Showing papers in "Journal of the Science of Food and Agriculture in 1999"

Chlorogenic acids and other cinnamates – nature, occurrence and dietary burden

Abstract: This review defines the range of forms in which cinnamates (p-coumarates, caffeates, ferulates and sinapates) occur in foods and beverages subdividing them into (i) the classic chlorogenic acids and close allies, (ii) other esters, amides and glycosides, and (iii) transformation products formed during processing. Cinnamate derivatives which would not release cinnamic acid by hydrolysis are excluded. The quantitative data are reviewed concisely and attention is drawn to certain shortcomings, in particular a complete absence of data for certain commodities (breakfast cereals, baked goods, tomato products and nuts) and minimal data for pulses, legumes and processed or cooked foods. In addition, more data are required for the edible portion of modern varieties. By extrapolating from such data as are available the important source(s) (i) of individual cinnamates (regardless of the conjugate type) and (ii) of each major class of conjugate, have been identified as follows: (i) Cinnamates: caffeic acid: coffee beverage, blueberries, apples, ciders; p-coumaric acid: spinach, sugar beet fibre, cereal brans; ferulic acid: coffee beverage, citrus juices, sugar beet fibre, cereal brans; sinapic acid: broccoli, kale, other leafy brassicas, citrus juices. (ii) Conjugates: caffeoylquinic acids: coffee beverage, blueberries, apples, ciders; p-coumaroylquinic acids: sweet cherries; feruloylquinic acids: coffee beverage; tartaric conjugates: spinach, lettuce, grapes and wines; malic conjugates: lettuce, spinach, possibly legumes; rosmarinic acid: culinary herbs, mixed herbs, possibly stuffings; cell wall conjugates: spinach, sugar beet fibre, cereal brans. It seems likely that the UK population will fall into several categories depending on (i) their consumption of coffee, (ii) their consumption of bran, and (iii) their consumption of citrus. Those who drink several cups of coffee per day augmented by bran and citrus might easily ingest 500-800mg cinnamates (or even 1 g for the greatest coffee ingest consumption) whereas those who eschew all these and take little fresh fruit or vegetables might struggle to consume 25 mg.

Antioxidant composition and activity of barley (Hordeum vulgare) and malt extracts and of isolated phenolic compounds

Abstract: Phenolics have been identified and quantified in nine varieties of barley and their corresponding malts as flavan-3-ols, flavonols, phenolic acids and apolar esters. Flavan-3-ols are monomers, (+)-catechin and (−)-epicatechin, and polymers constituted mainly by units of (+)-catechin and (+)-gallocatechin. The most abundant compounds were the dimers procyanidin B3 and prodelphinidin B3. The main trimeric procyanidin was procyanidin C2. After malting, the phenolic content decreased for all varieties. Catechin monomers were the most affected. Beside polyphenols, barley and malt extracts contained other antioxidants: carotenoids (lutein and zeaxanthin) and tocopherols (α, δ and γ). The antioxidant activity was measured using three methods: capacity to react with DPPH. (ARP), inhibition of lipoxygenase activity (LoxI) and inhibition of cooxidation of β-carotene in a linoleate model system (AOP). The inhibition of cooxidation of β-carotene in a linoleate model system did not allow varieties to be discriminated. They all have high antioxidative properties. Using this assay, tocopherols were the best antioxidants. The ARP (antiradical power) was correlated positively with the amount of total flavan-3-ols (r = 0.89) and increased with the degree of polymerisation. The LoxI assay allowed discrimination of the nine varieties of barley and their corresponding malts but was not correlated with any compound, although flavan-3-ols were good inhibitors of lipoxygenase activity. © 1999 Society of Chemical Industry

Bitterness and astringency of flavan-3-ol monomers, dimers and trimers.

Abstract: Intensity of astringency and bitterness of seven flavonoid compounds was evaluated by a time-intensity (TI) procedure. Eighteen trained judges rated intensity continuously from ingestion, through expectoration at 10 s until extinction of the sensation. The seven stimuli included two flavan-3-ol monomers, (+)-catechin and (−)-epicatechin, three dimers and two trimers synthesised from catechin or epicatechin by condensation with (+)-dihydroquercitin. As the degree of polymerisation increased, maximum bitterness intensity (Imax) and total duration (Ttot) decreased whereas astringency Imax increased. The monomers were significantly higher in bitterness at Imax than the dimers, which were significantly higher than the trimers. Astringency Imax of the monomers was lower than the dimers or trimers, although no significant difference was found in Ttot among the polymer classes. The bond linking the monomeric units had an influence on both sensory properties. The catechin-catechin dimer linked by a 4→6 bond was more bitter than both catechin-(4→8)-catechin and catechin-(4→8)-epicatechin. Astringency was affected by both the specific linkage and the identity of the monomeric units with the dimer, catechin-(4→8)-catechin, being lower in astringency than either catechin-(4→6)-catechin or catechin-(4→8)-epicatechin. © 1999 Society of Chemical Industry

A method for partitioning neutral detergent-soluble carbohydrates

Abstract: A method was developed to fractionate the neutral detergent-soluble carbohydrates (NDSC) in feedstuffs. Differential solubilities of carbohydrates in 80:20 (v/v) ethanol/water were used to partition NDSC into organic acids (OA) and mono- and oligosaccharides soluble in ethanol/water from starch and neutral detergent-soluble fibre (NDSF) which are insoluble. Mono- and oligosaccharides (total ethanol/water-soluble carbohydrate) were measured on the ethanol/water extract, and starch was measured on the ethanol/water-insoluble residue. The OA and NDSF, the two most compositionally diverse NDSC fractions, were estimated by difference. The method allows partitioning of the NDSC on a nutritionally relevant basis into (1) organic acids, (2) total ethanol/water-soluble carbohydrate, (3) starch and (4) neutral detergent-soluble fibre. The methods involved in this fractionation are relatively simple or are commonly used. © 1999 Society of Chemical Industry

Ferulic acid and diferulic acids as components of sugar-beet pectins and maize bran heteroxylans.

Abstract: Enzymatic hydrolysis of sugar-beet pulp, and subsequent isolation of feruloylated oligosaccharides, has shown that ferulic acid groups are ester-linked mainly on O-2 of arabinose residues and on O-6 of galactose residues in the pectin side-chains. After saponification of sugar-beet pulp enzymatic digests, dehydrodiferulic acids (0.14%, w/w) have also been identified and characterised as 8-5', 5-5', 8-8' and 8-O-4' isomers, suggesting that covalent cross-linking of pectic polysaccharides through diferulic bridges occurs in sugar-beet pulp. Feruloylated oligosaccharides from the side-chains of heteroxylans have been isolated from maize bran by acid hydrolysis. Ferulic acid is esterified on O-5 of arabinofuranose residues. 8-8', 8-5', 8-O-4' and 5-5' coupled dimers, which represent 2.5% (w/w) of the bran, have also been detected. It has been calculated that, in the cell wall, each heteroxylan macromolecule bore ∼ 75 esterified ferulic acid groups and could be cross-linked through ∼ 30 diferulic bridges. This result suggests a high degree of cross-linking of heteroxylans chains through ferulic acid in maize bran cell walls.

Cell wall cross‐linking by ferulates and diferulates in grasses

Abstract: Ferulate polysaccharide esters in grasses enter into free-radical condensation reactions in the cell wall. By radical dimerisation of ferulates, polysaccharide-polysaccharide cross-linking is effected. A range of diferulate isomers are produced, not solely the 5-5'-coupled dimer which has been quantified historically. Both ferulates and diferulates enter lignification reactions and become intimately bound up with the lignin complex. Again, under-quantification is significant since it is not possible to release ferulate or diferulates from some of the structures. Overall, ferulates play a significant role in cell wall development and impact polysaccharide utilisation in grasses.

Hydroxycinnamates in plants and food: current and future perspectives†

Abstract: The interest in hydroxycinnamates as bioactive components of the diet, as structural and functional components of plant cell walls, and as precursors for flavours in the food industry has expanded rapidly in the last 5–10 years. As a result, the first ever international conference devoted solely to hydroxycinnamates (eg ferulate, p-coumarate, sinapate, caffeate), Ferulate ‘98, was held in Norwich (UK) on 9–11 July 1998. The purpose of the conference was to bring together academics and industrialists from a broad spectrum of backgrounds with an interest in all aspect of hydroxycinnamates. There were five sections: Hydroxycinnamates in food-role in nutrition and health; Hydroxycinnamates in plant cell walls; Biosynthesis of hydroxycinnamates; Enzymology of biosynthesis and degradation; Exploitation of hydroxycinnamates. In this review the current state of the art is discussed and suggestions for future research which arose from this conference are given. © 1999 Society of Chemical Industry

A survey of nitrate and oxalate content in fresh vegetables

Abstract: A survey of nitrateONO ˇU and oxalate ((COO ˇ )2) content in fresh vegetables was conducted in Bari (Italy) over 15 months (from March 1994 to May 1995). A total of 327 samples (edible portions and related sub-samples) were taken from 26 different vegetable types on the wholesale fruit and vegetable market. The data revealed that leaf vegetables (namely rocket, celery, parsley and spinach) contained higher levels of nitrate than bulb, root, shoot, inflorescence and tuber vegetables. Higher oxalate levels were found in spinach and Swiss chard. Based on consumption data for the whole population provided by the National Institute of Nutrition, daily nitrate intake from vegetables was calculated to be 71 mg. Over 30% of nitrate intake was derived from the consumption of lettuce and Swiss chard. # 1999 Society of Chemical Industry The presence of nitrate in vegetables, as in water and generally in other food products, is a serious threat to man's health, although recent research has shown that nitrate also has beneficial effects on health related to its role in the body's mechanism against pathogenic micro-organisms. 3 The harmful effects of nitrate are related not so much to its toxicity, which is low, but to the dangerous compounds that are synthesised in the organism. Indeed, the most serious danger comes from nitrite which is produced by nitrate reduction and which can lead to methaemoglobinemia or form nitrosamines and nitrosamides by reacting with amines and amides, whose carcinogenic action is well known. 4,5

Picrate paper kits for determination of total cyanogens in cassava roots and all forms of cyanogens in cassava products

Abstract: The simple semiquantitative picrate method for the determination of total cyanogens in cassava flour has been modified by increasing the concentration of the picrate solution used to make up the picrate papers, such that a linear Beer's Law relation between absorbance and cyanogen content is obtained over the range 0–800 mg HCN equivalents kg−1 cassava The method has been adapted to determine the total cyanogen content of cassava roots and the results compared using the picrate method and the acid hydrolysis method for six different roots from five cultivars The agreement between the results is satisfactory The simple method for determination of total cyanogens in cassava roots in the field is available in kit form The methodology has been modified to allow determination of the three different forms of cyanogens present in cassava flour, viz HCN/CN−, acetone cyanohydrin and linamarin HCN/CN− is determined by the picrate method in which cassava flour is reacted with 01 M sulphuric acid for 3 h at room temperature HCN/CN− plus acetone cyanohydrin is also determined by the picrate method after treating cassava flour with 42 M guanidine hydrochloride at pH 8 for 3 h at room temperature A comparison has been made of the amounts of the three cyanogens present in six cassava flour samples using the semiquantitative picrate and the acid hydrolysis methods The agreement between the two methods is satisfactory, which shows that the new methodology works well The picrate method for determination of the three cyanogens in cassava flour is also available as a kit © 1999 Society of Chemical Industry

Variation in antioxidant components of tomato during vine and post-harvest ripening

Abstract: The variation in the antioxidant content (lycopene, β-carotene, ascorbic acid and total phenolics) was evaluated on two tomato genotypes during vine and post-harvest ripening. Tomatoes were sampled and analysed at seven ripening stages according to the colour value. The data indicate that ripening conditions affected both the antioxidant accumulation kinetics and the final content, which was higher in post-harvest-ripened fruits. In particular, lycopene mainly accumulated in the very last period of ripening and its content was not linearly related to colour changes. Antioxidant accumulation and other ripening indexes were not significantly different in the two tomato genotypes. © 1999 Society of Chemical Industry

Metabolism of chlorogenic acid by human plasma, liver, intestine and gut microflora

Abstract: Extracts of human small intestine epithelium, liver, plasma and colonic microflora (as a faecal sample) were prepared and esterase activity determined by incubation with chlorogenic acid and subsequent analysis by high-performance liquid chromatography. There was no evidence of enzymic hydrolysis by the intestine, liver or plasma extracts. However, esterase activity was observed in the faecal sample, and this activity was abolished if the extract was boiled prior to incubation. These results show that chlorogenic acid ingested by humans is most likely cleaved into caffeic acid and quinic acid by an esterase enzyme(s) provided by the colonic microflora.

Antioxidant properties of tomato juice as affected by heating

Abstract: The changes in the overall antioxidant properties of tomato juice samples and model solutions as a consequence of heat treatments were studied. The antioxidant properties were evaluated both through the measurement of the chain breaking and the oxygen scavenging activities. While a decrease in the antioxidant potential was found for short heat treatments, a recovery of these properties was measured by prolonging heating times. Results suggested that the initial reduction in the overall antioxidant activity can be attributed not only to the thermal degradation of naturally occurring antioxidants but also to the formation of early Maillard reaction products (MRP) with pro-oxidant properties. The gain in antioxidant activity coincided with the formation of brown MRP. © 1999 Society of Chemical Industry

Compositional and nutritional attributes of seeds from the multiple purpose tree Moringa oleifera Lamarck

Abstract: Moringa oleifera Lam is a multipurpose tree cultivated to use as a vegetable, for spice, for cooking and cosmetic oil and as a medicinal plant. Owing to the use of its seeds as food and as a clarifying agent of turbid water some nutritional and antinutritional characteristics were studied. The mature seeds contained 332.5 g crude protein, 412.0 g crude fat, 211.2 g carbohydrate and 44.3 g ash per kg dry matter. The essential amino acid profile compared with the FAO/WHO/UNU scoring pattern requirements for different age groups showed deficiency of lysine, threonine and valine. The content of methionine + cysteine (43.6 g kg−1 protein), however, was exceptionally higher and close to that of human milk, chicken egg and cow's milk. The seed extract agglutinated rabbit erythrocytes but did not show trypsin inhibitor and urease activities. Feeding rats with a diet containing the seed meal showed loss of appetite, impaired growth, lower NPU and enlargement of stomach, small intestine, caecum + colon, liver, pancreas, kidneys, heart and lungs and atrophy of thymus and spleen in comparison with rats fed on an egg-white diet. The results indicated that consumption of M oleifera raw mature seeds should be viewed with some caution until suitable processing methods are developed to abolish the yet unknown adverse factors. © 1999 Society of Chemical Industry

Identification of impact odorants of young red wines made with Merlot, Cabernet Sauvignon and Grenache grape varieties: a comparative study

Abstract: An Aroma Extract Dilution Analysis (AEDA) has been carried out on three monovarietal young red wines plus a mixture of wines aged one year. The aromograms contain 85 odour-active regions classified in four categories of intensity. The 11 most powerful odorants, 14 out of the 17 second-most powerful, and 34 of the rest could be identified using a HPLC prefractionation method and standard HRGC-MS-olfactometric techniques. The most active odorants of the monovarietal wines were isoamyl and β-phenylethyl alcohols, the ethyl esters of butyric, isobutyric, 2-methyl butyric and hexanoic acids, γ-nonalactone and eugenol. Some others worth mentioning are ethyl isovalerate, isoamyl acetate, hexanol, c-3-hexenol, linalool, geraniol, guaiacol, ethyl cinnamate, ethyl dihydrocinnamate, β-damascenone, δ-decalactone and wine lactone. Compounds with less aromatic intensity but also present in some of the wines were sotolon, isopropyl- and isobutylmethoxypyrazines and 4-mercapto-4-methylpentan-2-one. Data show that there are no impact compounds characteristic of only one variety, and that differences between varieties are quantitative rather than qualitative. © 1999 Society of Chemical Industry

Ferulic and caffeic acids as potential protective agents against photooxidative skin damage

Abstract: The biological properties and, particularly, the antioxidant activity of plant hydroxycinnamic acids, such as caffeic and ferulic acids, are well recognised. This preliminary study was designed to estimate the potential utility of caffeic and ferulic acids to prevent, when topically applied, photooxidative stress in the skin. With this aim we have evaluated the antioxidant activity of ferulic and caffeic acids in two experimental models: (1) the UV radiation-induced peroxidation in phosphatidylcholine (PC) liposomal membranes; (2) the scavenging activity against nitric oxide (a radical involved in oxidative reactions). In addition, given that a suitable percutaneous absorption is an essential requirement for successful topical photoprotective agents, we measured their in vitro permeation through excised human skin. Caffeic and ferulic acids efficiently protected PC liposomes from UV radiation-induced peroxidation and reacted with nitrogen oxides. In addition, caffeic and ferulic acids were able to permeate through the stratum corneum (the main barrier against the penetration of exogenous substances through the skin). Taken together, these findings suggest that caffeic and ferulic acids should be good canditates for successful employment as topical protective agents against UV radiation-induced skin damage. © 1999 Society of Chemical Industry

Changes in texture, microstructure and nutritional quality of carrot slices during blanching and freezing

Abstract: Thermal processing of vegetables has pronounced effects on the cell structure, often lowering the final textural properties of the product. In order to investigate the effect of thermal processing on carrot, slices were subjected to different blanching and freezing treatments before frozen storage. Microwave-, steam- or water-blanched material was frozen and then stored at −24 °C. Steam-blanched carrots were subjected to blast freezing or cryogenic freezing at different temperatures before frozen storage. The influence of these process conditions on the texture (maximum load and slope), microstructure, dry matter, sugars, carotene and drip loss was investigated. Microwave blanching differed from the other blanching methods by resulting in a heterogenic cell structure. The content of dry matter, carotene and sucrose was higher following microwave blanching. Blast freezing resulted in low maximum load which seemed to be caused by major tissue damage. Concerning cryogenic freezing, lowering the temperature from −30 °C to −70 °C resulted in better preservation of the native microstructure together with an increase in maximum load, which was most pronounced after one month of storage. No significant effect was observed when lowering the temperature from −30 °C to −70 °C for any of the other measured parameters. © 1999 Society of Chemical Industry

Enzymes as biocatalysts in the modification of natural lipids

Abstract: Though designed by nature to effect hydrolysis of lipids, lipases can, under appropriate reaction conditions, promote ester formation through reaction of acids and alcohols (esterification) or of esters with acids (acidolysis), alcohols (alcoholysis), or other esters (interesterification). Compared with chemical processes already carried out on an industrial scale enzymic reactions occur under milder (and ‘greener’) conditions though they may take longer. Of greater significance is the specificity shown by the enzymes which permits the formation of lipid derivatives not easily prepared by conventional laboratory procedures. This review describes the lipases and their various specificities and reports on their use in hydrolysis and in the production of phospholipids, fatty acids, alkyl esters, mono- and di-acylglycerols, triacylglycerols, other esters, and amides. Some of these have already led to marketable products but for the most part the full potential of these reactions has yet to be realised. The reactions of other enzymes promoting interesting reactions at unsaturated centres are also described. © 1999 Society of Chemical Industry

Free radical scavenging capacity of selected red, rosé and white wines

Abstract: The free radical scavenging capacity of selected red, rose and white Spanish wines from different grape varieties was determined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH·) method using a new methodology developed at our laboratory. The amount of sample necessary to decrease by 50% the initial DPPH· concentration (EC50), the time needed to reach the steady state at EC50 concentration (TEC50) and the antiradical efficiency (AE = 1/EC50TEC50) were determined in the wine samples. Some differences between rose wines made with Garnacha and Tempranillo grape varieties were observed in the UV-vis spectra and in the free radical scavenging parameters, those from Garnacha variety having the highest antioxidant activity. The antiradical efficiency of the wines followed a decreasing order: red wines (22.44 × 10−6) > rose wines (4.90 × 10−6) > white wines (1.88 × 10−6). There was a correlation between antiradical efficiency and total polyphenol (TP): AE = −3.33135 + 0.0180535TP; the correlation coefficient was r = 0.951454. © 1999 Society of Chemical Industry

Culinary herbs inhibit lipid oxidation in raw and cooked minced meat patties during storage

Abstract: The effect of dried spices and the ethanol extract of those spices was studied on the stability of fresh chicken minced meat, and fresh and cooked pork patties pretreated with NaCl during refrigerated and frozen storage. The antioxidant activities of the spices were measured by thiobarbituric acid reactive substances (TBARS) and peroxide value (POV) in meat samples. The lipid oxidation was effectively inhibited in the chicken meat treated with several dry spices diminishing the TBARS to a range of 32% and 83% of those found in the control samples in frozen stored meat for 6 months. Marjoram, wild marjoram and caraway were the most effective dry spices. Ethanolic extracts of the same spices were more potent as antioxidants by lowering the concentration of the TBARS to a range of 20–27% of those found in the control samples. Addition of sodium salt to the minced pork resulted very high concentrations of the oxidation products originated from the polyunsaturated fatty acids. The treatment with ethanolic extract of spices (sage, basil, thyme and ginger) significantly inhibited the lipid peroxidation in refrigerated and chilled pork patties pretreated with NaCl by reducing both POV and TBARS. Heat treatment with microwaves produced significantly elevated levels of both lipid peroxides and TBARS, but the amount of these oxidation products was less than 10% in spice-treated salted meat samples compared to that in untreated ones. Lipid peroxidation also grew continuously during the storage period at −18°C in raw and cooked samples. Ethanolic extracts of spices had a very strong antioxidative effect inhibiting lipid peroxidation in heat-treated meat products during frozen storage. The highest antioxidant activity was observed in the case of ginger. High correlation coefficients were found between TBARS and POV both in raw and cooked pork patties (0.86, 0.91, respectively) during frozen storage. It is supposed that these compounds originated from the polyunsaturated fatty acids during oxidation processes but at different stages. Utilization of spices, spice mixtures or spice extracts in semi-prepared meat products intended to be frozen for up to 6 months or more before consumption is proved to be advantageous in regard of shelf life of the food, as well as of human health, because of the beneficial effect of spices in inhibition of lipid peroxidation during heat treatment and chilling storage. © 1999 Society of Chemical Industry

Flavonoids quercetin, myricetin, kaemferol and (+)-catechin as antioxidants in methyl linoleate

Abstract: The antioxidant effect of the flavonoids quercetin, myricetin, kaemferol, (+)-catechin and rutin on methyl linoleate oxidation was investigated. In addition, the synergistic effects of flavonoids and alpha-tocopherol were studied. Oxidation was monitored by conjugated diene measurement and by determining the formation of hydroperoxide isomers by HPLC. The antioxidant activity of flavonoids in non-polar methyl linoleate differ from that previously reported in water-containing systems, such as LDL and liposome systems. The activity of antioxidants (10-1000 micromolar) measured by hydroperoxide formation decreased in the order: myricetin > quercetin > alpha-tocopherol > (+)-catechin > kaemferol = rutin. The antioxidant activity of flavonoids increased as the number of phenolic hydroxyl groups increased. In addition to the number of hydroxyl groups, other structural features such as the 2,3 double bond in the C-ring and a glycoside moiety in the molecule had an effect on the antioxidant activity. Myricetin and rutin, especially had a synergistic effect with alpha-tocopherol. Myricetin, quercetin and rutin protected alpha-tocopherol from decomposition, myricetin being the most protective. The relative hydrogen-donating activity measured by the ration of cis,trans- to trans,trans-hydroperoxide isomers formed during oxidation decreased in the order: alpha-tocopherol > myricetin > quercetin. Hydroperoxide isomeric distribution of the samples containing kaemferol or rutin did not differ from the control. Thus, although alpha-tocopherol was the most effective hydrogen-donor, myricetin and quercetin were more effective antioxidants in inhibiting the hydroperoxide formation in methyl linoleate.

The texture of Atlantic salmon (Salmo salar) muscle as measured instrumentally using TPA and Warner-Brazler shear test.

Abstract: Muscle texture measurements were performed on Atlantic salmon (Salmo salar) using two different instrumental methods; The Texture Profile Analysis, which is a uniaxial compression test, and the Warner-Brazler shear test. The performances of the two tests were evaluated as to their ability to differentiate between recently killed salmon and salmon stored on ice for up to 24 days. Both tests performed well, but the shear test was slightly more sensitive than the compression test. Further, salmon were either starved or fed for two weeks prior to slaughter. The muscle from fed salmon lost its strength slightly faster than that from starved salmon, but this difference was only detectable during the first two days of chilled storage. The effects of temperature, fish size and degree and mode of deformation on the instrumental test results were studied and were found to be significant. Also, the sample geometry, ie the thickness of the fillet was found to have a very significant effect on the TPA-test results.

Wheat bran particle size effects on bread baking performance and quality

Abstract: Commercial hard red spring, hard red winter, soft white and durum wheat brans were used to evaluate the particle size effect of wheat bran on bread baking performance and bread sensory quality. Three different particle size bran samples were obtained from each bran by grinding, not by sifting, the bran samples. The bran samples were similar in chemical composition, but different in particle sizes. Results of baking experiments showed that breads containing fine bran had lower specific loaf volume and darker crumb colour than breads containing coarse or medium size bran. Sensory test panellists found that fine bran contributed smoother crust appearance and less gritty mouthfeel than the coarse bran. The sensory panel also indicated that breads containing soft white wheat bran had significantly better flavour and mouthfeel than breads containing hard red spring wheat bran.

Effects of dietary quebracho tannin on nutrient utilisation and tissue metabolism in sheep and rats

Abstract: The effect of feeding quebracho tannin, a mixture of condensed tannins, on dietary nutrient utilisation and nitrogen (N) retention and its effects on the gastrointestinal (GI) tract was investigated in sheep and rats. Sheep (n = 24) were fed on a pelleted diet of dried grass alone (controls) or containing quebracho tannin at 50 g kg−1 diet dry matter (DM) (tannin-fed animals) at a level sufficient to achieve a daily liveweight gain (DLWG) of 100 g day−1. Complete collections of faeces and urine were made for two seven-day periods after two and six weeks of feeding these diets (n = 6 per group). Apparent digestibilities of dry matter, N and neutral detergent fibre (NDF) were significantly (P < 0.001) reduced in tannin-fed animals at both measurement periods. No evidence was obtained to suggest that rumen micro-organisms can adapt to the presence of dietary tannins with prolonged feeding. Tannin-fed animals excreted significantly (P < 0.01) more N in faeces and less in urine than controls suggesting an alteration in N metabolism. Histological examination of samples of the GI tract obtained from pairs of sheep slaughtered after two, five and seven weeks of feeding the diets indicated ulceration and an increase in mucosal histiocytes, particularly in the jejunum and ileum of most tannin-fed animals. In a subsequent experiment, rats were fed ad libitum a ground chow containing either cellulose or quebracho tannin at 40 g kg−1 DM. Tannin-fed rats had significantly (P < 0.05) reduced feed intakes, DLWG, N retention and body fat deposition compared to controls. Protein synthesis rates in the duodenal mucosa were not increased in tannin-fed rats suggesting that enterocyte proliferation was not stimulated in this region of the GI tract. These studies indicate that feeding quebracho tannin to ruminants has both ruminal and post-ruminal effects that, together, result in reduced nutrient utilisation and impaired animal performance. © 1999 Society of Chemical Industry

Influence of skimmed milk concentrate replacement by dry dairy products in a low fat set‐type yoghurt model system. I: Use of whey protein concentrates, milk protein concentrates and skimmed milk powder

Abstract: Ten commercial samples of dry dairy products used for protein fortification in a low fat yoghurt model system at industrial scale were studied. The products employed were whey protein concentratres, milk protein concentrates, skimmed milk concentrates and skimmed milk powder which originated from different countries. The gross chemical composition of these dried products were determined, including polyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing of the proteins, and minerals such as Na, Ca, K and Mg. Yoghurts were formulated using a skim milk concentrated as a milk base enriched with different dry dairy products up to a 43 g kg−1 protein content. Replacement percentage of skim milk concentrated by dry dairy products in the mix was between 1.49 and 3.77%. Yoghurts enriched with milk protein concentrates did not show significantly different viscosity (35.12 Pa s) and syneresis index (591.4 g kg−1) than the two control yoghurts obtained only from skimmed milk concentrates (35.6 Pa s and 565.7 g kg−1) and skimmed milk powder (32.77 Pa s and 551.5 g kg−1), respectively. Yoghurt fortified with the whey protein concentrates, however, was less firm (22.59 Pa s) and had less syneresis index (216 g kg−1) than control yoghurts. Therefore, whey protein concentrates may be useful for drinking yoghurt production. © 1999 Society of Chemical Industry

Collagen of edible jellyfish exumbrella

Abstract: The edible jellyfish exumbrella collagen was prepared by limited pepsin digestion. The yield of collagen was very high; 46.4% on the basis of lyophilised dry weight. This collagen was comprised of α1α2α3-heterotrimers, moreover it was relatively stable at 26.0 °C for 60 min. Thus, the edible jellyfish exumbrella will have potential as an important collagen source for use in various industries and it is expected that the development thus so far unutilised resource will advance in the future. © 1999 Society of Chemical Industry

Effect of emulsifiers, fat level and type on the rheological characteristics of biscuit dough and quality of biscuits

Abstract: The effect of level and type of fat as well as emulsifiers on the rheological characteristics of biscuit dough and quality of biscuits has been studied. Increasing the level of fat from 150 to 250 g kg−1 softened the dough, as indicated by a reduction in extrusion time from 108 to 18 s and an increase in compliance from 31.9 to 49.9%, while it reduced the development of gluten, as shown by a reduction in elastic recovery from 0.485 to 0.365 mm. Among the different types of fats used, hydrogenated fat produced the stiffest dough. Addition of any of the emulsifiers glycerol monostearate, lecithin or sodium stearoyl lactylate lowered the elastic recovery value, indicating their contribution to the shortening effect on gluten, and also resulted in a reduction in consistency and hardness and made the dough more cohesive. The maximum change was observed with sodium stearoyl lactylate. The density, breaking strength and compression strength of biscuits decreased, indicating an improvement in crispness, with increasing fat level. The thickness of biscuits was significantly higher when hydrogenated fat or oil was used in the formulation. Biscuits made with bakery shortening had better surface characteristics and higher crispness. Glycerol monostearate and lecithin brought about a greater improvement in the quality of biscuits when compared with sodium stearoyl lactylate. Studies indicated that emulsifiers in general had a greater beneficial effect, particularly in the case of biscuits made from medium hard wheat flour. © 1999 Society of Chemical Industry

An invertase fragment responsible for improving the protein stability of dry white wines

Abstract: The thermoprotective effect of yeast parietal mannoproteins improves the protein stability of white wines aged on their lees (sur lie) The substance responsible for this is an N-glycosylated, 318 kDa mannoprotein that corresponds to a parietal invertase fragment of Saccharomyces cerevisiae This mannoprotein is released into the wine during autolysis of the lees by the combined action of β-glucanases from the cell wall and the yeast's vacuolar protease This mannoprotein may be obtained industrially by extracting yeast mannoproteins using enzymatic digestion of the cell wall with commercially prepared β-glucanases (GlucanexTM -Novo-Nordisk) A wine's susceptibility to protein breakdown may be considerably reduced by adding this mannoprotein extract As a result, less bentonite is needed to stabilise the wine © 1999 Society of Chemical Industry

Release of ferulic acid dehydrodimers from plant cell walls by feruloyl esterases

Abstract: Dehydrodimers of hydroxycinnamic acids, such as ferulic and p-coumaric acids, are important structural components which serve to cross-link polymers in plant cell walls. Dehydrodiferulate oligosaccharide diesters were solubilised from wheat bran or sugar beet pulp by treatment with Driselase and release of dehydrodiferulic free acids from this substrate by purified feruloyl esterases was analysed by HPLC. We detected 5-5diFA, 8-O-4diFA and 8-5BendiFA in saponified extracts from wheat bran and sugar beet pulp. Driselase-treatment solubilised 21 and 97% of the saponifiable dehydrodimers from wheat bran and sugar beet pulp, respectively, but only as dehydrodiferulate esters, not as dehydrodiferulic acids. At low concentrations, feruloyl esterase A (FAEA) from Aspergillus niger and an esterase (XylD) from Pseudomonas fluorescens released 93% and 36% of the saponifiable 5-5diFA from solubilised wheat bran, respectively, but only 12 and 15% from solubilised sugar beet pulp. At higher concentrations, only FAEA also released 8-O-4diFA (65%) from solubilised wheat bran, but not sugar beet pulp. We could not detect release of any dehydrodiferulic acids from solubilised wheat bran or sugar beet pulp using either a cinnamoyl ester hydrolase from Piromyces equi (CEH) or from A niger (CinnAE). Our results demonstrate that FAEA and Xy1D hydrolyse dehydrodiferulate diesters to release the free acids, which means they have the potential to break the putative cross-links present in graminaceous monocot and dicot cell walls, while two other feruloyl esterases (CinnAE and CEH) did not release dehydrodiferulic acids from plant cell walls.

Effect of post-harvest treatments on the level of glucosinolates in broccoli

Abstract: Broccoli is a very perishable vegetable with a high water content (around 88%) which leads to rapid dehydration and probably to an alteration in composition if conditions after harvest are not controlled. This study evaluates the glucosinolate pattern and glucosinolate levels in the principal and secondary inflorescences of fresh broccoli cv 'Tokyodome', and after being submitted to some situations which are likely to occur during or after harvest: room temperature (20 °C) for 5 days, kept in the fridge at 4 °C for 5 days, and frozen after blanching. Another set of material was harvested 5 days later, simulating a post-maturation stage, and analysed. The highest total glucosinolate content was found at commercial maturation with 20 888 and 20 355 mmoles kg ˇ1 DW in the principal and secondary inflorescences, respectively. Keeping the inflorescences at room temperature caused the most significant (P< 0.05) reductions in total and individual glucosinolates, except for 4-hydroxyindol-3- ylmethyl-, 2-hydroxy-2-phenylethyl- and 2-phenylethyl-, when compared to the other situations. The highest levels (10 925 mmoles kg ˇ1 DW) of 4-methylsulphinylbutyl-, the precursor of the anti-cancer isothiocyanate sulphoraphane, were found in the inflorescences freshly harvested at commercial stage. Refrigeration at 4 °C and freezing were shown to be the best preservation processes for maintaining high levels of these and other glucosinolates in contrast with the other situations. # 1999 Society of Chemical Industry