Organic acids in two Portuguese chestnut (Castanea sativa Miller) varieties

The organic acids composition of two different chestnut (Castanea sativa Miller) varieties (Judia and Longal) were determined by HPLC/UV. In order to check the influence of the processing over these compounds, samples treated in three distinct manners (roasted, boiled and fried) were also analysed. The results showed that chestnut is characterized by the presence of seven organic acids: oxalic, cis-aconitic, citric, ascorbic, malic, quinic and fumaric acids. The organic acid quantitative profile allows the distinction of the two varieties. Longal variety samples presented higher organic acids contents than those from Judia variety. The contents of the pair malic plus quinic acids may be useful for the discrimination of the two varieties. Roasting, boiling and frying procedures lead to significant reduction of total organic acids contents.     

高效液相色谱法测定哈密大枣干制过程中6种有机酸的含量变化

建立了测定哈密大枣干制过程中有机酸含量的测定方法。色谱条件:WondaSil C₁₈-WR色谱柱(4.6 mm×50 mm,5 μm)进行分离,流动相0.05 mol/L的KH₂PO₄缓冲溶液:甲醇=9:1;pH=2.3;流速0.8 mL/min;柱温35 ℃;检测波长210 nm;进样量20 μL。在此条件下,草酸、苹果酸、酒石酸、柠檬酸、富马酸、琥珀酸6种有机酸可得到分离。结果表明:在干制过程中,苹果酸含量最高,琥珀酸未检出。自然晒干过程中5种有机酸含量呈现先下降后上升的趋势,苹果酸含量在第4 d降至最低7.58 mg/g,第12 d酸含量积累到最高10.15 mg/g。45 ℃热风干制过程中总有机酸呈现先降低后升高的趋势,苹果酸含量积累最高为10.41 mg/g。     

樱桃番茄干燥工艺的研究

以樱桃番茄为研究材料,通过对原料品种的选择、预处理方法、渗糖等方式的处理后,以热风干燥为主要干燥方法来加工产品。通过测定恒定干燥条件下的干燥曲线,研究不同干燥温度、高低风速、同温度不同厚度下对樱桃番茄水分、含糖量、抗坏血酸损失比和过程中色度的影响。结果表明,选用热风干燥,干燥温度为55℃时,干燥10 h,干燥樱桃番茄果脯效果最好;采用高风速干燥比低风速干燥所用干燥时间短,干燥效果更佳;干燥后产品所含抗坏血酸为3.48 mg/100 g;最终制得的产品还原糖含量为8.23 g/100 g;樱桃番茄选料200 g、铺料层数为两层,在55℃下采用风速干燥,其色泽最好。     

Determinations of Organic Acids in Potatoes by High Performance Liquid Chromatography

A high performance liquid chromatographic method has been developed to quantify the major organic acids in potatoes oxalic, citric, malic, fumaric and ascorbic acids. Tubers were extracted with 95% ethanol:water:concentrated sulfuric acid 60:40:0.2 followed by injection on an Aminex HPX-87 column with a mobile phase of 0.018N sulfuric acid. Ascorbic acid was detected at 260 nm while the other four acids were quantified at 210 nm unless fructose was present at a concentration of 6 mg/g or higher, in which case 220 or 230 nm was used. Greater than 90% recovery was observed for all acids with most recoveries near 100%. The method has been shown to be very reproducible with the CV% ranging from 1.3-12.3 while the majority were below 4%. Analyses of several potato varieties have shown a wide variation in acid content among varieties.     

Physiology of pre-cut mango II. Evolution of organic acids

The effect of a 30-min osmotic dehydration (OD) treatment under vacuum and storage temperature on the organic acid content in slices prepared from Haden and Kent mangoes was evaluated. Additionally, respiration rate (RR), titratable acidity, pH and soluble solids were monitored. Greater RR was detected in osmotically dehydrated slices. Citric, ascorbic and fumaric acids were measured in greater concentrations in Haden slices, while malic acid was predominant in Kent slices. No succinic acid was found in any sample. Low malate concentrations suggest that the observed increase in CO₂ production caused by the mechanical stress may be due to malic acid decarboxylation by the malic enzyme. OD caused lesser alterations in oganic acid balance than cutting and possibly allowed an extended operation of the tricarboxylic acid cycle.     

Influence of the cultivar on the organic acid and sugar composition of potatoes

BACKGROUND: Citric, malic, tartaric, oxalic, ascorbic, aconitic and fumaric acids, and sucrose, fructose and glucose, were determined in ten potato cultivars (Azucena negra, Bonita, Bonita negra, Borralla, Colorada de baga, Mora, Negra, Palmera lagarteada, Peluca blanca and Terrenta) from the Canary Islands in order to differentiate them. The influence of the production zone was also considered. RESULTS: Citric acid and sucrose were the most abundant organic acid and sugar, respectively. There were significant differences in all the analysed sugars and organic acids between the potato cultivars, except for oxalic and malic acids. Differences associated with the production zone were found in the contents of organic acids for some cultivars. Linear discriminant analysis is a useful tool to differentiate the potato samples according to the cultivar and the zone of production. CONCLUSIONS: Seven organic acids (citric, oxalic, malic, tartaric, aconitic, fumaric, and ascorbic acids) were identified and quantified in potatoes. The main sugars (sucrose, glucose and fructose) were also determined. The genetic information of the cultivars determines marked differences in sugars and organic acid contents among the analysed potato cultivars. The soil and climatic conditions affect the organic acid and sugar contents of some potato cultivars. Copyright © 2010 Society of Chemical Industry     

低糖板栗果脯微波-热风结合干燥技术的研究

采用微波和热风干燥,研究了低糖板栗果脯在干燥过程中的品质变化,并利用数学建模的方法对低糖板栗果脯的微波和热风干燥过程进行模拟。实验结果表明,最佳干燥工艺为:初始微波干燥功率密度为2W/g,水分含量干燥至20%时(干燥时间18min),再换用60℃热风干燥至水分含量15%,整个干燥过程总需138min。低糖板栗果脯前期微波干燥可用Page方程描述,后期热风干燥可用Henderson and Pabis模型描述。相比传统热风干燥,微波-热风结合干燥低糖板栗果脯不仅缩短了干燥时间,而且能提高果脯的品质。     

Osmotic-Convective Dehydrofreezing Process for Drying Kiwifruit

Osmotic and convective dehydrofreezing were studied to determine sugar concentration, ascorbic acid loss, and texture changes in dried and dehydrofrozen kiwifruit. Two concentrations of sucrose (60° and 72° Brix) were used as osmotic solutions after convective air drying. Time needed to reach desired moisture was reduced with combined drying compared with osmotic drying. Firmness was evaluated by the maximum force from a back extrusion test. A reduction in maximum force was observed after freezing, as compared with fresh and dried fruit. Addition of ascorbic and citric acid as antioxidants in the osmotic solution prevented browning, and significant loss of ascorbic acid during osmotic drying. Air drying at 30°C produced distinguishable color changes.     

Comparative Study of Selva and Camarosa Strawberries for the Commercial Market

ABSTRACT: Selva and Camarosa strawberry varieties were characterized chemically and physically. The importance of keeping the stem until processing, the influence of different transport periods under refrigerated conditions, the effects of freezing and exposure to air of damaged surfaces were evaluated. During freezing, losses of ascorbic acid, sucrose, fructose and glucose were reported for both varieties. However, keeping the stem intact minimizes the losses of ascorbic acid in frozen fruits. The exposure to air of cut surfaces affects ascorbic acid content of fresh fruits, with the highest losses reported in Camarosa. Selva showed properties important for commercial use, as compared to Camarosa , with regard to a higher resistance to thawing and higher contents of total phenolics, total protein, and ascorbic acid.     

Organic acids of various kinds of vegetables. IV. Changes in the acids and sugar in tomatoes, sweet peppers and cucumbers during development and ripening

Concentrations of organic acids and sugars in tomatoes and sweet peppers change notably during ripening. The concentration of malic acid decreases while that of citric acid increases considerably and in redripe fruits clearly exceeds the content of malic acid. Several maxima and minima in acid concentrations occur during development. Both species show constant proportions of citric and isocitric acid (200:1 and 30:1 respectively). In sweet pepper, quinic and ascorbic acid can be found in noticeably higher amounts than in tomatoes. Additionally, succinic acid was detected in tomatoes and fumaric and shikimic acid in sweet pepper. Glucose and fructose, in approximately equal amounts, are the main sugar components; their concentrations are increased during ripening, especially in sweet peppers. The leaves of tomatoes and sweet pepper contain more malic acid and less citric acid than redripe fruits, though here as well citric acid predominates. There is considerably less glucose and fructose present in the leaves of sweet pepper than in the fruits while sucrose is increased. Sucrose is the main sugar component in the leaves. Compared to tomatoes and sweet peppers, egg-plants contain more amounts. - Potatoes contain citric, malic, quinic, succinic, fumaric, and soluble oxalic acid (in order of decreasing amounts). - In cucumbers malic acid notably exceeds citric acid. Both acids hardly change in concentration during ripening. Sugar content decreases during ripening.     

西兰花干燥过程中还原型V_C与氧化型V_C的变化

研究西兰花脱水加工过程中还原型VC和氧化型VC的变化。结果表明:经过蒸汽热烫的西兰花,其还原型VC和氧化型VC的保存率高于热水热烫的保存率,其中80℃蒸汽热烫处理2min效果最好;热烫后冰水冷却的西兰花还原型VC和氧化型VC保存率高于自然冷却;真空冷冻干燥能将西兰花中还原型VC和氧化型VC最大程度的保留。西兰花脱水加工过程中氧化型VC的保存率高于还原型VC,说明西兰花中的还原型VC更易被破坏。     

Analysis of organic acid content in cultivars of tomato harvested in Tenerife

The determination of organic acids in tomato samples was optimized using the HPLC method with on-line photodiode array detection, previous to extraction with 80% ethanol at room temperature and clean-up in Accell Plus QMA cartridge. The organic acids (oxalic, pyruvic, malic, citric, fumaric and ascorbic), Brix degree, acidity and pH were determined in five tomato cultivars (Dorothy, Boludo, Dominique, Thomas and Dunkan) harvested in Tenerife. There are several significant differences among cultivars in the concentration of many acids. The cultivation method, sampling period and the region of production were also considered. Citric, malic and oxalic acids were the major organic acids in all the cultivars. Some significant differences in the studied parameters were observed between the cultivars. The cultivation method and sampling period influenced in a variable way the studied parameters, depending on the tomato cultivar. The production region influenced the ascorbic acid concentration of the tomatoes. Applying stepwise discriminant analysis, it was found that the sampling period is more important in the differentiation of the tomato samples than the cultivar, cultivation method and production region.     

Antioxidative properties and phytochemical composition of Ballota nigra infusion

The ability of Ballota nigra (Lamiaceae) infusion to act as a scavenger of DPPH radical, reactive oxygen species (superoxide radical, hydroxyl radical, hypochlorous acid) and nitric oxide was investigated. The tested infusion mainly exhibited a potent scavenging effect on DPPH, nitric oxide and superoxide radicals. In hydroxyl radical assay a potent pro-oxidant activity was noticed. No effect was found against hypochlorous acid. A phytochemical study was also undertaken, and seven phenolic compounds (chlorogenic, caffeic and caffeoylmalic acids, ballotetroside, forsythoside B, verbascoside and allysonoside) and eight organic acids (oxalic, aconitic, citric, ascorbic, malic, quinic, shikimic and fumaric acids) were identified and quantified by HPLC/DAD and HPLC/UV, respectively. Forsythoside B and quinic acid were revealed to be the main compounds in this infusion.     

未除气与除气淡爽型啤酒中9种有机酸的阈值

采用ASTM679标准方法测定了未除气与除气淡爽型啤酒中乙酸、乳酸、柠檬酸、苹果酸、琥珀酸、富马酸、丙酮酸、酒石酸和草酸的个人和小组阈值。结果发现,在未除气啤酒中,9种有机酸的小组阈值大小顺序为苹果酸、富马酸、乳酸、柠檬酸、丙酮酸、琥珀酸、乙酸、草酸、酒石酸。其中品评员对苹果酸、琥珀酸、富马酸、草酸和柠檬酸的口感差异相对较小,而对酒石酸、乙酸、丙酮酸和乳酸的口感差异较大。在除气啤酒中,9种有机酸的小组阈值大小顺序为丙酮酸、乳酸、乙酸、富马酸、琥珀酸、苹果酸、酒石酸、草酸、柠檬酸。品评员对柠檬酸、苹果酸和乳酸的口感差异相对较小,而对丙酮酸、草酸、酒石酸、富马酸、琥珀酸和乙酸的口感差异较大。此外还发现未除气和除气啤酒中有机酸阈值差异很大,其中差异最大的是三元酸柠檬酸,其次为二元酸,包括苹果酸、草酸、酒石酸、琥珀酸和富马酸,差异最小的是一元酸,包括乳酸、乙酸和丙酮酸。     

有机酸味剂对低钠盐增咸作用的研究

以1.0%(w/w)的氯化钠溶液为标准参照,重点研究了L-苹果酸、琥珀酸、柠檬酸、富马酸等有机酸味剂与低钠盐的复配效果。通过品尝小组对复配溶液的咸度、酸度等进行感官评定,结果表明:当单独添加L-苹果酸、琥珀酸、柠檬酸、富马酸的量依次分别为1.6%、0.8%、2.4%、0.8%(w/w)时,对低钠盐有明显的掩盖苦味及增咸效果,其中添加1.6%L-苹果酸的复配溶液咸味纯正,综合口感良好,增咸效果可达1.33倍。     

Comparative Study of Quality Changes Occurring on Dehydration and Rehydration of Cooked Chickpeas (Cicer Arietinum L.) Subjected to Combined Microwave–Convective and Convective Hot Air Dehydration

ABSTRACT:  Convective hot air dehydration (100 °C) of cooked chickpeas was compared with the combination of microwave–convective hot air dehydration, in terms of microstructure, density, color, texture, dehydration, and rehydration. In the combined drying experiments, 2 levels of microwave power (100 W and 200 W) were investigated, combined continuously with convective air drying at 100 °C. Compared with convective hot air drying, combination drying led to a considerable reduction in dehydration time. Combination drying also improved the porosity of the finished dehydrated product, leading to faster rehydration kinetics. Cryogenic scanning electron microscopy micrographs showed that chickpeas subjected to combined drying experienced less shrinkage than those dried by convective hot air. Combination drying at the higher (200 W) level produced a darker ( P < 0.05) rehydrated product with significantly lower relative rehydrated moisture content ( P < 0.05) when compared with the lower (100 W) level of combination drying.     

Assessment of convection,hot‐air combined with microwave‐vacuum and freeze‐drying methods for mushrooms with regard to product quality

Combined drying of hot air and microwave‐vacuum has been proposed as an alternative method to improve the quality of dried mushrooms, especially the structural and textural properties. In the present study, the effect of different drying methods namely, convective hot‐air drying, hot air combined with microwave‐vacuum drying and freeze‐drying on qualitative attributes of pretreated mushrooms was investigated. The quality assessment was based on colour, texture, density, porosity and rehydration characteristics of the dried mushrooms. Combined drying of hot air and microwave‐vacuum resulted in a dried product of superior quality when compared to the slices dried completely by conventional hot air, exhibiting lower overall colour variation, higher porosity, greater rehydration ratio and softer texture. In a dry state, mushrooms with a puffy structure and unique crispy texture were created by the combined drying method, which might be considered as important characteristics for developing nonfat snack‐type food products.     

Effects of different drying methods on phenolic contents,antioxidant, and tyrosinase inhibitory activity of peach blossoms

Fresh peach blossoms of two varieties were dried by using different methods, which include shade drying, freeze drying, microwave drying and hot air drying (at 30, 60, 90, 120 °C). The effects of different drying methods on phenolic contents, antioxidant and tyrosinase inhibitory activity were evaluated. Among the seven drying treatments, microwave drying yielded the highest contents of total phenolics, flavonoids, anthocyanins, proanthocyanidins and individual phenolic compounds in dried peach blossoms, while hot air drying at 30 °C gave the lowest retention of total phenolics, flavonoids, anthocyanins. As compared with shade drying and freeze drying, hot air drying at 60, 90, 120 °C resulted in higher retention of phenolic content. The highest antioxidant activity in dried peach blossoms was obtained by microwave drying, while hot air drying at 30 °C gave the lowest. The effect of different drying methods on antioxidant activity of dried peach blossoms was consistent with that of phenolic content. The highest tyrosinase inhibitory activity was achieved by hot air drying at 120 °C for variety ‘yingchun’ and 90 °C for variety ‘huangjinmeili’, but there was no significant difference among hot air drying at 60, 90, 120 °C for both varieties. The tyrosinase inhibitory activities of peach blossoms by microwave drying and freeze drying were comparable and much lower than that of shade drying. The results indicated that microwave drying was a desirable method for the preservation of phenolic compounds and antioxidant activity in peach blossoms, while shade drying and hot air drying at high temperature were favorable for tyrosinase inhibitory activity.     

烤烟基因型间多元有机酸含量差异性分析

为了解烟草不同基因型在不同生态条件下多元有机酸含量差异性,以52个不同基因型烤烟种质在山东和四川两个不同生态区试验得到的原烟样品,利用气相色谱进行了多元有机酸含量检测。检测结果分析表明,苹果酸、草酸和柠檬酸是烤烟各基因型的主要多元有机酸,其中苹果酸含量占多元有机酸总量的75%左右;两产区多元有机酸总量均高于平均值的基因型种质有17份,多为国外引进品种,两产区多元有机酸总量均低于平均值的基因型种质有18份,多为国内育成品种,这35个品种多元有机酸含量遗传相对稳定;四川产区整体上多元有机酸绝对含量较低、相对含量较高,特别是丙二酸、柠檬酸等绝对含量在所有基因型中普遍较低,丁二酸、草酸、苹果酸等相对含量普遍较高,山东产区则与之相反;基因型和生态条件对烤烟多元有机酸含量均有明显影响,相对而言基因型的作用较大。     

微波膨化板栗脆片的工艺研究

实验以板栗粉为主要原料,加入适量的白砂糖、食盐、蛋黄粉以及NaHCO3,采用热风干燥与微波相结合的方法加工成板栗脆片,对工艺过程的主要参数进行了研究。结果表明:最佳加水量为板栗粉∶水为1∶1(g∶mL);配料的最佳配方为白砂糖6%、食盐1%、蛋黄粉5%;NaHCO3的添加量为2.0%;热风干燥初始水分含量为16%左右;微波功率为800W;微波处理时间为90s。