番茄果实不同发育阶段糖分组成和含量变化的研究初报

对番茄果实不同发育阶段果穗各部位组织中的糖分组成和含量变化进行测定，结果表明：在番茄果实不同生育期，不同部位组织中的糖分组成和含量是不同的。花梗和果柄维管束中主要含有蔗糖，而果实的其他部位中则主要含有葡萄糖和果糖。葡萄糖和果糖在核桃期含量最低，至果实成熟期含量达到最高。在果皮细胞和果实维管中葡萄糖和果糖含量较高，果胶质和隔壁中含糖量较低。     

1,6-二磷酸果糖溶液基本性质

研究了 1 ,6-二磷酸果糖溶液在不同酒精浓度和 p H下的溶解度以及不同 1 ,6-二磷酸果糖溶液的浓度、温度及 p H下的粘度 ,并给出了浓度对粘度的关联式。实验发现 ,溶液的温度和 p H对溶液的粘度有很大的影响 ,因此升高溶液的温度和降低溶液的 p H有利于改善溶液的传质状况和结晶条件 ,为 1 ,6-二磷酸果糖的结晶新体系的研究提供依据。     

填充床电催化反应器制备甘露醇研究

自制了DSA电极为阳极,纯镍板为阴极馈电极,阳离子交换膜为隔膜,阴极室填充雷尼镍催化剂的填充床电化学反应器。在雷尼镍填充床电化学反应器中电还原果糖合成甘露醇,考察了雷尼镍用量、阴极馈电极电流强度、果糖起始浓度、槽电压、搅拌速度、支持电解质等因素对电还原反应的影响。结果表明:在无支持电解质存在下,当果糖起始浓度为2.0mol/L,阴极室中雷尼镍填充质量与果糖质量比为3,阴极馈电极电流强度为7A,通电量为2F/mol,槽电压为6V,搅拌速度150r/min,果糖的转化率可达97.68%,采用填充床电化学反应器制备甘露醇,反应效率高,可简化后续产品的提纯过程。     

Effects of pH on Caramelization and Maillard Reaction Kinetics in Fructose-Lysine Model Systems

ABSTRACT: The nonenzymatic browning reactions of fructose and fructose-lysine aqueous model systems were investigated at 100 °C between pH 4.0 and pH 12.0 by measuring the loss of reactants and monitoring the pattern of UV-absorbance and brown color development. At all the pH values tested, the loss of fructose was lower in the presence than in the absence of lysine. And, in lysine-containing fructose solution, the sugar disappeared more rapidly than the amino acid. Lysine was moderately lost below pH 8.0. Caramelization of fructose, which accounted for more than 40% of total UV-absorbance and 10 to 36% of brown color development, may therefore lead to overestimating the Maillard reaction in foods.     

Determination of simple sugars,malic acid and total phenolic compounds in apple pomace by infrared spectroscopy and PLSR

The aim of this work was to develop a fast, versatile, inexpensive and environmentally safe analytical method to quantify simple sugars, malic acid and total phenolic compounds in apple pomace, considering its potential use as a raw material with value instead of as an industrial waste. Diffuse reflectance infrared spectroscopy (DRIFTS) measurements of twenty‐six samples of apple pomace were analysed by partial least squares regression (PLSR), using several signal pre‐processing methods. Multivariate models developed with four to five latent variables (LVs) and based in the MIR (mid‐infrared) region had good prediction for the determination of sucrose, fructose, malic acid and total phenolic compounds, with average errors between 3.9% and 6.6%. By contrast, glucose was better determined by models developed in the NIR (near‐infrared) region and using six LVs, yielding an average error lower than 7.4%. These results confirmed the feasibility of the multivariate spectroscopic approach as an alternative for expensive and time‐consuming conventional chemical methods.     

Increased rate of lipase-catalyzed saccharide-fatty acid esterification by control of reaction medium

Through proper selection of initial conditions and control of the reaction medium composition, a productivity rate over 10-fold higher than that previously reported was achieved for lipase-catalyzed fructose-oleic acid esterification. From a screening process, tert-butanol (t-BuOH) was selected as the most effective solvent for cosolubilizing fructose and oleic acid during the initial stage of the reaction. A t-BuOH concentration of 0.35–0.55 w/w produced the highest rate and extent of reaction at 60°C. Neither water addition nor removal applied to initial reaction materials improved the rate. Since both fructose-oleic acid mono- and diester promoted higher fructose solubility than either oleic acid or oleic acid/t-BuOH mixtures, t-BuOH was not needed during the latter stage of the reaction. Also, the presence of t-BuOH hindered the removal of water by free evaporation. Thus, complete removal of t-BuOH during the middle-to-latter stage of reaction was found to enhance the reaction rate. In addition, the introduction of fructose to the reactor in small batchwise increments accelerated the reaction. The monoester to diester ratio decreased during the initial and middle stages of the reaction owing to the disappearance of t-BuOH, but increased slightly during the later stages presumably because of the ester formation.     

Thermodynamic measurement and modeling of hydrate dissociation for CO2/refrigerant + sucrose/fructose/glucose solutions

Hydrate dissociation conditions were studied for the CO₂/refrigerant + sucrose/fructose/glucose solution systems as a continuation of previous work into alternate separation technologies for the sugar manufacturing industries. Experimental data were measured following the isochoric pressure method for the CO₂ + sucrose/fructose solution systems. The refrigerants studied for the modeling purpose were R410a, R507, R134a, and R22 using literature data. The pressure and temperature ranges for the experimental data measured here were (1.80–4.10) MPa and (276.6–282.6) K, respectively, with solutions measured in the composition range between 0 to 0.40 mass fraction sucrose and fructose. Several models following the Van der Waals–Platteeuw solid solution theory were developed to predict the hydrate dissociation conditions of CO₂/fluorinated refrigerant in the presence of sucrose/fructose/glucose solutions. The modeling results provide a satisfactory representation of the experimental data, with AARD(P) % model errors in the overall range between 0.03% and 4.40%.     

Effects of Boiling and Storage on Dietary Fibre and Digestible Carbohydrates in Various Cultivars of Carrots

The influence of boiling and storage on dietary fibre and digestible carbohydrates was investigated in eight different carrot cultivars. The content of total dietary fibre was in the range 252–291 g kg^-1 DW and was generally at the higher end for the early cultivars and at the lower end for the late ones. During storage, there was a decrease in the soluble fibre content in all cultivars and generally an increase in insoluble fibre. Following boiling, the loss of dietary fibre varied considerably between cultivars. After storage, the loss could be correlated to the average root weight of the carrot cultivars. The total content of glucose, fructose and sucrose was rather similar in the various cultivars, whereas their individual distribution differed. Storage had generally minor influence on the sugar content, except in the cultivars Amarant and Bull. On boiling, the loss was solely dependent on the initial sugar concentration. After storage the loss increased, which could be related to the lower dry matter content. The choice of cultivar and storage time is important in interpreting analytical data from carrots and is probably of similar significance in other vegetables when studying effects of heat treatment. © 1997 SCI.