甜叶菊饮料的研制

以甜叶菊水提液为主要原料,配以柠檬酸、蜂蜜、食盐,调制出香味浓郁,色泽明亮,酸甜可口的甜叶菊饮料.通过单因素试验和正交试验,确定出甜叶菊水提液的提取工艺为:料水比1:150、浸提时间3 h、浸提温度60℃.结合感官评定结果,确定得出甜叶菊饮料的最佳配比为:甜叶菊水提液14%、柠檬酸添加量0.002%、蜂蜜添加量0.4%、食盐添加量0.05%.     

HPLC法快速测定甜叶菊中瑞鲍迪苷A

建立以甜叶菊叶片为原料,采用超声萃取法用体积浓度70%的乙醇对瑞鲍迪苷A进行提取,使用高效液相色谱仪检测甜叶菊样品液中瑞鲍迪苷A含量的方法。采用-NH2基柱(250 mm×4.6 mm,5μm),流动相为乙腈与水体积比80∶20,流速1.2 m L/min,紫外检测波长210 nm,进样量15μL。甜叶菊中瑞鲍迪苷A分别在纯水、体积浓度70%乙醇、80%乙腈中提取得率为10.25 mg/g、11.52 mg/g、13.49 mg/g,范围内线性关系良好相关系数R2=0.999 9。采用体积浓度70%乙醇对瑞鲍迪苷A进行提取,此方法安全有效、操作简单、定量准确。     

甜菊糖溶液活性炭脱色工艺研究

为解决甜菊糖产品的颜色问题,选用活性炭对甜菊糖苷溶液进行脱色,并对甜菊糖溶液的脱色率和甜菊糖的损失率进行研究。先通过单因素试验初步确定活性炭的添加条件及添加量,在脱色效果达到的情况下针对甜菊糖的损失率进行正交试验,对活性炭添加比例、溶液温度、吸附时间、pH值对溶液脱色率和甜菊糖损失率的影响进行试验,证明各种因素对脱色效果和甜菊糖损失的影响不同,活性炭的添加比例影响因素最大,其次是时间,再次是温度,影响最小的是pH值。单因素试验和正交试验确定最佳工艺条件为:最佳活性炭添加比例为1%,最佳温度10℃,最佳时间为0.5h,最佳pH值为7.0,产品吸光值达到标准要求,甜菊糖损失率为2.72%。     

Purification of stevia extract by chitosan precipitation and reversed-phase chromatography

To improve the shortness of the current purification technology of steviol glycosides (SG) extract, a two-step purification procedure consisting of chitosan precipitation and reversed-phase chromatography (RPC) was investigated. The impurity-to-SG ratio in the SG extract obtained from non-destructive soaking was 5:1 ~ 6:1. It was found that 80.90% of the impurities could be removed by RPC using 20% (v/v) ethanol solution as the eluent with a high SG recovery of 96.98%. When 25% ethanol was applied, the SG recovery was reduced to 71.23%. An adsorption test using D280 anionic resin suggested that the impurities were negatively charged; thus, chitosan was used to co-precipitate the impurities. An optimal decolourisation result of ~ 70% was obtained at 0.06 g·g⁻¹ (w/w, to solids in extract) chitosan addition, shaking at 28 °C for 1 h. Afterwards, the extract was further purified by RPC. The total removal rate of impurities was increased to 91.20%, and the SG recovery was 85.15%.     

Degradation kinetics of rebaudioside A in various buffer solutions

Rebaudioside A is a noncaloric high‐intensity sweetener extracted from Stevia rebaudiana. For it to be used in foods, rebaudioside A needs to be stable during processing and storage. This study evaluated the kinetics of rebaudioside A degradation in 0.02 and 0.1 m citrate and phosphate buffer solutions at pH 3, 5 and 7 stored at 20, 30 and 40 °C for 9 months. At pH 3 and temperatures less than 30 °C, degradation was slow (i.e. less than 6% loss in 6 months) and not affected by buffer type or buffer concentration. At pH 7, the degradation of rebaudioside A increased dramatically in phosphate buffer (losses of up to 25% in 6 months at 30 °C), while remaining relatively slow in citrate buffer (less than 5% loss). The degradation rates at pH 7 increased 2.6 times as the concentration of phosphate buffer increased. For optimum stability of beverages containing rebaudioside A, formulations with lower concentrations of citrate buffer stored at lower temperatures are recommended.     

Predictive modelling of the exposure to steviol glycosides in Irish patients aged 1-3 years with phenylketonuria and cow’s milk protein allergy

Children with Phenylketonuria (PKU) and severe cow’s milk protein allergy (CMPA) consume prescribed, specially formulated, foods for special medical purposes (FSMPs) as well as restricted amounts of normal foods. These patients are exposed to artificial sweeteners from the consumption of a combination of free and prescribed foods. Young patients with PKU and CMPA have a higher risk of exceeding acceptable daily intakes (ADI) for additives than age-matched healthy children. A predictive modelling approach has been adapted successfully to assess the additive exposure of young patients with PKU and CMPA to artificial sweeteners. Steviol glycosides (E960) are at various stages of regulatory approval for the various food categories in the EU but are not as yet permitted for use in products intended for young children. The aim of this study was to predict potential steviol glycoside exposure in young children with PKU and CMPA considering the potential for future provisions for the use of this sweetener. The recent introduction of steviol glycosides means that no exposure data are available for children with CMPA and PKU. Food consumption data were derived from the food consumption survey data of healthy young children in Ireland from the National Preschool and Nutrition Survey (NPNS, 2010–11). Specially formulated amino acid-based FSMPs are used to replace whole or milk protein foods and were included in the exposure model to replace restricted foods. The recommendations to ensure adequate protein intake in these patients were used to determine FSMP intake. Exposure assessment results indicated that the maximum permitted level (MPL) for FSMPs would warrant careful consideration to avoid exposures above the ADI. These data can be used to inform recommendations for the medical nutrition industry.     

甜叶菊水提取液的絮凝研究

研究了絮凝剂在甜叶菊提取液的澄清过程中的作用,选出最适絮凝剂,并对其澄清效果进行实验,确定了最佳的絮凝条件:温度为65~70℃,pH值为9~10,添加絮凝剂用量为4.5g/L,作用时间为40min左右。     

甜菊叶提取物清除DPPH能力的研究

以DPPH清除率为指标,研究甜菊叶提取物清除DPPH的能力.在单因素试验基础上,运用响应面法确定甜菊叶提取物的最佳提取条件为提取温度60.4℃、提取时间2.98 h、水料比15.4∶1.在此条件下得到的甜菊叶提取物对DPPH的清除率最大,88.78％;其清除DPPH的半数有效剂量EC50为32.3 μg/mL,自由基清除能力AE(1/EC50)为0.0310.研究表明,甜菊叶提取物具有一定的清除DPPH的能力.     

Modelling osmotic dehydration of lemon slices using new sweeteners

Lemon slices were osmotically dehydrated using the following healthy sweeteners as osmotic agents: tagatose, isomaltulose, oligofructose and aqueous extract of stevia. A kinetic study using a Fickian approach was performed, which also analysed the changes in water activity, total mass, mass of water and mass of soluble solids in lemon slices. The results showed that the greatest value of effective diffusivity (D_e) in osmodehydrated lemon slices was obtained from a combination of oligofructose and stevia [D_e = (10.2 ± 0.3) × 10^?9 m²·s^?1]. However, the level of water activity (a_w) reached with this syrup was the highest (a_w = 0.978 ± 0.004 after 1440 min) meaning that the product might be less stable. Additionally, isomaltulose favoured the total mass loss, whereas tagatose did the opposite. Finally, the syrup recommended for dehydrating lemon slices would be a combination of tagatose, oligofructose and aqueous extract of stevia as its D_e was similar to the value obtained when only oligofructose and stevia were used, but a_w values were lower.