不同酵母制作的馒头感官及品质分析

将市场收集的不同酵母制作馒头,采用活力仪和质构仪分别测定酵母的产气性能和馒头质构,结合感官评价的方式,探究不同酵母制作的馒头的感官和品质差异。结果表明,馒头制作中优先选择2#酵母,其面团发酵速度适中,产气性能良好,每100 g面团醒发1 h内产气（CO2） 59.96 mL,制作馒头质构优良,风味更好,感官评分最高为72.1分。     

不同酵母在青麦馒头面团中的发酵特性及品质对比分析

以馒头专用粉及青麦粉制作青麦馒头,采用发酵仪和流变仪对不同酵母种类(彩虹牌即发干酵母,安琪高活性干酵母,梅山即发干酵母,新良即发高活性干酵母)、不同质量分数的青麦粉(0%、5%、10%、15%、20%)制成的馒头面团的发酵特性和流变特性进行研究,并对此面团制成的馒头的比容、感官品质和质构特性进行分析。结果表明:4种酵母中安琪牌酵母面团的发酵特性(产气量、持气率、面团开始漏气时间)最好,弹性模量与黏性模量较大;加入青麦粉后,安琪牌酵母制作的馒头比容较大,感官评分较高,硬度、咀嚼性较小,弹性较大;在青麦粉添加量为质量分数10%时,馒头比容和质构指标适中,感官评分与普通馒头相差不大,膳食纤维含量较高。因此,选择安琪即发高活性干酵母发酵、添加质量分数10%青麦粉制作成的馒头品质较好,营养丰富。     

酵子与酵母混合对冷冻面团馒头品质的影响研究

研究了酵母与酵子不同混合比例对冷冻面团馒头品质的影响。通过测定不同发酵时间下馒头的基本指标、质构和感官总分,找出制作冷冻面团馒头最适的混合比例和解冻后的发酵时间。研究表明:酵母与酵子混合比例为4∶1,解冻后的发酵时间为45 min时,做出的冷冻面团外观较好,成品馒头的感官总分较高。单纯用酵母做出的冷冻面团表皮容易开裂和坍塌,但是酵子添加比例较大时,发酵剂的发酵活力降低,解冻后需要将长的发酵时间。添加适量的酵子制作出来的冷冻面团表皮较光滑,不易开裂和塌陷,制作馒头的口感和风味要比单纯使用酵母制作的馒头要好很多,同时大大的缩短了解冻后的发酵时间。     

藜麦-小麦混合粉面团特性及藜麦馒头加工工艺

探讨不同比例的藜麦全粉对高筋小麦粉面团流变学特性的影响,确定藜麦全粉馒头中最佳的藜麦全粉添加比例并进行馒头加工工艺的优化。通过混合实验仪和吹泡仪对面团流变学特性进行测定,以馒头的感官评价和质构特性为评价指标,对藜麦全粉馒头的酵母添加量、发酵时间和醒发时间进行优化。结果表明：藜麦全粉馒头的最佳藜麦全粉添加量为15%;当酵母添加量0.75%、发酵时间100 min、醒发时间15 min时,藜麦全粉馒头的感官评价总分达到最高值86.58,比容达到最高值3.02 mL/g,同时,硬度、咀嚼性和胶着性分别达到最低值9.76、45.53 N和6.66 N。     

不同商业酵母馒头发酵风味及品质分析

利用固相微萃取与气质（SPME-GC-MS）联用技术对五种商业酵母馒头进行风味物质测定,并通过模糊数学综合评价法对样品进行感官评价。结果显示,商业酵母发酵馒头中的挥发性成分种类相似;通过主成分分析（PCA）可知不同种类酵母发酵馒头关键性风味物质存在差异;结合聚类分析（CA）发现不同种类干酵母、半干酵母制得的发酵馒头风味差异明显,不同种类鲜酵母添加量较少、面团醒发时间较短时,其发酵馒头风味相似度很高,只有增大酵母添加量并延长醒发时间,不同种类鲜酵母发酵馒头风味才会发生显著性变化。在感官评价中,干酵母评价分数要优于鲜酵母。基于感官评价、主成分分析和聚类分析得出结论：选择不同酵母品种,通过控制酵母添加量和醒发时间可显著影响馒头的风味及品质。     

葡萄叶粉在馒头中的应用研究

为研究葡萄叶粉对馒头品质的影响,以不同比例的葡萄叶粉替代小麦粉制作馒头,并采用感官评价和质构分析的方法对馒头品质进行评价,对葡萄叶粉的添加量、水的添加量、面团发酵时间、馒头坯醒发时间4个因素进行单因素试验及正交试验分析,确定最优的葡萄叶粉馒头加工工艺参数:葡萄叶粉的添加量4%、小麦粉的添加量为96%、水的添加量为60%、面团发酵时间为35 min、馒头坯醒发时间30 min。     

响应面法优化酵母冷冻面团馒头生产工艺

为了确定酵母冷冻面团馒头的最佳生产工艺,选取酵母添加量、加水量、发酵温度、发酵时间进行试验。在单因素的基础上,进行Box-Behnken中心组合研究,建立了对酵母冷冻面团馒头感官总分影响的数学模型,确定了酵母冷冻面团馒头的最佳生产工艺。结果表明,各因素对酵母冷冻面团馒头感官总分的影响顺序为:发酵温度酵母添加量发酵时间加水量。最佳工艺条件为:酵母添加量1.2 g、加水量51.2 m L、发酵温度35.7℃、发酵时间43.7 min,在此条件下预期的酵母冷冻面团馒头感官总分是76.8分,实际感官评价得分为76分。     

预醒发酵子冷冻面团馒头发酵工艺的优化研究

为了确定酵子冷冻面团馒头最佳发酵工艺,首先研究了预醒发时间对冷冻面团馒头品质的影响,在单因素试验的基础上,选取酵子添加量、加水量、发酵温度、发酵时间进行了4因素3水平的正交试验,确定了酵子冷冻面团馒头的最佳发酵工艺。结果表明:预醒发时间60 min时,冷冻面团的外观较好,成品馒头的感官总分最高;各因素对馒头感官品质的影响顺序为:发酵时间>加水量>发酵温度>酵子添加量,酵子冷冻面团馒头的最佳发酵工艺为:酵子添加量8 g、加水量50 m L、发酵温度35℃、发酵时间135 min。对照试验中,酵子冷冻面团馒头感官总分比酵母冷冻面团馒头高,酵子冷冻面团馒头与新鲜馒头相比,新鲜馒头感官总分较高。     

不同酵母对冷冻面团发酵特性及馒头品质的影响

对市场上4种活性干酵母进行了无糖和低糖面团发酵活力及冷藏1周后发酵力的变化进行测定。结果表明:不同酵母在无糖面团和低糖面团中的发酵力存在差异,酵母Y2基本无差别,Y1、Y3和Y5发酵力都有不同程度的提高。冷藏7d后相对发酵力的测定表明:Y1、Y3和Y4在无糖面团中相对发酵力较高;Y2和Y3在低糖面团中的相对发酵力较高。通过无糖冷冻面团馒头感官评价及质构特性的测定,用酵母Y3来发酵的冷冻面团馒头品质较好。     

杏鲍菇粉对小麦面团、馒头质构及品质的影响

目的:研究杏鲍菇粉对小麦面团、馒头质构及馒头品质的影响。方法:在面粉中添加不同量(0、5、10、15、20 g/100 g)的杏鲍菇粉,采用质构仪分析测定小麦面团及馒头的质构特性,p H计测定面团及馒头的p H值,并对馒头制品的感官品质进行评价。结果表明:随着杏鲍菇粉添加量的增加,面团的发酵性能降低,面团及馒头的硬度、咀嚼度及胶着度均呈增大趋势,面团的弹性、黏聚性、胶着度及回复性与对照组比较,没有显著性差异(P0.05);馒头的弹性、比容和感官评分显著降低(P0.05),馒头的颜色逐渐加深,感官品质变差;杏鲍菇粉的添加使小麦面团和馒头的质构特性及感官品质均发生了改变,制作馒头时,杏鲍菇粉的添加量以不超过10 g为宜。     

酵母种类对空心挂面品质的影响

为优化空心挂面生产工艺,探究不同产地的四种酵母对空心挂面品质的影响。对四种酵母不同添加量下空心挂面的膨胀指数、蒸煮特性进行分析,并对酵母菌添加量为1.6%时面团的流变发酵特性、空心挂面的质构特性、径向指数及模糊感官评价进行研究。结果表明:四种酵母所制空心挂面的膨胀指数、最佳蒸煮时间及干物质吸水率均随着酵母添加量的增加先增大后减小,并在添加量为1.6%时达到峰值。当酵母菌添加量为1.6%时,B酵母、C酵母产气速度较快,空心挂面抗断裂应力较大;四种酵母所制空心挂面中,C酵母所制挂面的径向指数、抗断裂应力最大,口感软滑。结合挂面的径向膨胀指数、截面状态、质构特性和模糊感官评价结果可知,C酵母添加量为1.6%时所制挂面的综合品质最佳。     

Properties of yeast free bread produced by supercritical fluid extrusion (SCFX) and vacuum baking

A novel technology, supercritical fluid extrusion (SCFX), allows for continuous production of yeast-free dough leavened via incorporation of supercritical carbon dioxide (SC-CO₂). In this study, an optimum dough formulation, SCFX leavened dough production and baking procedures were developed. A premixed dough was leavened by 1% (feed basis) SC-CO₂ injection in a twin screw extruder at 37 °C. Specific mechanical energy input was 18 kW h/ton. SCFX leavened dough and bread density, moisture content, bake loss, texture profile analysis (TPA) and stress relaxation were evaluated and compared to conventional yeast leavened breads throughout 5-day storage. A combination of vacuum and conventional baking yielded the lowest SCFX leavened bread density of 0.19 g/cm³ and crumb hardness comparable to conventional yeast leavened and commercial products. This approach could be beneficial for a continuous production of consistent ready-to-bake dough and breads having equivalent quality to commercial products but produced in shorter time and without ethanol emission issues.

Industrial relevance

The dough leavening process in conventional bread production is an industrial hurdle for a number of reasons. First, it is very time consuming. Dough leavening through yeast fermentation can take up to eight hours, which is not conducive to high production rates. This long waiting period also means a great deal of storage space is required to produce a large amount of dough. This storage environment must be carefully controlled in terms of temperature, humidity, and air conditions in order to maintain optimal yeast fermentation, which can also be very costly. Finally, the emission of ethanol, a significant byproduct of yeast fermentation, must be controlled according to the EPA clean air act. Expensive catalytic converters must be installed and maintained in commercial bread production facilities.Bread produced by super critical fluid extrusion (SCFX) overcomes these problems. Total dough production time is less than an hour, and with the proper baking equipment, the entire process can be made continuous. This means constant output, less downtime, and none of the costly storage space used for conventional dough proofing. Furthermore, since there is no yeast being used, there is no ethanol being produced. This means no harmful volatile organic emissions and no expensive catalytic converter. Coupled with vacuum baking, this process results in bread with qualities similar to commercially produced bread in significantly less time.     

The influence of a baker's yeast pre-inoculum on bread-dough leavening

In order to investigate the influence of a pre-inoculum on the fermentation performance of compressed baker's yeast used for bread-dough leavening, pre-inocula were made by adding compressed baker's yeast to a premix-sugar broth and cultivating it for 30, 60, 90 and 120 min. The pre-inocula were added separately to the dough and the gas production measured with the aid of a fermento-manometer. The pre-inoculum cultivated for 120 min presented the highest increase (43·6%) in maximum gas produced (P_max) after 90 min of dough fermentation. The possibility of reducing lag time during dough fermentation, by using a cost-effective pre-inoculum, was assessed and results showed a significant (P ≤ 0·05) increase in gas production which could be highly beneficial to the bread industry.     

Simple improvement in freeze-tolerance of bakers' yeast with poly-gamma-glutamate

We examined the effect of poly-gamma-glutamate (PGA) on the freeze-tolerance of four types of commercial bakers' yeast (freeze-tolerant, osmotic-tolerant, low-temperature-sensitive, and ordinary bakers' yeasts). The survival ratio of ordinary bakers' yeast cells frozen at -30 degrees C for 3 d in a medium (0.5% yeast extract, 0.5% peptone, and 2% glucose: YPD medium) was improved by adding more than 1% PGA to the medium; the survival ratio increased from about 10% to more than 70%. All PGA preparations, which differed in average molecular mass (50, 2,000, 4,000, 6,000, 8,000, and 10,000 kDa), showed a similar cryoprotecive effect on the cells. Similar results were also obtained with other types of bakers' yeast, sake yeast and beer yeast. When the four types of bakers' yeast cell were frozen at -30 degrees C for 3 d in dough supplemented with more than 1% PGA, the cells (after freezing and thawing) showed higher leavening ability than those frozen in dough without PGA, irrespective of the molecular mass of PGA. Thus, PGA appears to protect bakers' yeast from lethal freeze injury, leading to a high leavening ability after freezing and thawing. PGA did not decrease the original leavening ability of the bakers' yeast, and was not decomposed by the yeast cells. PGA suppressed the decrease in leavening ability during a prolonged fermentation time, probably because PGA adsorbed inhibitory metabolites accumulated in the dough. PGA could prove useful for improving the freeze-tolerance of bakers' yeast by its addition to dough.     

中国不同地区老酵头对馒头质构和感官品质的影响

目的探讨中国不同地区传统老酵头对馒头品质特征的影响,筛选产品品质较为优良的老酵头。方法收集10个地区的传统面食发酵剂为实验材料制作老酵馒头,测定不同地区老酵面团在发酵过程中微生物的变化及馒头的品质指标,并进行感官评价。结果不同地区老酵馒头的品质指标间具有显著性差异(P0.05),老酵头制作面团发酵过程中不同地区间酵母菌和乳酸菌的生长趋势相似且具有一定的规律性,在发酵前期,酵母菌迅速生长至面团成熟期后,其数量趋于稳定;乳酸菌在发酵前期经过短暂的适应期后进入快速生长期,至面团成熟期后乳酸菌数量显著下降。综合馒头的质构指标、物性指标及感官评价来看,5#老酵头制作出的馒头其综合品质最佳,感官评分最高为89分。结论本研究结果为传统发酵剂在馒头工业化生产中的合理利用提供了理论依据。     

不同干燥方式对酵子储存品质影响的研究

酵子作为多菌体混合发酵剂,其品质明显受到干燥方式的影响。采用自然风干、鼓风干燥、真空干燥和真空冷冻干燥4种常用的干燥方式分别对同一批酵子进行干燥处理,测定不同干燥方式下酵子的发酵力、pH及其制做的馒头质构、白度和并作感官评分。结果显示:酵子在鼓风干燥过程中品质降低程度较小,且相比自然风干、真空干燥和真空冷冻干燥,鼓风干燥具有干燥时间短,费用低等优点。     

α-GLUCOSIDASE, α-GLUCOSIDE PERMEASE,MALTOSE FERMENTATION AND LEAVENING ABILITY OF BAKER'S YEAST

α-Glucosidase and α-glucoside permease are synthesized simultaneously in two different strains of baker's yeast (Saccharomyces cerevisiae) when the cells are induced with maltose. α-Thioethyl D-glucopyranoside (α-TEG) inhibits the transport of maltose into the cells, and the transport of maltose and α-TEG appeared to be mediated by the same permease system. There is an obvious correlation between α-glucosidase, α-glucoside permease and maltose fermentation activities in the yeasts while no correlation between these and the leavening ability of the yeasts can be demonstrated. Apparently the glucose concentration in dough is high enough to inhibit the permease-mediated transport of maltose into the cells thus impairing leavening ability from the maltose fermenting system.