l-薄荷脑层式熔融结晶过程及杂质的影响

采用层式熔融结晶技术对l-薄荷脑结晶过程进行了研究,考察不同温度梯度和薄荷酮的添加量对l-薄荷脑晶体生长速率的影响,并使用Avrami方程进一步研究其熔融结晶过程动力学行为。结果表明,在相同的熔融液温度下,冷剂温度越低,即温度梯度越大,l-薄荷脑晶体的生长速率越快;薄荷酮的添加会导致l-薄荷脑晶体生长速率的降低,且其添加量越多对l-薄荷脑晶体生长的抑制作用越强。Avrami方程可以较好地描述l-薄荷脑熔融结晶的前期过程,各情况下拟合得到的Avrami指数值接近,均在0.8左右,表明薄荷酮的添加未明显改变l-薄荷脑晶体的生长方式,且各种情况下l-薄荷脑晶体均以一维(针状)的生长方式生长。     

L-抗坏血酸棕榈酸酯对椰子油结晶行为的影响

以椰子油作为模型，利用结晶动力学方程、X-射线衍射（XRD）分析、热力学分析以及偏振光显微镜（PLM）观察等方法研究了L-抗坏血酸棕榈酸酯（L-AP）对椰子油结晶行为的影响。结果表明：L-AP提高了椰子油的结晶速率，改变了晶体成核和生长机制；L-AP以“晶种”的方式诱导椰子油的结晶，对其结晶过程产生了促进作用； L-AP没有改变椰子油晶体的晶型以及堆积方式，却增加了晶体纳米片层的厚度；随着L-AP添加量的增加，晶体结构更加致密有序。     

棕榈油等温结晶动力学

通过差示量热扫描法研究了24℃棕榈油的等温结晶过程。研究不同结晶速率、不同结晶温度（Tc）下的热行为,并通过Avrami方程计算出基本结晶参数。结果表明,等温结晶过程中以1、5、10、20 K/min的结晶速率观察结晶峰,随着速率的升高,峰更高、更尖锐,峰面积变大。在-20⁸℃不同的结晶温度下等温结晶所得结晶峰表明,随着温度的升高,结晶时间缩短,多重峰中部分会在温度升高过程中消失。在温度高于-6℃时,4个结晶峰消失1个;温度继续升高至2℃时,热曲线只剩下2个,直至6℃时峰变为一个独立峰。所得结晶参数可看出,随着结晶温度的升高,结晶速率降低。      

椰子油与棕榈硬脂油物理混合及其结构脂熔融特性的比较研究

油脂的相容性和非等温结晶性质对油脂的口感品质有重要影响。为了拓宽椰子油和棕榈油的应用范围,开发以其为主要原料的专用油脂产品,本文通过GC-MS测得椰子油和棕榈硬脂油不同混合比例的总脂肪酸和Sn-2位脂肪酸组成,研究了脂肪酸组成与熔融特性的相关性,再利用脉冲核磁共振仪研究了椰子油和棕榈油的相容性,并用差式扫描量热仪对二者按一定比例混合的复配体系和酶法制备结构脂的非等温结晶行为进行研究。结果表明:不同比例酶法制备结构脂中Sn-2位的月桂酸含量(12.35~46.72%)明显高于物理混合油(5.86~30.75%)。该复配体系整体上存在一定程度的共晶现象,在较高温度(25~45℃)时,相容性较好。在非等温结晶过程中,在同一降温速率条件下,随着椰子油比例的增加,2倍链长的β′型晶体,转变为低熔点的3倍链长β′晶型。     

干法分提制备液化猪油工艺

为使猪油在常温下可呈液态,采用两次干法分提的方法对结晶温度、冷却速率、养晶时间分别进行单因素和正交试验：将猪油加热平衡后以一定的速率冷却至一定的温度,在晶核形成后经过特定的时间进行养晶使晶体形成,最后通过离心法使固液相分离;同时探讨搅拌方式和一次干法分提的平衡温度对分提效果的影响。结果表明：一次分提最佳条件为结晶温度21℃、冷却速率2℃/h、养晶时间14h;二次分提最佳条件为结晶温度16℃、冷却速率0.5℃/h、养晶时间30h;一次分提液化猪油的得率可达81.59%,二次分提液化猪油的得率可达79.93%。经二次干法分提得到的猪油在室温下可呈液态。     

棕仁原油在温度梯度场中的结晶动力学研究

以棕仁原油为研究样品,借助于自行开发的试验装置,研究样品在不同温度梯度场中的结晶行为,得出晶体生长速率Rg以及结晶效率Y的变化规律并观察其晶体形态;同时借助于Avrami方程对试验数据进行模拟,得出确切的结晶动力学参数,如晶体形态n、结晶速率k、结晶半周期t1/2等,并采用双对数图对Avrami方程的拟合程度进行检验,以确定Avrami模型的适用性。     

湿面老化动力学研究

利用差示量热扫描仪测定在不同储藏温度条件下(-4、15、25、35℃)的湿面老化焓,应用Avrami模型描述淀粉在回生过程中的结晶行为,研究了贮存温度对湿面淀粉老化速率和淀粉结晶成核方式的影响。通过对模型线性回归后得到结晶速率常数k和Avrami指数n。结果表明,在本实验贮存温度区间内,湿面淀粉的老化结晶速率k随着贮存温度的升高而逐渐减小;在-4～15℃的贮存温度区间内,Avrami指数n均小于1,表明其结晶方式是瞬间成核,在25～35℃区间内,1相似文献   

湿面老化动力学研究

利用差示量热扫描仪测定在不同储藏温度条件下（-4、15、25、35℃）的湿面老化焓,应用Avrami模型描述淀粉在回生过程中的结晶行为,研究了贮存温度对湿面淀粉老化速率和淀粉结晶成核方式的影响。通过对模型线性回归后得到结晶速率常数k和Avrami指数n。结果表明,在本实验贮存温度区间内,湿面淀粉的老化结晶速率k随着贮存温度的升高而逐渐减小;在-4～15℃的贮存温度区间内,Avrami指数n均小于1,表明其结晶方式是瞬间成核,在25～35℃区间内,1相似文献   

12度棕榈油超声强化结晶分提工艺研究

目的 改良棕榈油干法分提工艺,开展12度棕榈油超声强化结晶分提工艺研究。方法 以24度棕榈油为原料,采用三因素三水平正交试验,考察不同油样温度、超声功率、超声时间下,超声处理对棕榈油脂晶成长初期的平均粒径、液油产率和主要理化指标(熔点、碘价、酸值、过氧化值)的影响。结果 在棕榈油分提过程的关键结晶点施加超声波对棕榈油结晶行为有显著影响,超声波功率越强,脂晶成长初期的平均粒径越小,液油产率越高。在油样温度17.5℃时,以135 W超声30 s可达到最高液油产率37.63%。分提的各液油产品的熔点、碘价、酸值、过氧化值等理化指标均符合生产企业标准或国家标准要求;各液油产品的熔点与碘价之间没有明显的相关性,熔点和碘价与液油得率之间也没有明显的相关性;超声处理没有引起液油产品游离脂肪酸含量的变化,对液油产品的过氧化值也无不良影响。结论 在优化的超声处理条件下,超声强化结晶工艺能实现良好的固液分离,液油产率比对照组提高45.06%,且主要理化指标均符合企业品控标准。     

椰子油基胆盐脂质体的制备及工艺优化

目的：提高椰子油的水溶性,扩展其在食品工业中的应用范围。方法：根据椰子油脂溶性的特点,以大豆卵磷脂—脱氧胆酸盐作为壁材,椰子油为芯材,利用薄膜分散法制备椰子油胆盐脂质体。考察了大豆卵磷脂/脱氧胆酸盐比、PBS/无水乙醇比、样脂比、超声时间、水化时间和水化温度等影响因素对包封率的影响,并优化了椰子油胆盐脂质体的制备工艺条件。结果：其最优制备工艺为大豆卵磷脂/脱氧胆酸盐比2.53、样脂比0.56、水化温度64.7 ℃,椰子油胆盐脂质体的包封率为58.09%。结论：薄膜分散法制备椰子油胆盐脂质体包封率较好,可以提高椰子油的水溶性。     

Avrami法研究微量司盘85对棕榈油结晶动力学的影响

采用差示扫描量热仪（differential scanning calorimetry,DSC）分析棕榈油及其与司盘85混合物的等温结晶及熔融行为,通过Hoffman-Weeks法计算出样品的平衡熔点。采用Avrami方程进一步研究样品的等温结晶动力学,从而得到与结晶动力学相关的参数。结果表明：DSC分析显示司盘85可明显降低棕榈油的结晶率和成核速率。通过Hoffman-Weeks法和Avrami方程求得的温度数据具有良好的线性关系,表明Avrami方程适用于棕榈油结晶过程的研究,但在结晶后期出现偏离。拟合得到的Avrami指数（n）在2.37～2.77之间,可知样品二维和三维晶体生长同时存在;结晶速率（k）和半结晶时间（t1/2）随着添加剂的添加均变小。     

Crystallization properties of palm oil by dry fractionation

The crystallization, thermal, physical, chemical and morphological properties of palm oil were investigated using differential scanning calorimetry, polarized microscopy, pulsed nuclear magnetic resonance (NMR) and gas chromatography (GC). The palm oil was fractionated into various stearin and olein (with iodine values (IV)>63) fractions by means of a dry fractionation process. During the cooling sequence, samples were taken at regular intervals from the crystallizer and analyzed for their iodine values, chemical compositions and physical behaviour. The physical properties of olein and stearin fractions, such as cloud point, slip melting point and solid fat content, were dependent on the crystallization temperatures. The iodine values of the olein and stearin fractions increased as the crystallization temperature decreased and both fractions started to cloud at lower temperatures. The palmitic acid content of stearin and olein fractions was also affected by the crystallization temperatures.     

Development of chemically interesterified healthy coconut oil blends

Edible vegetable oil blends, such as coconut:linseed; coconut:safflower; coconut:sunflower; coconut:rice‐bran oils; in the ratio of 70:30 and 60:40 v/v and pure coconut oil (CNO) were interesterified using sodium methoxide 0.5% and subsequently refined to prepare nutritionally superior flowable CNO blends which remained liquid even at sub‐zero temperatures. The slip melting point of chemically interesterified fats could not be determined as they are liquified just after removing from freezing chamber in comparison with the slip melting point of 21.5–26.5 °C for their uninteresterified counterparts. These interesterified fats were liquid and flowable at 6 °C for more than 4 h in a cooling chamber and their solidification temperature ranged between ?2.0 and ?5.5 °C. Free fatty acids showed an increasing trend from 0.35% to 2.0% resulting in decrease in triglycerides After refining these oil blends showed values similar to their controls. However, iodine value of interesterified and uninteresterified oils were close to each other. Differential scanning calorimetry showed the onset of crystallisation at lower temperatures and lower solid fat content for interesterified fats. A nutritionally superior combination of CNO blend which is flowable at low temperature could be prepared.     

椰子的成熟度和贮藏品质的介电评估方法

利用介电弛豫谱方法对椰子成熟度以及椰子水的贮藏温度和时间进行了研究。由于椰子水中蔗糖的质量浓度与成熟度有关,因此利用椰子水-蔗糖混合溶液的电导率与蔗糖质量浓度的依存关系,可以判断椰子的相对成熟度。低频电导率谱结果显示,椰子水的电导率随着贮藏时间的延长而逐渐降低,并且室温条件下贮藏时,电导率降低得更快,说明低温更利于椰子水的贮藏。此外,微波段弛豫实际包含了自由水分子和结合水分子两部分贡献,其中结合水分子弛豫强度的变化可以反映椰子水品质的改变。椰子水不同时间的颜色变化说明,开壳椰子水在室温条件下可以保存1 d,而在冰箱中可以保存3 d。     

Properties of high-oleic palm oils derived by fractional crystallization

ABSTRACT:  High-oleic palm oil (HOPO) with an oleic acid content of 59.0% and an iodine value (IV) of 78.2 was crystallized in a 200-kg De Smet crystallizer with a predetermined cooling program and appropriate agitation. The slurry was then fractionated by means of dry fractionation at 4, 8, 10, 12, and 15 °C. The oil and the fractionated products were subjected to physical and chemical analyses, including fatty acid composition, triacylglycerol and diacylglycerol composition, solid fat content, cloud point, slip melting point, and cold stability test. Fractionation at 15 °C resulted in the highest olein yield but with minimal oleic acid content. Due to the enhanced unsaturation of the oil, fractionation at relatively lower crystallization temperature showed a considerable effect on fatty acid composition as well as triacylglycerol and diacylglycerol composition of liquid fractions compared to higher crystallization temperature. The olein and stearin fractionated at 4 °C had the best cold stability at 0 °C and sharper melting profile, respectively.     

MONITORING THE ADULTERATION OF VIRGIN COCONUT OIL BY SELECTED VEGETABLE OILS USING DIFFERENTIAL SCANNING CALORIMETRY

The crystallization and melting enthalpy of virgin coconut oil adulterated with palm kernel oil (PKO) and soybean oil (SBO) were studied by using differential scanning calorimetry. Virgin coconut oil was spiked separately with PKO and SBO from 2% to 40% (w/w) of adulterant oils. Fatty acids of all oils were determined to complement the differential scanning calorimetry data. The heating curve of SBO-adulterated samples showed the adulteration peak appearing at the lower temperature region at 10% adulteration level. Regression analyses using stepwise multiple linear regression were used to predict the percentage adulterant with R ² of 0.9490. PKO-adulterated oils did not show any adulteration peak but demonstrated a gradual decrease in the peak height of the major exothermic peak.

PRACTICAL APPLICATIONS

An alternative method for detection of adulteration based on differential scanning calorimetry in virgin coconut oil is presented. Application of differential scanning calorimetry is rapid, does not require sample preparation and does not involve use of solvents or toxic chemicals.     

植物蜡及液态植物油构建油凝胶的物性研究

以米糠蜡、棕榈蜡、蜂蜡3种食品级植物蜡为凝胶剂,葵花籽油、油茶籽油、亚麻籽油、棉籽油为基料油,构建了植物油基油凝胶,系统分析了油凝胶的外观形态、持油能力、微观结构、硬度、晶型及熔化结晶行为。结果发现,棕榈蜡基油凝胶涂抹性能优良,蜂蜡基油凝胶在三者中具有最高的持油能力。微观分析表明,米糠蜡形成的油凝胶晶体结构较为清晰,呈细长的针状;蜂蜡形成的油凝胶晶体结构最为细小,呈细小的针状;棕榈蜡形成的油凝胶,针型细密,并呈絮状结晶。晶体密度及样品硬度均随凝胶剂质量分数增加而增加。油凝胶的晶型与凝胶剂质量分数、基料油的种类无太大关系,主要取决于凝胶剂的种类。熔化结晶行为表明,凝胶剂种类相同时,随着其质量分数的增加,油凝胶的结晶/熔化峰值温度均升高。     

加热条件下大豆油中TBHQ的挥发、转化规律及其对大豆油品质的影响

以大豆油为加热介质,采用烘箱法研究不同加热温度条件下叔丁基对苯二酚（tertiary butylhydroquinone,
TBHQ）的损耗规律、损耗途径及对大豆油品质的影响,并对其在加热条件下的挥发和转化产物进行了详尽的研
究。结果表明：较低加热温度条件下TBHQ的抗氧效果较好,高温条件下其抗氧化性能明显减弱;TBHQ的损耗随
着加热温度的升高而增加;高温加热条件下大豆油中的TBHQ主要以挥发形式损耗,同时会有少量TBHQ转化为叔
丁基对苯二醌（2-tert-butyl-1,4-benzoquinone,TQ）和其他物质,其中,主要转化产物是TQ;另外,挥发物中伴随
有少量的TQ等转化产物和分解产物。     

零反式脂肪酸涂抹脂基料油酶法酯交换制备研究

利用固定化脂肪酶催化棕榈油硬脂和葵花籽油进行酯交换反应,制备零反式脂肪酸涂抹脂基料油。考察了不同搅拌速度、反应温度、酶加量和反应时间对酯交换反应的影响,并对反应前后油脂的熔点、晶型和结晶速率等结晶行为进行了分析和比较。结果表明:搅拌速度200 r/min,酶加量6%,在70℃下反应3 h为最优的酯交换条件。酯交换产物的熔点大幅下降,晶型主要以β’晶型为主,结晶速率变慢。