Spanish-style green table olives pasteurized and stored in two types of pasteurizable plastic pou... more Spanish-style green table olives pasteurized and stored in two types of pasteurizable plastic pouches and glass bottles were analyzed for color parameters and volatile components after 6.5 months of storage at 30 ºC. Color parameters in pouches made of aluminium oxide coating on polyethylene terephthalate + medium-density polyethylene (AlOx-coated PET + MDPE) were acceptable and, in general, did not significantly differ from those in glass, but unacceptable values corresponding to dark visual colors of both olives and brine were found in pouches made of polyethylene terephthalate + medium-density polyethylene/ethylene vinyl alcohol (PET + MDPE/EVOH). Fortythree volatile compounds were identified and quantified in olive pulp by solid phase micro-extraction (SPME) and gas chromatography coupled to mass spectrometry (GC-MS), 36 of these compounds being significantly different between the plastic and glass treatments. The type of plastic container had an impact on the volatile composition of product. Oxidation and scalping were considered to be the most probable causes for the differences in volatile components between PET + MDPE/EVOH pouches and glass containers, but in AlOx-coated PET + MDPE pouches no oxidation process was apparent.
The volatile profile of Spanish-style green table olives after fermentation and the changes in vo... more The volatile profile of Spanish-style green table olives after fermentation and the changes in volatile compounds that occurred as a result of the post-fermentation and subsequent packing stage were explored by solid phase micro-extraction (SPME) and gas chromatography coupled to mass spectrometry (GC-MS).Three olive cultivars (Manzanilla, Gordal, and Hojiblanca) were processed and olive samples were taken at three different times throughout the elaboration: after fermentation, after postfermentation, and after packing. A total of 132 volatile compounds were identified, including 10 phenols, 25 alcohols, 11 acids, 39 esters, 8 hydrocarbons, 14 carbonyl compounds, 17 terpenes, and 6 other compounds. A varying number of compounds from each chemical family underwent significant changes because of the postfermentation and packing stages. Among them, some typical reaction products of lipid oxidation (e.g. (E)-2-decenal and (E,E)-2,4-decadienal) increased with the postfermentation in Manzanilla cultivar, and also as a result of packing in all three cultivars.
Journal of the science of food and agriculture, Jan 19, 2017
There is an increasing interest in the use of pasteurizable plastic packaging by the olive indust... more There is an increasing interest in the use of pasteurizable plastic packaging by the olive industry. In order to investigate the change from traditional glass or varnished can containers to plastic packaging, the proper plastic material that is compatible with fermented olives while maintaining color quality during pasteurization treatment and storage must be selected. This work is focused on color stability in two distinct pasteurizable plastic containers with different oxygen permeability. In PET + MDPE/EVOH (polyethylene terephthalate + medium-density polyethylene/ethylene vinyl alcohol) pouches, pasteurization provoked severe browning which drastically decreased their color shelf life (<6 weeks). However, this browning did not occur in the unpasteurized product without preservatives due to the presence of microorganisms. In AlOx-coated PET + MDPE (aluminum oxide coating on polyethylene terephthalate + medium-density polyethylene) pouches, color changes were small or negligibl...
The contents of total phenolic compounds, flavonoids, and phenolic acids were determined in selec... more The contents of total phenolic compounds, flavonoids, and phenolic acids were determined in selected garlic cultivars grown at four locations. The total phenolic content varied from 3.4 mg gallic acid equivalents (GAE)/g of dry matter (dm) to 10.8 mg GAE/g of dm with a mean value of 6.5 mg GAE/g of dm. The myricetin, quercetin, kaempferol, and apigenin flavonoids were not detected in any of the samples. Caffeic acid and ferulic acid were the major phenolic acids found with mean values of 2.9 mg/kg of dm and 2.6 mg/kg of dm, respectively. The mean contents of vanillic, p-hydroxybenzoic, and p-coumaric acids were comparable (0.4-0.8 mg/kg of dm), and the level of sinapic acid was negligible (< 0.1 mg/kg of dm). There was a significant effect of location but an insignificant effect of genotype on contents of caffeic, vanillic, p-hydroxybenzoic, and p-coumaric acids. However, genotype but not location affected the contents of total phenolics and ferulic acid. On average, the white garlic cultivars and Chinese garlic cultivars contained higher contents of total phenolics and ferulic acid than the purple garlic cultivars. However, the differences in the total phenolic content between the purple and white garlic cultivars were not significant.
ABSTRACT Nitrate-ammonium (N-A) and ammonium-nitrate (A-N) transition experiments were performed ... more ABSTRACT Nitrate-ammonium (N-A) and ammonium-nitrate (A-N) transition experiments were performed with tobacco (Nicotiana tabacum, cv Gatersleben) plants to study whether the increased expression of ammonium assimilation-related genes found under short-term boron (B) deficiency is maintained when the nitrogen source changes. Asparagine synthetase (AS), glutamate dehydrogenase (GDH) and glutamine synthetase (GS) gene overexpressions in roots under B deprivation were detected in both nitrogen transitions, although GS and, especially, AS up-regulations were observed earlier in the ammonium-nitrate transition. Transcript levels were inversely correlated with hexose contents after 24 h of B deprivation. Our results suggest that tobacco roots respond to short-term B deficiency by increasing the expression of AS, GDH and GS genes irrespectively of the nitrogen source. A hypothetical model to explain these results is proposed and discussed. Thus, the combined action of these enzymes would avoid the accumulation of ammonia and help maintain the activity of the tricarboxylic acid cycle when tobacco roots are affected by B deficiency, the plant organ that first senses this stress. Therefore, under B deficiency, they would act as an ammonium detoxifying mechanism, being a complement to the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway. We propose that the protective role of these enzymes could be extended to changing nitrogen-supply conditions.
To date, one asparagine synthetase (AS) mRNA has been identified in Nicotiana tabacum. Our result... more To date, one asparagine synthetase (AS) mRNA has been identified in Nicotiana tabacum. Our results point out that this gene encodes an actual AS protein. This proposal is supported by the following facts. (i) Blast analysis indicates that tobacco AS gene shows increased percent identity with several AS genes of different plant species. (ii) Leaf and root AS mRNA levels were inversely correlated with soluble carbohydrate concentrations, both in the presence of light and in darkness, and the addition of exogenous sucrose repressed the root AS gene expression. (iii) In light, a positive correlation between AS transcript levels and ammonium content was observed in both leaves and roots. (iv) A direct correlation between leaf AS gene expression and asparagine (Asn) concentration has been found. Furthermore, quantitative real-time PCR analyses showed that this gene expression was increased under boron (B) deficiency in roots, but not in leaves. Interestingly, soluble B concentration in roots of plants subjected to B deficiency was significantly lower than that of control plants. However, in leaves, there was no significant difference in soluble B content between both B treatments. We discuss the possible role of soluble B deficiency in the regulation of AS gene expression in tobacco roots.
The content of organosulfur compounds was determined in selected garlic cultivars grown at four l... more The content of organosulfur compounds was determined in selected garlic cultivars grown at four locations in Andalusia, Spain. The organosulfur compounds studied were three γ-glutamyl peptides, namely, γ-L-glutamyl-S-(2-propenyl)-Lcysteine (GSAC), γ-L-glutamyl-S-(trans-1-propenyl)-L-cysteine (GSPC), and γ-L-glutamyl-S-methyl-L-cysteine (GSMC), and four cysteine sulfoxides (alliin, isoalliin, methiin, and cycloalliin). There was a significant effect of the location, cultivar, and garlic ecotype on individual organosulfur compound contents. Purple-type cultivars showed on average the highest contents of GSMC, GSAC, alliin, and methiin but the lowest isoalliin content. The impact of genotype was relatively high for GSAC, whereas this factor hardly contributed to the total variability in alliin and isoalliin content. Planting date had a significant effect on the content of alliin and isoalliin. Discriminant analysis evidenced the ability of organosulfur compounds to distinguish among garlic bulbs from different locations or ecotypes with 81 or 86% accuracy, respectively.
The influence of processing, with and without fermentation, on the contents of organosulfur compo... more The influence of processing, with and without fermentation, on the contents of organosulfur compounds, namely, γ-glutamyl peptides, S-alk(en)yl-L-cysteine sulfoxides (ACSOs), and S-allyl-L-cysteine (SAC), in pickled blanched garlic was evaluated. For each processing type, the effect of the preservation method and storage time was also analyzed. Blanching in hot water (90 °C for 5 min) hardly affected the individual organosulfur compound content. The fermentation and packing steps negatively affected the levels of all compounds except for SAC. The content of this compound increased during storage at room temperature whereas γ-glutamyl peptides and ACSOs were degraded to various extents. The pasteurization treatment itself had no significant effect on the concentrations of organosulfur compounds. Use of the corresponding fermentation brine in the case of the fermented product in conjunction with refrigerated storage was found to be the best method to preserve the levels of organosulfur compounds in pickled garlic stored for up to one year.
International Journal of Food Science & Technology, 2012
ABSTRACT The evolution of two additives, potassium sorbate and ascorbic acid, during long-term st... more ABSTRACT The evolution of two additives, potassium sorbate and ascorbic acid, during long-term storage of pickled vegetables, as well as the impact of these additives on product colour, was investigated. For this investigation, cucumbers and caperberries packed in both glass bottles and plastic pouches were used. In general, the added sorbate level remained unchanged during long-term storage irrespective of the packaging material. However, the ascorbic acid gradually disappeared at a significantly higher rate in plastic than in glass containers, and its level was higher in caperberries than in cucumbers. In the latter, the presence of sorbate caused a higher degradation rate of ascorbic acid compared to the absence of sorbate. Ascorbic acid had a protective effect against surface colour degradation in cucumbers packed in plastic pouches, whereas sorbate enhanced such degradation. However, in both pickled vegetables, ascorbic acid degradation had a significant impact on brine browning, particularly in plastic pouches.
The aim of this research was to ascertain the lactic acid bacteria responsible for the degradatio... more The aim of this research was to ascertain the lactic acid bacteria responsible for the degradation of ascorbic acid and/or potassium sorbate, isolated from packed green olives where these additives had diminished. A total of 14 isolates were recovered from samples of different green olive containers. According to partial sequencing of the 16S rRNA coding gene, Lactobacillus parafarraginis, Lactobacillus rapi, Lactobacillus pentosus, Lactobacillus paracollinoides, and Pediococcus ethanolidurans were identified. With the exception of L. pentosus and L. paracollinoides, the other species had not been mentioned in table olives before this study. Only three of the 14 isolates metabolized ascorbic acid in MRS broth, and the products from ascorbic acid in modified MRS broth without carbon sources were acetic and lactic acids. Except for the two L. rapi and the two P. ethanolidurans strains, the remaining 10 isolates depleted potassium sorbate added into MRS broth to some extent. The product generated by three of these strains was confirmed to be trans-4-hexenoic acid. The degradation of ascorbate or sorbate by lactic acid bacteria should be taken into account when these additives are used in food products where this group of bacteria may be present.
The effects of different packing conditions and storage times on the stability of monosodium glut... more The effects of different packing conditions and storage times on the stability of monosodium glutamate (MSG) added to two different fermented vegetables (Spanish-type green table olives and pickled cucumbers) were studied. Factors such as packaging material (glass bottle versus plastic pouch), heat treatment (pasteurisation versus non-pasteurisation), and the presence or not of a preservative compound (potassium sorbate) were considered. The MSG content of pickled cucumbers was stable for up to 1 year of storage in all packing conditions studied. The MSG content also remained stable in pasteurised green table olives. On the contrary, MSG was extensively degraded (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;75% degradation) after 54 weeks of storage in unpasteurised green olives with a higher degradation rate in glass bottles compared with plastic pouches. In the presence of potassium sorbate, MSG was also considerably degraded in olives packed in plastic pouches…
The main purpose of this study was to evaluate the inhibitory effect on acrylamide (AA) formation... more The main purpose of this study was to evaluate the inhibitory effect on acrylamide (AA) formation and the impact on sensory characteristics in ripe olives of three selected amino acids (sarcosine, proline and glycine), which previously showed high AA inhibition rates in an olive model system. Each amino acid was separately added to packing solutions to give 100 or 200 mM at equilibrium, prior to a sterilisation treatment at 121°C. The results showed that sarcosine at 100 mM may be a good candidate for reducing the AA content in ripe olives with a limited effect on sensory characteristics. Studies with a model solution of AA and sarcosine heated at 121°C for 30 min suggested that the main mechanism for the inhibitory effect of sarcosine on AA formation was the Michael reaction.
Plant cell wall is a dynamic structure that is of fundamental importance in plant growth and deve... more Plant cell wall is a dynamic structure that is of fundamental importance in plant growth and development, as well as in the response to environmental stresses. There is direct evidence for a role of boron (B) in cross-linking of cell wall rhamnogalacturonan II (RG-II) and pectin assembly, which shows that B is essential for cell wall structure and function. The aim of the present work was to investigate the effects of B deficiency on the expression of cell wall-related genes in Arabidopsis roots. For this purpose, plants were grown hydroponically in a nutrient solution supplemented with 2 M B and then transferred to a boron-free medium for 6 and 24 h. A transcriptome analysis was carried out and several cell wall-related genes were identified, whose expressions were down-regulated by B deficiency. These genes belong to arabinogalactan protein, xyloglucan endotransglycosylase/hydrolase, polygalacturonase, pectate lyase, pectin methylesterase, expansin, and cellulose synthase-like gene families. These results suggest that in addition to the essential role that B plays in the structural organization of the cell wall, it could directly or indirectly have an impact on the expression levels of genes related to the cell wall.
Chemical and sensorial changes related to the use of benzoates and ascorbic acid as additives in ... more Chemical and sensorial changes related to the use of benzoates and ascorbic acid as additives in packed fermented vegetables were investigated. For this, three selected vegetables (green olives, cucumbers, and caperberries) stored under different conditions (glass or plastic containers, ambient or refrigerated storage) were used. In all cases, benzoic acid remained unchanged (glass bottle) or decreased slightly (plastic pouch) at prolonged storage. Ascorbic acid was partially or totally degraded during storage, the degradation rate depending on the storage conditions and the vegetable matrix. Benzene levels higher than 10 μg/L were found in cucumbers and caperberries containing both additives, but only when packed in plastic pouches and after prolonged storage at room temperature. In these conditions, an appreciable browning of brine, related to AA degradation, was also found. The use of benzoate alone had a significant influence on vegetable color, but flavor was not significantly affected at the benzoate levels tested. On the basis of the present study, benzoates should be removed from fermented vegetable formulations containing ascorbic acid to eliminate possible benzene formation during long-term storage.
A ripe olive model system was used to evaluate the potential inhibiting effects on acrylamide for... more A ripe olive model system was used to evaluate the potential inhibiting effects on acrylamide formation from a set of amino acids and water-soluble vitamins. The system was based on ripe olive juice heated at 121 ºC for 30 min in a stainless steel tubular reactor. The most potent acrylamide inhibitors were proline and sarcosine, both with inhibition rates of ~75% at a 100 mM level. In addition, glycine, ornithine, taurine, and γ-amino butyric acid were effective (50-65% inhibition) while the rest of the compounds demonstrated weak or non-significant effects. Acrylamide contents in the model system were found to be highly correlated with the corresponding contents in the real product. The kinetic pattern for the formation of acrylamide in the absence and presence of two selected amino acids, added separately or together, was well fitted using a simple logistic function.
Spanish-style green table olives pasteurized and stored in two types of pasteurizable plastic pou... more Spanish-style green table olives pasteurized and stored in two types of pasteurizable plastic pouches and glass bottles were analyzed for color parameters and volatile components after 6.5 months of storage at 30 ºC. Color parameters in pouches made of aluminium oxide coating on polyethylene terephthalate + medium-density polyethylene (AlOx-coated PET + MDPE) were acceptable and, in general, did not significantly differ from those in glass, but unacceptable values corresponding to dark visual colors of both olives and brine were found in pouches made of polyethylene terephthalate + medium-density polyethylene/ethylene vinyl alcohol (PET + MDPE/EVOH). Fortythree volatile compounds were identified and quantified in olive pulp by solid phase micro-extraction (SPME) and gas chromatography coupled to mass spectrometry (GC-MS), 36 of these compounds being significantly different between the plastic and glass treatments. The type of plastic container had an impact on the volatile composition of product. Oxidation and scalping were considered to be the most probable causes for the differences in volatile components between PET + MDPE/EVOH pouches and glass containers, but in AlOx-coated PET + MDPE pouches no oxidation process was apparent.
The volatile profile of Spanish-style green table olives after fermentation and the changes in vo... more The volatile profile of Spanish-style green table olives after fermentation and the changes in volatile compounds that occurred as a result of the post-fermentation and subsequent packing stage were explored by solid phase micro-extraction (SPME) and gas chromatography coupled to mass spectrometry (GC-MS).Three olive cultivars (Manzanilla, Gordal, and Hojiblanca) were processed and olive samples were taken at three different times throughout the elaboration: after fermentation, after postfermentation, and after packing. A total of 132 volatile compounds were identified, including 10 phenols, 25 alcohols, 11 acids, 39 esters, 8 hydrocarbons, 14 carbonyl compounds, 17 terpenes, and 6 other compounds. A varying number of compounds from each chemical family underwent significant changes because of the postfermentation and packing stages. Among them, some typical reaction products of lipid oxidation (e.g. (E)-2-decenal and (E,E)-2,4-decadienal) increased with the postfermentation in Manzanilla cultivar, and also as a result of packing in all three cultivars.
Journal of the science of food and agriculture, Jan 19, 2017
There is an increasing interest in the use of pasteurizable plastic packaging by the olive indust... more There is an increasing interest in the use of pasteurizable plastic packaging by the olive industry. In order to investigate the change from traditional glass or varnished can containers to plastic packaging, the proper plastic material that is compatible with fermented olives while maintaining color quality during pasteurization treatment and storage must be selected. This work is focused on color stability in two distinct pasteurizable plastic containers with different oxygen permeability. In PET + MDPE/EVOH (polyethylene terephthalate + medium-density polyethylene/ethylene vinyl alcohol) pouches, pasteurization provoked severe browning which drastically decreased their color shelf life (<6 weeks). However, this browning did not occur in the unpasteurized product without preservatives due to the presence of microorganisms. In AlOx-coated PET + MDPE (aluminum oxide coating on polyethylene terephthalate + medium-density polyethylene) pouches, color changes were small or negligibl...
The contents of total phenolic compounds, flavonoids, and phenolic acids were determined in selec... more The contents of total phenolic compounds, flavonoids, and phenolic acids were determined in selected garlic cultivars grown at four locations. The total phenolic content varied from 3.4 mg gallic acid equivalents (GAE)/g of dry matter (dm) to 10.8 mg GAE/g of dm with a mean value of 6.5 mg GAE/g of dm. The myricetin, quercetin, kaempferol, and apigenin flavonoids were not detected in any of the samples. Caffeic acid and ferulic acid were the major phenolic acids found with mean values of 2.9 mg/kg of dm and 2.6 mg/kg of dm, respectively. The mean contents of vanillic, p-hydroxybenzoic, and p-coumaric acids were comparable (0.4-0.8 mg/kg of dm), and the level of sinapic acid was negligible (< 0.1 mg/kg of dm). There was a significant effect of location but an insignificant effect of genotype on contents of caffeic, vanillic, p-hydroxybenzoic, and p-coumaric acids. However, genotype but not location affected the contents of total phenolics and ferulic acid. On average, the white garlic cultivars and Chinese garlic cultivars contained higher contents of total phenolics and ferulic acid than the purple garlic cultivars. However, the differences in the total phenolic content between the purple and white garlic cultivars were not significant.
ABSTRACT Nitrate-ammonium (N-A) and ammonium-nitrate (A-N) transition experiments were performed ... more ABSTRACT Nitrate-ammonium (N-A) and ammonium-nitrate (A-N) transition experiments were performed with tobacco (Nicotiana tabacum, cv Gatersleben) plants to study whether the increased expression of ammonium assimilation-related genes found under short-term boron (B) deficiency is maintained when the nitrogen source changes. Asparagine synthetase (AS), glutamate dehydrogenase (GDH) and glutamine synthetase (GS) gene overexpressions in roots under B deprivation were detected in both nitrogen transitions, although GS and, especially, AS up-regulations were observed earlier in the ammonium-nitrate transition. Transcript levels were inversely correlated with hexose contents after 24 h of B deprivation. Our results suggest that tobacco roots respond to short-term B deficiency by increasing the expression of AS, GDH and GS genes irrespectively of the nitrogen source. A hypothetical model to explain these results is proposed and discussed. Thus, the combined action of these enzymes would avoid the accumulation of ammonia and help maintain the activity of the tricarboxylic acid cycle when tobacco roots are affected by B deficiency, the plant organ that first senses this stress. Therefore, under B deficiency, they would act as an ammonium detoxifying mechanism, being a complement to the glutamine synthetase/glutamate synthase (GS/GOGAT) pathway. We propose that the protective role of these enzymes could be extended to changing nitrogen-supply conditions.
To date, one asparagine synthetase (AS) mRNA has been identified in Nicotiana tabacum. Our result... more To date, one asparagine synthetase (AS) mRNA has been identified in Nicotiana tabacum. Our results point out that this gene encodes an actual AS protein. This proposal is supported by the following facts. (i) Blast analysis indicates that tobacco AS gene shows increased percent identity with several AS genes of different plant species. (ii) Leaf and root AS mRNA levels were inversely correlated with soluble carbohydrate concentrations, both in the presence of light and in darkness, and the addition of exogenous sucrose repressed the root AS gene expression. (iii) In light, a positive correlation between AS transcript levels and ammonium content was observed in both leaves and roots. (iv) A direct correlation between leaf AS gene expression and asparagine (Asn) concentration has been found. Furthermore, quantitative real-time PCR analyses showed that this gene expression was increased under boron (B) deficiency in roots, but not in leaves. Interestingly, soluble B concentration in roots of plants subjected to B deficiency was significantly lower than that of control plants. However, in leaves, there was no significant difference in soluble B content between both B treatments. We discuss the possible role of soluble B deficiency in the regulation of AS gene expression in tobacco roots.
The content of organosulfur compounds was determined in selected garlic cultivars grown at four l... more The content of organosulfur compounds was determined in selected garlic cultivars grown at four locations in Andalusia, Spain. The organosulfur compounds studied were three γ-glutamyl peptides, namely, γ-L-glutamyl-S-(2-propenyl)-Lcysteine (GSAC), γ-L-glutamyl-S-(trans-1-propenyl)-L-cysteine (GSPC), and γ-L-glutamyl-S-methyl-L-cysteine (GSMC), and four cysteine sulfoxides (alliin, isoalliin, methiin, and cycloalliin). There was a significant effect of the location, cultivar, and garlic ecotype on individual organosulfur compound contents. Purple-type cultivars showed on average the highest contents of GSMC, GSAC, alliin, and methiin but the lowest isoalliin content. The impact of genotype was relatively high for GSAC, whereas this factor hardly contributed to the total variability in alliin and isoalliin content. Planting date had a significant effect on the content of alliin and isoalliin. Discriminant analysis evidenced the ability of organosulfur compounds to distinguish among garlic bulbs from different locations or ecotypes with 81 or 86% accuracy, respectively.
The influence of processing, with and without fermentation, on the contents of organosulfur compo... more The influence of processing, with and without fermentation, on the contents of organosulfur compounds, namely, γ-glutamyl peptides, S-alk(en)yl-L-cysteine sulfoxides (ACSOs), and S-allyl-L-cysteine (SAC), in pickled blanched garlic was evaluated. For each processing type, the effect of the preservation method and storage time was also analyzed. Blanching in hot water (90 °C for 5 min) hardly affected the individual organosulfur compound content. The fermentation and packing steps negatively affected the levels of all compounds except for SAC. The content of this compound increased during storage at room temperature whereas γ-glutamyl peptides and ACSOs were degraded to various extents. The pasteurization treatment itself had no significant effect on the concentrations of organosulfur compounds. Use of the corresponding fermentation brine in the case of the fermented product in conjunction with refrigerated storage was found to be the best method to preserve the levels of organosulfur compounds in pickled garlic stored for up to one year.
International Journal of Food Science & Technology, 2012
ABSTRACT The evolution of two additives, potassium sorbate and ascorbic acid, during long-term st... more ABSTRACT The evolution of two additives, potassium sorbate and ascorbic acid, during long-term storage of pickled vegetables, as well as the impact of these additives on product colour, was investigated. For this investigation, cucumbers and caperberries packed in both glass bottles and plastic pouches were used. In general, the added sorbate level remained unchanged during long-term storage irrespective of the packaging material. However, the ascorbic acid gradually disappeared at a significantly higher rate in plastic than in glass containers, and its level was higher in caperberries than in cucumbers. In the latter, the presence of sorbate caused a higher degradation rate of ascorbic acid compared to the absence of sorbate. Ascorbic acid had a protective effect against surface colour degradation in cucumbers packed in plastic pouches, whereas sorbate enhanced such degradation. However, in both pickled vegetables, ascorbic acid degradation had a significant impact on brine browning, particularly in plastic pouches.
The aim of this research was to ascertain the lactic acid bacteria responsible for the degradatio... more The aim of this research was to ascertain the lactic acid bacteria responsible for the degradation of ascorbic acid and/or potassium sorbate, isolated from packed green olives where these additives had diminished. A total of 14 isolates were recovered from samples of different green olive containers. According to partial sequencing of the 16S rRNA coding gene, Lactobacillus parafarraginis, Lactobacillus rapi, Lactobacillus pentosus, Lactobacillus paracollinoides, and Pediococcus ethanolidurans were identified. With the exception of L. pentosus and L. paracollinoides, the other species had not been mentioned in table olives before this study. Only three of the 14 isolates metabolized ascorbic acid in MRS broth, and the products from ascorbic acid in modified MRS broth without carbon sources were acetic and lactic acids. Except for the two L. rapi and the two P. ethanolidurans strains, the remaining 10 isolates depleted potassium sorbate added into MRS broth to some extent. The product generated by three of these strains was confirmed to be trans-4-hexenoic acid. The degradation of ascorbate or sorbate by lactic acid bacteria should be taken into account when these additives are used in food products where this group of bacteria may be present.
The effects of different packing conditions and storage times on the stability of monosodium glut... more The effects of different packing conditions and storage times on the stability of monosodium glutamate (MSG) added to two different fermented vegetables (Spanish-type green table olives and pickled cucumbers) were studied. Factors such as packaging material (glass bottle versus plastic pouch), heat treatment (pasteurisation versus non-pasteurisation), and the presence or not of a preservative compound (potassium sorbate) were considered. The MSG content of pickled cucumbers was stable for up to 1 year of storage in all packing conditions studied. The MSG content also remained stable in pasteurised green table olives. On the contrary, MSG was extensively degraded (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;75% degradation) after 54 weeks of storage in unpasteurised green olives with a higher degradation rate in glass bottles compared with plastic pouches. In the presence of potassium sorbate, MSG was also considerably degraded in olives packed in plastic pouches…
The main purpose of this study was to evaluate the inhibitory effect on acrylamide (AA) formation... more The main purpose of this study was to evaluate the inhibitory effect on acrylamide (AA) formation and the impact on sensory characteristics in ripe olives of three selected amino acids (sarcosine, proline and glycine), which previously showed high AA inhibition rates in an olive model system. Each amino acid was separately added to packing solutions to give 100 or 200 mM at equilibrium, prior to a sterilisation treatment at 121°C. The results showed that sarcosine at 100 mM may be a good candidate for reducing the AA content in ripe olives with a limited effect on sensory characteristics. Studies with a model solution of AA and sarcosine heated at 121°C for 30 min suggested that the main mechanism for the inhibitory effect of sarcosine on AA formation was the Michael reaction.
Plant cell wall is a dynamic structure that is of fundamental importance in plant growth and deve... more Plant cell wall is a dynamic structure that is of fundamental importance in plant growth and development, as well as in the response to environmental stresses. There is direct evidence for a role of boron (B) in cross-linking of cell wall rhamnogalacturonan II (RG-II) and pectin assembly, which shows that B is essential for cell wall structure and function. The aim of the present work was to investigate the effects of B deficiency on the expression of cell wall-related genes in Arabidopsis roots. For this purpose, plants were grown hydroponically in a nutrient solution supplemented with 2 M B and then transferred to a boron-free medium for 6 and 24 h. A transcriptome analysis was carried out and several cell wall-related genes were identified, whose expressions were down-regulated by B deficiency. These genes belong to arabinogalactan protein, xyloglucan endotransglycosylase/hydrolase, polygalacturonase, pectate lyase, pectin methylesterase, expansin, and cellulose synthase-like gene families. These results suggest that in addition to the essential role that B plays in the structural organization of the cell wall, it could directly or indirectly have an impact on the expression levels of genes related to the cell wall.
Chemical and sensorial changes related to the use of benzoates and ascorbic acid as additives in ... more Chemical and sensorial changes related to the use of benzoates and ascorbic acid as additives in packed fermented vegetables were investigated. For this, three selected vegetables (green olives, cucumbers, and caperberries) stored under different conditions (glass or plastic containers, ambient or refrigerated storage) were used. In all cases, benzoic acid remained unchanged (glass bottle) or decreased slightly (plastic pouch) at prolonged storage. Ascorbic acid was partially or totally degraded during storage, the degradation rate depending on the storage conditions and the vegetable matrix. Benzene levels higher than 10 μg/L were found in cucumbers and caperberries containing both additives, but only when packed in plastic pouches and after prolonged storage at room temperature. In these conditions, an appreciable browning of brine, related to AA degradation, was also found. The use of benzoate alone had a significant influence on vegetable color, but flavor was not significantly affected at the benzoate levels tested. On the basis of the present study, benzoates should be removed from fermented vegetable formulations containing ascorbic acid to eliminate possible benzene formation during long-term storage.
A ripe olive model system was used to evaluate the potential inhibiting effects on acrylamide for... more A ripe olive model system was used to evaluate the potential inhibiting effects on acrylamide formation from a set of amino acids and water-soluble vitamins. The system was based on ripe olive juice heated at 121 ºC for 30 min in a stainless steel tubular reactor. The most potent acrylamide inhibitors were proline and sarcosine, both with inhibition rates of ~75% at a 100 mM level. In addition, glycine, ornithine, taurine, and γ-amino butyric acid were effective (50-65% inhibition) while the rest of the compounds demonstrated weak or non-significant effects. Acrylamide contents in the model system were found to be highly correlated with the corresponding contents in the real product. The kinetic pattern for the formation of acrylamide in the absence and presence of two selected amino acids, added separately or together, was well fitted using a simple logistic function.
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