速冻山药热烫工艺研究

对山药的速冻预处理工艺进行了研究。在实验中,以清水为热烫液,通过测定Vc的含量、可溶性固形物的含量、过氧化物酶和多酚氧化酶的活性这四个指标来确定最佳的热烫时间和温度。同时对经热烫和不经热烫两种不同处理的山药在冻藏过程中的色泽变化进行了评价。研究表明,速冻山药必须进行热烫处理以使酶失活。最佳的热烫时间和温度为60s和90±1℃。      

烫漂预处理结合不同干燥方式对刺梨活性物质及抗氧化活性的影响

目的 探究不同干燥方式结合烫漂预处理对刺梨中主要活性物质及抗氧化活性的影响。方法 以刺梨鲜果为对象, 首先对其烫漂预处理, 再分别采用微波干燥、热风干燥、真空冷冻干燥进行初加工, 再测定刺梨的褐变度及其中游离酚、结合酚、黄酮、维生素C (vitamin C, VC)、多糖含量, 最后评价刺梨对2,2’-联氮-二(3-乙基-苯并噻唑啉-6-磺酸)二铵盐阳离子自由基清除能力、1,1-二苯基-2-三硝基苯肼自由基清除能力。结果 与热风干燥和微波干燥相比, 真空冷冻干燥条件下刺梨中游离酚[(139.26±2.94) mg/g]、多糖[(21.47±0.41) mg/g]和VC [(18.87±0.86) mg/g]的含量相对较高; 但是烫漂处理显著降低了真空冷冻干燥中刺梨的结合酚和多糖含量, 还升高了刺梨的褐变度。而烫漂联合热风干燥、微波干燥处理, 不仅实现了刺梨的护色, 还显著减少了刺梨中VC的流失。结论 刺梨在真空冷冻干燥后品质最佳, 但应避免过多的预处理联合加工; 而相比工艺成本较高的真空冷冻干燥, 热风干燥和微波干燥辅以烫漂也能使刺梨产品达到较好的外观品质。该研究结果可为较高价值的刺梨初加工乃至精深加工提供参考。     

Comparative evaluation of instant 'poundo' cocoyam (Colocasia esculenta) and yam (Dioscorea rotundata) flours produced by flash and cabinet drying

Cocoyam, an important staple crop especially among the low-income earners in tropical regions of the world, is highly underutilised for industrial applications. This study investigates the nutritional, colour and rheological properties of instant flours (‘poundo’) from two cultivars of Colocasia esculenta (white-NCe010 and purple-NCe003) and Dioscorea rotundata (var. Oginni), and sensory attributes of doughs prepared from reconstituted flours. Tubers were processed into instant flours using cabinet and flash drying methods. Significant differences (P < 0.05) in the proximate and mineral composition and pasting properties of flours were found. Sensory panellists rated reconstituted poundo yam (8.17–8.20) and white cocoyam (7.50–7.95) higher than purple cocoyam (6.60–7.10) meals. Influence of drying method on sensory characteristics of flours was not significant. Instant poundo cocoyam and yam flours could serve as novel convenience and ready-to-eat food products which could contribute to increasing the commercial and industrial application options for these underutilised tubers beyond their present basic use.     

烫漂方式对苹果脆片褐变和多酚及其抗氧化活性的影响

为阐明烫漂方式对热风干燥苹果片品质特性的影响,采用热水、蒸汽和微波对苹果片进行烫漂处理,测定苹果片在烫漂和干燥过程中的色泽、多酚及其抗氧化活性的变化情况。结果表明,热水烫漂苹果片的干燥时间最短,为270 min;不同烫漂方式对苹果片褐变有显著影响(P<0.05),其中热水烫漂的苹果片色泽变化最小,微波烫漂的苹果片色泽最差;与鲜样相比,烫漂方式对苹果片还原糖含量影响较小;干燥过程中微波烫漂的苹果片中产生的5-羟甲基糠醛含量最高,蒸汽烫漂次之,热水烫漂最低;苹果片经热水烫漂和干燥后维生素C损失率分别为34%和52%,而蒸汽烫漂和微波烫漂的苹果片中维生素C损失率较小;热水烫漂的苹果脆片总酚含量最高,达到11.82 mg GAE/g DW;苹果片经烫漂处理后游离多酚和结合多酚单体无显著性变化(P>0.05),但干燥后,所有样品中结合多酚单体含量均显著提高(P<0.05)而游离多酚单体的含量无显著性变化(P>0.05),表明3种烫漂方式都有利于多酚单体的保留;多酚抗氧化能力实验表明烫漂和干燥后苹果片中结合多酚抗氧化活性有显著性变化(P<0.05),其中热水烫漂的苹果...     

Anti-Fenton reaction activity of three taxa of water yam (Dioscorea alata L.)

In the present study, we compared the anti‐Fenton reaction activity of three taxa of water yam (Dioscorea alata L.): DS2, TN2 and PSY [D. alata L. var. purpurea (Roxb.) M. Pouch]. Anti‐Fenton reaction activity was evaluated by measuring the damage inflicted on calf thymus DNA by copper ions combined with hydrogen peroxide with the use of an ethidium bromide binding assay and agarose gel electrophoresis. We found that extracts of tuber pulp from all three taxa of yam had significant anti‐Fenton reaction activity. The protection pattern of the three tuber pulp extracts was similar to that of EDTA, a typical divalent metal ion chelator, which displayed a significant protection lag‐phase. With the use of thin‐layer chromatography, we found that a common, major ansialdehyde‐sulphuric acid stained spot (possibly a polysaccharide mucilage) with an R_f of 0.09 may be the most likely contributor to the anti‐Fenton reaction activities of the yam tuber extracts investigated. The present study identifies the mechanism of the health benefit of the Dioscorea family. The copper‐chelating and absorbing capability of yam tuber pulp extracts may be useful in functional screening.     

Genetic diversity of organoleptic properties in water yam (Dioscorea alata L)

Improving the food quality of yams (Dioscorea spp) is an ongoing challenge to yam breeders and researchers. Forty accessions of D alata were evaluated for the suitability of their tubers for the preparation of two dominant food forms (boiled and pounded) as part of an effort to identify potential parents for use in genetic improvement. Trained panellists were presented with randomised, replicated and coded samples of boiled yam tuber pieces and asked to rate them for mealiness, colour, wetness, softness and taste. The sensory attributes considered for pounded yam (dough from boiled and pounded tubers) were consistency, colour, sheen, smoothness, stickiness, elasticity and hardness. Ratings were based on hedonic scales. Cluster analysis revealed groupings of accessions into eight and nine similarity clusters for boiled yam and pounded yam respectively. The mean scores for general preference were regressed on individual attribute scores. Mealiness, colour and taste were important in the general preference for boiled yam. Consistency, colour and stickiness determined the general preference for pounded yam. Of the accessions, 67% were identified as being suitable for preparation as a boiled vegetable, while 55% were assessed to be good for pounded yam, based on the respective quality attributes evaluated. © 2003 Society of Chemical Industry     

微波干燥温度和物料厚度对铁棍山药片品质的影响

以新鲜铁棍山药为材料,采用光纤插入物料中心在线控制微波干燥的物料温度、厚度的方式进行干燥,通过单因素试验法进行干燥加工处理,采用索氏提取法提取样品中的多糖,同时采用苯酚硫酸比色法测定经不同干燥参数制备的样品的多糖得率,以自制作微波干燥系统进行重量记录以及物料的温度控制,色差计测样品色泽进而评价干燥的效果。结果发现:在控制不同的物料温度且厚度为5 mm时,最高的多糖得率的物料温度为50℃且此时白度值最大,但所需干燥时间最长;物料温度为60℃时改变物料的厚度,得到最高的多糖得率的物料厚度为5mm。综合比较可知,实际微波干燥生产时以温度60℃且物料厚5mm干燥的效果更好。     

怀山药酵素粉的制备及抗氧化作用

通过单因素和正交试验优化怀山药酵素液的发酵条件,利用喷雾干燥技术制备怀山药酵素粉,分析怀山药酵素原液喷雾干燥前后超氧化物歧化酶(superoxide dismutase,SOD)活性的变化,最后利用邻苯三酚自氧化法和H_2O_2/Fe体系反应法测定其对超氧阴离子和羟自由基的清除能力。结果表明,怀山药酵素液的最佳发酵工艺参数为糖浓度12%、接种量6%、发酵时间30 h、发酵温度42℃,该条件下怀山药酵素液SOD的活性为15. 35 U/mL。喷雾干燥后的怀山药酵素粉SOD活性没有显著的变化(P 0. 05)。抗氧化活性试验结果显示,怀山药酵素粉复原液能够有效地清除超氧阴离子和羟自由基。     

淮山微波真空干燥工艺优化及功能活性评价

以多糖含量、白度、复水率为评价指标,通过单因素与二次旋转正交试验优化了淮山微波真空干燥工艺,并对其功能活性成分和抗氧化能力进行了评价。得到最佳工艺条件为干燥温度55℃、切片厚度3 mm、真空度-0.08MPa,此条件下的淮山干燥产品多糖含量为(4.12±0.08)%、白度为(78.04±0.82)、复水率为(223.29±1.31)%,其清除DPPH自由基、羟自由基、超氧阴离子自由基的半抑制率浓度(IC_(50))分别为(18.61±0.11),(19.86±0.15),(21.06±0.14)mg/mL,多酚、黄酮、尿囊素含量分别为(0.71±0.05),(1.32±0.04),(6.86±0.08)mg/g。微波真空干燥产品质量好,活性成分损失少,具有较强的抗氧化能力。     

Spray drying of the soybean extract: Effects on chemical properties and antioxidant activity

Recent findings that many human chronic diseases are associated with oxidative stresses have instigated the search for dietary antioxidants. Isoflavones, a special phenolic group found in soybean, have been found to act as antioxidant in some model systems. The aim of this work was the evaluation the effects of spray drying on the chemical and biological properties of soybean extract. The total polyphenol contents in the concentrated soybean extract (CSE) and spray dried soybean extract (SDSE) were determined by Folin-Ciocalteau method and HPLC was utilized for the quantification of the genistein, active compound used as a chemical marker. The evaluation of antioxidant activity of CSE and SDSE was assessed by the hydrogen-donor ability to 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The results indicated that the inlet gas temperature showed significant effect on the total polyphenol, protein and genistein contents of the dried extracts. The SDSE obtained this work showed high antioxidant activity, opening perspectives for its use as food additive and/or ingredient.     

Phenolic compounds and antioxidant activity are differentially affected by drying processes in celery,coriander and parsley leaves

Convective drying (CO) is the most common technique for drying herbs, although it may diminish phenolic compounds content. Microwave drying (MW) has been suggested as an alternative, although its effects on phenolic compounds remain to be explored. The aim of this study is to compare the effects of different convective temperatures (40, 80 and 120 °C) and microwave powers (100, 500 and 1000 W) on drying time, polyphenols classes (HPLC-DAD) and antioxidant capacity in celery, coriander and parsley leaves. Microwave procedure reduced drying time (MW: 3 h–7 min; CO: 25–1.5 h) resulting more effective than CO. Increasing temperatures led to an initial decrease in total phenolic content (TPC) and antioxidant activity followed by an increase, potentially by the release of bound phenolic acids. Regarding MW, the highest polyphenol content was generally observed at 500 W, probably due to the hydroxycinnamic acid's rise. Antioxidant capacity was similar at 500 and 1000 W. There was a good agreement between TPC and antioxidant capacity. Consequently, MW seems a good alternative to reduce drying time. However, the maintenance or improvement of phenolic activity depends on the food matrix. Indeed, the best drying system and conditions to preserve phenolic compounds were variable depending on the herb type: celery (CO at 40 °C), coriander (both CO at 40 °C and MW at 500 W) and parsley (MW at 100 W).     

超声和烫漂预处理对红薯叶热风干燥的影响

采用超声、烫漂两种方式对红薯叶进行热风干燥前的预处理,研究超声时间、超声功率、超声温度和烫漂时间、烫漂液ZnAc_2与EDTA-2Na质量比、烫漂温度对红薯叶热风干燥后叶绿素、复水性、色差、干燥特性、能耗以及微观结构的影响。结果表明:超声处理的最佳工艺为超声时间10min、超声功率300W、超声温度40℃,经超声预处理的红薯叶干燥效率较高,皱缩率低,组织结构较为完整;烫漂处理的最佳工艺为烫漂时间60s、烫漂液ZnAc_2与EDTA-2Na质量比2:1、烫漂温度80℃,经护色液烫漂处理干燥后的红薯叶复水率、叶绿素含量和色泽都稍高,质构紧密均匀,细胞开孔率高,总能耗低。     

干燥方式对淮山全粉品质的影响

通过对热风干燥、变温压差干燥、喷雾干燥和真空冷冻干燥4种干燥方式所得淮山全粉的物理特性和营养成分进行分析测定,研究了不同干燥方式对淮山全粉品质的影响。结果表明:在物理特性方面:变温压差干燥、喷雾干燥和真空冷冻干燥淮山全粉色泽好,而热风干燥褐变严重;真空冷冻干燥淮山全粉的堆积密度显著低于其他干燥方式;喷雾干燥淮山全粉的吸水性显著低于其他干燥方式,溶解度显著高于其他干燥方式,且颗粒特征较好。在营养成分方面:4种淮山全粉的营养成分均有不同程度的差异,热风干燥淮山全粉的维生素B1含量显著低于其他干燥方式;喷雾干燥淮山全粉的蛋白质、氨基酸和尿囊素含量均较高;说明喷雾干燥淮山全粉的营养成分损失较小。喷雾干燥法干燥淮山全粉品质较好,且所需干燥时间短,生产效率高、成本低。      

山药催化式红外干燥特性及色泽评价

为了缩短山药干燥时间、减少色泽劣变,本文研究了山药在催化式红外干燥中不同烫漂前处理时间（0.5、1.0、2.0、3.0 min）、切片厚度（0.5、0.8、1.0、1.5 cm）和红外辐射距离（30、36、42、48 cm）条件下干燥曲线和产品色泽。研究表明:切片厚度和辐射距离对干燥时间有显著影响（p>0.05）,切片厚度0.5 cm下干燥时间比切片厚度1.5 cm缩短约47.73%,辐射距离30 cm下干燥时间比辐射距离48 cm缩短约46.67%,减少切片厚度、缩短辐射距离能够有效提高干燥效率;烫漂时间（1.0、2.0、3.0 min）对山药干燥时间没有显著影响（p>0.05）;山药整个干燥过程属于降速干燥,根据菲克第二定律,山药干燥水分有效扩散系数在1.4770×10-9⁵.5043×10-9m2/s。不同条件下山药干燥后白度值（Whiteness index,WI）为56.19⁷8.78。通过对山药干燥时间和色泽的综合分析,优化的烫漂和干燥工艺为:热水烫漂1² min,切片厚度1.0 cm,辐射距离30 cm,干燥时间约160 min,WI值约为77.36。本研究为山药催化式红外干燥加工提供理论依据和技术支持。      

胡萝卜的气体射流冲击烫漂与干燥试验研究

以胡萝卜为研究对象,研究气体射流冲击的烫漂湿度及干燥条件对胡萝卜复水特性和色泽的影响。结果表明,烫漂湿度和干燥温度对复水率的影响较大,胡萝卜的复水率在较高的烫漂湿度时较高,但随温度的升高而降低。烫漂湿度对色差值的影响最大,其次是干燥温度,干燥风速对色差值的影响不大。烫漂湿度越大,复水后色泽越佳。     

山药淀粉的特性及应用研究

详细介绍了山药淀粉的制备与组成,并对其物理化学特性和加工特性,包括淀粉的颗粒形态、溶解度和膨胀度、凝胶特性等进行了较全面的综述.     

Gelling properties of extruded yam (Dioscorea alata) starch

Yam (Dioscorea alata) starch was pregelatinized in a single screw extruder. Response Surface Methodology was used to study the effect of extrusion variables: feed moisture (18, 21, 24%), extruder temperature (120, 150, 180°C) and die diameter (3, 4, 5 mm) on cold viscosity, gel-forming capacity and retrogradation of extruded starches. Cold viscosity was higher from starch samples processed at higher moisture and die diameter, at lower temperatures. Slurries of the extruded starch (8%, w/v, d.b.) formed opaque and firm gels. Higher values for gel strength were found in samples extruded at highest and lowest moistures at intermediate temperature and increasing die diameter. Gels of extruded starch had lower retrogradation values than non-extruded gelatinized starch after one and two weeks storage at refrigeration temperature. Prediction equations for the studied functional properties can be used in selecting processing conditions for specific food applications.