首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Lactic acid fermentation of cereal flours resulted in a 100 (rye), 95-100 (wheat), and 39-47% (oat) reduction in phytate content within 24 h. The extent of phytate degradation was shown to be independent from the lactic acid bacteria strain used for fermentation. However, phytate degradation during cereal dough fermentation was positively correlated with endogenous plant phytase activity (rye, 6750 mU g(-1); wheat, 2930 mU g(-1); and oat, 23 mU g(-1)), and heat inactivation of the endogenous cereal phytases prior to lactic acid fermentation resulted in a complete loss of phytate degradation. Phytate degradation was restored after addition of a purified phytase to the liquid dough. Incubation of the cereal flours in buffered solutions resulted in a pH-dependent phytate degradation. The optimum of phytate degradation was shown to be around pH 5.5. Studies on phytase production of 50 lactic acid bacteria strains, previously isolated from sourdoughs, did not result in a significant production of intra- as well as extracellular phytase activity. Therefore, lactic acid bacteria do not participate directly in phytate degradation but provide favorable conditions for the endogenous cereal phytase activity by lowering the pH value.  相似文献   

2.
This work was designed to compare the effects of different leavens (yeast, sourdough, and a mixture of both) on phytic acid (PA) degradation and to assess the repercussions of PA breakdown on phosphorus and magnesium solubility during bread-making. Sourdough fermentation was more efficient than yeast fermentation in reducing the phytate content in whole wheat bread (-62 and -38%, respectively). Furthermore, lactic acid bacteria present in sourdough enhanced acidification, leading to increased magnesium and phosphorus solubility. To intensify phytate breakdown, bran was incubated with microorganisms (yeast or sourdough) before bread-making. Using this new method, the percentage of phytate breakdown was near 90%, whereas 40% of phytate remained in traditional French bread. In conclusion, a prolonged fermentation with sourdough still leads to improved Mg and P solubility by decreasing phytate content and through acidification.  相似文献   

3.
The possible use of phytase as a breadmaking improver has been tested in whole wheat breads by adding different amounts of fungal phytase. The effect of phytase addition on the fermentation stage and the final bread quality was analyzed. The phytase addition shortened the fermentation period, without affecting the bread dough pH. Regarding the whole wheat bread, a considerable increase of the specific bread volume, an improvement of the crumb texture, and the width/height ratio of the bread slice were obtained. An in vitro assay revealed that the improving effect of phytase on breadmaking might be associated with the activation of alpha-amylase, due to the release of calcium ions from calcium-phytate complexes promoted by phytase activity. As a conclusion, phytase offers excellent possibilities as a breadmaking improver, with two main advantages: first, the nutritional improvement produced by decreasing phytate content, and second, all the benefits produced by alpha-amylase addition can be obtained by adding phytase, which promotes the activation of endogenous alpha-amylase.  相似文献   

4.
Whole sorghum flour was fermented (a five‐day natural lactic acid fermentation) and dried under forced draught at 60°C, and evaluated for its effect on sorghum and wheat composite bread quality. In comparison with unfermented sorghum flour, fermentation decreased the flour pH from 6.2 to 3.4, decreased total starch and water‐soluble proteins, and increased enzyme‐susceptible starch, total protein, and the in vitro protein digestibility (IVPD). Fermentation and drying did not decrease the pasting temperature of sorghum flour, but slightly increased its peak and final viscosity. In comparison with composite bread dough containing unfermented sorghum flour, fermented and dried sorghum flour decreased the pH of the dough from 5.8 to 4.9, increased bread volume by ≈4%, improved crumb structure, and slightly decreased crumb firmness. IVPD of the composite bread was also improved. Mixing wet fermented sorghum flour directly with wheat flour (sourdough‐type process) further increased loaf volume and weight and reduced crumb firmness, and simplified the breadmaking process. It appears that the low pH of fermented sorghum flour inactivated amylases and increased the viscosity of sorghum flour, thus improving the gas‐holding capacity of sorghum and wheat composite dough. Fermentation of sorghum flour, particularly in a sourdough breadmaking process, appears to have considerable potential for increasing sorghum utilization in bread.  相似文献   

5.
This article aimed at investigating the synthesis of angiotensin I-converting enzyme (ACE)-inhibitory peptides and gamma-aminobutyric acid (GABA) during sourdough fermentation of white wheat, wholemeal wheat, and rye flours. Sourdough lactic acid bacteria, selected previously for proteinase and peptidase activities toward wheat proteins or for the capacity of synthesizing GABA, were used. The highest ACE-inhibitory activity was found by fermenting flour under semiliquid conditions (dough yield 330) and, especially, by using wholemeal wheat flour. Fourteen peptides, not previously reported as ACE-inhibitory, were identified from the water/salt-soluble extract of wholemeal wheat sourdough (IC 50 0.19-0.54 mg/mL). The major part of the identified peptides contained the well-known antihypertensive epitope VAP. The synthesis of GABA increased when the dough yield was decreased to 160. The highest synthesis of GABA (258.71 mg/kg) was found in wholemeal wheat sourdough.  相似文献   

6.
《Cereal Chemistry》2017,94(6):922-927
The degradation of inositol hexakisphosphate (IP6) was evaluated in whole meal wheat dough fermented with baker's yeast without phytase activity, different strains of Saccharomyces cerevisiae (L1.12 or L6.06), or Pichia kudriavzevii with extracellular phytase activity to see if the degradation of IP6 in whole meal dough and the corresponding bread could be increased by fermentation with phytase‐active yeasts. The IP6 degradation was measured after the dough was mixed for 19 min, after the completion of fermentation, and in bread after baking. Around 60–70% of the initial value of IP6 in the flour (10.02 mg/g) was reduced in the dough already after mixing, and additionally 10–20% was reduced after fermentation. The highest degradation of IP6 was seen in dough fermented with the phytase‐active yeast strains S. cerevisiae L1.12 and P. kudriavzevii L3.04. Activity of wheat phytase in whole meal wheat dough seems to be the primary source of phytate degradation, and the degradation is considerably higher in this study with a mixing time of 19 min compared with earlier studies. The additional degradation of IP6 by phytase‐active yeasts was not related to their extracellular phytase activities, suggesting that phytases from the yeasts are inhibited differently. Therefore, the highest degradation of IP6 and expected highest mineral bioavailability in whole meal wheat bread can be achieved by use of a phytase‐active yeast strain with less inhibition. The strain S. cerevisiae L1.12 is suitable for this because it was the most effective yeast strain in reducing the amount of IP6 in dough during a short fermentation time.  相似文献   

7.
This study was to examine the time course of sample-specific linearity of intrinsic phytase hydrolysis in major cereal grains and in ileal digesta and fecal samples and to determine the time course of the microbial phytase-catalyzed hydrolysis of various sources of phytate for estimating phytate phosphorus (P) content. The intrinsic phytase activity in barley, corn, oat, and wheat samples was measured over multiple time points from 0 to 120 min at 1.5 mmol.L(-1) of sodium phytate at pH 5.5 and 37 degrees C. Time courses of hydrolysis of purified phytate and phytate associated with the cereal grain samples and the pig digesta and fecal samples were examined with the Natuphos microbial phytase over multiple time points from 0 to 48 h of incubation. The intrinsic phytase hydrolysis was linear (P < 0.05) for up to 120 min for the barley, corn, and wheat samples, whereas in the oat sample the hydrolysis was linear (P < 0.05) for only up to 30 min of incubation. The intrinsic phytase activities (phytase unit: mumol.kg(-1) of dry matter.min(-1)) for the barley, corn, and wheat samples were estimated to be 693, 86, and 1189 by linear regression analysis. Intrinsic phytase activity (412 phytase units) for the oat sample based on a 30-min incubation was considerably higher than the value (103 phytase units) determined from the 120-min incubation for the same oat sample. There were quadratic with plateau relationships (P < 0.05) between the hydrolytic release of inorganic P from various sources of phytate and the incubation time. The minimal incubation times required for the complete hydrolysis of phytate were estimated to be 4, 3, and 11 h for the purified phytate, the cereal grain samples, and the pig digesta and feces, respectively. It was concluded that multiple time point experiments need to be conducted to determine valid intrinsic phytase activity and phytate P content in samples through intrinsic and microbial phytase hydrolysis incubations.  相似文献   

8.
The exopolysaccharide (EPS) produced from sucrose by Lactobacillus sanfranciscensis LTH2590 is predominantly composed of fructose. EPS production during sourdough fermentation has the potential to affect rheological properties of the dough as well as the volume, texture, and keepability of bread. Its in situ production by L. sanfranciscensis LTH2590 was demonstrated during sourdough fermentation after the hydrolysis of water soluble polysaccharides. In wheat and rye doughs with sucrose addition the concentration of fructose in the hydrolysate of polysaccharides was significantly higher than that in the hydrolysate of control doughs or doughs without sucrose addition. EPS production by L. sanfranciscensis in wheat doughs was confirmed by the determination of delta (13)C values of water soluble polysaccharides after the addition of naturally labeled sucrose, originating from C(3)- and C(4)-plants. In rye doughs, evidence for EPS production with the isotope technique could be demonstrated only by the determination of delta (13)C values of fructose from water soluble polysaccharides. In addition to EPS formation from sucrose, sucrose hydrolysis by L. sanfranciscensis in wheat and rye sourdoughs resulted in an increase of mannitol and acetate concentrations and in accumulation of glucose. It was furthermore observed that flour arabinoxylans were solublized during the fermentation.  相似文献   

9.
Flours obtained by a specific polishing process were used to prepare sourdough and bread. Three fractions designated C‐1 (100–90%), C‐5 (60–50%), and C‐8 (30–0%) were studied. The pH, total titratable acidity levels, and buffering capacity of sourdoughs made from polished flours were significantly different from those of the control sourdough with No. 1 Canada Western Red Spring (CW), and they provided sourdough breads with better qualities than that of CW. The growth of lactic acid bacteria and yeast in polished flour sourdoughs were significantly accelerated during fermentation over that in CW sourdough. Higher maturation of polished flour sourdoughs softened the hardness of mixed dough. The intricate network of honeycomb structure gluten and uneven surface of starch granules were distinctly observed in SEM images. Substitutions of C‐5 or C‐8 sourdoughs for CW significantly increased the loaf volume and softened breadcrumbs more than CW sourdough. Flour qualities of polished flours such as suitable acidity and good buffering capacity caused by the bran fraction were effective for better growth and longer life of yeast in the dough during fermentation. Therefore, application of polished flours in sourdough bread would improve rheological properties of dough and bread as compared with CW sourdough.  相似文献   

10.
Bakeries use sourdoughs to improve bread properties such as flavor and shelf life. The degradation of gluten proteins during fermentation may, however, crucially alter the gluten network formation. We observed changes that occurred in the HMW glutenins during wheat sourdough fermentations. As fermentation starters, we used either rye sourdough or pure cultures of lactobacilli and yeast. In addition, we incubated wheat flour (WF) in the presence of antibiotics under different pH conditions. The proteolytic activities of cereal and sourdough‐derived proteinases were studied with edestin and casein. During sourdough fermentations, most of the highly polymerized HMW glutenins degraded. A new area of alcohol‐soluble proteins (≈30.000 MW) appeared as a result of the proteolytic breakdown of gluten proteins. Very similar changes were observable as WF was incubated in the presence of antibiotics at pH 3.7. Cereal and sourdough‐derived proteinases hydrolyzed edestin at pH 3.5 but showed no activity at pH 5.5. An aspartic proteinase inhibitor (pepstatin A) arrested 88–100% of the activities of sourdough enzymes. According to these results, the most active proteinases in wheat sourdoughs were the cereal aspartic proteinases. Acidic conditions present in sourdoughs create an ideal environment for cereal aspartic proteinases to be active against gluten proteins.  相似文献   

11.
Five copper (Cu) sources were studied at pH 2.5, 5.5, and 6.5 to determine how Cu affects phytate phosphorus (PP) hydrolysis by phytase at concentrations up to 500 mg/kg diet (60 min, 40-41 degrees C). Subsequently, Cu solubility with and without sodium phytate was measured. Adding Cu inhibited PP hydrolysis at pH 5.5 and pH 6.5 (P < 0.05). This inhibition was greater with higher concentrations of Cu. Tri-basic copper chloride and copper lysinate inhibited PP hydrolysis much less than copper sulfate pentahydrate, copper chloride, and copper citrate (P < 0.05). A strong negative relationship was observed between PP hydrolysis and soluble Cu at pH 5.5 (r = -0.76, P < 0.0001) and 6.5 (r = -0.54, P < 0.0001). In conclusion, pH, Cu concentration, and source influenced PP hydrolysis by phytase in vitro and were related to the amount of soluble Cu and the formation of insoluble copper-phytin complexes.  相似文献   

12.
The influence of baking conditions and dough supplements on the amounts of the antioxidant and Phase II-Enzyme modulating, protein-bound 2,4-dihydroxy-2,5-dimethyl-1-(5-acetamino-5-methoxycarbonyl-pentyl)-3-oxo-2H-pyrrol (pronyl-L-lysine) in bakery products was investigated in quantitative studies. These studies revealed high amounts of the antioxidant in bread crust, only low amounts in the crumb, and the absence of this compound in untreated flour. The amounts of pronyl-L-lysine were found to be strongly influenced by the intensity of the thermal treatment. For example, increasing the baking time from 70 to 210 min or increasing the baking temperature from 220 to 260 degrees C led to a 5- or 3-fold increase in the concentrations of this antioxidant in the crust, respectively. In addition, modifications in the recipe showed to have a major impact on pronyl-L-lysine formation. For example, substituting 5% of the flour with the lysine-rich protein casein or with 10% of glucose increased the amounts of the antioxidant by more than 200%. Quantitative analyses of commercial bread samples collected from German bakeries revealed the highest amount of 43 mg/kg for a full grain bread, followed by a rye/wheat bread, both of which have been sourdough fermented. A mixed-grain bread as well as pale wheat bread, both prepared without sourdough fermentation, contained significantly lower amounts of pronyl-L-lysine, and German pretzels, which are treated with a dilute sodium hydroxide solution prior to baking, contained only trace amounts of pronyl-L-lysine (e.g., less than 5 mg/kg were detectable in pretzels). Systematic studies revealed that the decrease of the pH value induced by microbial acid formation during sourdough fermentation is the clue for producing high amounts of pronyl-L-lysine in baking products. These data clearly demonstrate for the first time that the amounts of the antioxidant and chemopreventive compound pronyl-L-lysine in bakery products is strongly dependent on the manufacturing conditions as well as the recipe.  相似文献   

13.
The effect of various sourdoughs and additives on bread firmness and staling was studied. Compared to the bread produced with Saccharomyces cerevisiae 141, the chemical acidification of dough fermented by S. cerevisiae 141 or the use of sourdoughs increased the volume of the breads. Only sourdough fermentation was effective in delaying starch retrogradation. The effect depended on the level of acidification and on the lactic acid bacteria strain. The effect of sourdough made of S. cerevisiae 141-Lactobacillus sanfranciscensis 57-Lactobacillus plantarum 13 was improved when fungal alpha-amylase or amylolytic strains such as L. amylovorus CNBL1008 or engineered L. sanfranciscensis CB1 Amy were added. When pentosans or pentosans, endoxylanase enzyme, and L. hilgardii S32 were added to the same sourdough, a greater delay of the bread firmness and staling was found. When pentosans were in part hydrolyzed by the endoxylanase enzyme, the bread also had the highest titratable acidity, due to the fermentation of pentoses by L. hilgardii S32. The addition of the bacterial protease to the sourdough increased the bread firmness and staling.  相似文献   

14.
Variations in physical and compositional bran characteristics among different sources and classes of wheat and their association with bread‐baking quality of whole grain wheat flour (WWF) were investigated with bran obtained from Quadrumat milling of 12 U.S. wheat varieties and Bühler milling of six Korean wheat varieties. Bran was characterized for composition including protein, fat, ash, dietary fiber, phenolics, and phytate. U.S. soft and club wheat brans were lower in insoluble dietary fiber (IDF) and phytate content (40.7–44.7% and 10.3–17.1 mg of phytate/g of bran, respectively) compared with U.S. hard wheat bran (46.0–51.3% and 16.5–22.2 mg of phytate/g of bran, respectively). Bran of various wheat varieties was blended with a hard red spring wheat flour at a ratio of 1:4 to prepare WWFs for determination of dough properties and bread‐baking quality. WWFs with U.S. hard wheat bran generally exhibited higher dough water absorption and longer dough mixing time, and they produced smaller loaf volume of bread than WWFs of U.S. soft and club wheat bran. WWFs of two U.S. hard wheat varieties (ID3735 and Scarlet) produced much smaller loaves of bread (<573 mL) than those of other U.S. hard wheat varieties (>625 mL). IDF content, phytate content, and water retention capacity of bran exhibited significant relationships with loaf volume of WWF bread, whereas no relationship was observed between protein content of bran and loaf volume of bread. It appears that U.S. soft and club wheat bran, probably owing to relatively low IDF and phytate contents, has smaller negative effects on mixing properties of WWF dough and loaf volume of bread than U.S. hard wheat bran.  相似文献   

15.
Alkylresorcinol (AR) content was determined in multiple-stage whole wheat and whole rye flour sours, as well as in whole wheat and whole rye flour doughs and breads. AR content decreased considerably during fermentation and baking. AR content was reduced by 20 and 46%, respectively, at the end of sourdough starter fermentation of whole wheat and whole rye flour sours. AR content, which was 512 and 210 μg/g in whole rye and whole wheat flour doughs, respectively, was 30 and 0 μg/g, respectively, after baking of breads. Synthetic AR added at different levels to doughs was also greatly reduced during fermentation and baking.  相似文献   

16.
The aim of this work was to study the influence of process parameters and the starter culture on the characteristics of wheat sourdough by using response surface methodology. Influence of fermentation temperature (16–32°C), ash content of flour (0.6–1.8%), and fermentation time (6–20 hr) were considered as independent factors and their effects were studied in sourdough fermented with Lactobacillus plantarum, L. brevis, Saccharomyces cerevisiae, or with a combination of yeast and lactic acid bacteria. Formation of acidity, free amino acids, and volatile compounds were considered the main responses. A possibility to enhance formation of potential flavor compounds and precursors without excessive acidity formation in wheat sourdoughs was established. The total amount of amino acids increased by 25–50%, depending on the strain and fermentation conditions. The total amount of volatile compounds increased seven‐ to 100‐fold, depending on the strain and fermentation conditions. Sourdough started with S. cerevisiae was an effective way to optimize the amount of volatile compounds without excessive acidity formation in appropriate processing conditions. Ash content of flour and fermentation time were the most significant factors to modify metabolic activity of wheat sourdoughs. Frequent interactions between the studied factors were observed on the formation of acidity, amino acids, and volatile compounds with most of the strains studied. Possibility to improve current industrial fermentation processes and control flavor attributes of breads by using optimized sourdough was established.  相似文献   

17.
The amino acid release was determined in wheat doughs supplied with salt, acid, dithiothreitol, or starter cultures to evaluate the relevance of the amino acid concentration on bread flavor. Wheat flour proteinases almost linearly released amino acids and the highest activity of wheat flour proteinases was found in acidified and reduced doughs. The effects of starter cultures on amino acid concentrations depended on their composition. Yeasts exhibited a high demand for amino acids, however, the total amino acid concentrations were not markedly affected by lactic acid bacteria. The individual amino acid contents were determined by the pH during fermentation and microbial metabolism. The formation of proline was favored by values higher than pH 5.5, whereas release of phenylalanine, leucine and cysteine mainly occurred at lower pH. Ornithine was found only in doughs fermented with Lactobacillus pontis. To determine effects of the amino acid concentration on bread aroma, fermented doughs were evaluated in baking experiments. An increased intensity of bread flavor was obtained by preferments prepared with lactic acid bacteria. The roasty note of wheat bread crust could be markedly enhanced by L. pontis. This results support the assumption that flavor of wheat bread is enhanced by increasing the concentration of free amino acids and especially ornithine in dough.  相似文献   

18.
Investigations were made to test the effect of two different sourdough starter culture types on wheat dough and bread quality. Two single‐strain starter cultures consisting of well‐defined strains of lactic acid bacteria (Lactobacillus plantarum, L. brevis) and a traditional mixed‐strain sourdough culture (containing L. crispatus, L. pontis, and Saccharomyces cerevisiae) were evaluated for their effects on the rheological characteristics of wheat dough using both fundamental rheological and standard baking tests. Two other doughs were also evaluated, one which was chemically acidified to a comparable pH value by the addition of lactic acid, and a control which was not acidified. Dynamic oscillation tests were performed using a controlled stress rheometer. The phase angle and the absolute value of the complex dynamic modulus were measured for all doughs at frequencies of 0.1–10 Hz. The addition of sourdough prepared using single‐strain or mixed‐strain cultures significantly increased the phase angle and reduced the complex modulus of the doughs at all frequencies (P < 0.05). Significant differences were found between the dough which was chemically acidified and those doughs which were biologically acidified. The addition of sourdough effected an increase in loaf specific volume relative to both the chemically acidified and the nonacidified doughs.  相似文献   

19.
Hydration of oat bran including fermentation by rye sourdough was studied. Three types of oat bran suspensions were prepared (a control, one with whole meal rye flour added, and one with rye starter added). The suspensions were incubated for 1, 2, 3 and 4 hr. β‐Glucan content and solubilities of protein and β‐glucan were analyzed. Viscosity of the supernatants of oat bran suspensions was determined. Neither the rye sourdough nor the rye flour alone had a significant effect on the total β‐glucan content of oat bran suspensions. However, the addition of rye, either as whole meal rye flour or as sourdough starter, markedly increased the solubility of β‐glucan and proteins and simultaneously decreased the viscosity of the water‐soluble fraction of oat bran suspension. This suggests that a hydrolysis of β‐glucan had occurred that could change the rheological properties of oat bran in baking and the physiological potential of oat bran in nutrition.  相似文献   

20.
A method for the quantitation of dityrosine in wheat flour and dough by high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) using an isotope dilution assay with the internal standard 3,3'-(13)C(2)-dityrosine in the single-reaction monitoring mode was developed. The method consisted of the release of protein-bound dityrosine by hydrolysis in 4 mol/L hydrochloric acid/8.9 mol/L propionic acid for 24 h at 110 degrees C after addition of the internal standard, cleanup by C(18) solid-phase extraction, and HPLC-MS/MS. The limit of detection of dityrosine was 80 ng/g of sample (0.22 nmol/g), and the limit of quantitation was 270 ng/g of sample (0.75 nmol/g). The method was sensitive enough to analyze wheat flour and dough and to study the effect of flour improvers on the dityrosine content. Furthermore, the effect of the mixing time was studied. The dityrosine concentration in the flour was 0.66 nmol/g. After we mixed a dough to peak consistency, the dityrosine concentration doubled and remained constant on further mixing. Overdoses of hydrogen peroxide and hexose oxidase (HOX, E.C. 1.1.3.5) resulted in a strongly increased dityrosine content, whereas no increase of the dityrosine concentration was found after the addition of ascorbic acid and potassium bromate. Calculation of the percentage of dimeric tyrosine showed that less than 0.1% of the tyrosine residues of wheat protein were cross-linked. Therefore, dityrosine residues seem to play only a very minor role in the structure of wheat gluten.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号