Showing papers in "Journal of the Science of Food and Agriculture in 1986"

Breakdown of resistant and readily digestible starch by human gut bacteria

Abstract: Cooking and processing of starch-containing foodstuffs results in a portion of the starch becoming resistant to hydrolytic enzymes secreted in the small intestine of man. In order to determine whether this resistant starch (RS) was degraded in the colon, samples of RS and readily digestible starch (RDS) for comparisons were incubated with (a) cell-free supernatants from faecal suspensions and (b) washed faecal bacterial cell suspensions. The data obtained showed that, whereas pancreatic amylase and faecal supernatants hydrolysed RDS, with the production of oligosaccharides, RS totally resisted breakdown. In contrast, both RS and RDS were completely degraded by the washed bacterial cells with the generation of volatile fatty acids (VFA) and organic acids. Hydrolysis and fermentation of RDS was extremely rapid and, as a consequence, oligosaccharides and lactate initially accumulated in the culture medium. RS was broken down more slowly, however, and oligosaccharides and lactate never accumulated. The rate of polysaccharide hydrolysis had a significant effect on the quantities of VFA produced, in that 54% of carbohydrate was fermented to VFA in cultures incubated with RDS as sole carbon source as compared to only 30% in cultures incubated with RS. However no qualitative difference was observed in the VFA produced by fermentation of RDS or RS.

Dynamic rheological measurements on heat‐induced myosin gels: Effect of ionic strength, protein concentration and addition of adenosine triphosphate or pyrophosphate

Abstract: Myosin solutions and suspensions have been monitored during heating at pH 6.0 by using dynamic rheological measurements. The storage modulus (G′), the loss modulus (G) and the phase angle (δ) all showed a marked dependence on ionic strength in the temperature range 25–75°C. The filamentous gels (ionic strength <0.34) displayed a temporary reduction in G′ at temperatures between 50 and 60°C, presumably due to denaturation in parts of the rod portion of the myosin molecule. In the same temperature region the concentration dependence of G′ changed by a power of 2. The loss modulus also showed a marked concentration dependence, while the phase angle varied with concentration primarily at low (<50°C) temperatures. For the final gels, heated to 75°C, only G′ indicated marked differences due to different protein concentrations and ionic strengths; all gels were almost completely elastic (δ⋍1°). Adenosine triphosphate was shown to have a pronounced temporary effect on the filamentous gel formed at low temperatures, i.e. on the gel with the highest concentration dependence, while pyrophosphate had no such effect. However, both adenosine triphosphate (or rather its hydrolysis product: adenosine diphosphate) and pyrophosphate appeared to have a small, lasting effect on the heat-gelling ability of myosin: the former a detrimental effect, the latter an improvement.

Interrelationships between the concentrations of total condensed tannin, free condensed tannin and lignin in Lotus sp. and their possible consequences in ruminant nutrition

Abstract: Interrelationships between the concentrations of total condensed tannin (TCT), free condensed tannin (FCT) and lignin were studied to gain knowledge of how to manipulate nutritive value of fresh herbages containing condensed tannins fed to ruminants. FCT was defined as condensed tannin not bound by macerates of fresh plants, with both FCT and TCT being determined with vanillin HCl. Effects of spraying lotus with polyethylene glycol (mol. wt 3350; PEG) upon the relationship between FCT and TCT was also studied. Increasing soil nutrient and climatic stress caused large and similar increases in the concentrations of TCT and of lignin. Over the range 0–90 g kg−1 DM, 10% of TCT in Lotus sp. was detected as FCT, with increments in TCT above 90 g kg−1 DM being released almost entirely as FCT. PEG formed much stronger chemical bonds with condensed tannins than did plant proteins, and did not release FCT; consequently PEG application reduced the concentration of condensed tannin that was detectable with vanillin HCl. After disintegration of plant material, it is proposed that most condensed tannin is bound and co-precipitated as an insoluble complex with protein, that FCT is in equilibrium with this complex, and that bound and free tannin are indices of nutritionally beneficial and detrimental effects produced by condensed tannins in fresh forages eaten by ruminants. It was concluded that growing Lotus pedunculatus under conditions of stress leads to depressions in nutritive value through simultaneously increasing concentrations of lignin and FCT, both of which depress rumen carbohydrate digestion and voluntary intake, and that treatment with PEG offers a convenient method of separating effects due to condensed tannins from other factors influencing nutritive value.

Formation of two types of gels from bovine myosin

Abstract: Myosin was isolated from bovine m. semimembranosus and gels were formed by heat treatment at different pH values and ionic strengths. The gels were subjected to rigidity measurements and their microstructure was studied by scanning electron microscopy. This article provides evidence that myosin can form two completely different gel structures in the pH range 5.5–6.0, depending on ionic strength. Fine stranded gel structures were formed at low ionic strength (0.25M KCl), whereas coarsely aggregated gel structures were formed at high ionic strength (0.6M KCl). The fine stranded structure had a higher rigidity than the coarsely aggregated structure. It was found that all fine strand myosin gels were formed from turbid solutions and the aggregate gels from clear solutions. When the pH was lowered to 4 in 0.6M KCl a strand-type gel structure formed spontaneously on dialysis, even without heat treatment. This structure did not change in character on heating. It was concluded that the conditions required for the formation of strand-type myosin gels were already present before the heat treatment and that the strands were made up of myosin filaments at certain pH and ionic strength combinations, which produced a turbid solution. The strand-type structures were considered specific with regard to myosin interactions which was not the case for the aggregated structures. Variation of the heating temperature in the range 55 to 65°C had no major effect on the type of structure formed.

Chemical and physical characteristics of phosphate rock materials of varying reactivity

Abstract: Several chemical and physical properties of 10 phosphate rock (PR) materials of varying reactivity were evaluated. These included North Carolina phosphate rock (NCPR), Sechura phosphate rock (SPR), Chatham Rise phosphorite (CRP), Arad phosphate rock (APR), Gafsa phosphate rock (GPR), North Florida phosphate rock (NFPR), Jordanian phosphate rock (JPR), Mexican phosphate rock (MPR), Nauru Island phosphate rock (NIPR), and Makatea Island phosphate rock (MIPR). Concentrations of As and Cd were highest in NCPR and U was higher in APR and CRP than in the other reactive PR materials. Because Cd and U can accumulate in biological systems, it may be necessary to direct more attention towards the likely implications of Cd and U concentrations when evaluating a PR for direct application. Three sequential extractions with 2% citric acid may be more useful for comparing the chemical solubility of PR materials, particularly for those containing appreciable CaCO3. For each particle-size fraction from 500 μm, SPR was more soluble in 2% citric acid than was NCPR. The higher solubility of SPR than NCPR in 2% citric acid, 2% formic acid, and neutral ammonium citrate possibly results from a higher chemical reactivity rather than from any difference in the surface area presented for dissolution. The poor relationship obtained between surface area and the solubility of the PR materials in the three chemical extractants suggests that surface area plays a secondary role to chemical reactivity in controlling the solubility of a PR in a chemical extractant. A Promesh plot provided an effective method for describing the particle-size characteristics of those PR materials which occurred as sands. Fundamental characteristics, such as mean particle size and uniformity, can readily be determined from a Promesh plot.

Identification and determination of volatile constituents in wines from different vine cultivars

Abstract: Volatile constituents of experimental wines from five white vine cultivars (Terret, Ugni Blanc, Clairette, Sauvignon, Picpoul) and from five red vine cultivars (Cinsaut, Carignan, Grenache, Cabernet-Sauvignon, Syrah) were analysed using standard liquid-liquid extraction, chemical fractionation, adsorption chromatography on silica gel, low- and high-performance gas-liquid chromatography and gas chromatography-mass spectrometry. One hundred and twenty two substances were positively identified and 15 tentatively identified. Fourteen of them had not been detected previously in wine. Some sensory evaluation of the various separated compounds was also attempted and a total of 131 volatile constituents were quantified in triplicate with calculation of the 95% confidence limits. The proportions and biogenesis of these constituents are briefly discussed.

The effect of dietary linoleic acid on the firmness of backfat in pigs of 85 kg live weight

Abstract: Three groups of 15 female pigs were fed diets containing 0.8%, 1.1%, or 1.8% linoleic acid from 20 to 35 kg followed by 1.0%, 1.2% or 1.4% linoleic acid respectively from 35 kg to slaughter at 85 kg live-weight. Pigs grew at similar rates on all three diets and had similar proportions of carcass fat. The mean proportions of linoleic acid in the backfat lipids were 8.6%, 11.0%, and 13.9% respectively as the amount of the diet increased. There was a significant correlation between the concentration of linoleic acid in the inner backfat lipid and P2 backfat thickness for those animals on the high and medium linoleic acid diets but not for those on the low diet. Backfat from pigs fed the high linoleic acid diet was softer than that from the other two groups of pigs which could not be distinguished using the subjective finger probe method. Using a mechanical probe backfat consistency was distinguished between all three groups and was inversely correlated (r=−0.775, P<0.001) with the concentration of linoleic acid in the lipid. However, none of the pigs had fat which was too soft for bacon production based on either consistency data or linoleic acid content. If 15% linoleic acid is taken to be the maximum acceptable in bacon, then extrapolation of the regression of linoleic acid concentration on backfat thickness suggested that only the 1.4% linoleic acid diet is likely to result in unacceptably soft fat as pigs become leaner. However, this high concentration, although frequently present in current feeds, is not necessary since it is twice that recommended for normal growth and development of pigs.

Saponin content of soya and some commercial soya products by means of high‐performance liquid chromatography of the sapogenins

Abstract: Quantitative high-performance liquid chromatography of the sapogenins was used to estimate the saponin content of soya beans (Glycine max (L.) Merr.) and commercially prepared soya flours, protein concentrate, protein isolate and soya milks. The level of saponin in whole soya beans as estimated (0.47%) was in agreement with other recent estimates. Saponins were also found in the various soya flours (0.43–0.67%), protein isolate (0.76%), soya milks (0.022–0.026%) but not in the protein concentrate.

Zinc, copper and nickel concentrations in ryegrass grown on sewage sludge‐contaminated soils of different pH

Abstract: Sewage sludges containing high concentrations of zinc, copper and nickel were added separately to samples of two soils, a silty clay loam and a sandy loam, on which pH levels between 4.5 and 7.5 had been established; there were also treatments with sludge of low metal content or no-sludge. Soil-sludge mixtures were either continuously cropped with ryegrass or kept uncropped in pots in the glasshouse for 6 months. Zinc and nickel concentrations in 0.1 μM calcium chloride extracts of soils from the cropped pots and in solutions displaced from the fallow pots decreased with increasing pH over the range tested, but copper concentrations remained steady above pH 5.5; individual metal concentrations in ryegrass tops followed the same pattern with pH as those in extracted solutions. Squared correlation coefficients (R7) between shoot metal concentrations and concentrations of metals in EDTA, DPTA or calcium chloride extracts or displaced solutions, when taken over all soil, pH and sludge treatments, were >0.60 (P<0.001). Ryegrass yield reductions occurred on soils contaminated with each of the three metal sludges when soil pH was 5.5 or below.

Changes during growth in anatomical and chemical composition and in‐vitro degradability of lucerne

Abstract: Lucerne (alfalfa) was harvested at different stages of maturity and the plants classified according to a phenological scale. The main class was separated into anatomical parts and analysed for content of extractives and crude protein and in-vitro degradability. Whole crop samples were also analysed for polysaccharide residues, Klason lignin and in-vitro degradability of crude protein and polysaccharide residues. The composition of the plant changed during maturation with an increase of the stem fraction from 18.5% to 50.7% of dry matter and a corresponding decrease in the leaf fraction from 72.9% to 18.4% of dry matter. The leaf fraction changed least in content of extractives and crude protein and in-vitro degradability while in the stems all these paramaters decreased radically. Chemical analysis of residues after incubation with rumen liquor in vitro of whole crop samples revealed that the degradability of crude protein declined from about 90% to about 80% and of non-starch polysaccharides from about 90% to about 60% during maturation. Xylose was the least degradable polysaccharide residue at all harvests. Xylose residues also showed the greatest decrease in degradability during growth. A comparison showed that stage of development and harvest date were of practically equal value as predictor of crude protein content in lucerne.

Changes in the nitrogenous components of gamma‐irradiated and inoculated ensiled ryegrass

Abstract: A study was made of the role of plant and microbial enzymes in the major nitrogenous changes during ensilage. Perennial ryegrass was ensiled directly, after gamma-irradiation, and after inoculation of the sterile grass with homofermentative lactobacilli. Plant enzymes mainly were responsible for proteolysis, whereas amino acid metabolism was the result of microbial activity. Inoculation reduced proteolysis: this was considered to be a result of rapid acidification. Lactobacillus plantarum and Streptococcus faecalis were shown to be non-proteolytic species with a limited ability to catabolise amino acids. Substantial quantities of water-soluble carbohydrates were made available during ensilage.

Yield and composition of cell wall residues isolated from various feedstuffs used for non-ruminant farm animals

Abstract: The contents of cell wall residue were measured in 14 common feedstuffs used for non-ruminant farm animals by utilising a technique involving pronase and α-amylase treatments. Comparison with the contents of neutral detergent fibre (NDF) revealed that the NDF procedure underestimated cell wall contents in the dicotyledonous plant materials. The losses of cell wall material due to the neutral detergent solution were correlated (r=0.931, P<0.01) with the amount of pectic substances present in the cell wall residues of the dicotyledonous plant materials. Cell wall residues were analysed for starch, crude protein, polysaccharides, condensed tannins, sulphuric acid lignin, acetyl bromide lignin, and ash. Condensed tannins in the cell wall residues of sorghum, rapeseed meal and field bean resulted in a large protein contamination (11.3–26.6%) of these residues and to an overestimation of their lignin content. Compositions of polysaccharides are discussed from chemical and nutritonal viewpoints.

Effect of processing on the antinutrient content of rapeseed.

Abstract: The effects of dry extrusion of mixtures of rapeseed and soya bean on total and individual glucosinolates, selected glucosinolate hydrolysis products, myrosinase, sinapine and tannins have been compared with those of more conventional processing, e.g. lime treatment, micronisation and ammoniation. Extrusion at 150°C effectively inactivated myrosinase but had relatively little effect on glucosinolate content unless chemicals were added before extrusion; the most effective combination, 5% alkali+1% ferrous sulphate, reduced the total glucosinolate content by 80%. Under the latter conditions very high (>30 μmol g−1 defatted meal) levels of nitriles were produced, leading to the suggestion that nitriles in addition to oxazolidine-2-thione and isothiocyanates be used to monitor the effectiveness of processing techniques. None of the extrusion conditions showed any significant effect on reducing sinapine or tannin contents. In view of the chemical data presented, and the probable adverse effects which the processing conditions selected have on the nutritional value of the processed meal it seems unlikely that extrusion will play a significant role in rapeseed detoxification.

The effects of α‐amylase inhibitors on insect storage pests: Inhibition of α‐amylase in vitro and effects on development in vivo

Abstract: Protein α-amylase inhibitors were prepared from wheat and their effects tested against insect storage pests both in vitro against the insect α-amylases and in vivo in insect feeding trials. Inhibitor fraction A was found to inhibit porcine pancreatic α-amylase but not insect α-amylases, whereas fractions B, C and D (0.28) did not inhibit porcine pancreatic α-amylase but were strong inhibitors of digestive α-amylases from larvae of Tribolium confusum, a storage pest of wheat products, and Callosobruchus maculatus, a storage pest of legume seeds. Fraction D, which was a single polypeptide of Mr 13 000 was the most effective inhibitor in vitro. It would appear that the degree of inhibition by the wheat α-amylase inhibitor preparations can be correlated with the presence of the Mr 13 000 (0.28) polypeptide since the purer this polypeptide the stronger was the inhibition; fraction A which contained two polypeptides of Mr 60 000 and 58 000 caused no inhibition. The effects of fractions B and C on larval development were determined in insect feeding trials. With C. maculatus both fractions were toxic, their relative effectiveness being directly paralleled by their effectiveness observed in vitro. Only fraction C was tested against T. confusum in feeding trials. Despite this fraction being equally effective against both pests in vitro it had very little effect upon larval development of T. confusum in vivo, thus suggesting that this organism is able to detoxify the wheat α-amylase inhibitors. As far as the authors are aware, this is the first time that the effects of identified inhibitor fractions have been monitored both in vitro and in vivo. The results, in contrast to previous proposals, suggest that selecting wheat varieties for high α-amylase inhibitory activity may not be a very reliable criterion in selecting for insect resistance.

Preliminary studies on acidity-astringency interactions in model solutions and wines

Abstract: Intensity of astringency in model solutions and wines varying in total acid and total phenols was evaluated by paired comparisons by 10 trained judges. Model solutions consisted of tannic (500, 1000, 2000 mg litre−1) and tartaric (0, 2, 4, 6 g litre−1) acids dissolved in aqueous solutions of ethanol (120 ml litre−1) and sucrose (5 g litre−1). Wine solutions were prepared by addition of citric acid (0, 0.5, 1, 2, 3 g litre−1 as tartaric acid) to a high phenol-red wine (2645 mg litre−1 GAE) and a moderate phenol-white wine (800 mg litre−1 GAE). At all three levels of tannic acid, astringency of model solutions increased significantly (P<0.001) with tartaric acid concentration. Astringency of white wine also increased significantly (P<0.05) with citric acid concentration. A negative linear relation was found between relative astringency and pH at a given tannin level for both model solutions and white wine. As pH was reduced, more phenolic molecules were in the phenol form thereby increasing the likelihood of hydrogen bonding between hydroxyl groups of wine tannins and ketoimide groups of mouth proteins. The preliminary hypothesis that hydrogen bonding is the main reaction involved in the formation of protein-tannin complexes resulting in the sensation of astringency was reinforced.

The saponin content and sapogenol composition of the seed of 13 varieties of legume

Abstract: The total saponin content of various legume seeds together with their sapogenol composition have been determined. Extraction of the defatted flours was effected with methanol and subsequent acid hydrolysis yielded the soyasapogenols which were analysed using gas and thin-layer chromatography. The saponin levels ranged from 0–0.65% for defatted seed while the major sapogenol present in these saponins was soyasapogenol B. The figures obtained are compared with those previously reported and reasons are suggested for the discrepancies.

Dynamic rheological measurements on heat‐induced myosin gels: An evaluation of the method's suitability for the filamentous gels

Abstract: Formation of bovine myosin gels (10 mg ml−1) by heat treatment at pH 6 and an ionic strength of 0.24 M has been monitored by using the Bohlin Rheometer System in the oscillatory mode. Rheological thermograms were determined with a general repeatability of about 2% for a given suspension. A pronounced maximum and an accompanying minimum in storage modulus (G′) were found at about 50 and 55°C, respectively. The thermograms for the loss modulus (G″) and the phase angle (δ) displayed complex behaviour as well, suggesting a multitransition process. Presumably, denaturational events in parts of the molecule are responsible for the complex rheology observed. This complexity is not related to trivial wall slippage as data obtained from cells with different gap sizes were highly reproducible and consistent with other measurements. A decrease in heating rate from 2.5 to 0.1°C min−1 had a large effect on G′; it increased from 905 to 1600 N m−2 for gels at 75°C. The phase angle was also affected by the heating rate, especially at about 55°C. The effect of increasing the strain from 0.003 to about 0.1 was significant in two temperature regions; G′ at temperatures higher than 65°C and δ at temperatures lower than 54°C increased with increasing strain.

Free α-amino nitrogen production in sorghum beer mashing

Abstract: Free α-amino nitrogen (FAN) is an essential nutrient for yeast growth during fermentation. Under normal conditions of sorghum beer mashing, 60°C at pH 4.0, production of FAN by proteolysis accounts for approximately 30% of wort FAN, the remaining 70% being preformed in the malt and adjunct. The quality of the FAN in sorghum beer worts is good as it does not contain a high percentage of proline. Optimum conditions for FAN production during mashing are 51°C and pH 4.6. Wort FAN was increased proportionally by raising the ratio of sorghum malt to adjunct and conversely decreased by raising the ratio of adjunct to malt. FAN was also increased by the addition to the mash of a microbial proteolytic enzyme. Wort FAN is directly proportional to malt FAN.

Effect of nitrogen fertiliser on the nitrate contents of field vegetables grown in Britain

Abstract: The nitrate and percentage organic nitrogen contents of 14 vegetable and two arable crops were measured after they had been grown with different levels of N-fertiliser. Foliage crops always contained substantial quantities of nitrate which increased with increase in the rate of N-fertiliser application. Grain of legumes and cereals, storage roots of carrots, parsnips and sugar beet, and onion bulbs and leeks contained no detectable amounts of nitrate even when N-fertiliser application rates were very high. Storage roots of red beet, swede and white turnip contained more than 3 mg NON g−1 dry weight when grown with exceptionally high levels of fertiliser-N but contained very little when grown with the optimum amount of fertiliser-N or less. An equation was developed that linked NON to percentage organic-N for those parts of plants that could accumulate nitrate. It gave good fits to the data from seven crop species grown at a range of different levels of N-nutrition. It is estimated from the foregoing data and a survey of household food consumption that the average British person consumes about 60 mg NON week−1 in field vegetables. If N-fertilisers were withheld consumption would be about 30 mg and if excess were applied it would be about 120 mg NON week−1.

Effects of temperature on the ripening of mango fruit (mangifera indica L. var. tommy atkins)

Abstract: The effects of temperature on the ripening of Tommy Atkins mango were studied. Ripening temperature can affect fruit colour, flavour and texture development differently. Fruits at 12°C did not ripen to full eating quality during the 16 days of the experiment. Sugar levels were comparable with those at other temperatures, but acid levels were higher; they retained some green coloration, had lower pulp carotenoids and showed incomplete softening. After 15 days at 17°C, fruits had softened and degreened to an acceptable level but had a poor pulp colour. They were comparatively high in sugars but were also high in acids, resulting in a low sugar:acid ratio. Fruits kept at 22, 27 and 32°C all showed the development of good quality characteristics of high chlorophyll breakdown, high pulp carotenoids, a good texture and a balanced sugar: acid ratio. Similar characteristics were shown at 37°C, although the peel generally appeared mottled and the pulp had slightly lower sugar:acid ratios.

Incidence of bitter pit in relation to the calcium content of apples: Problems and paradoxes, a review

Abstract: The problems of relating low fruit calcium concentrations in stored apples to the development of bitter pit lesions are reviewed. They include nomenclature, anomalous fruit analyses, variability in the susceptibility of apples to pitting and in the time and rate of pit development, effect of harvest date, accumulation of calcium in pitted tissue and the apparant translocation of calcium during storage from the core into zones of tissue most at risk. Recent evidence suggests that bitter pit lesions are induced by the removal of calcium from these outer zones to meet intermittent demands by the core tissue.

Nutritional value of acid stabilised silage and liquefied fish protein

Abstract: Fish silage made by a conventional method (pH 4.0) contained a variety of active enzyme systems which not only hydrolysed fish proteins to short peptides and free amino acids, but also caused the degradation of free amino acids to ammonia and other metabolic products. Acid-stabilised fish silage (pH 2.0) contained only those polypeptides released by endogenous pepsins with only slight accumulation of free amino acids and degradation products. Liquefied fish which was autolysed for less than 1 h at 60°C at physiological pH (6.2–6.6) and then pasteurised and acidified to pH 4.0 contained polypeptides of intermediate length which remained stable. These processes provide a means for adjusting the peptide and free amino acid content of autolysed fish protein to suit the nutritional requirements of a variety of aquatic and terrestrial species.

Correlation of theaflavins content and valuations of Kenyan black teas.

Abstract: Correlation between theaflavins content and tasters' valuations of Kenyan black teas generally give positive but statistically non-significant correlation coefficients. In 105 correlations using 12 samples each, only eight analyses gave statistically significant (P⩽0.05) correlations. Theaflavins contributed positively towards valuations but Kenyan black plain teas have high and possibly above optimum theaflavins content. Consequently other factors appear to play major roles in tea pricing, for example the generally higher prices realised by Kenyan black plain teas compared to Malawi black plain teas can only be partly attributed to the higher theaflavins content of the Kenyan teas.

Processing and fermentation of the african locust bean (Parkia filicoidea Welw.) to produce dawadawa

Abstract: African locust beans (Parkia filicoidea Welw.) were processed and fermented to the traditional West African condiment dawadawa. The beans were transformed to ‘processed substrate’ by boiling and dehulling, and then fermented at 37°C in static fermenter units. The overall mass balance and the mass balances of several bean components (moisture, fat, protein, ash and carbohydrate) were studied. It was found that 1.0 kg of raw beans (6.4% moisture) yielded 1.3 kg of processed substrate (63% moisture) which in turn was converted to 1.2 kg of dawadawa (65% moisture). The loss of bean solids during processing was due to the removal of adhering pulp and testa as well as to solids extraction during boiling and washing. Overall, 57% of the bean dry weight, 85% of the carbohydrate, 48% of the ash, 40% of the protein and 1% of the fat were lost in the conversion of raw beans to dawadawa. The dawadawa had considerably higher fat and protein contents than the raw beans and was a pleasant tasting food whereas the raw beans were inedible. Some microbiological aspects of the fermentation were also investigated. Normally prepared fermentation substrate was compared with both sterilised and radappertised beans in terms of conversion to dawadawa, number of colony forming units present, and the development of pH and titratable acidity. The presence of microorganisms was found to be obligatory for the conversion to proceed. Simultaneous increases in both pH and titratable acidity were observed during the fermentation.

Nutritive value of rapeseed meal: Effects of individual glucosinolates

Abstract: In the first of a series of studies on the nutritional value of rapeseed meal, rats were fed diets containing six individual glucosinolates over a period of 29 days. The diets included progoitrin and gluconapin both of which are major components of high glucosinolate rapeseed cultivars. No reduction of feed intake or growth rate was noted and thyroid weights were significantly affected only by the progoitrin diet, which also produced small increases in the weights of the livers and kidneys. There was no depression of plasma thyroid hormone levels.

Studies on the relationship between antioxidative activity of rice hull and germination ability of rice seeds

Abstract: An investigation of the germination potentials of seeds of Indica and Japonica rice varieties revealed that while the long-life rice seeds retained the germination ability even on storage for a year at 30°C, the germination ability of the short-life rice seeds tended to decrease when stored beyond 6 months. The role of rice hull constituents in the preservation of the germination property during ageing of rice seeds was investigated with special emphasis on rice antioxidants. Antioxidative assay with chloroform-methanol and methanol-water extracts of hull, bran-germ and grain fractions of two Indica and five Japonica rice varieties indicated that all of the seed varieties belonging to Indica and Japonica possessed a strong antioxidative activity in the hull fraction. Hull extracts of long-life rice seeds showed relatively higher activities than those of short-life rice seeds. In contrast, hull extracts of long-life rice seeds had higher inhibitory effects on lipoxygenase activity than did those of short-life varieties. Quantification of the natural antioxidants indicated that α-tocopherol in rice oil to be present in the range of 318.3–450.1 μg g−1 oil while the amount of oryzanol in the hull, bran-germ and grain fractions of rice was found to be 1.0–5.8, 95.4–279.8 and 3.0–9.4 μg g−1 sample respectively. The results, however, did not show any positive correlation between the amount of natural antioxidants in rice hull and germination potentials of rice seeds. The amount of total phenolic constituents in rice hull was found to range from 190–390 μg g−1 sample, the levels being far higher in long-life rice seeds in comparison with the short-life rice seeds. These values seemed to agree well with the germination data of the corresponding rice variety. The investigation revealed a strong influence of the level of phenolic constituents in rice hull on the storability of rice seeds.

Saponin content of chickpea and black gram: Varietal differences and effects of processing and cooking methods

Abstract: Differences were observed in saponin contents of eight varieties of chickpea (Cicer arietinum) and four of black gram (Phaseolus mungo). Common domestic processing and cooking treatments reduced the saponin level of the pulses significantly. Sprouting had the most pronounced effect followed by autoclaving, soaking and ordinary cooking. Cooking of soaked as well as unsoaked seeds had a similar diminishing effect.

Extractability and bioavailability of zinic, nickle, cadmium and copper in three Danish soils sampled 5 years after application of sewage sludge

Abstract: Soils from three Danish experiments testing identical quantities of sewage sludge were sampled 5 years after the application of sludge ceased. Chemical studies on the soils involving single and sequential extractions, displaced solution measurements and plant uptake experiments in a glasshouse showed that sludge-added Zn, Ni, Cd and Cu persisted in extractable and bioavailable forms in the topsoils and that soil pH and texture influenced their chemistry and availability. The EDTA-extractabilities of native and of sludge-added Cd were similar, but native Zn, Ni and Cu were less extractable than sludge-added metals. 0.1 M-calcium chloride was the best extractant for predicting plant uptake. In some cases a chelating extractant combined with pH measurements is suitable if a single reagent is to be used for all four metals.

A simplified procedure for quantification of potato glycoalkaloids in tuber extracts by h.p.l.c. ; comparison with ELISA and a colorimetric method

Abstract: An improved high-performance liquid chromatography (h.p.l.c.) procedure for determination of glycoalkaloid levels in potato tubers has been developed in which Sep-Pak cartridges replace the commonly used alkaline precipitation for clean-up of tuber extracts. Glycoalkaloids are extracted from fresh tuber tissue into an aqueous medium, the extract is submitted to clean-up and α-solanine and α-chaconine are quantitatively separated on a reversed phase column with ethanolamine modifier added to the mobile phase. Potato tubers were comparatively analysed for their glycoalkaloid content by this and two other methods: a recently developed immunoassay (ELISA) and a colorimetric procedure representing the traditional chemical approach. Agreement between the h.p.l.c. and the other methods was good.

Aflatoxin determination in peanut butter by enzyme‐linked immunosorbent assay

Abstract: High specificity, high titre antisera to aflatoxins B1 and G1 have been produced by immunisation of rabbits with a bovine serum albumin-aflatoxin B1 conjugate. The antiserum has been used to set up an indirect, double antibody microtitration plate enzyme-linked immunosorbent assay with a limit of detection of 0.1 pg toxin per well. The assay has been validated for application to peanut butter, and demonstrates many advantages over conventional methodology, including the requirement for minimal sample preparation before assay, its technical simplicity, and its potential high sample through-put.