Rapid concurrent analysis of fruit sugars and acids by gas--liquid chromatography

A rapid and simple procedure for the separation, identification and quantitative analysis of common fruit sugars and non-volatile organic acids has been developed. Acids were precipitated as their lead salts from fruit ethanolic extracts and the sugars in the remaining supernatant and washings were partitioned into aqueous methanol. These preparations with internal standards were dried and converted to their trimethylsilyl derivatives for analysis by gas-liquid chromatography. In model studies, conditions which permitted full recovery of sugars from the lead salts of acids, while minimising the loss of acids, were investigated. For fruit acids reported present in measurable amounts (10 mg/100 g of fruit), replicate analysis of aliquots from the same extract was within ±5% for malonic, phosphoric, succinic, malic, citric, ascorbic and galacturonic acids and within ±12% for quinic acid. The use of the method, its advantages and limitations, in determining individual and total sugars and acids is illustrated on some New Zealand grown fruit (New Zealand grapefruit, mountain pawpaw, tangelo, apricot). Total sugars and total acids determined by this procedure gave comparable results with those obtained by using standard A.O.A.C. procedures.     

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     

Instrumental based flavour characterisation of banana fruit

Different instrumental techniques are used to evaluate the integrated flavour profile, including taste and volatile components, of a common export banana cultivar (Gran Enano) during ripening. Besides standard techniques to assess fruit quality (firmness, soluble solids content), gas chromatography-mass spectrometry (GC–MS) with headspace solid-phase micro-extraction (HS SPME) was used for the quantification of the different volatile components. The most important taste components with respect to sweetness (d-glucose, d-fructose, sucrose) and sourness (l-malic acid and citric acid) were determined using an enzymatic high-throughput (EHT) method. The different parameters were monitored during a ripening process starting from a green colour stage until fully ripened bananas. Clear differences were observed between bananas at different ripening stages with respect to the main instrumental attributes (total acid and sugar content, total volatile production, SSC, and firmness) and the individual volatile components. In addition, differences in flavour profile were observed between ethylene and non-ethylene treated bananas at the same colour stage and between bananas from different origins.     

Application of ATR-FTIR for a rapid and simultaneous determination of sugars and organic acids in apricot fruit

A simple, fast and accurate Fourier transform mid-infrared spectroscopy method was developed for simultaneously determining sugar and organic acid contents in apricot fruit slurries using the attenuated total reflectance. The potential of this method coupled with chemometric techniques based on partial least squares was assessed by comparison with currently used enzymatic determination of sucrose, glucose, fructose, malic acid and citric acid. Fruits of eight contrasted cultivars harvested at different ripening stages were used in this study and randomly divided in a calibration set (505 apricots) and in a validation set (252 apricots). The most suitable region was found in the range between 1500 and 900 cm⁻¹. Good prediction performances were obtained (R² ? 0.74 and RMSEP ? 18%). Results concerning the prediction of other quality traits such as firmness, skin colour, ethylene production, soluble solids content and titratable acidity were discussed.     

Identification and quantitative analysis of sugars and non-volatile organic acids in Chinese gooseberry fruit (Actinidia chinensis Planch.).

The free sugars and non-volatile organic acids in Chinese gooseberry fruit were extracted and separated by lead salt and ion-exchange procedures. Sugars and acids were identified and quantitatively determined by gas-liquid chromatography (g.l.c.) of their trimethylsilyl (TMS) derivatives. Glucose, fructose, sucrose and trace amounts of sorbitol accounted for the total sugars. Citric, quinic and malic are the major acids, the outstanding feature being the high content of quinic acid in mature fruit. Small amounts of phosphoric, ascorbic, glucuronic, galacturonic, oxalic, succinic, fumaric, oxalacetic and p-coumaric acids are also present. Qualitative and quantitative analysis of acids prepared as lead salts agreed closely with the determination of acids isolated by the ion-exchange procedure. Identifications of sugars and acids were confirmed by paper and thin-layer chromatography. Reducing sugars, total sugars and titratable acidity were determined by AOAC methods and the results compared with those from g.l.c.     

Changes in sugars, acids and fatty acids in naturally parthenocarpic date plum persimmon (Diospyros lotus L.) fruit during maturation and ripening

The date plum persimmon fruit (Diospyros lotus L., fam: Ebenaceae) is cultivated throughout northern of Turkey for its edible fruits. Sugars and organic acids were measured during fruit maturation and ripening using HPLC. The analyses showed that fructose and glucose were the main sugars accumulated in the fruit pulp. Fructose and glucose increased up to 43,552.8 mg.100 g^–1 fw and 35,450.8 mg.100 g^–1 fw respectively during fruit ripening. Sucrose content remained relatively low and decreased during ripening. The major organic acids found in date plum fruit were citric and malic acids, which increased through the immature and midripe maturity, and then the levels decreased in the overripe fruit. Palmitic acid (16:0), palmitoleic acid (16:1), stearic acid (18:0), oleic acid (18:1) and linolenic acid (18:3) were among the major fatty acids determined by GC throughout the maturation and ripening of the fruits. The levels of these fatty acids were found to be significantly different (P=0.05) between the three maturity stages. The fruits displayed the level of linoleic acid (0.7%) in low and -linolenic acid (17.8%) in higher quantities, and the combined levels of linoleic and -linolenic acid comprised 19% (120.1 g.g^–1 dw) of the total fatty acid content in the over ripened fruit. These results show that naturally parthenocarpic date plum fruits have high levels of sugars and organic acids and moderate levels of fatty acids that significantly changed during maturation and ripening. This information can be used by nutritionalists and food technologists to improve the nutrition of local people and develop food products that would be beneficial to human health.     

Flavonoids, sugars and fruit acids of alpine bearberry (Arctostaphylos alpina) from Finnish Lapland

Alpine bearberry (Arctostaphylos alpina L.) is a special circumpolar edible berry primarily used for household purposes but with greater potential in commercial applications than utilized thus far. In this study, the flavonoids of alpine bearberry were investigated with HPLC-DAD and HPLC-MS, and the sugars and fruit acids as trimethylsilyl derivates with GC-FID. The most abundant anthocyanin was cyanidin-3-O-galactoside accounting for over 95% of the anthocyanins. Eight other anthocyanins existed in trace amounts only, the richest of them being cyanidin-3-O-arabinoside and cyanidin-3-O-glucoside. Cyanidin accounted for over 99% of the anthocyanin aglycones. All the flavonols identified were glycosides of quercetin. Majority of the sugars were glucose and fructose while the most abundant fruit acid was quinic acid. The unique anthocyanin composition of alpine bearberry encourages advanced use of the berry as a food ingredient in private households and in industrial applications. In addition, it serves as a unique reference material for research purposes.     

Changes in the individual sugars of tomato fruit during ripening

Changes in the concentrations of the individual sugars of the walls and locular contents of tomato fruit during ripening have been studied. The major sugars were glucose and fructose together with much smaller amounts of sucrose and myoinositol. During the initial stages of development the fruit contained approximately twice as much glucose as fructose, but with approaching maturity and the onset of ripening the glucose/fructose ratio declined to less than unity. On a per fruit basis the distribution of the major sugars between the walls and locular contents was about 3 : 1 at the green stage, falling to 2 : 1 as the fruit ripened. Total reducing sugars (% fresh weight or per fruit) increased markedly between the mature green and green-yellow stages with a tendency to decrease with subsequent ripening. These changes were predominantly influenced by changes in fructose content, with glucose changing little. The concentrations of sucrose and myoinositol, both less than 0.05% fresh weight, declined with ripening. The green areas of the outer walls of “blotchy” fruit contained much less glucose and fructose than did the walls of normal mature green fruit, while the red areas contained amounts similar to those encountered in normally ripened red fruit.     

Comparison of NIR and MIR spectroscopic methods for determination of individual sugars,organic acids and carotenoids in passion fruit

In this work, NIR and MIR spectroscopy was investigated and compared for predicting passion fruit ripening parameters as sugars, organic acids and carotenoids. Spectra of 56 samples of the lyophilized passion fruit were collected using an integrating sphere in NIR range and attenuated total reflectance accessory in MIR range. Individual sugars (sucrose, glucose and fructose), organic acids (malic and citric acids) and carotenoids (β-carotene) contents were determined by reference methods. Spectral and reference data were analyzed by principal component analysis. Partial least square regression (PLSR) was used to establish calibration models. MIR technique was better than the NIR technique for glucose (R²_v = 0.942), fructose (R²_v = 0.855), sucrose (R²_v = 0.818), total sugar (R²_v = 0.914) and citric acid (R²_v = 0.913) content determination. On the other hand, NIR was superior for total acids (R²_v = 0.903) content determination. For malic acid and β-carotene contents both methods were unsatisfactory due to low concentrations of these constituents in the passion fruits.     

Thermal degradation of precursors and formation of flavour compounds during heating of cereal products. Part I. Changes of amino acids and sugars

Extracts from wheat, rye and barley malt have been used as a source for free amino acids and sugars in MAILLARD reaction studies. By means of special GLC techniques we have determined the content of 16 amino acids and 6 sugars during heating under controlled conditions; temperature, time and pH were used as variables. Large differences in the reactivity between the single amino acids were registered. Lysine as well as arginine, glutamic acid and proline decreased in high amounts within 15 min of heating at 120 °C. While glucose, maltose and maltotriose were reduced significantly during the thermic process with fructose an increase with time and temperature up to 120 °C was observed. Extreme pH values below 5 and above 7 caused high losses in amino acids. Increasing pH values supported the formation of fructose during heating.     

Assessment of the flavour of fresh uncooked onions by taste‐panels and analysis of flavour precursors,pyruvate and sugars

Flavour in fresh onions is dominated by volatile sulphenic and thiosulphenic acids that are liberated once alk(en)yl cysteine sulphoxide (ACSO) flavour precursors are cleaved by the enzyme alliinase after tissue disruption. The levels of pyruvate and ACSOs in over 100 samples of onions marketed in the UK were measured, and compared with assessment by taste‐panels. There was a linear relationship between the content of ACSOs and pyruvate. Measurements of pyruvate indicated that the marketing classification of some types of onion did not correspond to their pyruvate levels. A significant linear relationship was found between a sensory measure of strength and pyruvate over the range 1.2–9.3 µmol pyruvate g^?1 fresh weight. In most cases, when a flavour classification of sweet, mild or strong was applied to a sample of onions based on pyruvate content, the taste‐panels agreed with the categorization. The taste‐panels were unable to identify a sweet flavour in onions, except at low levels of pyruvate. Taste‐panels were able to define a likeability character (attractiveness of flavour) for onions, which correlated with the level of pyruvate. However, for some varieties, the flavour classification or likeability did not correspond to predictions based on pyruvate levels alone. Pyruvate measurements were seen as a suitable method for routine quality control once the characteristics of a variety of onion had been established, but initial evaluations should include well‐designed taste‐panel assessments. Copyright © 2004 Society of Chemical Industry     

Effects of latitude and weather conditions on sugars,fruit acids and ascorbic acid in currant (Ribes sp.) cultivars

BACKGROUND: Sugars, acids and vitamin C are essential components influencing the sensory and nutritional properties of currants (Ribes sp.). In this study the effects of growth latitude and weather conditions on these components in red, white and green currant cultivars were systematically investigated for the first time. RESULTS: Red Dutch (a red Ribes rubrum cultivar) contained more malic acid but fewer sugars and had a lower sugar/acid ratio than Vertti (a green Ribes nigrum cultivar) and White Dutch (a white R. rubrum cultivar). Fructose (27–56 g L^?1 juice) and glucose (21–54 g L^?1) were the major sugars in all currant samples, but sucrose (7–20 g L^?1) was present only in Vertti. Vertti contained the most ascorbic acid. Sugars, malic acid and the sugar/acid ratio in Red Dutch were 11–28% higher in southern Finland than in northern Finland. The corresponding values in Vertti were 6–16% lower in the south than in the north, but no differences were found in White Dutch. As the relative humidity decreased, the amounts of citric acid and total acid increased in all cultivars, while the amount of sugars increased in Vertti but decreased in White Dutch and Red Dutch. In Red Dutch, high temperature and radiation levels increased the sugar content. CONCLUSION: The influence of latitude and weather conditions on qualitative parameters of currants varies with the cultivar. This study provides important guidance for currant cultivation and for further physiological and enzymological studies. Copyright © 2009 Society of Chemical Industry     

The effects of added sugars and alcohols on the induction of crystallization and the stability of the freeze-dried peki (Caryocar brasiliense Camb.) fruit pulps

Peki (Caryocar brasiliense Camb.) is a Brazilian fruit with an extremely high β-carotene content, but the β-carotene is unstable under dry storage conditions. This work reports on the product development and stability of freeze-dried peki fruit pulp. Freeze-dried products were made by adding alcohols (ethanol and isopropyl alcohol; at concentrations of 0, 5 and 10 mL/100 mL of extract) and sugars (sucrose and fructose; at concentrations of 0, 5 and 10 g/100 mL of extract) to the peki fruit pulps followed by freeze-drying. Scanning electron microscopy was used to analyze the microstructure of the freeze-dried products by visualizing the crystallized forms. The product hardness and total carotenoid content following the different treatments were measured using a texture analyzer and a spectrophotometer, respectively. The stability of these foods was evaluated by their water sorption during their storage in various relative humidity environments at 25 °C. There were characteristic differences in their hygroscopic behaviors. The pretreatment with sucrose and ethanol improved the freeze-dried product and yielded a lower number of collapsed structures. Changes during the storage were observed. The pulp pretreated with sucrose was amorphous and metastable, but the drying process was accelerated by the presence of alcohol (mainly ethanol), which resulted in protected structures without any sign of collapse.     

Interactions of gallotannins with proteins,amino acids,phospholipids and sugars

Gallotannins play contrasting roles in food quality. They exhibit strong antioxidative and antibacterial properties, and at the same time show certain antinutritional effects. To explore this possible effect of gallotannins, the interaction mechanism between gallotannins and typical food components was investigated. The molecular structure of gallotannins and their interactions with amino acids (glycine, alanine, proline and leucine) were first studied. It is proved that galloyl groups of gallotannins are hydrophobic sites and that these groups can interact with aliphatic side chains of amino acids through hydrophobic association. Further, the binding of gallotannins (1,2,6-tri-O-galloyl-d-glucose (TGG) and 1,2,3,4,6-penta-O-galloyl-d-glucose (PGG)) to typical proteins, phospholipids and sugars was examined quantitatively. It is indicated that gallotannins bound more to proteins (histone, bovine serum albumin, casein and gelatin) and phospholipids (l-α-lecithin, l-α-cephalin and sphingomyelin) than to sugars, and that PGG had stronger binding affinity to proteins, phospholipids and sugars than did TGG. The gallotannin–protein and gallotannin–phospholipid interactions were the result of cooperative effects of hydrogen bonding and hydrophobic association, and hydrogen bonding was the predominant effect in the interactions between gallotannins and sugars.     

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。     

The effect of sugars and pectin on flavour release from a soft drink-related model system

Three types of sugar and high-methoxyl pectin at different concentrations were added to a soft drink-related model system consisting of water and six flavour compounds. The addition of these ingredients contributes to changes in viscosity and water activity, which in turn affects the release of the flavour compounds to the gas phase above the soft drink. In the study, a higher concentration of sucrose and invert sugar increased the release of five flavour compounds, probably owing to a so-called “salting-out” effect. Starch syrup at a concentration of 60% increased the amount of three of the flavour compounds released and would probably increase the release of more compounds at a higher concentration. When pectin was added to the system, it was seen that viscosity does not influence release of the flavour molecules, but that the kind of stabiliser used is more important.     

果酒中有机酸及其对果酒作用的研究

介绍了果酒中主要有机酸的来源及其在发酵过程中的变化,综述了果酒中有机酸的分析检测方法以及有机酸对果酒风味、口感、稳定性等方面的影响,为果酒酿造过程中酸的控制提供了依据,以期达到通过控制酿造过程中有机酸的含量和比例改善并且进一步提高果酒质量之目的。     

Organic acids and sugars composition of harvested pomegranate fruits

For two consecutive seasons, 40 Spanish pomegranate cultivars (cvs) were analysed and their individual organic acids and sugars compositions were examined. Intervarietal differences in acidity content reported by different authors were confirmed. According to organoleptic characteristics and chemical compositions three groups of varieties were established: sweet (SWV), soursweet (SSWV) and sour (SV). On average, for two seasons, total organic acids on a dry basis ranged between 0.317 g/100 g (SWV) and 2.725 g/100 g (SV). Citric, malic, oxalic, acetic (first reported here), fumaric, tartaric and lactic acids were detected, although lactic and fumaric were not quantifiable. On average, for both seasons, citric acid was predominant with a range of 0.142–2.317 g/100 g (average content for all CVS, 0.282 g/100 g). Malic acid was the second most abundant, with a range of 0.135–0.176 g/100 g (average of 0.139 g/100 g). Total sugars ranged between 11.43 g/100 g and 13.5 g/100 g. Glucose, fructose, sucrose and maltose were detected, although maltose (first reported here) was not quantifiable. Fructose ranged between 5.96 g/100 g and 7.04 g/100 g, with an average of 6.58 g/100 g, quite similar to that of glucose (6.14 g/100 g). Sour cv showed the lowest fructose and glucose contents. The average sucrose content was 0.01 g/100 g. Other differences among the groups of cvs were detected. Low total sugars and high acids were found in SV. The SSWV group had higher sugars than the SV. However, no difference in total sugars between SSWV and SWV was found. A lower acids content than SV but higher than SWV was found in the SSWV group. No other studies have been published so far on the individual organic acids and sugars of pomegranate fruit. Received: 27 July 1999 / Revised version: 28 September 1999     

Effect of free fatty acids on the flavour of frying oil

Lauric acid imparts soapy taste to edible oil and to fried bread in the concentration of less than 1 g·kg^-1, palmitic acid and stearic acid taste neutral in the concentration of up to 20 g·kg^-1, oleic acid is neutral in the same concentration range, while purified linoleic acid tastes slightly bitter, and the flavour of linolenic acid is bitter and rancid at the concentration of 1 g·kg^-1.