Analysis of cooling curve to determine the end point of freezing

The cooling curve method used for the measurement of freezing point of food is further analyzed to explore whether it can be used to identify the end point of freezing or glass transition. In this method, slope of the cooling curve is determined and plotted as a function of time to identify the end point of freezing (T′_m). Initially, the slope is decreased and then reached a minimum value, which is identified as the nucleation of ice. Then the slope is increased until the end point of freezing. The end point of freezing is identified when the slope starts to decrease from its highest value or plateau. Sucrose solutions and starch gels were used to measure its T′_m in identifying validity of the proposed method. The measured values of T′_m by the proposed method is very close to the literature values.     

PROPERTIES OF A SUCROSE SOLUTION REUSED IN OSMOTIC DEHYDRATION OF APPLES

ABSTRACT

The reuse of concentrated solutions for osmotic dehydration (OD) must be clearly understood to guarantee the economic viability of this process. This study was carried out to determine the modifications that a sugar solution undergoes when used 20 times during the OD of apple cubes by measuring the evolution of its different physico-chemical properties. Before beginning a new OD process, the syrup's mass was readjusted lo its initial value by the addition of crystallized sucrose. An increase of 3.4% in the mass of the syrup was observed after each OD process. The pH of the syrup stabilized after the third reuse, while its acidity, reducing sugars, and electrical conductivity stabilized after six reuses to values similar to those of the osmodehydrated apples. Under the specific conditions of this experiment, neither acid hydrolysis nor enzymatic hydrolysis in the sugar solution was observed. Microbiological analysis of syrup showed high levels of yeast and molds only after the 15th use. Progressive increases in turbidity, browning, and insoluble solids in the syrup were observed during the course of its utilization.     

A comparison of the hydrolysis of sweet potato starch with β-amylase and infrared radiation allows prediction of reducing sugar production

The apparent reaction rate constants (k) of the reaction that generates reducing sugar (presented as mg maltose equivalents) from raw sweet potato starch by using β‐amylase were determined by varying enzyme concentration, starch concentration and pH. The Arrhenius plot of the k‐value reached a peak at approximately 86 °C; the activation energy and frequency factor were also determined. Moreover, the amount of reducing sugar produced in sweet potato heated by infrared irradiation was estimated by using the values of k and the kinetic parameters. The calculated amounts of reducing sugar produced generally agreed with the experimental values. These results indicate that the amount of reducing sugar produced in heat‐treated sweet potato can be predicted by the methodology described in this study.     

提高转化糖浆质量的研究

转化糖浆的质量受多种因素的影响 ,通过实验 ,确定了制备转化糖浆的最佳工艺条件 ,经工厂生产使用 ,证明这些选择是可行的     

METHODS FOR THE ANALYSIS OF C4 TO C10 FATTY ACIDS IN BEER,WORT AND CARBOHYDRATE SYRUPS

Methods have been developed for the analysis of C4 to C10 fatty acids in beer, wort and carbohydrate syrups. The methods are based on the adsorption of the aqueous samples on to solid supports followed by removal of the fatty acids with organic solvents. The methods are suitable for routine batchwise analysis of fatty acids and the reproducibility of the analysis and recoveries of the acids are generally good. Problems often encountered with analysis of C4 to C10 fatty acids and possible solutions are also discussed.     

HAP模板法制备有序多孔炭材料及其电性能研究

利用纳米羟基磷灰石(HAP)为模板,麦芽糖(MO)为碳源,通过固化、炭化等过程,制备有序多孔炭材料(HAP-C)。采用扫描电镜(SEM)、N2吸/脱附以及电化学分析方法等对HAP-C进行物理表征和电化学性能分析。结果显示,HAP/MO的质量比对HAP-C的比表面积、孔结构以及电化学性能有着重要影响。制备的多孔炭呈海绵骨架结构,具有较高的比表面积(1 073.5 m2/g)和大的孔容(3.28 cm3/g)。电化学测试显示,当HAP/MO的质量比为1∶2(HAP-C-1∶2)时,具有较高的质量比电容,在扫描速度为5 m V/s时,质量比电容达198 F/g;倍率性能测试显示,当电流密度增大25倍时,质量比电容保持率为58.0%,显示出良好的倍率性能。     

固定床色谱分离超高麦芽糖浆中的糊精

糊精是妨碍麦芽糖结晶和晶浆过滤的主要因素。从精制超高麦芽糖浆中除去糊精的有效方法之一是固定床色谱分离法。通过实验研究,证实色谱分离法可以有效地除去糊精,麦芽糖的单程收率可达50%,浓缩糖浆的结晶速度加快,晶浆过滤变得相对容易。结晶麦芽糖的纯度超过98%。     

Hydrolysis of topinambur (Jerusalem artichoke) fructans by extracellular inulinase of Kluyveromyces marxianus var. bulgaricus

Extracellular inulinase from Kluyveromyces marxianus var. bulgaricus catalysed the hydrolysis of pure inulin and the extracts of fresh and dried topinambur (Jerusalem artichoke). At an enzyme concentration of 10 IU g^?1 of substrate the three substrates were hydrolysed respectively to 65–3, 77–3 and 83–9%. The relationship between the extent of hydrolysis, reaction time and enzyme concentration was studied and a kinetic model of hydrolysis was derived.     

降低绵白糖中5-羟甲基糠醛含量的研究

研究了绵白糖生产用转化糖浆制备过程中影响5-羟甲基糠醛（5-HMF）形成、蔗糖转化率以及糖浆色值的因素,并通过正交试验,优化出酸法水解蔗糖生产转化糖浆的工艺条件,即糖浆锤度为75°B,pH值1．5,温度75℃,反应时间60min。在优化条件下每百克转化糖浆含有3．02mg5-HMF,糖浆色值为93．9IU,蔗糖转化率达到91．5％。     

糖浆气浮工艺条件的研究

研究了糖浆气浮工艺中磷酸加入量、预灰pH值、硫熏强度、硫熏中和pH值等因素对糖浆脱色率和气浮效果的影响,并对几种因素进行正交试验研究,确定了最佳气浮工艺条件的组合方案,结果表明最佳工艺条件是磷酸加入量为800mg/kg,预灰pH7.5,硫熏强度12ml,硫熏中和pH8.5。