Photochemical interaction of ascorbic acid with riboflavin, nicotinamide and alpha-tocopherol in cream formulations

The present work is based on a study of the effect of some vitamins such as riboflavin (RF), nicotinamide (NA) and alpha‐tocopherol (TP) on the photodegradation of ascorbic acid (vitamin C) (AH₂) in oil‐in‐water cream formulations using a UV irradiation source. A UV spectrophotometric and the official iodimetric methods have been used for the assay of AH₂ in cream formulations. These methods have been validated in the presence of RF, NA and TP before their application to the creams. The recoveries of AH₂ in the creams are in the range of 90–95% and the reproducibility of the method is within ±5%. The apparent first‐order rate constants (k_obs) for the photodegradation of AH₂ in the presence of RF, NA and TP, individually, in the creams have been obtained. The second‐order rate constants for the photochemical interaction of AH₂ and the vitamins RF, NA and TP have been determined from the plots of k_obs for AH₂ photolysis versus the individual vitamin concentration along with the values of k₀ from the intercept on the vertical axis. The values of k₀ in the presence of RF and NA are lower than those of the k_obs, indicating that these vitamins act as photosensitizers for the degradation of AH₂ in creams. On the contrary, the value of k₀ in the presence of TP is higher than that of the k_obs, suggesting a stabilizing effect of this vitamin on the degradation of AH₂ in creams. The mode of interaction of the individual vitamins with AH₂ on photolysis has been discussed.     

采用褪色光度法测定维生素C

在硫酸介质中,利用维生素C（L-VC）对高锰酸钾的褪色效应建立了褪色光度法测定维生素C的方法。在最大吸收波长为526nm,表观摩尔吸收系数为6.71×103L·mol-1·cm-1时,维生素C浓度在0～20μg/ml范围内与溶液的褪色程度（△A）服从比尔定律,最小检出限为0.91mg/L,相对标准偏差为0.54%～0.96%,回收率为92.5%～101.8%。     

抗坏血酸及抗坏血酸棕榈酸酯的稳定性研究

研究了光照、温度、pH、氧化剂、抗氧化剂、金属离子、糖类对抗坏血酸（AA）及抗坏血酸棕榈酸酯（AP）稳定性的影响。结果表明：目光、高温、氧化剂、中性及碱性环境都会不同程度地对两者造成损失,其中抗坏血酸棕榈酸酯的稳定性要强于抗坏血酸。维生素E可以有效保护AP。铜离子、铁离子、锰离子会引起AA较大的损失,锰离子对AP稳定性有显著影响。糖类对两者稳定性基本没有影响。     

气体射流冲击干燥对山楂抗坏血酸、还原糖、总酸及总黄酮的影响

为了提高山楂的干制品质,在通过单因素试验探讨不同因素对山楂营养成分影响的基础上,采用风温、风速和喷嘴高度三因素进行二次通用旋转组合设计优化实验。单因素实验表明,不同条件的气体射流冲击干燥对山楂的Vc、还原糖、总酸及总黄酮含量均有不同程度的影响。并且通过三因素的二次通用旋转组合设计优化试验得到了不同的优化方案。其中Vc含量的优化方案为:温度55.8℃,风速11 m/s,喷嘴高度148.0 mm,物料盒宽度130 mm。总酸含量的优化方案为:温度54.9℃,风速11.0 m/s,喷嘴高度137.0 mm,物料盒宽度130mm。还原糖含量的优化方案为:温度54.7℃,风速10.5 m/s,喷嘴高度139.2 mm,物料盒宽度130 mm。     

Antioxidant capacity of different fractions of vegetables and correlation with the contents of ascorbic acid, phenolics, and flavonoids

The antioxidant capacity of different fractions of 17 vegetables were analyzed using ferric reducing antioxidant power assay (FRAP assay) after water and acetone extractions. The contents of ascorbic acid, phenolics, and flavonoids were determined and their correlations with FRAP value were investigated. The results showed that the peel or leaf fractions of vegetables were stronger than the pulp or stem fractions in antioxidant capacity based on total FRAP value. Lotus root peel was the highest and cucumber pulp the lowest in total FRAP value among the vegetable fractions analyzed. All water extracts were higher in FRAP value than the acetone extracts. The FRAP value was significantly correlated with the contents of ascorbic acid, phenolics, or flavonoids in water extracts, in which the phenolics contributed most based on multivariate regression analysis. We conclude that different vegetable fractions were remarkably different in antioxidant capacity. The phenolics are responsible mostly for the antioxidant capacity of vegetables in vitro.     

冻干甜椒贮藏过程中抗坏血酸及还原糖的变化

以冻干甜椒为材料,研究其在不同贮藏温度下抗坏血酸及还原糖含量的变化,揭示其品质变化的情况。分别采用斐林试剂比色法、固蓝盐B分光光度法测定抗坏血酸及还原糖的含量。结果表明,在贮藏期间,冻干甜椒中的抗坏血酸和还原糖含量逐渐减少,并且随储藏温度上升减少的速率增大。     

不饱和单甘酯在低脂冰淇淋中的应用

分别将商品饱和单甘酯和另一种富含亚油酸的不饱和单甘酯作乳化剂添加到全脂冰淇淋(脂肪含量为10%)和低脂冰淇淋(脂肪含量为4%)中,共研发出不饱和单甘酯全脂冰淇淋、饱和单甘酯全脂冰淇淋、不饱和单甘酯低脂冰淇淋和饱和单甘酯低脂冰淇淋四个产品。通过对四个产品的冰冷感、硬度、粘度、平滑程度和包口感等进行感官评价,发现脂肪含量及乳化剂的种类对冰淇淋的冰冷感、硬度、粘度、平滑感、包口感等都有影响,全脂冰淇淋比低脂冰淇淋更粘,更滑,更具有包口感,低脂冰淇淋比全脂冰淇淋更硬,冰冷感更强。通过对四种冰淇淋老化料液的膨胀率及冰淇淋成品的抗融性进行了比较,发现不饱和单甘酯能提高低脂冰淇淋的膨胀率,并且不饱和单甘酯冰淇淋比饱和单甘酯冰淇淋具有更好的抗融性。     

Evolution of ascorbic acid and peroxidase during industrial processing of broccoli

The ascorbic acid content and peroxidase activity of raw, canned and frozen (after blanching times of 60, 90, 120 and 150 s) broccoli florets and stems were determined. The ascorbic acid content represented 1.12 and 0.78 g kg⁻¹ fresh weight in raw florets and stems respectively. After blanching (for different times) and freezing, the ascorbic acid content decreased to values of 0.55–0.56 g kg⁻¹ fresh weight in florets and 0.35–0.36 g kg⁻¹ fresh weight in stems. The industrial processing involved in canning decreased the ascorbic acid content to 0.18 g kg⁻¹ fresh weight in florets. The peroxidase activity observed in the florets and stems of raw broccoli was 308.8 and 278.6 µmol min⁻¹ per 100 g fresh weight respectively. The peroxidase activity remaining in frozen florets varied from 0.9 to 0.2%, while that in stems showed values of between 7.5 and 8.4%. These values for stems were within the range recommended for residual activity after blanching and freezing. The peroxidase activity of canned broccoli florets was practically undetectable. © 2000 Society of Chemical Industry     

Antioxidant effect of turmeric powder,nitrite and ascorbic acid on stored chicken mince

This investigation was carried out to evaluate the antioxidant effect of turmeric (turmeric 1000 ppm, turmeric 5000 ppm), nitrite (nitrite 200 ppm) and ascorbic acid (ascorbic acid 500 ppm) on raw minced chicken stored at 4 ± 1 °C. Physicochemical properties [pH, water activity, cooking loss, thiobarbituric acid (TBA) value, peroxide value (PV), free fatty acid (FFA)] were evaluated on 0, 2, 4 and 6th day of storage. Highly significant differences (P < 0.01) in pH, TBA value, PV and FFA value were noticed between treatments and between storage periods. TBA values were observed to be lowest for nitrite 200 ppm and then turmeric 5000 ppm, and there was no significant difference between nitrite 200 ppm and turmeric 5000 ppm, and both were superior to ascorbic acid 500 ppm and turmeric 1000 ppm. Among different treatments, PV was found to be lowest in turmeric 5000 ppm and highest in nitrite 200 ppm. FFA value was found to be lowest in turmeric 5000 ppm and highest in ascorbic acid 500 ppm among all treated samples. It can be concluded that turmeric has potential to replace synthetic antioxidants presently used in meat processing with many added advantages.     

Furan formation in starch-based model systems containing carbohydrates in combination with proteins,ascorbic acid and lipids

Formation of the “possibly carcinogenic” furan during thermal treatment of a starch-based model food system containing selected sugars alone and in the presence of proteins, ascorbic acid and lipids, respectively, was investigated. The results showed that in starch gels containing various sugars significantly more furan was formed at pH 6 than at pH 4. Moreover, addition of whey proteins enhanced the generation of furan considerably at both pH values tested. In acidic conditions, no significant difference was observed between the amounts of furan found in a starch–carbohydrate–ascorbic acid model system and those formed in a starch-based samples containing only ascorbic acid. Addition of fresh lipids did not affect furan formation. However, when oxidised soybean oil was applied, the generated amounts of furan were higher than expected from the sum of furan found in the separate starch–carbohydrate and starch–lipid samples. Interestingly, the most efficient carbohydrate in furan generation, among the sugars tested, at pH 6, was lactose, especially when heated in the presence of proteins. This is the first report on the generation of furan from lactose.     

Effects of ascorbic and citric acid on beef lumbar vertebrae marrow colour

Citric acid was evaluated as a way of improving ascorbic acid’s ability to stabilize beef lumbar vertebrae colour in high-oxygen packaging (MAP; 80% O₂/20% CO₂). Vertebrae were treated with citric acid (1%, 3%, or 10%), ascorbic acid (1%, 3%, or 10%), or a combination of both. Citric acid demonstrated no positive effects (P > 0.05), compared with ascorbic acid, which inhibited (P < 0.05) discolouration throughout the 7d display. Although ascorbic acid inhibited discolouration (visual colour and a^∗; P < 0.05), 3% and 10% ascorbic acid were most effective. However, if vertebrae are displayed for less than 7d, there may be no significant colour-stabilizing advantages associated with increasing ascorbic acid from 3 to 10%. The significant oxidizing effects of citric acid at 10% were reversed (P < 0.05) by ascorbic acid. Combining citric and ascorbic acid had no synergistic affect (P > 0.05) on vertebrae colour.     

Diffusion of citric and ascorbic acids in pre-peeled potatoes and their influence on microbial growth during refrigerated storage

The most common chemical preservatives used to inhibit both enzymatic browning and microbial growth in pre-peeled potatoes are sodium sulphite and bisulphite. Since 1987 the FDA has limited their use as food ingredients; consequently, during recent years the tendency to replace sulphites by GRAS chemical additives such as citric and ascorbic acids has become stronger. In the present work, surface colour variations, exudate production and microbial growth were analysed on pre-peeled potatoes treated with citric and ascorbic acids. These preservatives were applied individually and as mixtures; shelf-life was extended and microbiologically safe products were obtained. Mathematical models were solved to analyse the diffusion of these acids during immersion and storage periods in order to determine the concentration profiles within the product and to predict the surface concentration to which the microorganisms are exposed.     

冰淇淋生产中的稳定剂、乳化剂及复合乳化稳定剂

详细阐述了各种稳定剂、乳化剂及复合乳化稳定剂的独特性能及在冰淇淋生产中的应用技术     

Effect of ascorbic acid addition to peppers on paprika quality

The use of ascorbic acid addition to foods to protect pigments from oxidation has been widely applied. Control or ascorbic acid-added paprika peppers were processed in a similar way as for paprika manufacture. During the process, lipoxygenase activity, total colour, red/yellow pigment ratio and ascorbic acid levels were measured. In general, an increase of total colour and red pigments was observed in ascorbic acid-treated samples. The lipoxygenase activity was depressed in ascorbic acid-treated fruits on the first day of processing. However, the activity was increased again, at second day, when the ascorbic acid was oxidised, showing a close relationship between enzyme activity and the antioxidant. After the process, ascorbic acid was also added to half of the paprika from control peppers and its quality and stability of the pigments against light or heat was compared to the paprika from ascorbic acid-added peppers. At the end of the treatment a better quality was observed in paprika obtained from the ascorbic acid-added peppers. ©1997 SCI     

HPLC determination of thioglycolic acid and other aliphatic thiols in cosmetic formulations using ethacrynic acid as precolumn derivatization reagent

Limits imposed on the usage of thioglycolic acid, its salts and esters in cosmetic formulations require selective and sensitive analytical methods for their determination. In this study a convenient and reliable method based on high-performance liquid chromatography (HPLC) has been developed. The method involves a precolumn reaction of the thiol compounds with ethacrynic acid to give thiol adducts which can be separated by reversed-phase liquid chromatography and detected at λ= 273 nm.
The derivatization reaction proved to be quantitative under mild conditions (20 min at pH 7.4 and room temperature) and the chromatographic conditions allowed thioglycolic acid, glyceryl monothioglycolate, thiolactic acid, and thioglycolic acid ethyl ester to be discriminated.
The proposed method was successfully applied to the analysis of commercial cosmetic formulations containing thioglycolic acid and glyceryl monothioglycolate, fulfilling the requirements of a general and selective method for the analysis of aliphatic thiols in cosmetics.     

邻苯二甲醛-硫酸比色法测定稀奶油中胆固醇含量

为建立稀奶油中胆固醇含量的测定方法，采用邻苯二甲醛-硫酸比色法测定稀奶油中胆固醇含量。结果表明，胆固醇在553nm处有最大吸收峰，线性范围在1．00～1．73mg／g，平均回收率为95．07％(n=3，RSD=4．33％)：该方法快速准确，方法稳定，重复性好。     

L-抗坏血酸传感器在果汁中Vc含量的测定

本文利用花椰菜组织通过交联制备L-抗坏血酸传感器,该传感器在pH6.0、0.1mol/L的KH_2PO_4-Na_2HPO_4真缓冲溶液中对Vc标准溶液的线性范围为5.0×10~(-5)×1.8×10~(-3)mol/L,响应时间1min。电极使用寿命在1个月以上。利用该传感器测定了部分水果和果汁中Vc的含量,所得结果与分光光度法(2,4-二硝基苯肼法)测得结果一致。     

Quality maintenance of minimally processed Chinese cabbage with low temperature and citric acid dip

Chinese cabbage (Brassica campestris L pekinensis group) was minimally processed using best preparation techniques and stored at 0 and at 5°C with and without dips in either citric acid, calcium chloride or ascorbic acid, all at 10 g litre⁻¹. The visual quality, degree of chilling injury, pH and taste were evaluated. The most deleterious effects on quality were produced by black speck (gomasho) and browning. Citric acid inhibited the development of black speck and extended storage life from 10 days of the control to 14 days at 5°C. At 0°C the storage life was not extended by any dip, but citric acid improved quality by reducing black speck. Minimally processed Chinese cabbage treated with citric acid showed only a slight reduction of pH from 6·3 of the control to 6·1 (P⩽0·05) and taste was not significantly affected (P>0·05). Microbial spoilage was not apparent during storage at 0°C for 35 days and 5°C for 21 days under any treatment. © 1997 SCI.     

Effect of ascorbic acid on bone marrow-derived mesenchymal stem cell proliferation and differentiation

Mesenchymal stem cells (MSCs) derived from bone marrow are an important tool in tissue engineering and cell-based therapies because of their multipotent capacity. Majority of studies on MSCs have investigated the roles of growth factors, cytokines, and hormones. Antioxidants such as ascorbic acid can be used to expand MSCs while preserving their differentiation ability. Moreover, ascorbic acid can also stimulate MSC proliferation without reciprocal loss of phenotype and differentiation potency. In this study, we evaluated the effects of ascorbic acid on the proliferation, differentiation, extracellular matrix (ECM) secretion of MSCs. The MSCs were cultured in media containing various concentrations (0-500 microM) of L-ascorbate-2-phosphate (Asc-2-P) for 2 weeks, following which they were differentiated into adipocytes and osteoblasts. Ascorbic acid stimulated ECM secretion (collagen and glycosaminoglycan) and cell proliferation. Moreover, the phenotypes of the experimental groups as well as the differentiation potential of MSCs remained unchanged. The apparent absence of decreased cell density or morphologic change is consistent with the toxicity observed with 5-250 microM concentrations of Asc-2-P. The results demonstrate that MSC proliferation or differentiation depends on ascorbic acid concentration.