Synergistic effect of chemical preservatives with ethanol on the microbial shelf life of bread by factorial design

The shelf life, particularly the mould-free shelf life (MFSL) of bread, was evaluated either by adding a conventional chemical preservative or by spraying the surface of bread, in which a chemical preservative was added. As bread making is a complex process and bread is a multicomponent system, the investigation was based on statistical design experiments. Using first-order factorial designs, reliable models were constructed, revealing the effects of some common ingredients of bread (such as salt, sugar, glycerol, potassium sorbate, calcium propionate) and their interactions on the MFSL (optimisation parameter) with and without ethanol surface spraying. The effectiveness of preservation was ranked as potassium sorbate + ethanol > calcium propionate + ethanol > potassium sorbate > calcium propionate. Ethanol addition led to MFSL prolongation of 43.5% and 38.5% compared with MFSL of potassium sorbate and calcium propionate, respectively, when all the factors were fixed to their basic levels.     

响应面法优化汉堡面包的种面发酵工艺

为优化选出抑青霉菌效果最好的汉堡面包种面发酵基质及工艺,本文通过单因素实验结合Box-behnken响应面试验进行优化,以种面对青霉菌的抑菌率作为评价指标,选出最优的发酵剂和糖种类等发酵工艺,并对最优条件下制作的汉堡面包的理化性质、微生物数量、感官、质构以及保质期等指标进行测定。结果表明,最优发酵工艺为种面中添加乳酸菌发酵剂B和蔗糖,蔗糖浓度选择4.1%,发酵时间及温度分别选择20 h和30℃。此条件下发酵后的种面对青霉菌的抑菌率为32.67%,与理论预测值相比,其相对误差约为4.41%。最优发酵工艺下制作的汉堡面包抑菌效果较好且具备良好的理化特性,其中酸价2.68 mg/g、比容3.07 mL/g、过氧化值0.15 g/100 g、硬度1158.65 g、弹性0.88 mm。冷却包装2 h后菌落总数及霉菌均未检出,在20℃室温下保质期长至15 d。     

Multiparametric investigation of mould‐free shelf life of bread via factorial design

The investigation of a complex process, such as the bread making process, can be greatly favored by the approach of statistical design of experiments. Using simple first order factorial designs, reliable models were constructed investigating the effects of salt, sugar, sorbic acid, calcium propionate, vegetable fibers, fat and emulsifier on the shelf life of bread (optimization parameter). These effects were in general linear. An exception was observed in the case of use of calcium propionate where an interaction between salt and sugar was determined. The effects of all significant factors on optimization parameter were reasonable. Sorbic acid and calcium propionate proved to be more effective preservatives than salt and sugar by an order of magnitude. Antifungal efficiency of sorbic acid was found to be about three times that of calcium propionate. Prolongation of shelf life reached 117% for sorbic acid and 63 % for calcium propionate, when salt and sugar were fixed to their basic levels. Vegetable fibers had a detrimental effect on shelf life greatly decreasing it by as much as 65 % of the control samples (without fibers). Addition of fat and emulsifier in the dough showed a slightly negative effect on the mould‐free shelf life of bread.     

Sourdough fermented by Lactobacillus plantarum FST 1.7 improves the quality and shelf life of gluten-free bread

Lactobacillus plantarum FST 1.7 has been recently shown to produce antifungal compounds, which improve the shelf life of wheat bread. In the present study, this strain was investigated for its ability to improve the quality and shelf life of gluten-free bread. Effects of incorporation of sourdough fermented by strain FST 1.7 into a gluten-free bread mixture were compared to those obtained with sourdough fermented by the non-antifungal strain Lactobacillus sanfranciscensis TMW 1.52 as well as to those obtained with chemically or non-acidified batters. Fundamental rheological tests revealed that the addition of sourdough to the gluten-free mix led to an increase in firmness and increase in elasticity overtime (P < 0.05). Bread characteristics such as pH, total titratable acidity, and crumb hardness (5-day storage) were evaluated. Results showed that the biologically acidified gluten-free breads were softer after 5 days than the chemically acidified gluten-free breads (P < 0.001). Antifungal challenge tests employing conidial suspensions of Fusarium culmorum were carried out using the sourdough, non-acidified batter and bread. The rate of mould growth for the fungal species used was retarded by L. plantarum FST 1.7 when compared to the controls. In conclusion, the results of this study indicate that L. plantarum FST 1.7 can be used to produce gluten-free bread with increased quality and shelf life.     

Effect of loaf specific volume on the rate and extent of staling in bread

The quantitative relationships between loaf specific volume and the rate and extent of staling in bread as measured by changes in crumb elastic modulus have been examined. The results show that loaf specific volume is a major factor in determining both the rate and extent of staling, both of which decrease in a linear manner, over the range studied, as loaf volume increases. Only two factors have been found that have a significant influence on these curves, the basic breadmaking process and the storage temperature. The influence of changes in loaf specific volume on staling characteristics is greater in bread prepared by bulk fermentation than in bread prepared by the Chorleywood Bread Process. Bread made by the Chorleywood Bread Process stales less rapidly than bread made by the conventional bulk fermentation process. The effect of loaf specific volume on the rate of staling is more marked as the storage temperature is lowered.     

黑啤酒面包的研制

以面包专用粉为主要原料,添加黑啤酒、白砂糖、酵母、盐、面包改良剂等辅料,采用一次发酵工艺生产黑啤酒面包,通过单因素实验和正交实验确定黑啤酒面包的最佳工艺配方。结果表明,白砂糖投入量对黑啤酒面包品质影响最大,其次是黑啤酒的投入量,酵母的影响最小。黑啤酒面包的最佳工艺参数为:白砂糖量为48g、黑啤酒量为140g、酵母量为6g(以面粉270g计)。      

Investigation of product quality, sensory profile and ultrastructure of breads made from a range of commercial gluten-free flours compared to their wheat counterparts

Bread is a major staple food consumed daily in all parts of the world. A significant part of the human population cannot tolerate gluten, a storage protein found in wheat, rye and barley, and therefore, products made from alternative cereals are required. During this study, the bread-making potential of seven gluten-free flours, wheat and wholemeal wheat flour was compared. Fermentation potential of the different flours was determined, showing that dough development height of gluten-free and wholemeal wheat samples was lower than for wheat and oat flour. Apart from standard bread quality parameters such as loaf-specific volume and physical crumb texture, also water activity and shelf life have been determined. The shelf life of gluten-free breads was reduced compared to wheat bread. Aroma profiles were evaluated by a trained panel. Wheat, oat and wholemeal wheat breads were liked moderately, while the remaining samples had lower liking scores. Crumb grain characteristics were investigated using image analysis, and microstructure was observed by scanning electron microscopy. Overall, only breads produced from oat flour were of similar quality to wheat bread, and the utilization of buckwheat, rice, maize, quinoa, sorghum and teff flours resulted in breads of inferior quality.     

Application of Raisin Extracts as Preservatives in Liquid Bread and Bread Systems

ABSTRACT:  Interest in natural ingredients with multifunctions in food has led to the investigation of the antimicrobial activity of raisins, a traditional baking ingredient. Water and 60% ethanol extracts, and raisin juice concentrate (RJC, a commercial food ingredient) were assessed for their ability to inhibit the growth of ropy-bread-causing Bacillus species. The ability of these additives and raisin paste were tested for antifungal activity in liquid bread model system and bread. In the liquid bread model, concentrations as low as 20 and 36 mg crude extract or RJC per gram media significantly ( P < 0.05) reduced the populations of B. licheniformis and B . subtilis , respectively. A significant reduction in the population of Aspergillus flavus and Penicillium chrysogenum was achieved at 80 and 470 mg crude extract per gram media, respectively. Bread formulas containing 7.5% of a water extract (equivalent to 70 mg extract per gram dough) or RJC (70 mg/g dough) produced bread that had equivalent mold-free shelf life. The mean mold-free shelf life of the bread containing 7.5% water extract was 18.1 ± 3.3 d at room temperature while the negative control was mold free for 9.4 ± 2.4 d. The antifungal efficacy of the extracts in bread was equivalent to 0.24% calcium propionate in 21 d of storage. Doubling the concentration of the extract did not improve the mold-retarding property in bread. The bread containing raisin paste, the percentage of which in dough was equivalent to 15% raisin extract, exhibited a stronger antifungal activity than did the extracts in bread.     

Sourdough Technology—A Traditional Way for Wholesome Foods: A Review

Abstract: In the present era, consumers wish to have a wide range of foods that are nutritious and flavorful and have long shelf life without added preservatives. Sourdough is an important modern fermentation of cereal flours and water based upon an earlier spontaneous process. The sourdough microflora is dominated by lactic acid bacteria and, along with yeast, they play a key role in the fermentation of bread dough. Factors that affect the quality of sourdough are dough yield, temperature, type of starter culture, acidity of the medium, and the substrate. Sourdough is classified into 3 types (Types I, II, and III); the most widely used for commercial production is Type III. The sourdough fermentation has a number of beneficial effects that include prolonged shelf life, accelerated volume gain, delayed staling, improved bread flavor, and good nutritional value. Sourdough also improves sensory characteristics such as loaf volume, evenness of baking, color, aroma, taste, and texture of breads. Sourdough has been reported to contribute to extended shelf life by inhibiting spoilage bacteria and mold growth.     

新型酶制剂对面包品质的改良研究

面包是一种经过发酵的烘焙食品。烤制的新鲜面包松软可口、品味宜人,深受大多数消费者的喜爱。然而,随着贮存时间的延长,面包的上述特征发生变化,即老化发生。如何改善或解决面包老化问题是众多食品行业从业者及研究人员关注的焦点。通过选用不同酶制剂,以面包的比容和有效贮藏期内其硬度的变化比较,获得不同酶制剂对面包品质的影响,最后通过正交试验,确定对面包品质改良有显著作用的复配酶制剂用量、组合及配比。     

Exopolysaccharides from Sourdough Lactic Acid Bacteria

The use of sourdough improves the quality and increases the shelf life of bread. The positive effects are associated with metabolites produced by lactic acid bacteria (LAB) during sourdough fermentation, including organic acids, exopolysaccharides (EPS), and enzymes. EPS formed during sourdough fermentation by glycansucrase activity from sucrose influence the viscoelastic properties of the dough and beneficially affect the texture and shelf life (in particular, starch retrogradation) of bread. Accordingly, EPS have the potential to replace hydrocolloids currently used as bread improvers and meet so the consumer demands for a reduced use of food additives. In this review, the current knowledge about the functional aspects of EPS formation by sourdough LAB especially in baking applications is summarized.     

Keeping qualities of white pan bread upon storage: effect of selected enzymes on bread firmness and elasticity

 Several different types of enzymes and their blends were added to dough with the object of improving the shelf-life of white, lidded-pan bread during storage. Bread firmness and elasticity were determined at 24, 48 and 72 h to determine the influence of the enzymes. Addition of bacterial a-amylase, specially to blends of enzymes also containing lipase and pentosanase, improved white, lidded-pan bread quality by increasing elasticity and lowering firmness of crumb, and enhanced the keeping quality over time by providing a significant 2-day increase in the shelf life.     

Bread Dough and Baker's Yeast: An Uplifting Synergy

Yeast‐mediated dough fermentation is an important phase in the bread making process. The fermentative performance of yeast cells during fermentation is of critical importance for final bread quality, since yeast cells produce CO₂ and other metabolites that have an influence on dough rheology and bread texture, volume, and taste. Different factors affect the fermentative performance of yeast cells during dough fermentation, including dough ingredients, fermentation conditions, the type of yeast strain used and yeast pregrowth conditions. Bread dough is a complex matrix that contains several ingredients that can affect the fermentation rate of yeast cells. Although the individual effects of sugar availability and salt level on the leavening ability of yeast have been studied extensively, a comprehensive overview of the relationship between bread dough constituents, fermentation conditions and yeast functionality is still lacking. Moreover, the dough environment is highly variable as several types of dough like lean, sweet or frozen doughs are currently produced by commercial bread producers. For optimal fermentation rates in different types of dough, the use of appropriate yeast strains with specific phenotypic traits is required. Therefore, many researchers have focused on the improvement of yeast strains for optimal fermentation in different types of dough like lean, sweet or frozen dough. Against this background, this review summarizes the current knowledge on the interaction between bread dough and baker's yeast and how to improve this interaction, thereby providing a useful background for further research concerning the functionality of yeast in bread dough.     

The effect of fermentation temperature, flour type, and starter on the properties of sour wheat bread

The effects of the type of wheat flour (white or dark), fermentation temperature (25°C or 30°C) and origin of starter (bakery A compared with bakery B) on acid production and bread properties were examined in a factorial design. The type of flour was the most important factor; with dark flour (ash content 1.64%) the acetic acid concentration in the bread was almost double that from white flour (ash content 0.86%); lactic acid was 30 to 50% higher. Acid production increased as fermentation temperature increased to 30°C, but was not influenced by the origin of the starter.
Loaf specific volume decreased with acid concentrations, but souring lengthened the mould-free time from 4 days to 5 to 8 days or more as acidity increased. Sour wheat bread had a characteristic taste. Those with higher acidity values were more bitter and pungent.
Rye sour and rye sour bread production technology could also be utilized in white bread making.     

一种含肉桂醛包装纸对面包腐败发霉的抑制作用

为研究含肉桂醛的包装纸对面包腐败发霉的抑制作用。将含有不同含量肉桂醛的石蜡涂层涂于包装纸上,进行体外实验和切片面包包装实验,分别研究活性包装纸抑制黑面包霉(Rhizopus stolonifer)的生长和切片面包的腐败霉变情况,另通过固相微萃取-气相色谱-质谱联用定量分析了不同位置切片面包中的肉桂醛含量。结果表明,将含6%肉桂醛的石蜡涂层用于面包包装纸,在体外一定时间内能完全抑制黑面包霉的生长,而达到抑制黑面包霉生长的肉桂醛最小浓度为4%。切片面包保存24 d后,含6%肉桂醛的活性包装纸中的面包才开始发生霉变,大大延长了面包的保存时间。且随着包装纸涂层中肉桂醛的含量的增大,肉桂醛活性包装纸对黑面包霉的抑制作用增强,两者存在很大的相关性。而不同位置切片面包中的肉桂醛含量及霉变程度没有显著差异,说明肉桂醛可以通过非接触方式发挥抑制霉变作用。本研究中的含肉桂醛包装纸可抑制黑面包霉的生长,可用于抑制面包的腐败发霉,保障面包品质,延长面包货架期。     

发酵麦麸对面包膳食纤维组成及烘焙特性的影响

采用马克斯克鲁维酵母发酵麦麸制得富含天然酶的功能配料,分析麦麸发酵过程中纤维素酶活力变化,比较制作的麦麸面包(B₁)、发酵麦麸面包(B₂)、木聚糖酶麦麸面包(B₃)和复合麦麸面包(B₄)的膳食纤维组成及烘焙特性的差异。结果表明:马克斯克鲁维酵母具有较强的胞外β-葡萄糖苷酶生产能力,其酶活为6.98 U/g;在48 h麦麸发酵过程中,外切葡聚糖酶和β-葡萄糖苷酶的酶活不断提高,其酶活分别增加至6.06和21.70 U/g,不溶性膳食纤维(IDF)也持续降解至38.30 g/100 g。面团搅拌、醒发过程中,还原糖含量不断增加,且添加发酵麦麸的面包效果最明显。相比未发酵麦麸面包,添加发酵麦麸的面包体积、弹性及持水力都显著提升(p<0.05),气孔结构更加细腻。制作的4种面包中总膳食纤维(TDF)和阿拉伯木聚糖(AX)含量没有显著差异,而添加发酵麦麸及木聚糖酶都能促进面包中IDF和AX溶解。     

海藻酸钠对面包烘焙特性的影响研究

主要研究了添加不同比例(0%、0.1%、0.3%、0.5%、0.7%和0.9%)的海藻酸钠对面包烘焙特性的影响。研究结果表明,海藻酸钠的引入能增大面包的比容,尤其对添加0.3%和0.5%的海藻酸钠面包比容增加显著(p<0.05),与对照相比分别增大了8.2%和6.7%;添加海藻酸钠后,面包硬度变小(p<0.05),胶粘性和咀嚼性下降(p<0.05),内聚性和弹性增大(p<0.05),对面包品质有较好的改良效果。在长期放置过程中添加海藻酸钠后,面包的硬度显著降低(p<0.05),水分迁移速率较慢,表明有较好的抗老化效果,能够延长面包的货架期。      

Effect of Fermentation Time on the Inositol Phosphates of Bread

Bread was made by an AACC procedure using whole wheat flour and 70%-extraction wheat flour. Five different fermentation times were applied. Six inositol phosphates and inorganic phosphate were separated, identified and quantified in the bread. It was found that phytate decreased and the inorganic phosphate increased, with the largest decrease in phytate occurring during first 30 min of fermentation. The content in intermediate inositol phosphates also changed and it was only after considering their phosphorus content that an overall phosphorus balance could be achieved.     

Oxidative stability of whole wheat bread during storage

The oxidative stability was examined in whole wheat bread packed in modified atmosphere (nitrogen) using vacuum grade plastic bags and stored for up to 5 weeks. Small, but significant, differences in oxidative stability developed with time for whole wheat bread crumb and crust. The samples were evaluated by direct electron spin resonance (ESR) spectroscopy for detection of free radicals, peroxide value (POV), overall antioxidative capacity using Trolox equivalent antioxidant capacity (TEAC) and oxygen radical absorbance capacity (ORAC) assays, and by the content of tocopherols as determined by HPLC. The overall antioxidative capacity was reduced during storage with an accumulation of lipid hydroperoxides peaking after 2-3 weeks of storage. Bread crust was generally found to be more oxidative stable when compared to crumb. Quality of bread with extended shelf life may accordingly be improved minimising oxidation.     

响应面分析法优化黑小麦全麦面包工艺配方研究

以面包比容和感官评分为评价指标,采用单因素试验分析了黑小麦全麦粉、水、酵母、蔗糖添加量对面包品质的影响.通过响应面设计对黑小麦全麦面包的工艺配方进行优化,确定其最佳工艺配方,实验结果表明:以混合粉为基重,黑小麦全麦粉添加量为23%,水52%,酵母1.3%,蔗糖21%.采用优化工艺配方制作的全麦面包比容为5.21 cm3/g,综合评分为85.37.与普通面包相比,黑小麦全麦面包风味独特、质地柔软、老化速率明显降低,面包货架期延长,外观性状和内在品质均得到较大程度的改善.