Studies on the effect of protectants on Lactobacillus acidophilus strain dehydrated under controlled low-temperature vacuum dehydration and freeze-drying by using response surface methodology

Ca²⁺ (0–60 g litre^?1), glycerol (0–100 g litre^?1), and non-fat dry milk solids (NFDMS, 0–140 g litre^?1) were combined to study their effects on the survival of Lactobacillus acidophilus in controlled low-temperature vacuum dehydration and freeze-drying. A three-variable (each at three-levels) design method was used and analysed by fitting a quadratic response surface. These factors were found to be significantly effective on survival. Fitted quadratic regression equations were plotted using a graphing software package. Conditions for the best survival of freeze-drying was found to be Ca²⁺ 5.34 g litre^?1. NFDMS 100.8 g litre^?1, and glycerol 41.5 g litre^?1 and that of controlled low-temperature vacuum dehydration was Ca²⁺ 5.67 g litre^?1, NFDMS 107.1 g litre^?1, and glycerol 41.0 g litre^?1. Models obtained were tested using t-tests. Survival of freezing under different conditions was found to be not significantly different.     

Inexpensive,rapid screening method for aflatoxins in peanuts and peanut products

Surveys of major Brazilian foodstuffs demonstrated that peanuts and peanut products continue to be very susceptible to aflatoxin contamination. To prevent, or at least minimise, the problem the aflatoxins need to be monitored by a rapid and inexpensive screening method. The AOAC Romer method has been used and found highly reliable. However, the clean-up step utilises anhydrous FeCl₃ and basic CuCO₃ which are expensive and not readily available in Brazil. Thus, the extraction (with a mixture of 270 ml methanol plus 30ml 40 g litre^?1 aqueous KCl) and clean-up (150 ml 100 g litre^?1 aqueous CuSO₄) steps of the method of Soares and Rodriguez-Amaya (1985) were combined with the AOAC minicolumn to provide a rapid, inexpensive screening technique. Fifty-two sample lots of peanuts and peanut products were screened by this and Romer's method, and the results were in complete agreement: 28 samples were negative, four < 20 μg kg^?1, 12 in the range 20–50 μg kg^?1, three in the range 50–100 μg kg^?1 and 5 >100 μg kg^?1. The results also agreed well when the extracts obtained by the two methods were submitted to quantitative TLC.     

The yeast flora of ensiled whole-crop maize

The yeast flora in samples of 13 different whole-crop maize silages was shown to be predominated by Candida krusei, C. lambica, Saccharomyces dairensis, S. exiguus, C. holmii or C. milleri. All these strains fermented glucose but, except for the latter three species, not sucrose, α-trehalose or raffinose. Under conditions resembling those in silage, i.e. at pH 4.0 in the presence of a complex nitrogen source, all strains assimilated lactic and acetic acids. This result suggests that the predominant yeasts in silage should not be distinguished into lactate utilisers and lactate non-utilisers. All strains, except those of Saccharomyces dairensis, tolerated acetic acid (5 g litre^?1) and grew at pH 4.0 in a mineral salts medium containing lactic acid (10 g litre^?1), acetic acid (5 g litre^?1) and yeast extract (1 g litre^?1). Growth in this medium was completely inhibited by the cationic detergent Arquad C33W (20 mg litre^?1), propionic acid (5 g litre^?1), benzoic acid (5 g litre^?1) or salicylic acid (10 g litre^?1).     

ESTIMATION OF VOLATILE SULPHUR COMPOUNDS IN BEER

A method has been developed for the quantitative estimation of volatile sulphur compounds in beer at levels below 0.1 μg litre^?1. The method relies on the concentration of beer headspace volatiles onto a porous polymer followed by injection into a capillary gas chromatographic column using a thermal desorption cold trap injector. The volatile components are separated using temperature programming and detected by a flame photometric detector specific for sulphur compounds. The mean concentrations and the estimates of r₉₅ (μg litre^?1) for volatile sulphur compounds measured in a commercial lager were respectively: methanethiol (0.33, 0.30); dimethyl sulphide (19.3, 5.3); carbon disulphide (0.42, 0.32); ethylene sulphide (0.37, 0.05); 1-propanethiol (0.11, 0.02); methyl thioacetate (11.7; 2.7); methyl disulphide (0.34, 0.42). The method is a significant improvement over previous techniques for the quantification of sulphur-containing volatiles in beer .     

Effects of acidity,calcium, and aluminium on fish survival and productivity—a review

Fish survival, growth and productivity are dependent on both biological and environmental factors. The latter can be distinguished as edaphic (which includes water quality) and morphometric (which includes lake and stream morphology). Climatic factors are relatively less significant in temperate waters, except over a long time scale, or over wide geographic areas. In the conditions characteristic of acid lakes— low pH, low calcium and high aluminium concentrations—survival may be reduced, growth may be affected and, consequently, productivity will be low. In spite of inconsistencies in the literature, it can be shown that at low pH (? 4.5), a limiting concentration of calcium is about 1 mg litre^?1 and aluminium can have adverse effects at 250 μg litre^?1 within a limited range of pH. These three factors appear to interact. Taking age specific fecundity of adults and survival of eggs and fry, it is possible to predict the limiting conditions for maintenance, growth or decline of a fish population. At pH 4.5 and calcium < 0.8 mg litre^?1 it may be expected that many lakes will be fishless.     

The effects of defaunation on the metabolism of lactic acid in the rumen

Two experiments examined the effects of defaunation on the ruminal metabolism of lactate. Three rumen-cannulated sheep given a diet of molassed sugar beet pulp and barley (80:20) were used to study the effects of defaunation (with manoxol-OT) on the metabolism of lactic acid produced endogenously from rumen fermentation. Defaunation increased mean ruminal concentrations of lactate from 3.4 mmol litre^?1 to 8.9 mmol litre^?1 but other rumen measurements remained virtually unchanged: pH, 6.3 and 6.3; molar proportions of acetic acid, 645 and 645 mmol mol^?1; propionic acid, 189 and 197 mmol mol^?1 and butyric acid 142 and 115 mmol mol^?1 for the faunated and defaunated states respectively. In a second experiment, two groups each of four rumen-cannulated sheep were used to study the effect of defaunation on the ruminal metabolism of added Na-D, L lactate. One group of four was defaunated using a rumen-washing technique whilst the other group of four remained faunated. The animals were given a diet of rolled barley and hay (60:40) and were given a series of intraruminal doses of Na-D, L lactate from 0 to 100 g day^?1, increasing by 20 g day^?1 every third day. Disappearance of added lactate was much more rapid in faunated animals: at the 100 g day^?1 dose rate, L-lactate concentrations had fallen from a peak of 6 g litre^?1 to >1 g litre^?1 after 3 h whereas in defaunated sheep the peak of 6.5 g litre^?1 was reduced to >1 g litre^?1 only after 7 h. In faunated animals lactate addition caused an increase in the ruminal concentration of total volatile fatty acids (VFA) from 147 to 217 mmol litre^?1 between the zero and 100 g day^?1 dose rates, accompanied by an increase in the molar proportion of propionic acid from 190 to 320 mmol mol^?1. However, in defaunated animals there was only a small increase in total VFA concentrations from 94 to 106 mmol ml^?1 with no change in the molar proportion of propionic acid and a small increase in butryric acid from 140 to 180 mmol mol^?1.     

D-Amino acids in reconstituted infant formula: A comparison between conventional and microwave heating

It was recently claimed that microwave heating of reconstituted formulas for infants could induce racemisation of amino acids, in particular, of proline. In the present work we investigated the presence of D-amino acids in different samples of a reconstituted infant formula heated by a conventional heat-transfer way (oil bath), in a commercially available domestic microwave oven and in a wave-guide device. The analyses were carried out both by gas chromatography and by high performance liquid chromatography. The presence of D-enantiomers was determined both in proteins after hydrolysis (6 M HCl at 100°C for 6 h) and in the free amino acid pool. Regarding protein-bound amino acids, there is no evidence of racemisation in all samples examined under the different experimental conditions (conventionally and microwave-treated samples). In particular, D-proline was not detected at least above 1 mg litre^?1 in proteins and above 20 μg litre^?1 in free amino acids. Although small percentages (D/D + L %) of D-glu and D-asp and higher percentages of D-ala were detected among free amino acids, in all samples, no significant differences could be found between untreated and treated samples.     

Aflatoxins and their Metabolites in the Tissues,Faeces and Urine from Lambs Feeding on an Aflatoxin-Contaminated Diet

Twenty-four lambs were intoxicated with 2·5 mg of aflatoxin (AF) kg^-1 in their feed for 21 days. Twelve lambs were slaughtered at day 21 and the remaining animals had an 8 day clearance period. Aflatoxins and their metabolites were detected in liver, kidneys, faeces and urine using TLC and fluorescence densitometry. During the intoxication period, the samples gave a wide range of concentrations, the lower extreme being in the liver and the kidney (0·03 μg kg^-1 of AFG₁) and the higher extreme in faeces (61·82 μg kg^-1 of AFM₁) and urine (27·84 μg litre^-1 of AFM₁). The average value of AFB₁ (1·94±0·9 μg kg^-1) was higher than AFM₁ (0·35±0·17 μg kg^-1) in the liver. In the kidney AFM₁ (5·45±4·01 μg kg^-1) was higher than AFB₁ (1·29±0·84 μg kg^-1). There were higher concentrations of AFM₁ (27·2±16·1 μg kg^-1, 7·37±6·53 μg litre^-1, respectively, of average level) in faeces and urine, than of AFB₁ (17·25±8·1 and 1·78±1·57 μg litre^-1, respectively). AFB_2a appeared in the kidney (0·05±0·03 μg kg^-1) and urine (0·35±0·25 μg litre^-1). The clearance time of AFB₁ from the faeces was less than or equal to 8 days and in all samples aflatoxin residues were still detected on the 8th day of the clearance period although in low quantities. These results suggest that aflatoxin transfer to and elimination by the liver and the renal tissue is small and that the danger to humans consuming lamb meat is also small. The examination of the faeces and urine could be useful as markers to detect lambs consuming a contaminated diet. © 1997 SCI.     

Effects of explant source,culture medium: Strength and growth regulators on the in-vitro propagation of three Jamaican yams: (Dioscorea cayenensis,D trifida and d rotundata)

Explants of tuber, meristem and vines from three widely cultivated yam species in Jamaica—D cayenensis, D rotundata and D trifida—were examined for their responses to mineral media strength, inorganic ammonium and growth regulator supplements. Tuber pieces (5mm³) showed some positive growth responses but did not produce in-vitro plantlets on all the media tested. Meristem tips of D trifida grew rapidly on basal media (BM) supplemented with either 0.1 mglitre^?1 6-benzylamino purine (BAP) and 0.01 mg litre^?1indole butyric acid or 0.2 mg litre^?1 BAP and 1.0 mg litre^?1 naphthalene acetic acid (NAA) producing plantlets by 28 weeks. The nodal explants grew rapidly with plantlets obtained from all the cultivars within 4 weeks. Use of young, vigorously growing vines of 8 weeks or less, as explant source, gave low contamination levels (16–25%) in culture when sterilised for 30 min in 200 g litre^?1 NaOCl in the case of D trifida and 300 g litre^?1 NaOCl in the case of D cayenesis prior to culturing. Initiation of growth was optimal when explants were taken from monopodial vines grown in October or January and placed on BM supplemented with 0.5 mg litre^?1 BAP (BM0.5BAP). Addition of 0.5 mg litre^?1 kinetin to the BM or 0.05 mg litre^?1 NAA to BM0.5BAP depressed shoot production, while 5.0 mg litre^?1 kinetin increased swelling of the nodal region in explants from sympodial shoots and from vines grown in March. The results suggest that nodal segments excised from young, fast growing vines of these species are the best explant source for the purpose of commercial micropropagation.     

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

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.     

Post-harvest application of diphenylamine and ethoxyquin for the control of superficial scald on Bramley's seedling apples

Recent changes in the antioxidant regulations in the UK and the need to evaluate the effectiveness of scald control chemicals in the presence of other post-harvest chemicals led to a comparative study of the effects of diphenylamine (DPA) and ethoxyquin on scald development in Bramley's Seedling apples. A range of concentrations (1000–4000 mg litre^?1 a.i.) of DPA completely controlled scald on Bramley apples kept in controlled atmosphere storage for 241 days; ethoxyquin at equivalent rates was less effective. Only partial control of scald was achieved with 500 mg litre^?1 a.i. DPA. None of the treatments injured the fruit. Control of scald by 2000 mg litre^?1 a.i. DPA or ethoxyquin was not impaired by adding thiophanate-methyl (l g litre^?1 a.i.) or calcium chloride (10 g litre^?1) although the measure of control was reduced when both fungicide and calcium chloride were added. Calcium chloride caused lenticel injury which was aggravated by adding ethoxyquin but reduced by incorporating DPA. The concentrations of ethoxyquin and DPA residues on the fruit immediately after treatment were within the limits required by UK legislation (see reference 1) of 3 mg kg^?1 and 10 mg kg^?1, respectively, even where 4000 mg litre^?1 had been applied. An initial residue concentration of 2.3 mg kg^?1 DPA was associated with complete control of scald. Residue levels, particularly of DPA, declined rapidly during the first month of storage.     

The effects of heating and chemical treatment on the haem and non-haem iron content of heat-induced porcine blood curd

The effect of heating temperature (40–80°C), time (0–50 min), additions of ascorbic acid (0–5 g litre^?1) and sodium nitrite (0–200 mg litre^?1) on total, non-haem and haem iron of heat-induced porcine blood curd (a famous edible blood food in Taiwan) was investigated. The results show that non-haem iron content increased significantly (P < 0.05) when heated at above 55°C and was enhanced linearly (r = 0.96) with heating time at 80°C, while haem iron decreased relatively. In addition, a non-haem iron increase was observed in ascorbic acid, the maximum found with treatment at 4 g litre^?1. On the contrary, haem iron content increased with the presence of sodium nitrite and there was a significant change with addition above 50 mg litre^?1.     

Total mercury in milled rice and brown rice from China and health risk evaluation

Total mercury (THg) levels in 440 pairs of milled rice samples and brown rice samples from 15 major rice grain-producing provinces of China were measured and the associated health risk via rice consumption for different age categories of Chinese population was also assessed. THg contents were measured by a direct mercury analyser and the limit of detection (LOD) was 1.5 μg kg^?1. The THg levels for milled rice samples and brown rice samples varied from non-detected to 17.8 μg kg^?1 and 1.5 to 25.4 μg kg^?1, respectively, with a mean level of 3.4 μg kg^?1 and 4.9 μg kg^?1, respectively. The THg levels in all milled and brown rice samples were generally low, except three brown rice samples having concentrations above the legally set value for cereals (20 μg kg^?1 Hg). THg intakes for different age categories were estimated according to THg content and corresponding rice consumption and the associated health risk was evaluated by the corresponding provisional tolerable weekly intake (PTWI) for THg (5.0 μg kg^?1 bw week^?1), which was established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). The 50th percentile of the THg intakes via milled rice and brown rice consumption for different age categories was in the range 0.09–0.19 μg kg^?1 bw week^?1 and 0.14–0.27 μg kg^?1 bw week^?1, respectively, well below the PTWI, suggesting that the associated health risk is relatively low. However, the 99.9th percentile of the THg intakes for 2–4-year-old children amounted up to 20.6% of the PTWI (milled rice) and 29.5% of the PTWI (brown rice), which deserves attention.     

Determination of free fatty acids in foods by flow injection

A flow injection manifold has been developed for the spectrophotometric determination of free fatty acids (FFA) at 716 nm after continuous extraction into an organic phase of soaps formed by the reaction of copper acetate with the analytes. The carrier system stream was toluene and the reagent stream aqueous copper acetate-pyridine (50 g litre^?1). The calibration graph was linear over the range 1 × 10^?4 to 5 × 10^?3 M oleic acid using an injection volume of 115 μl. The injection rate was 75 samples h^?1 with a precision of 109% (RSD). Though this procedure does not permit the total recovery of short-chain fatty acids it is very effective in reflecting the total concentration of FFA. The system has been applied to the determination of total FFA in olive oil, milk fat and cocoa butter. Although the values obtained by the proposed method are lower than those obtained by the reference method (titration) and by chromatography, their comparison shows good linearity.     

Biogenic amines in alcoholic beverages produced in Taiwan

The biogenic amines tyramine, putrescine, cadaverine, 2-phenylethylamine, histamine and tryptamine were determined in 13 kinds of alcoholic beverages produced in Taiwan. They were derivatised with dansyl chloride and analysed using a high-performance liquid chromatographic method. Total amine content ranged from 0.23 to 11.4 μg ml^?1 with Charng Chuen liqueur containing the highest level and Mei Kwei Lu the lowest. Tryptamine was found in all samples in amounts between 0.01 and 1.79 μg ml^?1. The levels of the other five amines in the tested samples were 0-7.0 μg ml^?1 for 2-phenylethylamine, 0-3.0 μg ml^?1 for putrescine, 0-2.9 μg ml^?1 for cadaverine, 0-4.5 μg ml^?1 for histamine, and 0-1.4 μg ml^?1 for tyramine. These levels seem unlikely to have adverse effects on human health.     

Stability of two Ca2+-dependent neutral proteinases and their specific inhibitor during post-mortem storage of rabbit skeletal muscle

The variation in the amounts of the two forms of Calcium Activated Neutral Proteinase (high Ca²⁺ requiring and low Ca²⁺ requiring forms) and their specific inhibitor was determined during storage of skeletal muscle at 4°C for 0, 1, 3 and 6 days. Whereas the activity of the high Ca²⁺ requiring form remained nearly constant during this period, there was a progressive decrease in the levels of both the low Ca²⁺ requiring form and the specific inhibitor. The effect of different Ca²⁺ concentration on the two purified forms of the enzyme in the presence and absence of the inhibitor was also examined. Both enzyme forms were labile to preincubation at 30°C without inhibitor in 3 mmol litre^?1 Ca²⁺ whereas in 50 μmol litre^?1 Ca²⁺ only the low Ca²⁺ requiring form was inactivated, i.e. at a concentration which can be reached in muscle cells during contraction or after death of the animal. When the specific inhibitor was added, preincubation in 3 mmol litre^?1 Ca²⁺ did not affect either enzyme form since they were found to retain full activity on subsequent removal of the inhibitor. A possible role for the Calcium Activated Neutral Proteinases in the development of meat tenderness is discussed.     

Aflatoxins in acid-treated grain in Sweden and occurrence of aflatoxin M1 in milk

A survey of aflatoxins in acid-treated grain and milk from farms using such grain was conducted in Sweden during 1986. Aflatoxins occurred most frequently (40%) in grain treated with a new formula of diluted (700 g litre^?1) aqueous formic acid, but also in 31% of the samples of grain treated with 850 g litre^?1 aqueous formic acid. The lowest incidence was found in grain treated with propionic acid, where aflatoxins were found in only one sample (3%). Aspergillus flavus/A parasiticus occurred in the same manner, but were more frequent than the aflatoxins. When cultivated on aflatoxin-producing agar, positive reactions were more common (56%) among strains originating from grain treated with formic acid than among strains originating from grain treated with propionic acid (4%). Aflatoxin M¹ in concentrations over 50 ng kg^?1 was mainly found in milk from farms using formic acid, and in most of these cases aflatoxins were also detected in the grain samples. In some cases, milk from a single farm was contaminated enough to generate consumption milk from the dairy with aflatoxin M¹ concentrations above or close to 50 ng kg^?1. The risk of aflatoxin formation after inadequate treatment of grain with formic acid is very high and is considerably lower with propionic acid. Formic acid has now been prohibited for use as a preservative of high moisture grain in Sweden.     

The effects of urea and artificial saliva on rumen bacterial protein synthesis in sheep receiving a high-cereal diet

Four sheep fitted with cannulas in the rumen and duodenum and given a basal diet of 18% chopped hay, 41% rolled barley and 41% flaked maize, known to be associated with low rates of bacterial protein synthesis in the rumen, were used in a 4 × 4 Latin Square experiment to study the effects of continuous intraruminal infusions of water (2 litres day^?1; control), urea solution (7.5 g urea litre^?1, 2 litres day^?1; urea), artificial saliva (4 litres day^?1; saliva) and artificial saliva with added urea (3.75 g urea litre^?1, 4 litres day^?1; saliva+urea) on rumen ammonia-nitrogen concentration, pH, liquid clearance rates and bacterial protein synthesis. Rumen ammonia-nitrogen concentrations for control, urea, saliva and saliva + urea treatments were 81, 158, 38 and 151 mg litre^?1, respectively. Corresponding mean values for rumen pH were 6.18, 6.09, 6.37 and 6.41 units and for rumen liquid clearance rates 0.082, 0.057, 0.062 and 0.051 h^?1. The mean rate of bacterial protein synthesis in the rumen, estimated from the duodenal entry of α-?-diaminopimelic acid, for the control treatment was 163 g crude protein (CP) kg^?1 organic matter (OM) apparently digested in the stomach. Corresponding rates for the saliva and saliva + urea treatments were 169 g CP kg^?1 OM apparently digested and 215 g CP kg^?1 OM apparently digested, indicating responses in protein synthesis to the urea+saliva treatment but not to the saliva alone treatment. Infusion of urea solution increased the mean rate of protein synthesis to 204 g CP kg^?1 OM apparently digested in the stomach but the responses were variable between animals and in three of the animals were small. It is concluded that with the type of diet used an enhanced entry of saliva into the rumen is necessary to ensure that supplementary urea produces a consistent improvement in ruminal protein synthesis.     

Lead and arsenic levels in wines produced from vineyards where lead arsenate sprays are used for caterpillar control

Twenty-seven dry table wines from 14 wineries throughout Victoria were analysed for lead and arsenic. Wines originating from vineyards using lead arsenate insecticide for caterpillar control had mean levels of 0.31 mg litre^?-1 lead and 0.08 mg litre^?-1 arsenic. The mean levels in similar wines from wineries not using lead arsenate sprays were 0.03 mg litre^?-1 and less than 0.01 mg litre^?-1 respectively.     

Occurrence of 3-MCPD fatty acid esters in human breast milk

A series of twelve breast milk samples were analysed by gas chromatography-mass spectrometry (GC/MS) operated in selected ion monitoring mode for 3-chloropropane-1,2-diol (3-MCPD). Whilst none of the samples contained 3-MCPD above the limit of detection of 3 μg kg^?1 milk, all contained high amounts of 3-MCPD esterified with higher fatty acids. The levels of 3-MCPD released by hydrolysis of these esters (bound 3-MCPD) ranged from the limit of detection (300 μg kg^?1, expressed on a fat basis) to 2195 μg kg^?1; with a mean level of bound 3-MCPD of 1014 μg kg^?1, which corresponded to 35.5 μg kg^?1 milk. The presence of bound 3-MCPD was confirmed using orthogonal gas chromatography coupled with high-speed time-of-flight mass spectrometry analysis for four randomly selected breast milk samples. Six breast milks collected from one of the nursing mothers 14–76 days after childbirth contained bound 3-MCPD within the range of 328–2078 μg kg^?1 fat (mean 930 μg kg^?1 fat). The calculated bound 3-MCPD content of these samples was within the range of 6 and 19 μg kg^?1 milk (mean of 12 μg kg^?1 milk). The major types of 3-MCPD esters were the symmetric diesters with lauric, palmitic, and oleic acids, and asymmetric diesters with palmitic acid/oleic acid among which 3-chloro-1,2-propanediol 1,2-dioleate prevailed.