Structure,physicochemical properties and in vitro fermentation of enzymatically degraded cell wall materials from apples

Cell wall materials (CWM) prepared from apple parenchyma tissue by treatment with commercial enzymes for maceration, mash fermentation and liquefaction were characterised with regard to their composition and structure as well as their physicochemical and physiological properties. Increasing enzymatic degradation of the CWM resulted in growing loss of the pectin matrix, decreasing porosity as well as increasing particle aggregation. Due to these structural alterations the water binding, the viscoelastic properties of the CWM‐water‐suspensions and the in vitro fermentation, forming short chain fatty acids, were reduced. The investigations showed that interrelations exist between enzymatic treatment and changes of (i) structure and state of matrices (evaluated by means of thermal analysis( (ii) physicochemical properties and (iii) physiological properties. So the application of liquefying enzymes can lead to a complete removal of the pectin matrix, causing an essentially improved thermal stability of the CWM preparation, but strongly reduced water binding and reduced structure‐forming properties into the CWM‐water‐suspensions. The formation of short‐chain fatty acids during in vitro fermentation of the CWM preparations by fresh human faeces flora depended on the portion and the state of the pectin matrix and the cellulose network, respectively.     

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

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.     

Phenolic composition and free radical scavenging activity of different apple varieties in relation to the cultivar,tissue type and storage

The aim of this research was to evaluate the influence of genotype, tissue type and cold storage on the bioactive compounds content and on the antiradical activity (AA) of different apple cultivars (Golden cl. B, Fuji cl. Kiku8, Braeburn cl. Hillwell). The content of analysed phyto-compounds depended on the clone, on the part of fruit, and to a minor extent, on the storage. For EC₅₀ data, the cultivar represented the main source of variation and the interaction with the type of tissue, was significant. The AA of apples, measured by means of the DPPH test, was highly correlated to the flavan-3-ols content, which represents a good predictor of the apple antiradical power. The new Braeburn’s clone, the Hillwell, had the worst AA related to a minor phyto-chemical content. Also, its phenolic content was dramatically reduced after cold storage (flesh: −50%; peels: −20%; p < 0.05). Obtained results underlined the key role of the genotype on the content of the nutraceutical power of apples, which is important to improve their quality and consumption benefits, suggesting to the breeders to pay more attention to the potential healthy compounds in the development of new hybrids.     

Incidence of bitter pit in relation to the calcium content of apples: Calcium distribution in the fruit

The distribution of calcium at harvest, its subsequent redistribution within the fruit during storage in air at 2.8°C and bitter pit development in samples of Cox's Orange Pippin apples picked at intervals during September and October were investigated. The distribution of calcium in the fruit changed on the tree and during storage. The percentages of pitted apples, assessed in January, were poorly related to calcium concentrations in the whole fruit or in any fruit zone at harvest. Redistribution of calcium from the mid and outer cortical tissues to the core zone was followed, at longer intervals over successive picks, by the appearance of bitter pit lesions. The earliest-picked sample was less affected by bitter pit than samples picked later in September. The least bitter pit occurred in samples picked in October, after the climacteric rise in respiration, and these fruits were apparently less subject to fluctuations in calcium concentrations during storage.     

Model studies on the diffusion behavior of the mycotoxin patulin in apples, tomatoes, and wheat bread

 Quantitative studies on the diffusion behavior of the mycotoxin patulin (Pat) performed by stable isotope dilution assays using a carbon-13-labeled analogue as the internal standard revealed that Pat did not diffuse into apples affected by the fungus Penicillium expansum. At a distance of more than 2 cm from the infected zone the mycotoxin was not detectable. However, in a similar experiment with tomatoes the mycotoxin was found to penetrate into the whole fruit. These different characteristics were related to the physical laws of diffusion and attributed to differences in the texture of the foods. Like in apple tissue, the patulin content in molded wheat bread crumb fell sharply at a longer distance from the fungal mycelium. A comparison with aflatoxins revealed that these mycotoxins show much faster diffusion into the crumb as compared to patulin. Received: 14 March / Revised version: 8 June 2000     

Lenticel blotch pit,watercore, splitting and cracking in relation to calcium concentration in the apple fruit

Analyses of apples, of various varieties and from many sources, affected by lenticel blotch pit and/or watercore showed that calcium concentrations in the fruit were usually extremely low. The severity of lenticel blotch pit, either on the tree or during storage, increased with decreasing concentrations of calcium and/or increasing concentrations of potassium. Split and cracked apples had lower concentrations of calcium or higher concentrations of potassium than sound fruit from the same sources. The disorders usually occurred when mean concentrations of calcium in bulked random samples of fruit fell below 4 mg 100 g^?1 fresh wt and lenticel spotting was noted on apples with concentrations at this level. Incidences of these disorders in the orchard therefore indicate that the fruit is likely to develop bitter pit and breakdown during storage.     

Microspectrophotometry of bermudagrass (Cynodon dactylon) cell walls in relation to lignification and wall biodegradability

The walls of the major plant cell types, sclerenchyma and parenchyma, of the second (upper) and fifth (lower) internodes from the apex of bermudagrass (Cynodon dactylon L) stem have been examined by ultraviolet absorption microspectrophotometry and the results related to wall digestibility (measured in vitro with rumen liquor) and to histochemical reactions for ‘lignin’ and phenolics. Sclerenchyma walls from the lower internode gave high values of absorbance in the ultraviolet region of the spectrum equivalent to 109 mg trans-ferulic acid g^?1 dry walls; similar walls from the upper internode also gave high values but these were lower than values from the lower internode. Histochemical examination showed that the sclerenchyma walls, which were indigestible to rumen microorganisms, gave positive tests with acid phloroglucinol reagent for lignin. Parenchyma walls, which were either digested or partially digested, gave much lower absorbance values in the ultraviolet region and negative tests with acid phloroglucinol but positive tests with diazotised sulphanilic acid (upper and lower internodes) and chlorine-sulphite (lower internode) reagents. Ultraviolet absorption microspectrophotometry is a useful technique for examining phenolics within individual cell walls that vary in biodegradability.     

Composition and digestibility during ageing of consecutive leaves on the main stem of Italian ryegrass plants,growing undisturbed or regrowing after cutting

For modelling of grass digestibility throughout the growing season, the impact of cutting on individual leaves needs to be quantified. Therefore, a glasshouse experiment was carried out with Italian ryegrass (Lolium multiflorum Lam) grown from seed. Half of the plants were grown undisturbed until leaf stage 8, while the other half were cut at leaf stage 4, after which they were allowed to grow until leaf stage 9. The composition and digestibility characteristics of leaves 6, 7 and 8 on the main shoot of plants from both treatments were quantified. In the uncut plants, leaf blade length and mass and specific cell wall (CW) and organic matter (OM) mass (mg cm⁻²) was higher for consecutive leaves. During leaf ageing specific CW mass remained unchanged, while specific OM mass and CW digestibility declined, resulting in a decline of OM digestibility. CW digestibility of leaves decreased to c 78%, a value also found in an earlier experiment. The newly formed leaves after cutting had a reduced leaf size and specific leaf mass (SLM, mg DM cm⁻²). Leaf 6, that was damaged by cutting, showed a lower initial CW content and a rapid decline of specific CW and OM mass and of digestibility during ageing. Its low specific mass and digestibility of CW could have been related to cessation of CW synthesis during its growth after cutting, as was evidenced by the lower CW thickness of sclerenchyma cells. The later-formed leaves, 7 and 8, had digestibility characteristics similar to those of the uncut plants. Since leaf 6 hardly contributed to the total plant dry matter mass, the cut and the uncut plants differed only slightly in digestibility of the total leaf fraction. It can be concluded that cutting sets back leaf size and growth rate but has little effect on digestibility characteristics during ageing. © 1999 Society of Chemical Industry     

The effect of cultivar,sample date and grazing on the concentration of s-methylcysteine sulphoxide in oilseed and forage rapes (brassica napus)

A study of the S-methylcysteine sulphoxide (SMCO) concentration in foliage from four double-zero, three single-zero cultivars of oilseed rape and four cultivars of forage rape revealed little inter-cultivar variation. Significant differences were however found with respect to harvest date, with the concentration of SMCO remaining fairly constant over the early winter period but then increasing as the plants commenced regrowth in the late winter-early spring. Continual exposure of plots to grazing wild rabbits produced small but statistically significant changes in SMCO concentration but compared with seasonal differences the changes due to grazing were small and inconsistant. These findings are discussed in relation to the recently reported harmful effects of double zero oilseed rape cultivars on browsing wildlife.     

Effect of addition of amino acids, treatment with β-galactosidase and use of heat-shocked cultures on the acetaldehyde level in yoghurt

In this study, the biochemical activities of nonviscous and viscous yoghurt starter cultures were investigated. Yoghurt samples produced with nonviscous and viscous cultures, and viscous cultures + methionine (10 and 30 mg/100 mL milk), + threonine (5 and 10 mg/100 mL milk), + β-galactosidase (1 mg/100 mL milk), and with a heat-shocked culture were analysed. In the experimental yoghurts, the pH, titratable acidity, lactic acid, tyrosine and acetaldehyde contents and the number of total starter organisms were determined. According to the results obtained, the samples produced with the viscous culture had the lowest acetaldehyde levels, whereas the highest acetaldehyde level was found in the samples manufactured with the nonviscous culture. Compared with the samples inoculated with the viscous culture alone, the amino acid supplementation, lactose hydrolysis and heat-shock treatments caused a significant increase in the level of acetaldehyde.     

Cellular,biological, and physicochemical basis for the hard‐to‐cook defect in legume seeds

This review integrates current knowledge on the hard‐to‐cook (HTC) defect in legume seeds, with emphasis on the cellular and biological changes during storage and soaking, and the physicochemical changes during heating. Several postulated mechanisms, including the pectin‐cation‐phytate model, cell lignification, pectin β‐eliminative degradation, and protein denaturation in relation to starch gelatinization, are discussed in the context of current evidence. Subsequently, a developmental model of legume hardening is presented. It is held that the HTC defect develops during aging and soaking and is exhibited through cooking. During the process, there are many events involved. Free radical formation, lipid peroxidation, acid formation, membrane deterioration, protein denaturation, and leakage are events associated with aging and soaking, whereas pectin decomposition and solubilization, protein coagulation, and starch gelatinization are events that occur during cooking. Cooked HTC seeds are characterized by limited cell separation and restricted starch gelatinization. These defective features result from a restriction in pectin decomposition and solubilization as well as the protein coagulation that prevails over starch gelatinization during heating. This multichannel mechanism points to the direct involvement of two amphoteric colloids, cell wall pectin and storage protein, both of which are sensitive to pH and/or ion composition. The model also indicates the indirect involvement of cell membranes and starch granules. Except for events that occur during aging and soaking, it is likely that heat‐related textural problems in other plant tissues may proceed via a mechanism similar to legume hardening.     

Completion of the Saccharomyces cerevisiae Genome Sequence Allows Identification of KTR5, KTR6 and KTR7 and Definition of the Nine-Membered KRE2/MNT1 Mannosyltransferase Gene Family in this Organism

The KRE2/MNT1 mannosyltransferase gene family of Saccharomyces cerevisiae currently consists of the KRE2, YUR1, KTR1, KTR2, KTR3 and KTR4 genes. All six encode putative type II membrane proteins with a short cytoplasmic N-terminus, a membrane-spanning region and a highly conserved catalytic lumenal domain. Here we report the identification of the three remaining members of this family in the yeast genome. KTR5 corresponds to an open reading frame (ORF) of the left arm of chromosome XIV, and KTR6 and KTR7 to ORFs on the left arms of chromosomes XVI and IX respectively. The KTR5, KTR6 and KTR7 gene products are highly similar to the Kre2p/Mnt1p family members. Initial functional characterization revealed that some mutant yeast strains containing null copies of these genes displayed cell wall phenotypes. None was K1 killer toxin resistant but ktr6 and ktr7 null mutants were found to be hypersensitive and resistant, respectively, to the drug Calcofluor White. The sequences have been deposited in the GenBank data library under Accession Numbers Z71305; U39205; Z46728.©1997 John Wiley & Sons, Ltd.     

Modelling the effects of pH, storage temperature and redox potential (Eh) on the survival of bifidobacteria in fermented milk

The effects of storage temperature, pH and E _h on the survival of Bifidobacterium longum and Bifidobacterium animalis ssp. lactis were modelled in a 3 × 4 × 3 factorial design using three storage temperatures (4, 8, 12 °C), four pH (4.0, 4.25, 4.5, 4.75) and three E _h (0, 200, 400 mV) values. Bifidobacterium animalis ssp. lactis showed significantly better survival than B. longum ( P  < 0.0001) in fermented milk under normal environmental conditions. Bifidobacterium longum was more susceptible to acidity and survival was log-linear at low pH values whereas at higher pH pronounced shouldering and tailing effects were apparent. Both individual environmental conditions ( T , pH, E _h) and interactions between E _h and pH affected survival and death was always more rapid in B. longum . Bifidobacterium animalis ssp. lactis generally showed a simple log-linear reduction over time. Temperature, pH and E _h could be manipulated to enhance survival but E _h reduction appears to be the best way to enhance survival without adversely affecting other properties.     

Application of cavitation system to accelerate the endogenous enzymatic hydrolysis of baicalin and wogonoside in Radix Scutellariae

Baicalinase is an endogenous enzyme present in the roots of Scutellaria baicalensis that can hydrolyse baicalin and wogonoside into baicalein and wogonin directly, which have higher bioactivity and bioavailability than their glycosides. Baicalinase-catalysed hydrolysis with cavitation was examined as a highly efficient and green alternative method for large scale production of baicalein and wogonin. Effect of cavitation system on the transformation and extraction efficiency was investigated by using reaction kinetic and mass transfer kinetic models at three levels of temperature (20-50 °C). Experimental results showed that cavitation had a significant effect (p < 0.01) on the biocatalysis process; the transformation of baicalin and wogonoside reached 98.21% and 96.60% at 50 °C for 60 min, and the yields of baicalein and wogonin were about 4.47- and 2.86-fold higher than those of the raw sample without enzymatic hydrolysis, respectively.     

Cloning and characterization of WMSU1, a Williopsis saturnus var. mrakii gene encoding a new yeast SUN protein involved in the cell wall structure

SUN proteins of Saccharomyces cerevisiae have been defined on the basis of high homologies in their C-terminal domain. Recently, two of these four proteins were shown to be involved in cell wall morphogenesis (Mouassite et al., 2000a). In the present study, we have isolated WMSU1 (Accession No. AF418983), a new SUN-related gene, from W. saturnus var. mrakii MUCL 41968. Sequencing of the gene revealed an open reading frame coding for 402 amino acids. The predicted amino acid sequence of WMSU1 is closely related to the S. cerevisiae SUN proteins and to other yeast proteins involved in cell wall metabolism. WMSU1 is proposed to encode a cell wall protein since its predicted product contains a signal sequence, a Kex2p cleavage site and a serine/threonine-rich N-terminal domain. Southern blot analysis of the W. saturnus var. mrakii MUCL 41968 genome using the highly conserved domain of WMSU1 as a probe suggested that the isolated gene belongs to a multigenic family. Expression of WMSU1 in E. coli led to a 45 kDa protein, which appeared to be toxic to this host. Scanning electron microscopy analysis of a recombinant S. cerevisiae producing Wmsu1p showed that this strain exhibited an altered cell wall, thus pointing to a probable role of this protein in the cell wall structure.     

Identification and characterisation of allergens related to Bet v I,the major birch pollen allergen,in apple,cherry, celery and carrot by two-dimensional immunoblotting and N-terminal microsequencing

Low temperature extracts taken from Granny Smith and Braeburn apples, cherries, celery and carrots were separated by two-dimensional electrophoresis. Bet v I, the major birch pollen allergen, related allergens in apple, cherry, celery and carrot extracts were detected by means of two-dimensional immunoblotting with patients' sera containing IgE antibodies specific to Bet v I, a rabbit polyclonal antiserum raised against Bet v I , and two Bet v I specific mouse monoclonal antibodies. The major cross-reacting allergen spots were observed with molecular weights/isoelectric points of 18.0 kDa/pI 5.5 for apple (Granny Smith and Braeburn) and 18.0 kDa/pI 5.8 for cherry, 15.5 kDa/pI 4.4–4.6 for celery and 16.0 kDa/pI 4.4 for carrot extract. Additional antibody reactivities with certain isoprotein spots were observed, which may indicate the presence of Bet v I-related epitopes on these proteins. Based on the first 15 N-terminal amino acid residues, the major allergen spots revealed 53% sequence identity between Bet v I and the Granny Smith apple allergen, 50% between Braeburn apple allergen and Bet v I , 67% between Bet v I and the cherry allergen, and 40 and 28% for celery and carrot, respectively. Furthermore, the N-terminal sequences showed identities ranging from 40% (apple/cherry) to 66% (celery) with PcPR l-l, a pathogenesis-related protein in parsley.     

The effect of housing system on apparent digestibility in pigs,using the classical and marker (chromic oxide,acid-insoluble ash) techniques,in relation to dietary composition

The present study examined differences in faecal digestibilities of organic matter (dOM) and crude protein (dXP), between growing pigs housed either in pens as groups or individually in metabolism cages. In addition, a study was made of the influence of dietary composition on these observed differences. Four experimental diets were composed by iso-energetic exchange of maize starch in the control diet with purified cellulose (260 g kg^-1), toasted soyabean hulls (280 g kg^-1) or renderers fat (67 g kg^-1), respectively. Both in pens and in metabolism cages, dOM and dXP were measured, using both chromic oxide (Cr₂O₃) and acid-insoluble ash (AIA) as markers. In metabolism cages, the results of the marker method were compared to those of the classical method, where dOM and dXP were measured by collecting faeces quantitatively. Recoveries of both markers were measured, after a period of 10 and 3 days. With Cr₂O₃ as marker, pen-housing resulted in a dOM which was on average 2.5 (1.7–4.5) units lower and a dXP averaging 4.5 (3.0–5.8) units lower than measured in the metabolism cages (P≤0.001). No significant interactions were demonstrated between housing system and dietary composition. In contrast, with AIA as marker significantly higher digestibility values were observed for pigs in pens, when fed the cellulose diet. With this diets, the dOM was on average 14.7 units higher and the dXP was on average 10.9 units higher for the penned pigs. For the pigs fed one of the other three diets, the dOM was on average 1.5 (0.1–2.7) units lower and the dXP was on average 3.7 (1.9–5.7) units lower. Thus, with AIA as a marker, the effect of housing system on digestibility interacted with the type of diet (P≤0.05 on dOM and P≤0.01 on dXP). Comparison between the marker method with the classical method, showed that Cr₂O₃ provided similar results. In contrast, AIA displayed significantly higher dOM and dXP, except with the cellulose diet. This could be explained by differences in the recoveries of both markers. For Cr₂O₃ this was close to 100% and for AIA it varied from 97% on the cellulose diet to 183% on the control diet. The analytical procedure for AIA requires more research. Shortening the measuring period from 10 to 3 days did not prove to be significant, but increased the standard deviations. It was concluded that for practical application, faecal digestibilities should be measured with penned pigs. According to the findings, under such conditions Cr₂O₃ is a good marker. AIA was found to be unsuitable.     

Exposure assessment to ochratoxin A in Catalonia (Spain) based on the consumption of cereals,nuts, coffee,wine, and beer

Ochratoxin A (OTA) was analysed in composite samples of cereal-based baby foods, beer, breakfast cereals (corn- and rice and wheat-based), loaf bread, peanuts and pistachios. Foodstuffs were collected in hypermarkets and supermarkets from 12 cities in the Spanish region of Catalonia, and composite samples were prepared for analysis involving liquid–liquid extraction, followed by immunoaffinity column clean-up and HPLC with fluorescence detection. Consumption data for the selected foodstuffs were collected by means of a food-frequency questionnaire. The studied population was grouped by age in infants, children, adolescents and adults; and exposure to OTA through the specified foodstuffs, and through wine and coffee, was assessed. Exposure assessment was done through deterministic and probabilistic modelling of the contamination and consumption data. OTA occurrence and mean of positive samples (ng?g^?1 or ng?ml^?1, for beer) were the following: 8.7% and 0.233 in baby foods; 88.7% and 0.022 in beer; 2.8% and 0.728 in corn-based breakfast cereals; 25% and 0.293 in wheat-based breakfast cereals; 12.9% and 0.283 in loaf bread; 41.7% and 0.241 in peanuts; and 2.9% and 0.228 in pistachios. The median estimated daily intake of OTA through the foodstuffs by each age group were below the latest provisional tolerable daily intakes (PTDIs) of 17 and 14?ng?kg^?1?bw?day^?1 recommended by the European Food Safety Authority (EFSA) in 2006 and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 2007, respectively, ranging from 1% and 2% of those values in adolescents and children, to 3% and 11% in adults and infants.     

Quality and hygiene of beef burgers in relation to the addition of sodium ascorbate,sodium citrate and sodium acetate

We evaluated the effects of two additive mixtures (sodium ascorbate 1 g kg^?1, sodium citrate 1 g kg^?1 and sodium acetate 1.75 or 2.5 g kg^?1) on the microbiological and physical–chemical characteristics of non‐prepacked beef burgers stored in air at 4 °C or 12 °C for 96 h. Total microbial count reached 7 Log CFU g^?1 48 h later in treated samples at 4 °C. The mixture containing the higher acetate concentration led to a smaller increase in Gram‐negatives, in particular Pseudomonas (2 Log of difference towards control samples at 96 h); at 12 °C, a 1.7 Log difference in Enterobacteriaceae was also shown. Total viable basic nitrogen was significantly lower in the treated samples at 12 °C. The addition resulted in pH stabilisation and lower cooking loss and positively influenced the a* index of burgers at 4 °C. Clearly, the use of these mixtures should not be a substitute of good hygienic practices and optimal storage conditions.