The microbiology of ogiri production from castor seed (Ricinus communis)

The micro-organisms involved in the fermentation of castor seeds (Ricinus communis) by the traditional method were enumerated and isolated. The effect of using pure cultures to ferment the seeds were also investigated. Using the surface spread plate technique and plate count agar, aerobic counts obtained after seven days of fermentation was 1·7 × 10¹¹ cfu g⁻¹. Similarly anaerobic counts obtained on reinforced clostridial agar was 1·2 × 10⁵ cfu g⁻¹. Bacillus sp., Pseudomonas sp., Micrococcus sp. and Streptococcus sp. were isolated from fermenting castor seeds. The pH of fermenting castor seeds increased from 6·5 to 8·1 during the seven days of fermentation while the total titratable acidity decreased from 47 ml to 36 ml 0.1 N NaOH 100 g⁻¹ sample.The use of pure isolates to ferment the sterile seeds showed that only Bacillus sp. could ferment the seeds in pure cultures.     

Determination of the betaine content of feed ingredients using high‐performance liquid chromatography

A series of studies was conducted to establish a methodology for the accurate and efficient determination of betaine in different feed ingredients. The final methodology involves an extraction step in which the feed sample is heated for 3 h in a methanolic KOH solution using a Goldfisch apparatus. Impurities are removed by the addition of activated charcoal and concentrated (36%) HCl. After centrifugation the extractant is passed through a strong cation exchange resin (Dowex 50W‐X12, H⁺). The betaine retained in the column is eluted with 1.5 N HCl. A 2 ml aliquot of the elute is air dried and reconstituted with 1 ml of deionised water. HPLC separation with a cation exchange column (Partisil SCX‐10) is used for the separation of betaine from other compounds. The mobile phase is kept constant at 50 mM KH₂PO₄ in water, and eluted compounds are detected by UV absorbance (200 nm). The flow rate is maintained at 1.5 ml min^?1. This assay is very accurate over the range of betaine concentrations from 15 to 650 µg ml^?1, with a lower detection limit in feeds of approximately 500 µg g^?1 when 4 g of sample is extracted. Recovery assays done with standard betaine hydrochloride and hard red wheat resulted in a consistent recovery of 80%. Betaine content was quantified in several feed ingredients, including alfalfa (1.77 mg kg^?1), wheat (3.96 mg kg^?1), wheat middlings (4.98 mg kg^?1) and poultry meal (0.77 mg kg^?1). Betaine in corn and soybean meal was not detectable by this method, even when 16 g of sample was used (<125 mg kg^?1). Betaine present in several feed ingredients should influence choline supplementation to animal feeds and may have implications for human health. © 2002 Society of Chemical Industry     

Nonenzymatic Browning in Pear Juice Concentrate at Elevated Temperatures

The effect of temperature and soluble solids (°Brix) on nonenzymatic browning in pear juice concentrate was determined by following absorbance at 420 nm (A₄₂₀) over the temperature range of 50–80°C. Browning could be modeled as a zero order rate process with rates of 22.2 × 10⁻⁴ (45.2 °Brix), 36.9 × 10⁻⁴ (55.4 °Brix), 53.5 × 10⁻⁴ (65.1 °Brix) and 107 × 10⁻⁴ (72.5 °Brix) A₄₂₀· min⁻¹ at 80°C. Temperature dependence was described by the Arrhenius relationship with an average activation energy of 21.9 kcal · mole⁻¹. Formol titration indicated a 20% loss of amino acids during heating 4.4 hr at 80°C and no loss of carbohydrates was observed after any heating period.     

Isolation and characteristics of yeasts able to grow at low concentrations of nutrients

Seven oligotrophic yeasts, which can grow in a 10⁴-fold dilution of malt–yeast–glucose–peptone medium (10⁻⁴ YM), were mainly isolated from soil. These yeasts belong to the Cryptococcaceae. When inoculated at about 10² cells/ml in 10⁻⁴ YM, the isolates grew to 1·4×10³–2·4×10⁵ cells/ml after 3 days. Some culture collection yeasts fell into three groups according to their growth characteristics in 10⁻⁴ YM, one group showing characteristics of the oligotrophic yeasts. The half-saturation values of uptake by the five isolated oligotrophic yeasts for D-glucose, L-leucine and L-amino acids were 6·0–25·0, 1·7–43·3 and 3·5–21·6 μM, respectively. The oligotrophic yeasts suspended in 10 mM-phosphate buffer (pH 6·0) had high tolerances for starvation, and remained more than 15% viable after 90 days of starvation. © 1998 John Wiley & Sons, Ltd.     

Modified Atmosphere Packaging of Fresh Beansprouts

Freshly harvested beansprouts displayed a respiration rate of about 1 mmol O₂ kg⁻¹ h⁻¹ at 10°C which was strongly dependent on temperature, a 10-fold increase being observed every 16·5°C (z=16·5°C, ie Q₁₀=4·4). This commodity is also characterised by a high initial microbial load (about 10⁷ cells g⁻¹). During storage at various temperatures from 1 to 20°C, oxygen uptake rates dramatically increased with time and this phenomenon was well correlated with the development of aerobic microorganisms which reached 10⁹ cells g⁻¹ after 2 days at 20°C or 9 days at 1°C. Beansprouts were packaged in films, with permeabilities ranging from 950 to 200000 ml O₂ m⁻² day⁻¹ atm⁻¹, and stored at 8°C. Due to plant and microbial metabolism, oxygen concentrations decreased steadily within all packs until the onset of plant tissue decay. The latter occurred after 5–6 days with the least permeable films but did not occur within when the film permeability was over 100000 ml O₂ m⁻² day⁻¹ atm⁻¹. However, such films favoured brown discolouration, exudation texture and breakdown. The orientated polypropylene film (OPP) induced anoxic condition within 2 days and favoured anaerobic metabolism and necrosis of the sprouts. In all packages there was a rapid development of aerobic microorganisms and lactic acid bacteria that resulted in the accumulation of acetate and lactate and a decrease in pH. Thus, it clearly appeared that tissue decay was enhanced by microbial activity. At 8°C, 0·24 m² of film per kg of sprouts provided the optimal atmosphere composition (ie 5% oxygen and 15% carbon dioxide) when a film permeability of 50000 ml O₂ m⁻² day⁻¹ atm⁻¹ was used. These conditions allowed a shelf-life of 4–5 days.     

Emission rates of odorous compounds from pig slurries

Techniques to identify odorous compounds and to determine their emission rates from liquid wastes are described. Odorous compounds, or odorants, were analysed by GC-MS and odour concentration was measured by olfactometry after being emitted from slurry under controlled environmental conditions using a specially designed odour emission chamber. The slurries were obtained from pigs fed commercial and reduced crude protein diets and stored for 6 weeks, the effects of age and sex upon the odours produced in the headspace of the chamber were evaluated. The major odorous compounds were identified as belonging to the sulphide, volatile fatty acid, phenolic and indolic chemical groups. The mean emission rates from 200 litres of stirred slurry samples with a surface area of 1 m² using a wind speed of 4 m s⁻¹ were 1·35 million Odour Units min⁻¹ for odour and 214, 2·15, 0·21, 0·44, 0·068 and 0·02 mg min⁻¹ for hydrogen sulphide, ammonia, phenol, 4-methyl phenol, 4-ethyl phenol and indole respectively. Sex and sex/diet interaction effects were demonstrated for emission rates. © 1998 SCI.     

Modeling the inactivation of pectin methylesterase in pineapple puree during combined high-pressure and temperature treatments

The inactivation of pectin methylesterase (PME) in pineapple puree was studied within the domain of 0.1–600 MPa/30–70 °C/1 s–40 min. The combined effect of pressure-build up and decompression, as characterized by pulse inactivation (PI value), was modeled by the artificial neural network (ANN) through a tan-sigmoidal function of target pressure, target temperature, compression, and decompression time. Besides, nth order kinetic model was fitted during the isobaric-isothermal hold period. The extent of pulse inactivation of PME ranged from 15% (200 MPa/30 °C) to 67% (600 MPa/70 °C) and it increased at a higher temperature and/or pressure. The inactivation orders (n) during thermal (0.1 MPa/30–70 °C) and high pressure (100–600 MPa/30–70 °C) treatments were 1.15 and 1.3, respectively. The rate constant (k) ranged within 4.0 to 71.2 × 10⁻³ Uⁿ⁻¹·min⁻¹. A nonlinear model considering the pressure dependency of activation energy, and temperature dependency of activation volume was developed which adequately described the inactivation behavior of PME within the domain.Industrial relevancePectin methylesterase (PME) in the pineapple puree results in a product with a modified texture and consistency that is usually not entertained by the consumer. Therefore, pineapple puree has to be processed to inactivate PME to avoid the cloud loss. Now-a-days, high-pressure processing is being used for fruit products to retain the heat sensitive nutrients. In this sense, a model capable of predicting the exact inactivation behavior of PME during the treatment is very much obligatory for process design. This combined model developed in the study will help the food industry to come-up with the exact pressure-temperature-holding time combination achieving a certain degree of PME inactivation.     

Seasonal variations of the sugars in birch sap

The content of the main sugars of birch sap (Betula pendula Roth. and B. pubescens Ehrh.), which will be used for syrup production in Finland, were monitored by GLC as TMS-derivatives. Glucose and fructose had a concentration maximum at the end of April or at the beginning of May (5–8 g litre⁻¹). This sugar can be regarded as invert sugar. The content of sucrose (0–0·7 g litre⁻¹) decreased and in many cases it had totally disappeared by April. A correlation between sucrose and other sugars was not observed. The concentration of galactose was always low (0·01–0·03 g litre⁻¹). No diurnal variation was observed in the content of any sugar. The highest sap flow was obtained in the third flow week at the end of April and more than one-third of the total sugar yield could be collected during that period.     

Determination of lactose in sugar-free milk powder by capillary electrophoresis with electrochemical detection

Lactose in three sugar-free milk powder samples were satisfactorily determined by capillary electrophoresis with electrochemical detection using a 300 μm copper disk electrode as the working electrode in 0.1 mol/l NaOH medium. There was acceptable linearity (0.9969) between the peak current and concentration of lactose in the range from 5.0×10⁻⁶ to 5.0×10⁻³ g/ml with the detection limit (S/N=3) of 1×10⁻⁷g/ml. The proposed method was successfully applied to analyze the actual milk powder samples.     

The extraction of radiolabelled inorganic sulphate from blood plasma

A study was conducted into factors governing the efficiency of the ion exchange method for extracting ³⁵S-labelled inorganic sulphate (SO) from blood plasma, using Dowex′1-X8 ion exchange resin. The study compared effects of trichloroacetic acid (TCA) strength as protein precipitant, different HCl strengths as resin eluent, sodium citrate/HCl (SC/HCl) versus HCl as eluents, and evaluated ultrafiltrated (UF) plasma upon the adsorption and recovery of added ³⁵SO. Both adsorption and release of ³⁵SO from the resin were inhibited by the presence of TCA, and HCl was not as effective as 1 M SC/2 M HCl in releasing ³⁵SO adsorbed to resin. The rates of ³⁵SO adsorbed onto resin and recovered were markedly increased by using UF plasma and 1 M SC/2 M HCl as eluent, with the values being 96.3 ± 0.11% and 91.1 ± 0.39%, respectively, where 1 g resin was used. Therefore, the use of UF for deproteinising and 1 M SC/2M HCl as eluent are recommended for extracting ³⁵SO from blood plasma when Dowex′1-X8 resin is used as the ion exchanger.     

Proximate Composition and Seed Lipid Components of Sorghum Cultivars from Argentina

Seeds of 11 sorghum cultivars ( Sorghum bicolor ) from Argentina were analysed for proximate composition, fatty acids and sterols. Oil, protein, carbohydrate and ash contents varied between 41 and 66 g kg⁻¹, 111 and 156 g kg⁻¹, 670 and 730 g kg⁻¹ and 13·8 and 20·6 g kg⁻¹ of dry matter, respectively. Fatty acid profiles revealed that the major acids were palmitic (15·1–24·8%), oleic (29·9–41·8%) and linoleic (35·9–51·3%). Unsaponifiable matter was examined for sterols. Sitosterol was the prominent component in all cultivars (43·8–57·9%), followed by campesterol (18·7–29·1%) and stigmasterol (12·4–20·5%).     

Pyruvate decarboxylase: An indispensable enzyme for growth of Saccharomyces cerevisiae on glucose

In Saccharomyces cerevisiae, the structural genes PDC1, PDC5 and PDC6 each encode an active pyruvate decarboxylase. Replacement mutations in these genes were introduced in a homothallic wild-type strain, using the dominant marker genes APT1 and Tn5ble. A pyruvate-decarboxylase-negative (Pdc⁻) mutant lacking all three PDC genes exhibited a three-fold lower growth rate in complex medium with glucose than the isogenic wild-type strain. Growth in batch cultures on complex and defined media with ethanol was not impaired in Pdc⁻ strains. Furthermore, in ethanol-limited chemostat cultures, the biomass yield of Pdc⁻ and wild-type S. cerevisiae were identical. However, Pdc⁻ S. cerevisiae was unable to grow in batch cultures on a defined mineral medium with glucose as the sole carbon source. When aerobic, ethanol-limited chemostat cultures (D = 0·10 h⁻¹) were switched to a feed containing glucose as the sole carbon source, growth ceased after approximately 4 h and, consequently, the cultures washed out. The mutant was, however, able to grow in chemostat cultures on mixtures of glucose and small amounts of ethanol or acetate (5% on a carbon basis). No growth was observed when such cultures were used to inoculate batch cultures on glucose. Furthermore, when the mixed-substrate cultures were switched to a feed containing glucose as the sole carbon source, wash-out occurred. It is concluded that the mitochondrial pyruvate dehydrogenase complex cannot function as the sole source of acetyl-CoA during growth of S. cerevisiae on glucose, neither in batch cultures nor in glucose-limited chemostat cultures.     

Long-Term Cell Suspension Culture and Regeneration of the Single-Leafed Strawberry Fragaria vesca monophylla

Cell suspensions have been used for obtaining somaclonal variability and for the production of secondary metabolites, such as aroma compounds, natural dyes and drugs. Undifferentiated growing cells completely lose their regeneration capacity due to the formation of cells with abnormal DNA content during this phase. Callus culture of Fragaria vesca monophylla was obtained on agarised media supplemented with different growth regulators. Afterwards, a stable cell suspension was obtained on an SH (1972) medium supplemented with BSAA 0·25 mg litre⁻¹ and BA 0·1 mg litre⁻¹. The cells were poured onto an agarised regeneration medium, where it was possible to obtain regenerants. This is the first report of a stable cell suspension of a diploid Fragaria and regeneration after 2 years of unorganised cell culture.     

Rapid separation of soft drinks ingredients using high performance liquid chromatography

A method is described which uses high performance liquid chromatography in the reverse phase mode to separate amaranth, quinoline yellow, quinine sulphate, sunset yellow, caffeine, aspartame, saccharin, vanillin, sorbic acid, benzoic acid and green S in 4 min in samples of soft drinks. The final separation was achieved using 17·5% acetonitrile, 12·5% methanol, 70% buffer (0·85% v/v sulphuric acid and 17·5% mm potassium dihydrogen orthophosphate in water with the pH adjusted to 1·8), with a flow rate of 1·35 ml/min through a 100 mm × 4·6 mm column containing 3 μm Spherisorb octylsilane. The octylsilane material is fully capped with monolayer coverage and a carbon loading of 6% w/w, pore diameter of 8 nm and a surface area of 220 m²/g. This material was used in preference to the more widely used octadecylsilane as it provides shorter analysis time and allows for the use of more polar eluting solvents. Detection was at 220 nm, 0·1 AUFSD with an injection of 5 μl samples using a rotary injection valve. The standard solution concentration was 100 mg litre⁻¹ for aspartame; 20 mg litre⁻¹ for quinine sulphate, caffeine, vanillin, sorbic acid and benzoic acid and 5 mg litre⁻¹ for amaranth, quinoline yellow, sunset yellow, green S, tartrazine, indigo carmine and carmoisine.     

Nutrient contents,rumen protein degradability and antinutritional factors in some colour- and white-flowering cultivars of Vicia faba beans

Six colour-flowering (Scirocco, Alfred, Carola, Condor, Tina and Herz Freya) and six white-flowering (Caspar, Albatros, Gloria, Tyrol, Vasco and Cresta) cultivars of Vicia faba were studied. The crude protein contents of colour- and white-flowering cultivars were 267±13·6 and 283±18·8 g kg⁻¹, respectively, which did not differ significantly at P<0·05. The levels of lipids, crude fibre, starch and ash varied from 14 to 22 g kg⁻¹, 88 to 143 g kg⁻¹, 407 to 485 g kg⁻¹ and 32 to 42 g kg⁻¹, respectively. The calculated organic matter digestibility (OMD) and metabolisable energy (ME) of the white-flowering cultivars were significantly higher (P<0·001) than those of the colour-flowering cultivars (OMD: 889·1±26·6 g kg⁻¹ vs 797·5±17·1 g kg⁻¹; ME: 13·97±0·49 vs 12·30±0·34 MJ kg⁻¹). In all cultivars, sulphur amino acids were lower than adequate concentration when compared with recommended amino acid pattern of FAO/WHO/UNO reference protein for a 2–5-year-old child. The in vitro rumen nitrogen degradability of colour-flowering cultivars was significantly lower (P<0·01) compared to that of white-flowering cultivars (71·4±9·3% vs 88·0±11·1%). Amongst colour-flowering varieties, the contents of total phenols (TP), tannins (T) and condensed tannins (CT) were highest in Alfred (28·3, 21·0 and 35·4 g kg⁻¹, respectively). The contents of TP and T were similar (about 15 and 10 g kg⁻¹, respectively) in Carola, Tina and Herz Freya, and the CT were in the order: Condor>Herz Freya>Carola. The CT were not detected in white-flowering varieties, T were virtually absent and TP were extremely low (4·0–4·9 g kg⁻¹). The activities of other antinutritional factors (white- and colour-flowering cultivars, respectively: trypsin inhibitor activity 3·05±0·34 and 1·85±0·09 mg trypsin inhibited g⁻¹; lectin 27·2±9·4 and 27·1±5·1 mg ml⁻¹ assay medium producing haemagglutination; phytate 15·0±2·7 and 16·6±2·3 g kg⁻¹) were very low. A strong negative correlation (r=-0·92, P<0·001) between tannins and in vitro rumen protein degradability was observed which suggested that tannins have adverse effect on protein degradability. Similarly negative correlations between tannin levels and metabolisable energy (r=-0·89; P<0·001) and organic matter digestibility (r=-0·89; P<0·001) were observed. The correlation coefficient between trypsin inhibitor activity and tannins was negative and highly significant (r=-0·88, P<0·001), whereas between tannins and saponins it was significantly positive (r=0·96, P<0·001). ©1997 SCI     

High carbon dioxide pressure inactivation kinetics of Escherichia coli in broth

The inactivation kinetics of Escherichia coli by high pressure carbon dioxide was investigated. Inactivation rates increased with increasing pressure (25, 50, 75 and 100 atm), temperature, and exposure time. Microbial inactivation followed first order reaction kinetics, with inactivation rates (k) and decimal reduction times (D) that varied from 0·0848 to 0·4717 min⁻¹and from 4·90 to 27·46 min, respectively, at treatment temperatures (20, 30 and 40°C). The inactivation rates of E. coli were described by the apparent activation volume (ΔV^*) and a ‘pressure z value’, and they were greatly dependent on both temperature and pressure.     

Response of pancreatic secretions to feeding diets with low and high levels of soybean trypsin inhibitors in growing pigs

Studies were carried out to determine the effect of soybean trypsin inhibitors (SBTI) on exocrine pancreatic secretions in growing pigs. Six barrows with an average initial body weight (BW) of 27·1±1·4 kg were fitted with permanent pancreatic re-entrant cannulas and fed two diets according to a crossover design. Two maize starch-based diets were formulated to contain 200 g kg⁻¹ crude protein from either Nutrisoy (food grade defatted soy flour) or autoclaved Nutrisoy. The concentrations of SBTI in Nutrisoy and autoclaved Nutrisoy diets were 13·4 and 3·0 g kg⁻¹, respectively. The experiment consisted of two periods of 9 days each. The average BW at the start of the first and second experimental periods was 33·5±2·7 and 37·2±3·7 kg, respectively. The average BW at the conclusion of the experiment was 41·8±3·9 kg. The volume of pancreatic secretion was higher (P<0·01) when the Nutrisoy, as opposed to the autoclaved Nutrisoy diet was fed (3804 vs 2634 ml (24 h)⁻¹). The concen-tration of nitrogen and protein and specific activities (units litre⁻¹) of amylase, chymotrypsin and trypsin were lower (P<0·05) in pancreatic juice of pigs fed the Nutrisoy diet. There were no differences (P>0·05) in the total secretions of nitrogen (g (24 h)⁻¹) and total activities (units (24 h)⁻¹) of amylase, lipase, chymotrypsin and trypsin in pancreatic juice of pigs fed the Nutrisoy and autoclaved Nutrisoy diets. However, the total secretion of protein was slightly higher (25·7 vs 22·8 g (24 h)⁻¹; P<0·05) in pancreatic juice of pigs fed the autoclaved Nutrisoy diet, which corresponded with the increase in the secretion of protein-bound amino acids. There was also an increase in the total secretion of free amino acids in pancreatic juice. These studies show no effect of SBTI on the total enzyme activities in pancreatic juice of growing pigs. © 1998 SCI.     

Physicochemical characteristics and sensory optimisation of pineapple leather snack as affected by glucose syrup and pectin concentrations

Effects of glucose syrup (2%, 4%, and 6%) and pectin (0.5%, 1.0%, and 1.5%) concentrations on physicochemical characteristics and sensory acceptability of machine‐formed pineapple leather snack were investigated. Changes in glucose syrup and pectin concentrations significantly affected velocity of forming and total soluble solids content of pineapple paste, but did not affect thickness of pineapple leathers. Increasing pectin concentrations generally increased redness (a*) and yellowness (b*), and hardness (tensile force and work) while decreased moisture content and a_w of pineapple leathers. Two most acceptable pineapple leathers were prepared with 6% glucose syrup and 0.5–1.0% pectin. Increasing pectin concentration from 1.0% to 1.5% negatively affected toughness acceptability, which was attributed to reduced moisture and a_w, and increased tensile force and work. The optimum formulation range consisted of 3.5–6.0% glucose syrup and 0.5–1.0% pectin, yielding products with acceptability scores of 6.7–7.3 (on a 9‐point hedonic scale) for appearance, sourness, sweetness, overall‐taste, toughness and overall‐liking.     

Preparation of wheat gluten hydrolysates with high opioid activity

The opioid activity of wheat gluten hydrolysates (WGHs) prepared with several proteases was investigated in vitro by the contraction of guinea pig ileum (GPI), and WGHs with high opioid activity were further obtained through desalting and ultrafiltration (UF). The opioid activity varied with different wheat gluten hydrolysates. AWGH (WGH prepared with Alcalase), PPWGH (WGH prepared with Pepsin followed by Pancreatin) and PWGH (WGH prepared with pepsin) had relatively stronger inhibitory effects on the contraction of GPI with IC₅₀ values of 1.21 ± 0.25, 1.29 ± 0.38 and 1.57 ± 0.21 mg protein/ml, respectively. Subsequently, AWGH and PPWGH were desalted using cation exchange resin and anion exchange resin, with high nitrogen recovery (88.51 and 89.28%, respectively) and high desalting ratio (84.67 and 85.20%). The resultant hydrolysates were further fractionated by UF performed with a 3 kDa molecular weight cut-off membrane. Compared with AWGH and PPWGH, the 3 kDa-permeates have higher opioid activities with high protein content above 90% and low ash content about 1.5%. The molecular weight distributions of the two 3 kDa-permeates were concentrated below 2,000 Da.