygdalin by the cells. The temperature optimum for all activities was at 40 degrees C. Activities of amygdalase (assayed at pH 4) and linamarase (at pH 6) evolving during the growth of E. fibuliger were generally higher in cultures grown at 25 degrees C and 30 degrees C. TLC analysis of amygdalin degradation products show a two-stage sequential mechanism as follows: (1) amygdalin to prunasin and (2) prunasin to cyanohydrin.

Amygdalin↗

PubMed1997

A computerised system for the identification of lactic acid bacteria.

A generic computerised system for the identification of bacteria was developed. The system is equipped with a key to the identification of lactic acid bacteria. The identification is carried out in two steps. The first step distinguishes groups of bacteria by following a decision tree with general identification tests. The second step in the identification is the distinction of species within a group on the basis of biochemical fermentation patterns. During grouping, probabilities for test failure are used. These probabilities can be used for assessing the quality of a given test answer. The probabilities are also used to select the most probable test answer in cases where the test result is inconclusive. The probabilities of test failure were determined by a group of experts and a group of potential users of the identification system. During species identification, similarity indices are calculated for all bacteria in a group. The described identification system has the ability to "learn" from different sessions in the species identification step, improving both identification speed and accuracy. Because of the versatile way in which the system is set up, it can very easily be expanded with identification keys to other organisms.

Carbohydrate Metabolism↗

PubMed1997

In vitro cariogenicity of trans-galactosyl-oligosaccharides.

Trans-galactosyl-oligosaccharides (TOS) are a class of oligosaccharides produced by transgalactosylation of lactose. TOS are used as bifidogenic factors in human and animal nutrition. TOS can be present in the oral cavity and form a risk of caries. All oral bacteria tested were able to degrade and ferment both TOS and galactosyllactose (GLL), one of its components. Growth was improved compared with carbohydrate-free media and acid was produced after 24 h incubation of the bacteria with TOS and GLL. Degradation patterns, using HPAEC, showed degradation of most components. GLL was degraded only partially. Rapid acidification was only observed for Streptococcus mutans, resulting in a pH of 5.4 within 30 min. All other strains fermented TOS and GLL only slowly. Plaque formation could not be detected on both substrates. It can be concluded that TOS and GLL present only a small risk of caries formation, unless proven otherwise in animal studies.

Dental Caries↗

PubMed1997

Biodiversity of yeasts from Illinois maize.

Microflora in wound sites of preharvest maize (including bacteria, yeasts, and filamentous fungi) may play a role in attracting insects to maize plants and may also interact with growth and mycotoxin production by filamentous fungi. As little data are available about the yeasts occurring on maize from the U.S. corn belt, samples of milled maize from experimental plantings at the University of Illinois River Valley Sand Field were analyzed. Yeast counts showed slight yearly fluctuation and varied between 3.60 and 5.88 (log cfu/g maize). The majority of the yeasts were Candida guilliermondii (approximately 55%), Candida zeylanoides (24%), Candida shehatae (11%), and Debaryomyces hansenii (3%). Also present were Trichosporon cutaneum, Cryptococcus albidus var. aerius, and Pichia membranifaciens. The occurrence of killer yeasts was also evaluated. Killer yeasts were detected in maize for the first time and were identified as Trichosporon cutaneum and Candid zeylanoides. These were able to kill some representative yeasts isolated from maize, including Candida guilliermondii, Candida shehatae, and Cryptococcus albidus var. aerius. Other maize yeasts (Candida zeylanoides, Debaryomyces hansenii, Pichia membranifaciens) were not affected. The majority of yeasts found on maize were unable to ferment its major sugars, i.e., sucrose and maltose. Some (e.g., Candida zeylanoides) were not even able to assimilate these sugars. The importance of these properties in relation to insect attraction to preharvest ears of maize is discussed.

Yeasts↗

PubMed1996

Food fermentation: a safety and nutritional assessment. Joint FAO/WHO Workshop on Assessment of Fermentation as a Household Technology for Improving Food Safety.

An assessment of the food-safety and nutritional aspects of lactic acid fermentation for the preparation of weaning food at the household level was carried out during a Joint FAO/WHO Workshop held in Pretoria, South Africa, in December 1995. In particular, lactic acid fermentation was evaluated as a part of food preparation processes involving other operations such as soaking, cooking, and the germination of cereal grains. The use of germinated cereals is of particular interest since they can be used to prepare semi-liquid porridges of high nutrient density. After reviewing the present state of knowledge concerning the antimicrobial effects of the lactic acid in fermented foods, and the nutritional benefits of fermentation and the use of germinated cereals, the Workshop made an inventory of gaps in current knowledge and priorities for further research. High priority areas for research include the following: the effect of lactic acid fermentation on viruses, parasites, certain bacteria, and mycotoxins; certain physiological and nutritional effects of the consumption of fermented foods; the characterization and optimization of fermentation processes and the development of appropriate fermentation starters; and risk mitigation using the Hazard Analysis Critical Control Point system, the health education of food handlers, and efforts to change the consumer perception of fermented foods.

Bacteria↗

PubMed1995

Microbial degradation of amygdalin of bitter apricot seeds (Prunus armeniaca).

Amygdalin is a cyanogenic glycoside occurring among others in almonds and bitter apricot seeds with interesting levels of dietary protein. Utilization of seeds for human or animal nutrition requires adequate detoxification. In the present paper, selected filamentous fungi (Mucor circinelloides, Penicillium nalgiovense) and yeasts (Hanseniaspora valbyensis, Endomyces fibuliger) were tested for their in-situ ability to decompose amygdalin. The latter (Endomyces fibuliger) was best able to grow on autoclaved bitter apricot seeds and detoxify them from 30 microMol CN/g dry matter to less than 1 microMol CN/g dry matter after 48 h of incubation at 27 degrees C.

Amygdalin↗

PubMed1995

Contribution of selected fungi to the reduction of cyanogen levels during solid substrate fermentation of cassava.

The effect of six individual strains of the dominant microflora in solid substrate fermenting cassava on cyanogen levels was examined. Six out of eight batches of disinfected cassava root pieces were incubated for 72 h after inoculation with either of the fungi Geotrichum candidum, Mucor racemosus, Neurospora sitophila, Rhizopus oryzae and Rhizopus stolonifer, or a Bacillus sp., isolated from on-farm fermented cassava flours from Uganda. One non-inoculated batch was incubated as a reference. Levels of initial and final moisture and cyanogens were assayed. The experiment was done in quadruplicate. Incubation of disinfected root pieces reduced cyanogenic glucoside levels significantly to 62.7% (SD 2.8) of the initial value. Microbial growth resulted in significant additional reduction of the cyanogenic glucoside levels to 29.8% (SD 18.9) of the levels which were obtained after non-inoculated incubation. Among the tested strains, N. sitophila reduced cyanogenic glucoside levels most effectively, followed by R. stolonifer and R. oryzae. Of all fermented samples, both Rhizopus spp. showed highest proportion of residual cyanogens in the cyanohydrin form. Flours showed similar patterns of cyanogens as the batches they were prepared from. Cyanogenic glucoside level reduction was significantly correlated (r = 0.86) with the extent of root softening. It is concluded that both incubation and microbial activity are instrumental in reducing the potential toxicity of cassava during the solid substrate fermentation and that effectiveness varies considerably between the species of microorganisms applied.

Fermentation↗

PubMed1995

Degradation and fermentation of fructo-oligosaccharides by oral streptococci.

Fructo-oligosaccharides (FOS) are claimed to have a positive effect on the intestinal flora. They are being used in functional foods in Japan and Europe. This group have tested the degradation of two commercial FOS preparations by oral streptococci in order to predict the cariogenicity of these products. Both preparations could be fermented to some extent by the species of oral streptococci tested. The enzymes necessary for the degradation of FOS were inducible. Each strain showed a specific degradation pattern. All strains, particularly Streptococcus mutans rapidly produced acid, mainly lactic acid. Streptococcus mitis also produced high concentrations of acetic acid. Plaque formation by Strep. mutans was similar to the sucrose control. It is concluded that FOS are cariogenic to a similar extent as sucrose.

Acetates↗

PubMed1995

Reducing cassava toxicity by heap-fermentation in Uganda.

Processing of cassava roots by the Alur tribe in Uganda includes a stage of solid substrate fermentation in heaps. Changes in cyanogen levels during the process, microflora involved, and protein levels, amino acid patterns and mycotoxin contamination of the final products were studied. Processing was monitored at six rural households and repeated at laboratory site, comparing it to sun-drying. Flour samples from rural households were analysed for residual cyanogens, mutagenicity, cytotoxicity and aflatoxins. Mean (+/- SD) total cyanogen levels in flours collected at rural households were 20.3 (+/- 16.8) mg CN equivalents kg-1 dry weight in 1990 (n = 23) and 65.7 (+/- 56.7) in 1992 (n = 21). Mean (+/- SD) levels of cyanohydrins plus HCN were 9.1 (+/- 8.7) in the 1992 flours. Total cyanogen levels in the village monitored batches were reduced considerably by heap-fermentation from 436.3 (+/- 140.7) to 20.4 (+/- 14.0) mg CN equivalents kg-1 dry weight cassava. Residual cyanogen levels were positively correlated with particle size of the resulting crumbs. Heap-fermentation was significantly more effective in reducing cyanogen levels than sun-drying alone, but did not always result in innocuous levels of of cyanogens. Dominant mycelial growth was from the fungi Neurospora sitophila, Geotrichum candidum and Rhizopus oryzae. No mutagenicity, cytotoxicity nor aflatoxins could be detected in the flours. Protein quantity and quality were not significantly reduced. Cassava gel viscosity pattern was modified to the consumers' preference by this method. As the removal of cyanogens was more efficient and we found no new obvious health risk, heap-fermentation can be regarded as an improvement compared to sun-drying alone in areas where cassava varieties with higher cyanogen levels prevail, but we recommend optimisation of the process for ensuring still safer products.

Dietary Proteins↗

PubMed1995

The effects of processing on the availability of lysine in kenkey, a Ghanaian fermented maize food.

The effects of processing steps such as soaking, fermentation, cooking and drying on the availability of lysine in kenkey were investigated. Soaking increased lysine availability by 21% and 22% for maize and maize-cowpea mixtures, respectively. Cooking of soaked samples further improved lysine availability by 68% and 31% for maize and maize-cowpea mixtures, respectively. Further significant improvements in lysine availability were effected by fermentation and cooking and values of 3.42 and 4.43 g/16 g N were recorded, respectively for maize and maize-cowpea doughs fermented for 4 days and cooked for 3 h. Cabinet drying had no significant effect on lysine availability, but drum drying of fermented maize and maize-cowpea doughs significantly lowered lysine availability in the resulting kenkey. A 1:1 mixture of cabinet and drum dried flours gave a product with higher available lysine content than the drum dried flour.

Biological Availability↗

PubMed1995

Feeding of lactic acid-fermented high nutrient density weaning formula in paediatric settings in Ghana and Nigeria: acceptance by mother and infant and performance during recovery from acute diarrhoea.

A period of acute diarrhoea in infants is often associated with anorexia and weight loss. Catch-up growth is, therefore, necessary and this depends very much on the type of food, in terms of nutrient density, protein quality and digestibility, given to the child. Fermented (F) and non-fermented (NF) maize-soybean porridges of increased nutrient density were formulated and compared with traditionally fermented maize-only porridge (P) for acceptability using mothers in peri-urban Ghana as well as urban Nigeria as subjects. Subsequently, infants hospitalised in paediatric wards for acute diarrhoea, from the same communities in both countries, were assigned randomly to one or other of the three porridges. Infant subjects in all cases fell within the ages of 6-15 months. Complementary to regular breast-feeding, infants could consume as much porridge as they wanted and their total daily consumption was interpreted as an indication of acceptance. Although mothers in both the environments of Ghana and Nigeria rated P as more acceptable than F and NF, no significant difference was recorded in the quantitative intake by infants of the three formula groups. By adding enzyme-rich cereal malt flour (at the 1-5% level by weight) as a viscosity-thinning agent to F and NF porridges, it was possible to feed these porridges to infants at total solids concentration levels of 20-25% (wet basis) which is approximately double the solid matter content of the P porridge. Consequently, the daily nutrient intake by infants consuming F and NF porridges was considerably higher compared to the P porridge group. It is concluded that the concept of high nutrient density weaning foods is a feasible vehicle for an improvement of nutrient supply to infants.

Acute Disease↗

PubMed1994

Effect of roasting and fermentation on viscosity of cereal-legume based food formulas.

With the view of preparing semi-liquid weaning foods of high energy content, the influence of roasting (stationary hot air treatment) and fermentation (with natural and pure culture inocula) on the viscosity of maize-sorghum-soya porridges was investigated. Roasting resulted in porridges of significantly higher viscosity (cooked porridge cooled to 40 degrees C). Porridges made from the individual ingredients (maize, sorghum, soya) did not show this behaviour. Natural fermentation of mixed ingredients resulted in lower porridge viscosities (cooked porridge cooled to 40 degrees C, as well as hot-paste peak viscosity) when pH was 5.0-5.5. At lower pH the viscosity of the final porridges increased. Fermentation experiments of individual ingredients inoculated with pure cultures of Lactobacillus plantarum and Candida famata lead to the conclusion that various factors contribute to the effect of fermentation on porridge viscosity. Porridges of minimum viscosity are obtained at pH 5.0-5.5 corresponding with a moderate extent of fermentation. From a consumer safety point of view, it would be preferable to acidify to lower pH values (pH < 4.5). If necessary, viscosity adjustments could be made using malted cereals.

Candida↗

PubMed1993

Characterization and frequency distribution of species of lactic acid bacteria involved in the processing of mawè, a fermented maize dough from Benin.

Lactic acid bacteria involved in the natural fermentation of both home-produced and commercial mawè were investigated during a 72 h fermentation period. Lactobacillus spp. constitute the majority (94%) of the strains of the lactic acid bacteria isolated, among which 89% represent the Betabacterium group. They include L. fermentum (biotype cellobiosus) (41%), L. fermentum or L. reuteri (19%), L. brevis (26%), L. confusus (less than 2%), L. curvatus (less than 1%) and L. buchneri (less than 1%). Other isolated lactic acid bacteria were L. salivarius, Lactococcus lactis, Pediococcus pentosaceus, Pediococcus acidilactici and Leuconostoc mesenteroides. Several species were detected at the early stage of fermentation, but the final stage was dominated by L. fermentum (biotype cellobiosus) and L. fermentum or L. reuteri totalling 90% of the isolated strains. The trend was the same for both home-produced and commercial mawè. No strains of L. plantarum, generally reported as dominating lactic acid bacteria at the final stage of fermentation of most plant foods, were isolated.

Benin↗

PubMed1992

Formation of antigenic extracellular polysaccharides by selected strains of Mucor spp., Rhizopus spp., Rhizomucor spp., Absidia corymbifera and Syncephalastrum racemosum.

In this study, polyclonal IgG antibodies raised against extracellular polysaccharides (EPS) of Mucor racemosus were characterised as almost specific for moulds belonging to the order of Mucorales. Cross-reactivity in the ELISA could be observed only towards the yeast Pichia membranaefaciens. EPS were isolated from various cultures of M. hiemalis growing on six different carbon sources and two nitrogen sources, with ratios varying from 0.13 to 0.44 relative to the amount of biomass. Other strains including Mucor spp., Rhizopus spp., Rhizomucor spp., Absidia corymbifera and Syncephalastrum racemosum also excreted EPS, with ratios varying from 0.05 to 0.23. In all cases, the excreted EPS had similar antigenic properties as determined by ELISA. No enzymatic degradation of the antigenic parts of the polysaccharides could be observed upon prolonged incubation. Considering that all tested strains formed similar amounts of antigenic EPS there might be scope for the specific detection of biomass of Mucoralean moulds using ELISA techniques for example in food.

Antibodies, Fungal↗

PubMed1992

Accelerated natural lactic fermentation of cereal-based formulas at reduced water activity.

Energy required to dehydrate fermented cereal-based food formulas plays a significant part in the production cost. Therefore the effect of reduced moisture content on the fermentation was investigated. Generally, lactic fermentation at reduced moisture content resulted in increased final pH. Significant acidification still occurred at 0.33 kg water/kg dry matter corresponding to either aW = 0.925 in a sorghum-maize-soya (SMS) mixture, or aW = 0.950 in a sorghum-maize-milk powder (SMM) mixture. Acidification adequate for microbiological safety (pH < or = 4.5) was achieved at 0.54 kg water/kg dm in SMS (aW = 0.950) and 0.43 kg/kg dm in SMM (aW = 0.965). In stable accelerated natural lactic fermentations obtained by inoculum recycling ('back-slopping') at 30 degrees C, dominant lactic acid bacteria included Lactobacillus plantarum, L. brevis, L. acidophilus and Lactococcus lactis. Dominating yeasts were Saccharomyces cerevisiae and Candida krusei. L. plantarum isolated from high-moisture (1.5 kg/kg dry matter) SMS fermentations had higher specific growth rates than L. plantarum isolated from reduced moisture (0.54 kg/kg dm) SMS fermentations, when tested under similar aW conditions. This effect was not caused by previous culturing conditions; probably different strains of L. plantarum having different aW-optima dominate at high or reduced moisture conditions.

Edible Grain↗