Effects of Microwave Blanching Treatment on POD Activity and Crispness in Capsicum frutescens L.

[Objective] To study the effects of microwave blanching treatment on POD activity and crispness in Capsicum frutescens L., and to compare the effects of microwave blanching method, normal blanching method, boiling water blanching and steam blanching. [Methods] In order to obtain the optimal condition for microwave blanching, response surface methodology was used to construct a quadratic regression model describing the effects of microwave power, microwave time and calcium lactate concentration on the POD activity in C. frutescens. [Results] The optimal technology was obtained based on central composite design： 525 W microwave power, 64.5 s microwave time, and 0.08% calcium lactate concentration. Under this condition, POD enzyme activity of C. frutescens was desactivated and crispness of C. frutescens was 68.77 N. [Conclusions] This research would provide references for the crispness protection and enzyme deactivation of C. frutescens.

Experimental Investigation on Simultaneous Dry Blanching and Drying of Mushroom Slices Using Microwave Enhanced Hot Air Heating System

The study evaluated the feasibility of using microwave enhanced hot air heating system for simultaneous dry blanching and dehydration of mushroom slices. The technology involves application of microwave energy at the beginning of dehydration process to inactivate enzymes as well as to remove a certain amount of moisture at the same time and then followed by hot air drying to complete the process. The study investigated effects of different processing parameters, i.e., microwave power level and exposure time on dehydration and quality characteristics of mushroom slices. Mushroom slices were pretreated with different microwave power levels of 240, 360 and 480 W for 1, 3 and 5 min before the hot air-drying. The optimum range of the microwave power level and pretreatment time was found to be 360 W, 3 min and 360 W, 1 min in obtaining the maximum and minimum levels of response parameters.

Effect of Pre-Gelatinization Conditions on the Total Oxalate Content and Techno-Functional Properties of Taro (Colocasia esculenta) Flour

Like most roots and tubers, taro (Colocasia esculenta) corms have a short shelf-life due to the high moisture content, which aggravates their post-harvest losses. They also contain high amounts of calcium oxalates, limiting their use in food applications. To help add value and diversify the use of taro corms as well as curb food losses, various strategies have been proposed, such processing of the corms into flour. This study aimed at evaluating the total oxalate content and techno-functional properties of taro flour as affected by the pre-gelatinization conditions (i.e., method and time). Pre-gelatinized taro flour was prepared by subjecting peeled and cleaned taro corms to roasting (190°C), boiling (100°C), and steaming (100°C) for 10 min, 20 min and 30 min, respectively, for each method, followed by drying at 55°C and milling. Generally, all the properties of flour were significantly affected by the pre-gelatinization conditions (P 0.05). The total oxalate content of the pre-gelatinized taro flour ranged from 33.26 to 76.90 mg/100g. Pre-gelatinization by boiling significantly reduced the oxalate content (56.7%), while roasting resulted in the least reduction (36.2%). The flour colour i.e. L*, hue, and chroma ranged from 38.47° - 70.30°, 42.64° - 69.43°, and 7.78° - 10.58°, respectively. Roasting resulted in flour with the largest L* (70.30°) and hue angle (69.43°). Boiling also resulted in flour with the highest bulk density (BD) (0.86 g/cm3) and the lowest water solubility index (WSI) (9.39%). Steamed flour had the highest water absorption index (WAI) (3.81 g/g), water holding capacity (WHC) (4.59 g/g), and swelling capacity (SC) (4.86 g/g). This study shows that pre-gelatinization (i.e. by boiling, steaming or roasting) significantly affects the total oxalate content and techno-functional properties of taro flour, which in turn influences its use in other food applications thus increasing the utilization and production of taro simultaneously.

Optimization of Blanching Time, Sodium Metabisulphite （Na2S205） Concentration and Processing Time on Vitamin C Content, Microbial Quality and Sensory Characteristics during Canning of Green Pepper （Capsicum sinensis） Using Response Surface Methodology

Response surface methodology and central composite rotatable design （CCRD） for K = 3 were used to investigate the combined effect of blanching time （0-1 min）, processing time （10-30 min） and sodium metabisulphite （Na2S205） salt concentration （0%-2%） on vitamin C content, hardness （texture）, microbial count and color intensity of green pepper （Capsicum sinensis） during canning. Blanching, processing time and sodium metabisulphite （Na2S205） salt concentration all had variable effects on the vitamin C, microbial quality and sensory characteristics of the canned green peppers. Significant （P 〈 0.05） interactions were noted between all the factors with high regression coefficients （78.7%-97.0%）. Increasing processing time caused significant decreases in vitamin C and microbial load of the product. However, salt concentration had only marginal and insignificant effect on the vitamin C content of the canned product. Sensory evaluation on the product showed that both the pre-processing conditions and of blanching and salt concentrations, and the processing time had varied effects on the color and hardness of the products. Hardness of the canned products generally decreased with increasing processing time and blanching time, while only minimal and insignificant effects were noted with blanching time. Increasing blanching time caused significant increasing retention of the dark green color of the peppers with only slight but insignificant increases noted with processing time, while increases in salt concentration consistently reduced the dark green color of the products. The optimum pre-processing and processing conditions that yielded products with high preference and consumer-acceptability were： blanching time of 0 min, processing time of 10 min and sodium metabisulphite concentration of 0.2%.

Research progress on properties of pre-gelatinized starch and its application in wheat flour products

Starch is the most abundant organic compound in nature,second only to cellulose.However,the conserved structure of native starches limits their properties and applications.Therefore,it is often necessary to modify them to obtain specific properties.As a common green and safe physical modification method,pre-gelatinization can improve the cold water solubility and swelling power of starch.The typical preparation methods of pre-gelatinized starch include spray drying,extrusion,and drum drying.Spray-dried pre-gelatinized starch still had good granule shape,but the increase of cold water solubility and cold paste viscosity was relatively small.Extruded and drum-dried pre-gelatinized starch showed serious structure destruction,significant increases in cold water solubility and cold paste viscosity,but relatively low hot paste viscosity.The properties of pre-gelatinized starch obtained by different methods are different,so do their effects on the quality of flour products.Wheat flour products,as one of the leading staple food for the people all over the world,play a vital role in people's daily life.With the improvement of people's living standards,more and more special flour products with unique features have received attentions of consumers and researchers.However,the sensory characteristics of special flour products are often inferior to traditional flour products,which limits its development.The unique functional characteristics of pre-gelatinized starch make it expected to play an essential role in the quality improvement of featured flour products.In this paper,the granule morphology,crystal structure,hydration and gelatinization properties of pre-gelatinized starch prepared by three common methods and their application in flour products were reviewed,which provides a theoretical basis for the application of pre-gelatinized starch in food industry.

Symbolic Representation of Blanche DuBois' s Tragic Fate in A Streetcar Named Desire

A Streetcar Named Desire is regarded as one of the most successful masterpieces of Tennessee Williams. An outstanding feature of the play is the wide use of symbolism. Symbols can be seen everywhere and even all the symbols in the play are con nected with the protagonist Blanche DuBois. Williams applies symbolism throughout the play to make Blanche's tragic fate more vivid to the readers. Her tragic fate lies in her clinging to illusion, thus she is bound to be abandoned by the harsh reality. There fore, the thesis attempts to give a comprehensive analysis of some specific symbols: symbols of illusion represented by the Chinese paper lantern and a paper moon, and symbol of reality represented by the light to further illustrate Blanche's tragically symbolic fate.

A World Destroys A World——On the Tragic Inevitability of Blanche

A Streetcar Named Desire, which has been widely accepted as the world-renowned work of Tennessee Williams, is a play with both of complexity and charm. After its publication, this play has attracted a lot of scholars and critics to interpret and study on it from the different aspects of views. The present paper attempts to certificate that the main character Blanche, in this play, who is live in a social background with the highlights of the conflict between the American southern plantation culture and the northern industrial civilization, suffers from the consistent change of her living space, her original world continually encounters destruction and invasion. Therefore, she has to step into another world; and she has to survive among different world. In addition, through digging into and interpreting the character Blanche, it investigates that people are of suffering and pain when they were in the process of adjusting and adapting themselves from their original world to their present- living world, and all Blanche's roads lead to a tragic.

Antioxidant Contents (Vitamin C) of Raw and Blanched Different Fresh Vegetable Samples

The study was aimed to determine the antioxidant contents and the effect of different blanching times (5 min, 10 min, 15 min and 20 min) on antioxidant contents of three different selected fresh vegetables. Three different types of vegeta- ble were used namely Amaranthus specie locally known as spinach, namely “tete”, (Celosia argentea), soko, (Solonum nodifiorum) and odu, (Telfeira occidentalis) were analyzed for their antioxidant contents. The analysis revealed that raw vegetables have the highest amount of antioxidant contents. Telferia occidentalis had the highest antioxidant content followed by Solonum nodifiorum. It was observed that blanching time had an adverse effect on the antioxidant contents of the blanched vegetables. The antioxidant contents of tete, soko and odu were significantly decreased (p < 0.05) after blanching.

Zinc Levels in Raw and Blanched Slenderleaf sp. (<i>Crotalaria ochroleuca</i>&<i>Crotalaria brevidens</i>) Indigenous Vegetables

An estimated 20% of the world’s population is at risk for zinc (Zn) deficiency. Micronutrient deficiencies are most prevalent in Africa and remain a major problem facing poor populations, whose impact is worsened by HIV/AIDS pandemic. Adequate zinc nutrition is essential for adequate growth, immunocompetence and neurobehavioral development. In Sub-Saharan Africa, Zn deficiency risk stands at 34.6% with 25.6% of its population having inadequate zinc intake. It is widespread in areas where diets lack diversity and it has been implicated as a contributing factor to stunting in approximately a third of children in low-income countries. In Kenya, it is a public health problem that about 50% of children under 6 years and 50% of women are affected. Zn deficiency rates are severe and pose severe consequences whose impact would translate into poor economic development and would set a vicious cycle effect that will take many generations to correct if left unchecked. It is important to examine zinc in the diet but its concentration in food varies depending partly on processing besides other factors. The objective of this study was to assess blanching as a food preparation method’s implication to Zn levels in vegetables. Blanching is a method where vegetables are dipped in boiling water for around two minutes and removed to avoid over cooking. Zn levels in slenderleaf sp. Indigenous vegetable commonly found in the Lake Victoria Basin region is not known. An experimental study was carried out to analyze zinc levels in raw and blanched slenderleaf sp. (Crotalaria ochroleuca & Crotalaria brevidens) vegetables. Results indicated that blanching reduces Zinc levels in slenderleaf vegetables, however, the reductions are not significant;the levels after blanching are still vital. It is, therefore, recommended to minimize blanching time in order to reduce loss of the vital nutrient in slenderleaf sp. vegetables.

A Study of Identity Crisis From the Perspective of Identity Negotiation Theory——Taking Blanche in A Streetcar Named Desire as Example

A Streetcar Named Desire unfolds the tragedy of a southern lady.The conflict betwixt southern Blanche and northern Stanley is the main contradiction in the play.In the end,Stanley drives Blanche crazy and sends her to an asylum.This paper attempts to analyze Blanche’s identity crisis from identity negotiation theory in cross-cultural communication,including identity security,identity inclusion,and identity predictability.Thereby it figures out that one who suffers hostile gazes from others in a strange environment,is unable to carry out an intimate and effective communication,which will eventually lead to a sense of loss and despair.This paper puts forward the methods to obtain identity recognition:be honest with others,be sure of oneself,and try one’s best to fit in the new environment,aiming to help people avoid identity crisis in interpersonal communication and establish a positive identity.

不同处理方式对黑加仑果汁出汁率及品质的影响

为探讨不同处理方式对黑加仑果汁出汁率及品质的影响,以解冻后的黑加仑冻果实为试验原料,研究热烫处理、酶解处理、超声处理对黑加仑果汁出汁率的影响,对比分析不同处理方式的出汁率、多酚含量、色度、总糖含量、蛋白质含量和抗氧化能力。结果显示:先经过80℃热烫处理15 s,然后在超声频率400 W、超声时间40 min、超声温度40℃条件下进行超声波处理,最后再利用0.2%复合酶(纤维素酶和果胶酶质量比1∶1)在50℃下酶解40 min,出汁率相较于直接解冻组提高了40.28%。

烫漂预处理对苹果干燥过程中微观结构及质构品质的影响

为提高烫漂预处理后苹果片的热风干燥效率和品质,本研究系统评估了热水烫漂与真空蒸汽脉动烫漂两种预处理方法对苹果片的宏观干燥效果。研究结果表明,在真空度0.07 MPa、烫漂2次和烫漂时间3 min条件下真空蒸汽脉动烫漂预处理提升了苹果片的复水比和质构品质,同时缩短了干燥时间。通过石蜡切片、显微观测、图像处理等技术对两种预处理方法干燥的苹果片微观结构进行研究,对比分析在不同烫漂条件(热水烫漂:温度和时间;真空蒸汽脉动烫漂:真空度、次数和时间)下苹果片的细胞横截面面积、周长、当量直径、细胞圆度、壁面粗糙度因子和孔隙率的变化规律。结果显示,随着漂烫温度的升高、时间的延长和烫漂次数的增加,苹果片的细胞会产生使后续干燥过程中水分加速蒸发的变化,从而缩短干燥时间。此外,通过多项式拟合建立了微观结构参数与复水比之间的关系方程。研究结果可为揭示真空蒸汽脉动烫漂预处理对苹果微观结构和宏观品质影响的机理提供理论依据。

响应面法优化秋葵预制菜真空蒸汽脉动烫漂工艺

将真空蒸汽脉动烫漂技术应用到秋葵预制菜处理中,以色差、脆度、蛋白质含量、感官评分为指标,分别进行蒸汽烫漂单因素试验和四因素三水平响应面试验,通过响应面法分析烫漂真空度、烫漂温度、烫漂时间和脉动次数对综合评分的影响,建立二次回归数学模型,对秋葵预制菜真空蒸汽脉动烫漂工艺参数进行优化。结果表明:各秋葵预制菜品质的影响顺序为烫漂时间>脉动次数>烫漂温度>烫漂真空度。最佳工艺参数:烫漂真空度0.04 MPa,烫漂温度108℃,烫漂时间70 s,脉动次数2次,此工艺条件下,色差值6.36,脆度1824.68,蛋白质含量1.66%,感官评分31,综合评分0.8795分。研究结果可为预制秋葵菜品的加工提供参考。

蒸汽烫漂与热风干燥箱流场优化设计及仿真

农产品的烫漂与干燥是农产品加工的关键技术。农产品蒸汽烫漂与热风干燥箱是集烫漂与干燥一体的新型农产品绿色保质低碳智能干燥技术装备。农产品蒸汽烫漂与热风干燥箱内部流场均匀性直接影响着农产品烫漂与干燥效果。为提高其内部速度均匀性与温湿度均匀性,同时减少冷凝现象发生,采用计算流体力学(computational fluid dynamics,CFD)方法建立蒸汽烫漂与热风干燥箱模型,对其送风方式和送风口数量进行研究。结果表明:侧送侧回的送风方式在速度场以及温湿度场的均匀性总体优于上送下回,能量利用系数提高约18%,箱内壁面冷凝面积小于上送下回。仿真研究表明,当送风口数量为4个时,箱内的温度场和相对湿度场均匀性更好,能量利用系数最高。试验表明,蒸汽烫漂与热风干燥箱的试验值和仿真值最大温度偏差为2.3℃,相对湿度误差不超过1.3%,误差在合理范围内,仿真结果可靠,研究结果可为农产品低碳智能干燥新技术的研究提供参考。

干制前处理对切分杏褐变内源酶及色泽的影响

目的:采用4种方式对切分杏干制前进行处理,研究对多酚氧化酶、过氧化物酶及色差的影响,确定切分杏干制前处理的最佳条件。方法:以切分、去核的赛买提杏为材料,探究热水、蒸汽漂烫、微波处理、浸硫处理的杏果内源酶活性、失活率和色差的变化,研究4种最佳前处理条件下对杏果色差(干制前后)的影响,并进行色差各指标间的相关性分析。结果:热水、蒸汽漂烫下酶活性随热烫时间的增加而降低,100℃、90 s为该处理的最佳条件;微波处理下内源酶失活率随功率的增大、时间的延长而增加,最佳条件为50%(350 W),5 min,失活率分别为92.83%、91.05%;浸硫处理下酶失活率分别为98.73%、16.35%。结论:热水漂烫和浸硫处理结合热风干燥在温度为60℃时色泽保持较好,而蒸汽漂烫和微波处理选择40℃为宜。通过相关性分析得出热水漂烫对杏干色泽损伤较大,硫处理可有效保持杏干色泽。

宣木瓜药材烫晒法有效物质含量变化及干燥工艺优化

目的:以山楂酸、齐墩果酸、熊果酸含量来阐述宣木瓜药材烫晒法的科学内涵,以期确定宣木瓜最适宜的产地加工工艺和关键技术参数。方法:采用反相高效液相色谱法测定设计不同的干燥方法制备不同的样品。结果:通过对烫晒、生晒和直接烘干等9个不同干燥方法处理的宣木瓜样品进行含量测定,发现最佳干燥成药材的方法是烫晒;宣木瓜山楂酸、齐墩果酸和熊果酸分别是0.0076、0.5259和0.2571;发现最佳干燥成饮片的方法为烫晒后烘48 h用水润48 h再在60℃烘48 h的方法,其主要化学成分含量高,山楂酸、齐墩果酸和熊果酸分别是0.0071、0.4425和0.291。结论:本研究为宣木瓜药材烫晒法科学内涵及干燥工艺提供了试验理论依据。

海带漂烫-盐渍加工过程中碘形态含量变化规律

通过测定漂烫水、漂洗水、盐渍水以及剩余海带中碘离子(I^(-))、碘酸根(IO_(3)^(-))、一碘酪氨酸(mono-iodotyrosine,MIT)和二碘酪氨酸(diiodotyrosine,DIT)4种碘形态的含量,研究海带漂烫-漂洗-盐渍过程中碘形态的溶出规律。鲜海带、漂烫海带、一次漂洗海带和二次漂洗海带I^(-)含量在1689.41~8753.24 mg/kg,IO_(3)^(-)含量在42.67~442.00mg/kg之间,MIT和DIT含量分别在698.22~861.90mg/kg和123.97~158.67mg/kg之间。其中漂烫过程I^(-)、MIT和DIT溶出率最高,分别为(64.38±2.99)%、(19.35±0.97)%和(6.55±0.53)%。随着海带加入量的增大,除漂烫水的DTT外,所有水体中I^(-)、MIT和DIT含量整体上呈先增大后趋于平稳的趋势,所有水体中IO_(3)^(-)含量均呈上升趋势。随海带漂烫颗数增加,I^(-)溶出率先降低后基本保持不变,与鲜海带相比,第1颗盐渍海带的I^(-)含量降低(80.72±2.66)%,碘主要以I^(-)的形式释放到水体中,并且在漂烫过程中释放量最大。

不同脱皮方式对榄钱品质的影响

以鲜榄钱为原料,采用沸水漂烫、蒸汽热烫和80℃超声辅助3种方式脱皮处理,探究不同脱皮方式对榄钱脱皮率、色泽、质地等物理性质,可溶性蛋白质、淀粉、可溶性糖等营养成分及总叶绿素、可溶性单宁、抗坏血酸、类黄酮、总酚等化学成分变化的影响,结果表明:沸水漂烫法脱皮率最高;沸水漂烫与蒸汽热烫均能起到护色效果;80℃超声辅助脱皮对硬度、脆度、黏性、咀嚼性影响最小;沸水漂烫脱皮的榄钱抗坏血酸含量和总酚含量最高,可溶性糖含量与蒸汽热烫脱皮无显著差异;蒸汽热烫脱皮的可溶性蛋白质含量和类黄酮含量最高;80℃超声辅助脱皮的榄钱总叶绿素含量最高,脱涩效果最好;3种脱皮方式处理的榄钱淀粉含量均无显著差异。经加权分析可知,采用沸水漂烫脱皮的榄钱品质优于蒸汽热烫和80℃超声辅助脱皮的榄钱品质。

哈密瓜幼瓜佐餐小菜护绿和保脆工艺研究

针对哈密瓜幼瓜佐餐小菜在加工过程中易出现褐变、软化等问题,以哈密瓜幼瓜为原料,通过单因素试验结合正交试验对NaHCO_(3)漂烫条件、护绿剂(柠檬酸、D-异抗坏血酸钠和植酸)和保脆剂(CaCl_(2)、乳酸钙和海藻酸钠)配方进行优化,并对哈密瓜幼瓜佐餐小菜的Δa∗、PPO活性、POD活性、硬度等进行分析。结果表明:最佳漂烫条件为NaHCO3质量分数0.08%、漂烫时间60 s;最佳护绿剂和保脆剂配方为柠檬酸质量分数0.3%、D-异抗坏血酸钠质量分数0.4%、植酸质量分数0.3%、CaCl_(2)质量分数0.4%、乳酸钙质量分数0.6%和海藻酸钠质量分数0.3%。在此配方下浸泡20 min,哈密瓜幼瓜佐餐小菜的Δa∗为0.93,硬度为5188.75 g,PPO活性为11.35 U/g,POD活性为8.49 U/g,感官评分为89.19分,且该佐餐小菜色泽均匀,爽脆可口,品质较佳。经过30 d贮藏,哈密瓜幼瓜佐餐小菜的感官评分维持在84~89分,具有较好的贮藏稳定性和市场推广潜力。

传统广式烤鸭烫皮工艺中蛋白质变性与品质关系分析

以樱桃谷鸭为原料,研究了烫皮过程温度变化和烫皮前后的水分、色泽、蛋白变性、显微结构等变化规律。结果表明:90~95℃,5 s的烫皮程度已达到传统烫皮感官要求,鸭皮表面温度到达80℃以上,皮内温度达到45℃以上;晾皮失水速度差异不显著(P>0.05),与鸭皮中的蛋白质变性程度测定(DSC)实验结果一致,显示该温度下蛋白发生变性、聚集。进一步探究90℃烫皮条件,结果表明,90℃烫皮7 s(90℃-7 s)晾皮3 h(含水量22.01%)比90℃烫皮9 s(90℃-9 s)晾皮4 h(含水量20.52%)膨化效果更好;DSC数据也显示90℃-7 s蛋白质热聚集程度大于烫皮5 s(P<0.05),90℃-9 s的样品蛋白质存在凝胶结构。综上所述,传统广式烤鸭鸭皮脆化与膨化的核心是控制烫皮后鸭皮中蛋白质处于变性聚集的状态及此状态下皮的水分含量,研究结果为探究传统广式烤鸭烫皮机理并为其烫皮工艺改良提供理论支持和技术参考。