超声场中L-抗坏血酸亚油酸酯的酶法合成及其抗氧化性研究

以L-抗坏血酸和人体必需不饱和脂肪酸亚油酸为原料,通过超声-酶法协同法合成L-抗坏血酸亚油酸酯,并通过条件优化确定了最佳合成条件:L-抗坏血酸10 mmol,亚油酸30 mmol,4分子筛5 g,叔戊醇50 m L,固定化脂肪酶(Novozym435)0.44 g,反应温度55℃,反应时间6 h,产率为35%。采用红外光谱、质谱及核磁共振碳谱对最终产物进行结构鉴定,确定终产物为L-抗坏血酸亚油酸酯。并对比了L-抗坏血酸亚油酸酯与抗氧化剂L-抗坏血酸、L-抗坏血酸棕榈酸酯和维生素E的抗氧化能力,结果表明,4者的清除羟基自由基、DPPH自由基的能力及还原能力大小为L-抗坏血酸L-抗坏血酸棕榈酸酯L-抗坏血酸亚油酸酯维生素E,油脂抗氧化能力强弱为L-抗坏血酸棕榈酸酯L-抗坏血酸亚油酸酯维生素EL-抗坏血酸。     

酶催化合成L-抗坏血酸棕榈酸酯的研究

L-抗坏血酸棕榈酸酯是一种新型的抗氧化剂,因其有安全、稳定、无毒的优越性,备受食品、医药、化妆品等行业的青睐。酶催化合成L-抗坏血酸棕榈酸酯的条件温和,不会对环境造成危害;酶催化反应的选择性强,使得产物单一,分离纯化过程较为简单。综述了L-抗坏血酸棕榈酸酯酶法合成的影响因素,如酶、反应介质、水含量、反应底物摩尔比、温度等。     

L-抗坏血酸棕榈酸酯的合成工艺研究

以L-抗坏血酸和棕榈酸乙酯为原料、H2SO4为催化剂,酯交换法合成L-抗坏血酸棕榈酸酯。研究了L-抗坏血酸与棕榈酸乙酯的摩尔比、催化剂浓度、反应温度、反应时间等工艺条件对产率的影响。工艺条件优化后,产率达到75%,产品质量符合GB16314-1996标准。     

L-抗坏血酸棕榈酸酯的化学合成工艺优化

详细研究了一种以L-抗坏血酸和棕榈酸为原料,浓硫酸为催化剂和溶剂,直接酯化合成新型抗氧化剂L-抗坏血酸棕榈酸酯的改进方法.通过实验改进了产物的精制方法,选用了更适宜的重结晶及洗涤试剂.同时考察了反应温度,反应时间及L-抗坏血酸与棕榈酸的物质的量比等关键因素对L-抗坏血酸棕榈酸酯产率的影响,确定了合成L-抗坏血酸棕榈酸酯的最佳工艺条件为:L-抗坏血酸与棕榈酸以物质的量比1 :1.35的比例,于25℃的反应温度下,在98%浓硫酸中反应40h后,反应混合物经过冰水洗涤、甲苯重结晶、石油醚洗涤,产率可达86.3%.该方法后处理工序简单,分离效果好,产率高,生产成本相对较低,更适宜工业化生产.合成的产品经熔点、红外光谱及质谱进行鉴定,符合GB16314-1996标准.     

三种抗坏血酸脂肪酸酯对共轭亚油酸的抗氧化性研究

本实验以葵花籽油为原料制备共轭亚油酸,以L-抗坏血酸、D-异抗坏血酸、棕榈酸和月桂酸为原料合成L-抗坏血酸棕榈酸酯、L-抗坏血酸月桂酸酯和D-异抗坏血酸棕榈酸酯,并研究上述酯对于共轭亚油酸的抗氧化效果。结果表明,添加0.02%、0.04%和0.08%的上述酯对于CLA具有明显且相似的的抗氧化作用,它们可以作为商品CLA的良好、安全的抗氧化剂。     

重组复合肉干贮藏过程中脂肪氧化控制研究

对重组复合肉干贮藏中的抗氧化进行研究。以天然抗氧化剂茶多酚结合VE和L-抗坏血酸棕榈酸酯为试验对象,运用三因素二次通用旋转设计,以POV值为检测指标,得到复合抗氧化剂最佳配比为:茶多酚0.139%、VE0.027%、L-抗坏血酸棕榈酸酯0.142%。3种天然抗氧化剂对重组复合肉干POV值的影响大小顺序依次为:L-抗坏血酸棕榈酸酯VE茶多酚。3种抗氧化剂之间,VE和L-抗坏血酸棕榈酸酯有明显的交互作用,茶多酚和VE以及茶多酚和L-抗坏血酸棕榈酸酯之间有一定的交互作用,但并不显著。     

最优混料设计法优化牡丹籽油的抗氧化剂配方北大核心CSCD

以过氧化值(POV)和丙二醛(MDA)值为指标,采用Schaal烘箱加速氧化法,研究了茶多酚棕榈酸酯、L-抗坏血酸棕榈酸酯、V_(E)、β-胡萝卜素4种脂溶性抗氧化剂对牡丹籽油氧化稳定性的影响,并采用最优混料设计法优化牡丹籽油的抗氧化剂配方。然后,通过Oxitest油脂氧化分析仪测定了添加复合抗氧化剂牡丹籽油的氧化诱导期。结果表明:添加量均为0.02%时,几种抗氧化剂的抗氧化能力大小为阳性对照(TBHQ)>茶多酚棕榈酸酯>L-抗坏血酸棕榈酸酯>V_(E)>β-胡萝卜素,通过最优混料设计法得到3组较佳的抗氧化剂配方,可以显著降低牡丹籽油的POV和MDA值;两个复合抗氧化剂组的氧化诱导期大于TBHQ组,分别为0.012%茶多酚棕榈酸酯+0.005%L-抗坏血酸棕榈酸酯+0.003%V_(E)、0.013%茶多酚棕榈酸酯+0.003% L-抗坏血酸棕榈酸酯+0.003%V_(E)+0.001%β-胡萝卜素。复合抗氧化剂能显著提高牡丹籽油的氧化稳定性。     

L-抗坏血酸棕榈酸酯在配方乳品中的应用

本文主要论述L-抗坏血酸棕榈酸酯在配方乳品中作用机理、使用方法、法律法规、应用效果等,及对L-抗坏血酸棕榈酸酯在乳品中发展趋势进行分析总结。     

抗坏血酸棕榈酸酯对油脂的抗氧化效果观察

抗坏血酸棕榈酸酯国外已用作食品抗氧化剂，１９７７年世界粮农组织已批准作为强化剂和食品抗氧化剂，本研究试用本实验室合成的抗坏血酸棕酸酯，进行了对食用同的抗氧化效果观察，结果说明合成的抗坏血酸棕榈酸酯具有明显的防止油脂氧化的作用，效果优于ＢＨＡ和茶多酚。     

2种抗氧化剂对α-葡萄糖苷酶的抑制作用

研究2种抗氧化剂(植酸、L-抗坏血酸棕榈酸酯)对α-葡萄糖苷酶的抑制作用,并通过分子对接技术探究2种化合物分别与酶的相互作用。植酸和L-抗坏血酸棕榈酸酯对α-葡萄糖苷酶IC_(50)值分别为(0.207±3.137)mol/L和(0.39±0.00838)mmol/L,L-抗坏血酸棕榈酸酯的抑制效果较好。植酸和L-抗坏血酸棕榈酸酯对α-葡萄糖苷酶的抑制类型为可逆混合型抑制、可逆竞争型抑制。分子对接结果显示,2种化合物能很好地与α-葡萄糖苷酶活性位点的氨基酸相互作用。L-抗坏血酸棕榈酸酯对α-葡萄糖苷酶的抑制表现出高效性,为酶抑制剂提供了理论基础,使其在食品中起到抗氧化作用并减缓糖尿病患者餐后血糖水平的升高。     

食用油中L-抗坏血酸棕榈酸酯含量测定方法研究

研究了直接滴定法测定食用油中L-抗坏血酸棕榈酸酯的方法.用甲醇对油样中L-抗坏血酸棕榈酸酯进行提取,对提取物在酸性条件下水解,用水解产物对2,6-二氯酚靛酚钠溶液进行滴定.该方法灵敏性高、准确可靠.     

Stability of vitamin C derivatives in topical formulations containing lipoic acid,vitamins A and E

The stability of ascorbyl palmitate, sodium ascorbyl phosphate and magnesium ascorbyl phosphate in topical formulations was investigated by direct reverse phase high performance liquid chromatography after sample dilution with a suitable buffer – organic solvent mixture. Ascorbyl palmitate, sodium ascorbyl phosphate and magnesium ascorbyl phosphate are derivatives of ascorbic acid which differ in hydrolipophilic properties. They are widely used in cosmetic and pharmaceutical preparations. According to the results, ascorbyl esters showed significant differences: sodium ascorbyl phosphate and magnesium ascorbyl phosphate are more stable derivatives of vitamin C than ascorbyl palmitate and may be easily used in cosmetic products.     

Enzymatic Synthesis of Ascorbyl Palmitate in Organic Solvents: Process Optimization and Kinetic Evaluation

This work is focused on the optimization of reaction parameters for the synthesis of ascorbyl palmitate catalyzed by Candida antarctica lipase in different organic solvents. The sequential strategy of experimental designs proved to be useful in maximizing the conditions for product conversion in tert-butanol system using Novozym 435 as catalyst. The optimum production were achieved at ascorbic acid to palmitic acid mole ratio of 1:9, stirring rate of 150 rpm, 70 °C, enzyme concentration of 5 wt.% at 17 h of reaction, resulting in an ascorbyl palmitate conversion of about 67%. Reaction kinetics for ascorbyl palmitate production showed that very satisfactory reaction conversions (∼56%) could be achieved in short reaction times (6 h). The kinetic empirical model proposed showed ability to satisfactory represents and predict the experimental data.     

不同贮存条件对海藻油氧化稳定性影响

以过氧化值为指标,考察空气、温度、光照等环境条件对海藻油稳定性影响,然后采用Schall烘箱加速氧化法,以POV和DHA含量为指标,通过L9(34)正交试验,从抗氧化剂TBHQ、VE、Vc棕榈酸酯优选海藻油复合抗氧化剂;及研究充N2保护、充N2保护结合添加抗氧化剂对海藻油稳定性影响。结果表明:空气,高温及光照均可显著加速海藻油氧化,降低海藻油稳定性;抗氧化剂TBHQ、VE、Vc棕榈酸酯能明显延缓海藻油氧化,影响顺序为Vc棕榈酸酯TBHQVE,最佳抗氧化剂组合为0.01%Vc棕榈酸酯+0.02%TBHQ+0.50%VE;充N2保护也能提高海藻油氧化稳定性,但效果比最佳复合抗氧化剂为差;充N2保护结合添加抗氧化剂能有效提高海藻油氧化稳定性。     

天然抗氧化剂的增效作用及其对花生油抗氧化效果研究

对迷迭香提取物、茶多酚、植酸、VE、抗坏血酸棕榈酸酯在花生油中的抗氧化性能和五种天然抗氧化剂相互之间的增效作用进行了研究。通过Rancimat法测定了添加各种抗氧剂的花生油的诱导时间,根据正交实验结果,各种天然抗氧化剂在组分中的主次因素为迷迭香提取物>茶多酚>植酸>抗坏血酸棕榈酸酯,优化得出天然抗氧化剂的复配配方为迷迭香提取物0.07%、茶多酚0.03%、植酸0.02%、抗坏血酸棕榈酸酯0.02%。此配方对花生油的抗氧化能力优于TBHQ。     

硅钼兰分光光度法测定微量L—抗坏血酸棕榈酸酯

研究了Ｌ－抗坏血酸棕榈酸酯在硅钼杂多兰形成反应中的影响，优选了测定条件，建立了测定其含量的硅钼分光光度法。本法显色体系的最大吸收波长在７２０ｎｍ，检测范围为０．２５－２．０ｍｇ／５０ｍｌ，相对标准偏差为０．４３％，回收率为９９．４％－１００．４％。     

抗坏血酸棕榈酸酯测定方法的比较

将改进滴定碘法应用于抗坏血酸棕榈酸酯含量的测定,并与碘滴定法和硅钼兰分光光度法进行了比较。结果表明,几种常用方法的测定结果略有差异,《食品添加剂手册》中的碘滴定法由于溶液混浊影响终点判断,导致结果偏高,重现性较差;硅钼兰分光光度法灵敏度较高,但需要试剂多,测定周期长;滴定碘法与GB 16314-1996中方法的测定结果在5%水平上无显著差异,但由于滴定碘法中淀粉指示剂变色更明显,易于判断滴定终点,方法的精密度更高,且简单快速,可用于抗坏血酸棕榈酸酯含量的日常检测。     

Effect of selected antioxidants on the stability of dehydrated mashed potatoes

The antioxidants TBHQ, alpha-tocopherol, Prolong P (rosemary, thyme, marjoram mixture) or ascorbyl palmitate were not found able to replace the antioxidant BHA in potato flakes production if stored for up to 24 months. Ascorbyl palmitate gave good antioxidative protection up to 16 months of storage, and also protected against carotenoid degradation better than the other antioxidants. The ascorbyl palmitate lost its antioxidative effect after longer storage.     

THE EFFECT OF ANTIOXIDANTS ON THE KEEPING QUALITY OF SPRAY-DRIED WHOLE MILK POWDER

Spray-dried whole milk powders containing either 0.01 per cent ascorbyl palmitate or this compound plus 0.01 per cent citric acid were prepared and their keeping quality under accelerated storage conditions at 37°C compared with control powders and powders containing dodecyl gallate. Ascorbyl palmitate alone afforded little protection against oxidative deterioration but together with citric acid considerably improved keeping quality. Although the addition of several antioxidants to edible oils and fats and butter intended for manufacture is permitted, their addition to milk powder is forbidden (Regulations, 1966). There are several reasons for this discrimination, the chief of which lies in the phenolic nature of the most effective antioxidants in spray-dried whole milk powder (Findlay, Smith & Lea, 1945). More recently ascorbyl palmitate has been used to delay the onset of oxidation in butter (Koops, 1964) and milk fat (Englelhardt & de Man, 1963). It seemed appropriate therefore, despite the different chemical composition and physical condition of the fat in butter and in milk powder, to examine its effectiveness in the latter product. In the quantity employed (0–01 per cent), ascorbyl palmitate would not present a risk to health, and its usefulness could probably be enhanced by the addition of a simple synergist such as citric acid, known to be effective with dodecyl gallate in lard (Lea, 1958).     

INTERACTIONS BETWEEN CARNOSINE AND SELECTED ANTIOXIDANTS IN GROUND TURKEY1

The antioxidant activity of 0.5% carnosine alone and in combination with selected antioxidants was investigated in uncooked ground turkey stored at 4C. A combination of tocopherol (0.05%) and carnosine exhibited additive antioxidant activity in salted and unsalted ground turkey. An ascorbyl palmitate (0.05%)/carnosine combination decreased TBARS 1.5 fold in salted ground turkey but was less effective in unsalted muscle (0.15% ascorbyl palmitate). Combining carnosine with STP (0.5%) or citrate (0.01 or 0.05%) did not increase the antioxidant activity of carnosine in ground turkey. These data suggest that tocopherol and ascorbyl palmitate could enhance the antioxidant activity of carnosine.