不同贮藏期大豆蛋白对千页豆腐品质的影响

为了研究不同贮藏期大豆分离蛋白（soy protein isolate,SPI）对千页豆腐品质的影响,该文首先研究了贮藏期对大豆分离蛋白结构的影响,进而探讨贮藏期对大豆蛋白制备千页豆腐的品质的影响。对不同贮藏期的大豆蛋白分别采用了凝胶质构特性、感官评价、羰基含量、大豆蛋白亚基以及巯基的测定,并采用拉曼光谱对大豆蛋白二级结构、二硫键构型以及侧链结构进行了分析,同时采用扫描电镜观察千页豆腐的微结构。结果表明：随着贮藏期的延长,千页豆腐的感官评价变差,由88分降低至44分;其凝胶网络结构逐渐疏松;大豆蛋白羰基含量逐渐上升;巯基含量逐渐下降;二级结构含量改变;凝胶硬度呈下降趋势,硬度值低于234 g时,将无法达到千页豆腐的质量要求。这表明在贮藏期内SPI发生了氧化,导致大豆蛋白质结构发生改变,使其凝胶性质下降。     

不同热处理大豆分离蛋白凝胶冻藏特性

为探究冻藏过程中不同加热温度处理大豆分离蛋白(soybean isolate protein,SPI)凝胶特性变化及评估不同热处理对SPI凝胶冻藏特性的影响。该文以65、90和135℃3个不同温度处理所得SPI为研究对象(分别记为65SPI、90SPI和USPI),采用离心法、质构分析法、可溶蛋白含量测定和电泳等方法对其冻藏过程中的凝胶持水性、凝胶硬度、凝胶弹性、可溶蛋白含量及亚基组成和凝胶作用力进行了分析研究。结果表明:随冻藏时间延长,不同温度处理SPI凝胶持水性、凝胶弹性和凝胶可溶蛋白含量呈下降趋势,而凝胶硬度呈增大趋势。凝胶持水性、弹性的下降和凝胶硬度的升高标志着凝胶品质的劣变。不同温度处理对SPI凝胶的冻前凝胶特性和冻藏特性有较大影响,65和90℃的温度处理降低了冻前SPI凝胶的持水性,增强了冻前SPI凝胶硬度,有更多的β和B亚基参与了凝胶形成,冻藏前后的亚基组成没有变化;超高温瞬时加热(ultra high temperature,UHT)处理则降低了冻前SPI凝胶硬度,冻藏过程中可溶蛋白含量大幅下降且可溶蛋白中β和B亚基含量下降。3种温度处理SPI的凝胶劣变程度均高于未处理SPI。加热处理会造成SPI发生部分或完全变性,变性后疏水基团的暴露会加快蛋白凝胶形成过程中聚集速率,进而增大粗糙凝胶结构形成的几率,而粗糙凝胶网络在冻藏过程中其劣变程度更甚于未加热SPI。由此可知,加热处理尽管在一定程度上增大了凝胶硬度,但会加速其凝胶品质冻藏劣变。     

大豆蛋白热变性程度对速溶豆腐花粉凝胶成型的影响

针对速溶豆腐花粉的制备工艺中需要对大豆进行热处理,热处理过程中大豆蛋白的热变性程度对豆腐花粉凝结的凝胶强度与凝结所需的时间具有显著影响,而现在速溶豆腐花粉的工业生产中还没有对豆浆热处理程度较为合适的标准。该文以大豆、大豆分离蛋白(soybean protein isolate,SPI)、大豆球蛋白(glycinin,11S)、β-伴大豆球蛋白(beta-conglycinin,7S)为原料,研究大豆蛋白热变性程度对速溶豆腐花粉凝胶成型的影响。研究表明11S比7S更难发生完全变性,SPI中的7S和11S比单独存在的7S、11S更难发生完全变性。传统制备方式、前热处理后喷雾干燥或冷冻干燥制备方式、先喷雾干燥或冷冻干燥后热处理制备方式对豆腐花凝结成型影响不同,其中传统方式制备的豆腐花凝胶效果最好,先干燥后热处理制备的豆粉凝胶效果比前热处理后干燥的豆粉好,引起豆腐花凝胶强度差异的主要原因是大豆蛋白中7S和11S热变性程度不同。制备同一凝胶强度的豆腐花,热处理温度越低,所需的热处理时间越长;制备高凝胶强度的豆腐花比制备低凝胶强度的豆腐花所能进行的热处理温度与时间范围小。大豆蛋白的7S处于完全变性而11S处于未完全变性的状态时,适合制备速溶豆腐花粉的大豆蛋白变性程度应控制热处理温度与时间范围为80℃时热处理20~65 min,85℃时热处理15~50 min,90℃时热处理10~35 min,95℃时热处理5~20 min。该研究结果为调控速溶豆腐花粉的凝胶特性提供理论依据。     

谷朊粉基共混黏合体系的构建及在素肉饼中的应用

谷朊粉经水合作用形成面筋蛋白（Wheat Gluten Protein，WGP）网络结构，具有良好的黏弹性和延展性，但加热后其网络结构易破裂，稳定性较低。该研究利用谷朊粉、大豆分离蛋白（Soy Isolated Protein，SPI）、甲基纤维素（Methylcellulose，MC）、谷氨酰胺转氨酶（Glutamine Transaminage，TG酶）的原料特性，建立植物蛋白、亲水胶体、促凝胶酶的共混黏合体系，研究各组分对其理化性质、凝胶特性及结构的贡献和影响。结果表明，随着三种原料依次递进加入WGP，混合体系中二硫键含量分别较前一组降低81.03%、升高248.50%和0.70%，游离巯基含量升高68.79%、降低28.90%和20.44%，表面疏水性升高5.33%、降低6.85%、再升高17.17%，高分子量麦谷蛋白组分分子量则逐渐增加；持水性升高5.07%、2.91%、2.79%，凝胶强度升高104.14%、24.66%、3.52%；共混凝胶的储能模量和损耗模量均逐渐升高；TG酶加入后，阻止了α-螺旋逐渐向β-转角、无规则卷曲的转化，α-螺旋和β-折叠含量上升。可见共混黏合体系凝胶的分子间缠结点增多、凝胶性变强。虽然SPI的添加部分破坏了WGP网络结构，但SPI、MC、TG酶增加了蛋白的聚集程度和凝胶强度。扫描电镜观察显示，SPI镶嵌在WGP网络骨架中，形成半网络半填充的新架构形式；随着MC和TG酶的依次加入，在形成大量交联丝状结构的基础上，局部形成连续膜状结构将大豆拉丝蛋白（Soy Drawing Protein，SDP）粒子覆盖。说明SDP粒子被完整、紧密地包裹于谷朊粉-SPI-MC-TG酶共混黏合体系中。利用此黏合体系制成SDP基素肉饼，依次向复水SDP中添加四种原料，显示素肉饼的硬度、内聚性、咀嚼性和弹性等均得以提升。因此，该研究建立谷朊粉基共混黏合体系是改善SDP为主要原料的素肉制品品质的有效方法。     

高场强超声-加热联用增强大豆分离蛋白冷凝胶凝胶特性

为探究高场强超声技术对大豆分离蛋白葡萄糖酸内酯冷凝胶性的影响,该研究将高场强超声技术与加热处理联用,对大豆蛋白进行预处理后形成冷凝胶。采用质构仪、圆二色谱、荧光色谱、扫描电镜、电泳、粒度仪等多种表征手段,比较了2种高场强超声-加热联用工艺对大豆分离蛋白冷凝胶凝胶性的影响,并推测其作用机理。研究发现:与传统加热预处理相比,2种高场强超声-加热联用预处理都能够显著(P0.05)增强大豆分离蛋白冷凝胶的持水性和凝胶强度。工艺一(20 k Hz,400 W下先超声0、2、4、10 min后加热20 min)制备的冷凝胶的凝胶强度与持水性随超声时间的增加逐步增加(凝胶强度由(5.83±0.31)g增加到(46.37±1.15)g;持水性由42.04%±1.59%增加到81.74%±6.22%),而工艺二(先加热20 min后超声0、2、4、10 min)制备的冷凝胶的凝胶强度与持水性在较短超声时间内(4 min内)迅速增加(凝胶强度由(5.83±0.31)g增加到(37.57±2.57)g;持水性由42.03%±1.85%增加到79.31%±3.00%)。与工艺一相比,工艺二能够在较短超声时间内增强大豆分离蛋白冷凝胶性的机理可能在于:工艺二的处理方式,大豆蛋白经过热处理后充分展开、变性,使超声作用能在较短的时间内对大豆分离蛋白的二级结构和三级结构明显改变,暴露更多疏水基团,增加疏水环境和表面疏水性,增强蛋白在溶液中的溶解性,并增强大豆蛋白分子间的静电相互作用,从而形成致密、均一的微观凝胶结构,增加凝胶的持水性和凝胶强度。研究结果可为高场强超声-加热联用技术在大豆加工领域中的应用提供参考。     

适宜物理-酶联合改性提高酸性条件下大豆分离蛋白乳化性

为提高酸性条件下大豆分离蛋白（soy protein isolates,SPI）的乳化性能,该文研究了物理-酶联合改性对SPI（pH值为4）的乳化性能影响,通过对比确定了物理-酶联合改性,即超声波-酶复合改性和挤压膨化-酶复合改性两种改性方法在酸性条件下的乳化性能效果最好;并通过对改性后 SPI（pH 值为4）进行溶解性、游离巯基、二硫键、粒径、扫描电镜（scanning electron microscope,SEM）和激光共焦扫描显微镜（confocal laser scanning microscopy,CLSM）分析,从蛋白结构变化上进一步揭示了乳化性能提高现象的原因。结果表明：超声波联合植酸酶-酸性蛋白酶改性的 SPI （Uphy-aci-SPI）的乳化活性（emulsifying activity index,EAI）为0.53 m2/g,比未改性SPI（0.18 m2/g）显著提高了196%（P<0.05）,乳化稳定性（emulsifying stability index,ESI）为17 min,比未改性SPI（13.5 min）显著提高了25.9%（P<0.05）;挤压膨化联合菠萝蛋白酶改性的SPI（Ebro-SPI）的EAI为0.46 m2/g,比未改性SPI显著增加了155%（P<0.05）,ESI为17 min,比未改性SPI显著增加了25.9%（P<0.05）。在pH值为4的条件下对物理-酶联合改性的SPI的性质分析发现,物理-酶联合改性的SPI与未改性SPI相比,物理-酶联合改性的SPI的溶解性显著增加（P<0.05）;物理-酶联合改性的SPI的乳状液平均粒径减小,CLSM观察乳状液中油与蛋白溶液稳定共融,改善了油滴之间的空间排斥力。物理-酶联合改性的SPI游离巯基的含量显著增加（P<0.05）,二硫键含量显著降低（P<0.05）。SEM观察物理-酶联合改性的SPI为结构松散、破碎均一的微观结构。由此可见,乳化性能的提高是通过深层改变蛋白的结构来实现的。该研究可为探索提高酸性条件下SPI的乳化性能的方法提供理论依据。     

加水量与和面时间对面片质构及蛋白特性的影响

为研究加水量对不同和面时间下面片质构及蛋白特性的影响,该研究采用质构仪、傅里叶红外光谱仪和高效液相色谱仪分别探究面片质构、二级结构和蛋白含量的变化,同时对面片色泽、巯基含量进行测定。结果显示随着加水量的增加,面片的拉伸力与硬度呈下降趋势,延展性与黏性呈上升趋势,面片亮度(L*)值和红-绿(a*)值升高。加水量为40%时,蛋白质二级结构中稳定型的β-折叠与α-螺旋含量较高,巯基、大分子量聚合体蛋白含量较低,面片综合质构特性较好,有利于高水分含量面制食品的生产。不同加水量下,和面时间对面片质构及蛋白特性的影响不同。和面15 min时,面片延展性较好,拉伸力、硬度适中,黏性、巯基含量较低,β-折叠含量较高,适度的和面时间能够促进面片面筋网络的形成,有利于提高面片的品质特性。     

油脂预乳化提高大豆拉丝蛋白素食香肠品质

为了提高大豆拉丝蛋白(Textured Fibril Soy Protein,TFSP)素食香肠的品质,该研究将油脂预乳化工艺应用于TFSP素食香肠的加工,利用响应面试验设计优化了预乳化工艺条件,采用质构分析仪测定分析了产品的质构特性,并进行了感官评价。结果表明优化后的最佳预乳化工艺条件为菜籽油含量445g/L、大豆分离蛋白浓度105g/L、乳化机剪切速率9.0×103r/min。与对照组相比,此条件下制作的预乳化-TFSP素食香肠的凝胶强度、硬度和咀嚼性分别提高了约1倍、10%和26%,且产品口感鲜嫩、富有汁液感,感官评价得分显著提高。采用激光共聚焦显微镜观察分析了不同工艺制作的TFSP素食香肠在煮制前后微观结构的变化,结果发现油脂预乳化工艺可大大提高乳化油脂的稳定性和在香肠凝胶基质中的均匀分布,从而使乳化油脂的‘填充作用’得以发挥,不仅增强了TFSP素食香肠的保水保油能力,降低了蒸煮损失率,而且对香肠的质构和感官特性产生了重要影响。因此油脂预乳化工艺是一种辅助提高素食香肠整体品质行之有效的方法。     

大豆胰蛋白酶抑制剂对带鱼鱼糜蛋白降解及其凝胶特性的影响

为提高带鱼鱼糜制品品质,以鱼糜蛋白组成、TCA-溶解肽含量及其凝胶强度等为指标,研究大豆胰蛋白酶抑制剂(STI)对带鱼鱼糜蛋白降解及其凝胶特性的影响。结果表明,带鱼鱼糜蛋白的降解与温度显著相关,随温度升高,肌原纤维蛋白重链(MHC)逐渐降解,TCA-溶解肽含量增加,在70℃时达到最高值(1.3μmol酪氨酸·g~(-1))。添加STI能够一定程度抑制带鱼鱼糜凝胶劣化样品和凝胶化样品中肌原纤维蛋白的降解,降低TCA-溶解肽含量。当STI添加量为0.10‰时,凝胶劣化样品和凝胶化样品的TCA-溶解肽含量达到最低值,分别为0.13和0.30μmol酪氨酸·g~(-1),凝胶强度达到最高值,分别为414.74 g·mm和1 262.28 g·mm,而失水率分别下降为5.44%和3.76%;电镜微观结构显示,此时凝胶结构更致密、均匀,但凝胶白度值轻微下降。因此,STI可有效提高带鱼鱼糜制品品质,从而为生产高品质的带鱼鱼糜制品提供参考和依据。     

α和α'亚基缺失对大豆分离蛋白乳化特性的影响

为了探究β-伴大豆球蛋白(7S)中α和α′亚基缺失对大豆分离蛋白乳化特性的影响,该文以东农47(对照)和3种不同蛋白亚基缺失型(α缺失、α′缺失以及α、α′缺失)大豆为原料提取大豆分离蛋白(SoyProteinIsolate,SPI),通过十二烷基磺酸钠聚丙烯酰胺凝胶电泳(Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis,SDS-PAGE)技术分析其亚基组成,然后制备乳状液并测定乳化活性指数(Emulsifying Activity Index,EAI)、ζ-电位、粒径、微观结构、稳定动力学指数(Turbiscan Stability Index,TSI)及界面蛋白吸附量。结果表明:α′亚基缺失型SPI乳状液乳化活性指数最大,为87.59 m2/g;ζ-电位绝对值最大,为47.7 mV;粒径最小,为2.223μm;显微结构显示其分子最小且分布最均匀,稳定动力学指数最小;界面蛋白吸附量最大,为31.40%。4种不同SPI乳状液的稳定性结果由大到小为α′亚基缺失型、东农47、α亚基缺失型、α和α′亚基缺失型。研究结果可为高乳化性大豆蛋白系列产品的开发应用提供理论支撑和技术支持。     

蛋白原料及其混合粉料理化性质对颗粒饲料加工质量的影响

该研究旨在探究豆粕、棉粕、菜粕、酒糟蛋白(Distillers Dried Grains with Solubles,DDGS)、乙醇梭菌蛋白5种蛋白原料及其混合粉料的营养指标和理化性质的差异,确定影响颗粒饲料质量和制粒能耗的关键指标,对5种蛋白原料的制粒效果进行综合评价。以豆粕为对照组,仅改变蛋白原料,采用相同的加工参数制备颗粒饲料,比较不同蛋白原料的制粒效果,进行主成分分析及偏最小二乘回归分析(Partial Least Squares Regression,PLS)。结果表明:在原料营养指标和理化特性方面,乙醇梭菌蛋白具有高蛋白含量、高蛋白溶解度、低脂肪、低纤维的特点,棉粕具有高纤维的特点,菜粕具有高纤维和低蛋白溶解度的特点,DDGS具有低蛋白和高脂肪的特点。蛋白原料吸水性强弱排列顺序为乙醇梭菌蛋白、豆粕、棉粕、菜粕、DDGS,水溶性与之相反。乙醇梭菌蛋白组和棉粕组的制粒能耗较高,豆粕组的制粒能耗最低;棉粕组和乙醇梭菌蛋白组的修正耐久性(Modified Pellet Durability Index,MPDI)较高分别为92.72%和90.57%,菜粕组的MPDI最低为79.68%;乙醇梭菌蛋白组的硬度最高为130.95N,DDGS组的硬度最低为74.26N;乙醇梭菌蛋白组的糊化度最高为45.56%,DDGS组的糊化度最低为31.36%。通过偏最小二乘回归模型得到,蛋白含量、蛋白溶解度和吸水性的增加会提高颗粒饲料硬度、PDI和MPDI;粗纤维含量、蛋白溶解度和吸水性的增加会增加制粒能耗。综合分析5种蛋白原料制粒特性,由高到低排序为乙醇梭菌蛋白、棉粕、豆粕、菜粕、DDGS。研究结果为实际生产颗粒饲料时蛋白原料的选择提供参考依据。     

Effect of Moisture Content and Soluble Level on the Physical,Chemical, and Flow Properties of Distillers Dried Grains with Solubles (DDGS)

Distillers dried grains with solubles (DDGS) is a bulk material that has been widely used as a protein source for ruminants and nonruminants for more than two decades. DDGS is the nonfermentable processing residue (i.e., protein, fiber, fat, and ash) from fuel ethanol manufacturing. With the exponential growth of the fuel ethanol industry in the past several years, significant quantities (≈13.0 million tons in 2007) of distillers grains are now being produced. To effectively utilize these coproduct streams in the domestic market, DDGS must be transported greater distances and must be stored until final use. DDGS flow is often problematic as it can become restricted by caking and bridging that occur during shipping and storage. This flowability problem can present itself during dynamic and static flow conditions. This issue most likely results from physical or chemical interactions between particles (including particle size and shape), storage moisture, temperature, and relative humidity variations, as well as storage time. The objective of this study was to examine the effect of five moisture content levels (10, 15, 20, 25, and 30% db) on the resulting physical and chemical properties of DDGS with four soluble levels (10, 15, 20, and 25% db). To produce these materials, condensed distillers solubles (CDS) were combined with DDG, and appropriate quantities of water were added to adjust moisture contents. Carr indices were used to quantify the flowability of the DDGS samples. The results showed that both soluble level and moisture content had noticeable effects on physical and flow properties (e.g., aerated bulk density, packed bulk density, and compressibility). According to dispersibility, flowability index, and floodability index, flowability generally declined significantly (P < 0.05) with an increase in moisture content for most of the soluble levels under consideration. The color values and protein content of the DDGS were significantly affected (P < 0.05) as soluble level increased as well.     

Cross‐Sectional Staining and Surface Properties of DDGS Particles and Their Influence on Flowability

With the U.S. fuel ethanol industry projected to grow during the next several years, supplies of distillers dried grains with solubles (DDGS) are anticipated to continue to grow as well. DDGS is used primarily as livestock feed. Much of the DDGS must be shipped, often over large distances, outside the Corn Belt (which is where most of the corn‐based ethanol plants are currently located). Stickiness and caking among particles is a common issue for DDGS, and it often leads to flowability problems. To address this, the objective of this study was to understand the cross‐sectional and surface natures of DDGS particles from five ethanol plants, and how they interact with DDGS properties. This study examined the distribution patterns of chemical components within cross‐sections, within section edges (i.e., surface layers), and on surfaces using standard staining techniques; chemical composition was determined using standard protocols; and physical and flowability properties were also determined. Crude protein in the samples was 28.33–30.65% db, crude fat was 9.40–10.98% db, and neutral detergent fiber (NDF) was 31.84–39.90% db. Moisture contents were 4.61–8.08% db, and geometric mean diameters were 0.37–0.52 mm. Cross‐sectional staining showed protein levels of 19.57–40.39%, and carbohydrate levels of 22.17–43.06%, depending on the particle size examined and the production plant from which the DDGS was sampled. Staining of DDGS particles indicated a higher amount of surface layer protein compared with carbohydrate thickness in DDGS particles that had a lower flow function index (which indicated potential flow issues). Additionally, surface fat staining suggested that higher surface fat also occurred in samples with worse flow problems. This study represents another step toward understanding why DDGS particles stick together during storage and transport, and will hopefully help to improve DDGS material handling strategies.     

Flowability Properties of Commercial Distillers Dried Grains with Solubles (DDGS)

Distillers dried grains with solubles (DDGS), the major coproduct from the corn‐based fuel ethanol industry, is primarily used as livestock feed. Due to high protein, fiber, and energy contents, there is a high demand for DDGS. Flowability of DDGS is often hindered due the phenomenon of caking. Shipping and handling of DDGS has thus become a major issue due to bridge formation between the DDGS particles. The objective of this investigation was to measure flowability characteristics of DDGS samples from five ethanol plants in the north central region of the United States. Carr and Jenike tests were performed and the resulting data were mathematically compared with a previously developed empirical model. The largest particles had an average geometric mean diameter (GMD) of 1.19 mm, while the lowest particle size had an average GMD of 0.5 mm. Soluble solid levels were ≈10.5–14.8% (db). The effective angle of friction (δ) was 43.00–57.00°. Additionally, a few parameters exhibited fairly high linear correlations, including aerated and packed bulk densities (r = 0.97), geometric standard deviation and Carr compressibility (r = 0.71), geometric standard deviation and Hausner ratio (r = –0.70). Overall flowability assessment indicated that the commercial DDGS samples did have the potential for flow problems, although no samples exhibited complete bridging. Quantifying DDGS flowability is a necessary step toward overcoming this logistical challenge facing the fuel ethanol industry.     

用于地膜原料的大豆秸秆粉碎预处理工艺参数优化

为了满足植物纤维制取机对大豆秸秆原料长度的要求,采用改进的揉切式粉碎机对大豆秸秆进行预处理,选取揉切机的主轴转速、喂入量以及秸秆的含水率为试验因素,以大豆秸秆粉碎长度为响应函数,对大豆秸秆原料的预处理工艺参数进行了组合试验研究。结果表明:1)各因素对于秸秆粉碎长度影响的贡献率从高到低排序为主轴转速、含水率和喂入量;2)预处理工艺的最优参数组合为喂入量168 kg/h、大豆秸秆含水率处于36%~58%、揉切机主轴转速处于1 100~1 300 r/min。在此工艺参数条件下,大豆秸秆粉碎长度分布符合植物纤维制取机所要求的70~85 mm的理想范围。研究结果为完善植物纤维地膜制造工艺体系提供了参考。     

Air and Moisture Transport Properties of Low‐Oil DDGS

Distillers dried grains with solubles (DDGS) are widely used as feed for cattle, dairy, and swine because of their protein, fiber, amino acids, fat, and other vital nutrients. Corn ethanol plants in the United States recently have started extracting oil from DDGS to gain additional profit, thus producing low‐oil DDGS. So far, there has been no comprehensive study reported with bulk handling and flowability properties of low‐oil DDGS. We measured the air resistance, moisture diffusivity, and air permeability properties for low‐oil DDGS at different temperature and relative humidity conditions, along with some important physical and chemical properties. Physical property comparisons between regular and low‐oil DDGS showed differences in key properties such as particle size, color, density, porosity, and angle of repose. The modified Henderson model predicted the equilibrium moisture content (EMC)–equilibrium relative humidity (ERH) relationship of low‐oil DDGS with a low standard error of regression value (0.008); it showed no pattern in the residuals and was judged the most appropriate model tested for EMC‐ERH predictions. Results of EMC‐ERH nonlinear modeling were used to define conditions for moisture diffusivity. Moisture diffusivities of low‐oil DDGS at varying drying temperatures ranged from 0.74 × 10⁻¹¹ to 1.77 ×10⁻¹¹m²/s. The properties are important for understanding and modeling heat and moisture transport through and flow properties of low‐oil DDGS.     

Twin‐Screw Extrusion Processing of Rainbow Trout (Oncorhynchus mykiss) Feeds Using Various Levels of Corn‐Based Distillers Dried Grains with Solubles (DDGS)

Increasing demand for seafood products and rising demand for fish meal for commercial fish feeds is driving the search for effective alternative protein sources. Twin‐screw extrusion trials were conducted to study the production of nutritionally balanced feeds for rainbow trout fingerlings (Oncorhynchus mykiss). Six isocaloric (≈4.61 kcal/g) ingredient blends with a target protein content of >45% db were formulated with 0, 10, 20, 30, 40, and 50% distillers dried grains with solubles (DDGS) and other feed ingredients. The moisture contents of the diets were initially adjusted to 5–7% db, and then extruded at 250 rpm using dual 1.9 mm dies with varying amounts of steam (7.2–7.7 kg/hr) injected into the conditioner and water (4.3–6.5 kg/hr) into the extruder. Mass flow rates, moisture contents, and temperatures were measured during processing and moisture content, water activity, unit density, bulk density, expansion ratio, compressive strength, compressive modulus, pellet durability index, water stability, and color were analyzed to quantify the effects of varying DDGS content on the extrudate physical properties. Significant differences (P < 0.05) among the blends were observed for color and bulk density for both the raw and extruded materials, respectively, and for the unit density and pellet durability index of the extruded products. There were also significant changes in redness and yellowness, but only minor changes in brightness, among the final products with increasing DDGS content. The compressive strength of the extrudates increased significantly with increasing DDGS. Expansion ratio of all pellets was low. All extruded diets achieved very good water stability.     

Single‐Screw Extrusion Processing of Distillers Dried Grains with Solubles (DDGS)‐Based Yellow Perch (Perca flavescens) Feeds

This study was conducted to investigate the production of balanced diets for juvenile yellow perch (Perca flavescens) feeds. Six isocaloric (≈3.21 kcal/g), isonitrogenous (30.1 ± 0.4% db) ingredient blends were formulated with 0, 10, 20, 30, 40, and 50% distillers dried grains with solubles (DDGS), and appropriate amounts of soybean meal, fish meal, vitamins, and minerals. Extrusion cooking was performed using a laboratory‐scale single‐screw extruder at a constant barrel temperature profile of 40–90–100°C, and a constant screw speed of 230 rpm (24.1 rad/sec). The mass flow rate was determined during processing; it generally increased with progressively higher DDGS content. Additionally, moisture content, water activity, unit density, expansion ratio, compressive strength, compressive modulus, pellet durability index, water stability, and color were extensively analyzed to quantify the effects of DDGS content on the physical properties of the resulting extrudates. Significant differences (P < 0.05) between blends were observed for color and water activity for both the raw material and extrudates, respectively, and for the unit density of the extrudates. There were significant changes in brightness (L), redness (a), and yellowness (b) among the final products when increasing the DDGS content of the blends. Expansion ratio and compressive strength of the extrudates were low. On the other hand, all blends showed high pellet durability (PDI ≥ 96.18%). Overall, it was ascertained that DDGS could be successfully included at rates of <50%, and that each of the ingredient blends resulted in viable, high quality extrudates.     

Selected Factors Affecting Crude Oil Analysis of Distillers Dried Grains with Solubles (DDGS) as Compared with Milled Corn

With increasing production of distillers dried grains with solubles (DDGS), both fuel ethanol and animal feed industries are demanding standardized protocols for characterizing quality. AOCS Approved Procedure (Am 5‐04) was used for measuring crude oil content in milled corn and resulting DDGS. Selected factors, including sample type (milled corn, DDGS), sample origin (ethanol plant 1, 2, 3), sample particle size (original matrix, <0.71 mm, <0.50 mm mesh opening; the last two materials were obtained by grinding and sieving), solvent type (petroleum ether, hexane), extraction time (30, 60 min), and postextraction drying time (30, 60 min) were investigated by a complete factorial design. For milled corn, only sample origin and extraction time had significant effects (P < 0.05) on crude oil values measured, but for DDGS, besides those two factors, sample particle size, solvent type, and drying time also had significant effects. Among them, the particle size of DDGS had the most effect. On average, measured oil content in DDGS ranged from 11.11% (original matrix) to 12.12% (<0.71 mm) and to 12.55% (<0.50 mm). For measuring the crude oil content of DDGS, particle size reduction, 60 min of extraction, and 60 min of drying are recommended. Regardless of the underlining factors, the method was very repeatable (standard errors <0.05). The observed particle size effect on crude oil analysis of DDGS suggests the need for similar confirmations using other analytical methods.     

Measurement and Comparison of Glass Transition and Sticky Point Temperatures of Distillers Dried Grains with Solubles (DDGS) with Varying Condensed Distillers Solubles (CDS) and Drying Temperature Levels

Distillers dried grains with solubles (DDGS) is the main coproduct of the U.S. fuel ethanol industry and has significantly impacted the livestock feed markets in recent years. Particle agglomeration and subsequent flowability problems during storage and transport are often a hindrance, a nuisance, and expensive. This paper aims at characterizing the glass transition (T_g) and sticky point (T_s) temperatures of DDGS samples prepared with varying condensed distillers solubles (CDS) levels (10, 15, and 20%, wb), drying temperatures (100, 200, and 300°C), and moisture contents (0, 10, and 20%, db), and it discusses implications on DDGS flowability behavior. Distillers wet grains were combined with specified levels of CDS and dried in a convection‐style laboratory oven to produce DDGS. Subsequently, predetermined amounts of water were added to the DDGS to achieve desired moisture content levels. To determine T_g (°C), a differential scanning calorimeter was used, whereas T_s (°C) was determined through a novel technique with a rheometer. Results indicated high correlations between observed T_s and observed T_g (R² = 0.87) data for DDGS samples. Also, the empirical model for predicted T_g = f (drying temperature, CDS level, and moisture content) based on the Gordon–Taylor model showed favorable R² (0.74). Stickiness of DDGS increased with an increase in moisture content, indicating flow problems resulting from moisture. It was found that drying temperatures and CDS levels each had significant effects on T_g and T_s as well.