Physiology of pre-cut mango. I. ACC and ACC oxidase activity of slices subjected to osmotic dehydration

Physiologically mature mangoes were ripened for 6 days at 24°C and 98% relative humidity. Slices from these fruits were osmotically dehydrated by immersion in sucrose 65°Brix at 30°C and 211 mbar vacuum during 30 min. Slices not subjected to osmotic dehydration (NOD) and slices with osmotic dehydration (OD) were stored at 24, 13 or 5°C. The respiration rate of both slice types was affected by the storage temperature. 1-Aminocyclopropane-1-carboxylic acid (ACC) synthesis indicated activity of ACC synthase in both slices as well as in the whole fruit. ACC oxidase activity was greater in OD slices as compared to NOD and that was associated to better membrane stability. OD favored compaction of external layer in slices. No ethylene was detected in slices; however, the tissues did not lose their ability to synthesize ethylene. Results suggest that OD under vacuum may be beneficial as a pre-treatment of mango slices for longer shelf life under refrigeration.     

苹果品种(系)制酒适性的研究

为增加苹果发酵酒的口感与风味,提升苹果酒的营养价值,以红富士苹果与宁夏枸杞为发酵原料,以总多酚、酒精度及感官品评为主要指标,分别考察安琪果酒酵母（SY）、和谐A酵母（LA AROM）、诺盟B酵母（LA BAYANUS）、卓越XR酵母（EXECLLENCE XR）、诺盟C酵母（LA CEREVISIAE）5株酿酒酵母的发酵能力,并通过单因素实验与正交试验优化苹果枸杞酒发酵工艺,利用气相色谱-质谱联用仪（gas chromatography-mass spectrometry,GC-MS）分析检测苹果枸杞酒的挥发性成分。结果表明,诺盟B酵母发酵速度最快,发酵所得酒体澄清透亮,香味协调,适合于发酵苹果枸杞酒,其最佳工艺条件为：苹果汁与枸杞汁比例为4:1,初始可溶性固形物10°Brix,接种量3%,20 ℃发酵6 d,所得果酒酒精度为5.7%vol,可溶性固形物为6°Brix,还原糖含量2.15 g/L,感官评分为89.6分。在苹果枸杞酒中共检出32种香气成分,包括乙酸乙酯（17.38%）、辛酸乙酯（1.74%）、癸酸乙酯（2.27%）、苯乙醇（28.2%）、对羟基苯乙醇（12.61%）、异戊醇（9.49%）等香味物质,这些香气成分能在一定程度上增加苹果枸杞酒的风味。实验优化了枸杞苹果酒发酵工艺,提升了苹果酒品质,为果酒的生产研发提供基础理论支撑。     

Analysis of sugars and organic acids in ripening mango fruits (Mangifera indica L. var Keitt) by high performance liquid chromatography

The sugars and organic acids present in the pulp of Keitt mangoes at various stages of ripeness were analysed by h.p.l.c. Ripening was associated with a loss in firmness, peel chlorophyll and pulp acidity, with increasing soluble solids and total sugars. The major sugars were identified as glucose, fructose and sucrose. All three increased during ripening; sucrose was found to be in the greatest concentration throughout, with fructose the predominant reducing sugar. Acidity loss was shown by decreasing titratable acidity and increasing pH values. Citric and malic acids were found to be the major organic acids. A large decrease in citric acid and a small reduction in malic acid were responsible for the loss of acidity. Tartaric, ascorbic, oxalic and α-ketoglutaric acids were also shown to be present at low concentrations.     

Leaf:fruit ratio and irrigation supply affect seasonal changes in minerals,organic acids and sugars of mango fruit

To determine the effects of assimilate and water supply on the determination of mango fruit quality, the seasonal variations of minerals, acids and sugar concentrations were investigated over two successive years. To manipulate the assimilate supply, selected branches were girdled to provide ratios of 10, 25, 50 and 100 leaves per fruit. Irrigation was managed to provide two types of water supply treatments. Fruit growth rate was greater when increasing the leaf:fruit ratio. Structural dry matter content and total dry matter content of flesh were higher in fruit with higher leaf:fruit ratios. Treatments had no effect on the structural to total dry matter ratio of flesh. Potassium and magnesium to structural dry weight ratios were not affected by treatments, whereas the calcium to structural dry weight ratio was higher in the flesh of fruit grown under low leaf:fruit ratios. Low assimilate supply increased the ratios of malic and citric acid to structural dry weight. This treatment had little effect on acid concentrations. Glucose and fructose to structural dry weight ratios were higher when assimilate supply was lower. Low leaf:fruit ratios increased fructose concentration but not glucose concentration. Irrigation treatment strongly affected fructose concentration. Sucrose concentration, based either on structural dry matter or on fresh matter, was significantly increased by higher leaf‐to‐fruit ratios. When the fruit was close to maturity, levels of sucrose storage and starch breakdown were positively correlated with assimilate supply. Levels of starch breakdown were correlated with irrigation supply. The effects of these treatments on sugar concentrations may change fruit taste. Copyright © 2004 Society of Chemical Industry     

Egyptian mango by-product 1. Compositional quality of mango seed kernel

Egyptian mango seeds were collected as wastes from local fruit processing units and the kernels were separated and dried. This study was carried out on mango seed kernels to clarify their proximate composition, amino acids, phenolic compounds and the characteristics of the extracted oil including unsaponifiable matter constituents, lipid classes and fatty acid composition. Mango seed kernels contained a considerable amount of total phenolic compounds, total lipid, unsaponifiable matter, and a low amount of crude protein, but the quality of protein was good because it was rich in all essential amino acids. Eight phenolic compounds were identified; tannin and vanillin were in highest amounts. Unsaponifiable matter showed the occurrence of high amounts of squaline followed by sterols and tocopherols. Stearic acid was the main saturated fatty acid, while oleic acid was the major unsaturated fatty acid in all lipid classes. The fatty acid composition of total lipid and neutral lipid was similar, while phospholipid had a high amount of palmitic, linoleic and linolenic acids.     

Non-volatile organic acids of grasses

Non-volatile organic acids have been determined in S24 ryegrass and S37 cocksfoot harvested on three cutting dates over the period of ear emergence and in eight grasses harvested on two cutting dates. In both S24 ryegrass and S37 cocksfoot the concentrations of shikimic, quinic and total acids decreased with increased age of the plant. Correlation coefficients are given between the concentrations of acids in eight grasses and the ‘preference ranking’ of the grasses estimated in an investigation into the grazing preferences of sheep and cattle, and a regression is given for relating ‘preference ranking’ to the contents of citric and quinic acids.     

有机酸提取技术研究进展

有机酸提取对于研究和利用有机酸具有重要意义。文章综述了近年来有机酸的提取技术,系统介绍了不同技术在有机酸提取方面的原理、特点和应用。     

Modeling the inhibitory effects of organic acids on bacteria.

The inhibitory effect of acids on microbial growth has long been used to preserve foods from spoilage. While much of the effect can be accounted for by pH, it is well known that different organic acids vary considerably in their inhibitory effects. Because organic acids are not members of a homologous series, but vary in the numbers of carboxy groups, hydroxy groups and carbon-carbon double bonds in the molecule, it has typically not been possible to predict the magnitude, or in some cases even the direction, of the change in inhibitory effect upon substituting one acid for another or to predict the net result in food systems containing more than one acid. The objective of this investigation was to attempt to construct a mathematical model that would enable such prediction as a function of the physical and chemical properties of organic acids. Principal Components Analysis (PCA) was applied to 11 properties for each of 17 acids commonly found in food systems; this resulted in four significant principal components (PCs), presumably representing fundamental properties of the acids and indicating each acid's location along each of these four scales. These properties correspond to polar groups, the number of double bonds, molecular size, and solubility in non-polar solvents. Minimum inhibitory concentrations (MICs) for each of eight acids for six test microorganisms were determined at pH 5.25. The MICs for each organism were modeled as a function of the four PCs using partial least squares (PLS) regression. This produced models with high correlations for five of the bacteria (R2 = 0.856, 0.941, 0.968, 0.968 and 0.970) and one with a slightly lower value (R2 = 0.785). Acid susceptible organisms (Bacillus cereus, Bacillus subtilis, and Alicyclobacillus) exhibited a similar response pattern. There appeared to be two separate response patterns for acid resistant organisms; one was exhibited by the two lactobacilli studied and the other by E. coli. Predicting the inhibitory effects of the organic acids as a function of their chemical and physical properties is clearly possible.     

Studies on potassium nutrition of plants. II.—Some effects of potassium deficiency on the organic acids of leaves

Leaf organic acids of a series of plants have been determined by silica gel chromatography. Red beet and cabbage were grown in sand culture at six levels of potassium nutrition ranging from extreme deficiency to high potassium concentration. Potassium deficiency in cabbage, beet and potato leaves resulted in large increases of total organic acids, whereas there was a decrease in lettuce and no effect in Italian rye grass. Volatile organic acids of cabbage leaf were quantitatively minor components but at two extreme levels of potassium nutrition, they were present in the same relative proportions as total organic acid. Shikimic acid was tentatively identified in field-grown rye grass (0.96% of dry weight).     

Production of the mycotoxin, zearalenone, by Fusarium graminearum growing on stored grain. II. Treatment of wheat grain with organic acids

The concentrations of formic, acetic, propionic and butyric acids required to prevent growth of Fusarium in wheat grain cultures were determined. The cultures were maintained at 31% moisture content and stored for 4 weeks at 25 ºC followed by 6 weeks at 12 ºC, which were optimum conditions for growth of Fusarium and synthesis of the mycotoxin, zearalenone. Under these conditions the critical concentration of all the acids, whether used singly or in combination, was between 1000 and 10 000 parts/million (equivalent to 0.1% and 1% w/w). At 1000 parts/million and below the fungus was able to develop and zearalenone synthesis was not affected except where acetic acid was used alone, when higher toxin yields were recorded.     

芒果原浆、芒果糖浆的研制

本文研究了以芒果为原料加工成芒果原浆、芒果糖浆的适宜加工品种、加工工艺和配方、色泽风味保持、产品评价,提出了适宜加工品种、合理工艺和操作要点、产品配方和质量标准。是一项适宜芒果产地的芒果加工技术。     

Photoformation of low-molecular-weight organic acids from brown water dissolved organic matter

This work describes the effects of simulated solar UV light on the bulk properties of dissolved organic matter (DOM) of bog lake water and on the formation of low-molecular-weight organic acids (LMWOAs). By means of size-exclusion chromatography it was shown that the more hydrophilic moieties of the DOM were preferentially photodegraded while the more hydrophobic ones remained relatively unaffected or were even formed. The combined photochemical-biological degradation proved to be more important than the pure photochemical mineralization. Formic, acetic, pyruvic, oxalic, malonic, and succinic acids were identified as important degradation products. Their contribution to the dissolved organic carbon increased from 0.31% before to 6.4% after 24 h irradiation. About 33% of the bioavailable photoproducts of DOM were comprised of these LMWOAs. The influence of nitrate on the formation of carboxylic acids could not be observed in the investigated system. Kinetic experiments indicated that degradation of LMWOAs occurred simultaneously during irradiation experiments, alpha-oxygen-substituted LMWOAs being more amenable to these processes. Dissolved iron acted as a catalyst of DOM photodegradation and LMWOA photoformation. Copper played an antagonistic role in the irradiation experiments, reducing the formation of formic, acetic, and malonic acids while increasing the formation of oxalic acid.     

Effect of six organic acids on staphylococcal growth and enterotoxin production.

Four Staphylococcus aureus strains were incubated at 37 degrees C for 24 h in broth progressively acidified with lactic, citric, ascorbic, acetic, pyruvic and propionic acids, and their survival rate and enterotoxin producing ability was studied. Acids were chosen based on their frequent use by the food industry. Periodically, samples were withdrawn to determine counts, pH and the presence of enterotoxins A, B, C, and D. For a given acid, the effect on growth and enterotoxin synthesis was different. The most inhibitory acid for the growth of strains FRI-100 and FRI-472 was pyruvic acid, for strain FRI-137 was lactic acid, all six acids were equally effective on strain S6. Lactic acid was very inhibitory to enterotoxin synthesis, but the effect on this parameter of acetic and citric acids was almost nil. Enterotoxins were seen to be inactivated at acid pH values; enterotoxin B was the most resistant to inactivation.     

苹果醋中有机酸成分的GC-MS分析

文章以陈醋作对照分析,采用气相色谱-质谱联用(GC-MS)对苹果醋中的有机酸含量进行了分析测试。实验数据显示,苹果醋含有特殊的有机酸,具有较高的营养保健功效。     

Significance of nonaromatic organic acids in honey

Although organic acids represent < 0.5% of honey's constituents, they make important contributions to the organoleptic, physical, and chemical properties of honey. To date, approximately 30 nonaromatic organic acids have been identified in honey, but relatively little attention has been paid to these components. This article reviews the current literature related to the significance of nonaromatic organic acids in honey; it was written with a goal of attracting researchers to study these interesting honey components. Previous research contributions on nonaromatic organic acids in honey may be classified into five main areas: (i) the antibacterial activities of these acids, (ii) the antioxidant activities of these acids, (iii) the use of these acids as possible indicators of incipient fermentation, (iv) the use of these acids for treatment of Varroa infestation, and (v) the use of these acids as factors for the characterization of both botanical and geographical origins of honeys. We conclude that nonaromatic organic acids are of interest for diverse reasons and that there is a particular need for studies regarding their possible antibacterial and antioxidant activities.     

Quality changes of pasteurised mango juice during storage. Part II: Kinetic modelling of the shelf-life markers

The present work shows the potential of the integrated fingerprinting-kinetics approach in evaluating shelf-life changes of pasteurised mango juice (cv. ‘Totapuri’). Seven mango juice formulations (i.e. control (mango puree and water), ascorbic acid-enriched (AA₂₅₀ and AA₅₀₀), citric acid-enriched (CA, CA + AA₂₅₀ and CA + AA₅₀₀) and sugar-enriched (S) samples) were pasteurised and stored at 42 °C for 8 weeks. In this part, the kinetics of the shelf-life markers selected from the multivariate fingerprinting approach was modelled. Changes in selected targeted parameters could be best described by a zero-order (colour values, °Brix, furfural, HMF), a first-order (ascorbic acid), a fractional conversion (fructose, glucose, oxygen) and a second-order model (sucrose). Differences in the rate constant were observed, with faster ascorbic acid degradation and furfural formation in AA-enriched samples and faster hydrolysis of sugars and HMF formation in CA-enriched samples compared to control samples. To describe changes in selected volatiles (terpenes, sulphur compounds, acids, ketones and esters), different kinetic models were selected. Two trends were observed: changes as affected by different mango juice formulations (e.g., faster reaction in CA-enriched samples or in a lower pH condition) and changes irrespective of the formulations. Referring to the literature, in general, acid-catalysed reactions, ascorbic acid degradation and oxidation reactions are the main reactions responsible for the observed quality changes in stored mango juice.     

On the phenolic acids of vegetables. II. Hydroxycinnamic acids and hydroxybenzoic acids of fruit and seed vegetables (author's transl)]

Fruits of solanaceae (tomatoes, eggplant, and sweet peppers) almost exclusively contain hydroxycinnamic acid derivatives with caffeic acid dominating. Fruits of cucurbitaceae (cucumbers, melons, pumpkins, and zucchini) are extraordinary, because they show very low concentrations of phenolic acids (up to 10 mg/kg) accumulated in the peels. Peas and broad beans have relatively small contents of phenolic acids too. Their husks show like beans considerable concentrations of hydroxycinnamic acid derivatives with dominating p-coumaric acid. In the group of hydroxybenzoic acids derivatives of salicylic, gentisic and vanillic acid could be determined frequently, but mostly as traces.     

Protein haze formation in wines revisited. The stabilising effect of organic acids

The effect on the wine protein haze potential of five organic acids commonly encountered in wines (l(+)-tartaric, l(−)-malic, citric, succinic and gluconic acids) was assessed. All five acids, tested at 20 mM, reduced dramatically the haze potential of proteins, either in wine or dissolved in water, throughout the range of pH values typical of wines (i.e., from 2.8 through 3.8). Subtle differences among the acid effects did not correlate with the number of their carboxyl groups, but were attributed to electrostatic interactions that depend upon the acid pK_a values, the protein pI values and the medium pH. These results invalidate or question the validity of all experiments on wine proteins involving wine model solutions containing organic acids. Overall, the results obtained in the present work clearly indicate that organic acids with a common occurrence in wines exhibit a stabilising effect upon the haze potential of the wine proteins.     

Potato starch factory waste effluents III. Recovery of organic acids and phosphate

The use of anion-exchange resins for removal of acids from potato starch factory waste-water (after prior removal of proteins and amino acids) was studied. Over 99% of the acids were removed by the process. Data are given on the effect of influent temperature and flow-rate on column efficiency during the acid adsorption step. Data are also given on methods of increasing the concentration of acids in the eluate by increasing the alkalinity of the eluting agent or by recycling the eluate. Possible uses for the eluate are discussed.