Volatile monocarbonyl compounds of carrot roots at various stages of maturity

Volatile carbonyl compounds of carrot variety Feonia Hunderup S-64 at various stages of maturity were analysed as their 2,4-DNPH's by a combined TLC-GLC-MS method. Twenty-three different carbonyl compounds were identified, of which undecanal, buten-2-al, methylbutenal, pentan-2-one, 6-methyl-5-hepten-2-one and 5-methylfurfural have not previously been found in carrot. During maturation the content of acetaldehyde and acetone increased significantly, while that of methylbutenal decreased.     

Volatile monocarbonyl compounds of arctic bramble (Rubus arcticus L.) at various stages of ripeness

Summary Volatile carbonyl compounds of arctic brambles at various stages of ripeness were analyzed as their 2,4-DNPH's by a combined TLC-GLC-MS method. Twenty-one different carbonyl compounds could be identified. During the ripening process the content of most carbonyl compounds increased, the largest changes occuring in the amounts of acetaldehyde, pentenal, acetone, acetonn and diacetyl but the content of hexenal decreased.

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Zusammenfassung Die leichtflüchtigen Carbonylverbindungen der Brombeere wurden in verschiedenen Stufen der Reife als 2,4-DNPH mit der kombinierten DC-GC-MS-Methode analysiert. 21 verschiedene Carbonylverbindungen wurden entdeckt. Während des Reifens vermehrte sich die Quantität der meisten Carbonylverbindungen; die größten Veränderungen geschahen in der Menge des Acetaldehyds, Pentenals, Acetons, Acetons und Diacetyls. Der Gehalt an Hexenal verminderte sich.

     

Volatile compounds of Cantonese sausage released at different stages of processing and storage

The volatile compounds of Cantonese sausage at different stages of processing and storage were analysed by gas chromatography/mass spectrometry (GC/MS) with solid-phase microextraction (SPME). One hundred and four volatile compounds were identified. Esters and alcohols were the most important chemicals in all the samples, accounting for 16.94–50.12% and 30.01–65.54% of the total area, respectively. Ethanol and its alcohol esters were the major volatile compounds of Cantonese sausage, which suggested that the alcohol added to sausage at the preparation stage was the most important factor for the characteristic flavour of Cantonese sausage. Aldehydes (especially hexanal) contributed between 3.33% and 17.42% to the total areas. The presence of carboxylic acids in esters indicated that lipid oxidation played a key role on the flavour formation of Cantonese sausage. Amino acid catabolism and microbial activity also played an active role in the formation of volatile compounds.     

Volatile components of mangaba fruit (Hancornia speciosa Gomes) at three stages of maturity

The effect of stage of maturity on the volatile components of mangaba fruit (Hancornia speciosa Gomes) growing at Sergipe State, Brazil, was investigated at three different stages. The volatile profile obtained by hydrodistillation, using a Clevenger-type apparatus, was analysed by GC–FID and GC–MS. It was possible to identify 33 compounds in the immature fruits, such as 1-octen-3-ol (2.8%), (Z)-linalool oxide (9.1%), (E)-linalool oxide (6.3%), linalool (16.1%), 2-phenylethanol (4.5%), α-terpineol (5.5%), geraniol (3.1%), hexadecanal (2.5%) and octadecanol (2.7%); 34 compounds in the fruits at the intermediate stage, such as ethyl propanoate (4.1%), n-propyl acetate (11.1%), 3-methyl-3-buten-1-ol (6.8%), 2-methyl propyl acetate (2.5%), furfural (18.6%), (Z)-3-hexenol (3.2%), 1-hexanol (2.4%), 3-methyl-3-buten-1-yl acetate (5.4%), (Z)-3-hexen-1-yl acetate (2.9%), n-hexyl acetate (3.3%), (Z)-linalool oxide (3.9%), (E)-linalool oxide (2.4%), linalool (3.8%), 2-phenylethanol (2.8%) and α-terpineol (2.5%); and 32 components in the mature fruits, such as 3-hydroxy-2-butanone (9.1%), 2,4,5-trimethyl-1,3-dioxolane (6.8%), 3-methyl-3-buten-1-ol (12.1%), 3-methyl-1-butanol (5.2%), furfural (8.3%), 3-methyl-1-butanyl acetate (8.8%) and 3-methyl-3-buten-1-yl acetate (28.2%).     

Volatile and nonvolatile chemical composition of some date fruits (Phoenix dactylifera L.) harvested at different stages of maturity

Physico‐chemical and aroma volatile compositions of three date palm cultivars were studied throughout fruit maturation (besser, rutab and tamr stages) during 2008 harvest season. The studied parameters varied significantly through the different stages, with some variations also depending on the cultivar. Length and width of the three types of dates showed a progressive decrease during ripening. The pH level, total sugars and ash contents significantly increased up to tamr stage. Conversely, moisture, lipid and protein contents decreased. The profile of the volatile aroma compounds was evaluated using solid‐phase micro‐extraction. Sixty‐nine compounds were detected during maturation, accounting from 98.5% to 99.6% at besser, 93.1% to 99.2% at rutab and 94.3% to 98.4% at tamr stages of the total identified volatiles. The present study sheds more light on chemical characteristics of the studied cultivars that can be used in many industrial processes.     

Volatile compounds formation in alcoholic fermentation from grapes collected at 2 maturation stages: influence of nitrogen compounds and grape variety

The aim of this work was to study the influence of nitrogen compounds on the formation of volatile compounds during the alcoholic fermentation carried out with 4 nonaromatic grape varieties collected at 2 different maturation stages. To do this, Monastrell, Merlot, Syrah, and Petit Verdot grapes were collected 1 wk before harvest and at harvest. Then, the musts were inoculated with the same Saccharomyces cerevisiae yeast strain and were fermented in the same winemaking conditions. Amino acids that showed the highest and the lowest concentration in the must were the same, regardless of the grape variety and maturation stage. Moreover, the consumption of amino acids during the fermentation increased with their concentration in the must. The formation of volatile compounds was not nitrogen composition dependent. However, the concentration of amino acids in the must from grapes collected 1 wk before harvest can be used as a parameter to estimate the concentration of esters in wines from grapes collected at harvest and therefore to have more information to know the grape oenological capacity. Application of principal components analysis (PCA) confirmed the possibility to estimate the concentration of esters in the wines with the concentration of nitrogen compounds in the must.     

不同成熟度柑橘力学特性研究

为避免机器人在采摘柑橘过程中对柑橘造成破坏,利用TA-XT2i型质地分析仪对青色柑橘、半成熟柑橘和成熟柑橘整果进行纵向压缩和横向最大截面处穿刺实验,研究不同成熟度柑橘的压缩抗力和最大抗穿刺力,结果表明,青色柑橘的抗破坏能力最强,承受的最大压力不宜超过190N,最大穿刺力不宜超过8N;成熟柑橘的抗破坏能力最差,承受的最大压力不宜超过100N,最大穿刺力不宜超过3N;半成熟期柑橘承受的最大压力不宜超过120N,最大穿刺力不宜超过5N。      

Volatile and non-volatile chemical composition of the white guava fruit (Psidium guajava) at different stages of maturity

The effect of the maturation stages on the chemical composition and volatile compounds of the white Guava (Psidium guajava) Cv. Cortibel was investigated during three different stages. The stages were characterized by evolution of color, pH, titratable acidity, sugars, soluble solids, vitamin C and volatile components. The fruits were stored at 24 °C and air humidity of 74% for 13 days. The volatile extracts were obtained using headspace technique and analyzed using gas chromatograph/mass spectrometry (GC/MS) system. The titratable acidity and sugars decreased. The pH level and amount of vitamin C increased throughout progress of maturation. The behavior of volatile compounds of fruits in the three stages of maturation was: in immature fruits and those in their intermediate stage of maturation, were predominantly the aldehydes such as (E)-2-hexenal and (Z)-3-hexenal. In mature fruits, esters like Z-3-hexenyl acetate and E-3-hexenyl acetate and sesquiterpenes caryophyllene, α-humulene and β-bisabollene are present.     

Pectinesterase activity of some Iraqi dates at different stages of maturity

Changes in the pectinesterase (PE) activity in four Iraqi date varieties at different stages of maturity were followed. The enzyme activity was determined by titration of the carboxylic groups released by the hydrolysis of pectin. The results obtained show that there was an increase in PE activity in these varieties with ripening. The greatest increase occurred during the period when the fruit had passed the yellowish stage and turned soft. This increase in the enzyme activity was then followed by a general decrease as the fruit matured and ripened on the tree. The data also indicate that there was a qualitative difference in the behaviour of these varieties.     

Polyphenol composition and antioxidant capacity in pulp and peel of apricot fruits of various varieties and maturity stages at harvest

Polyphenol composition and antioxidant capacities of peel and pulp tissues of six apricot varieties were determined. Variations in polyphenol and antioxidant capacity based on variety (early‐maturing varieties and late‐maturing varieties) and harvest maturity (green mature and full mature) were assessed. The results of principal component analysis revealed that (+)‐catechin made the most important contributions to the antioxidant capacities of the pulp. As the (+)‐catechin content in ‘Dajie’ apricot decreased by 36.8% from green mature to full mature, the antioxidant capacities determined by ABTS free radical scavenging assay, DPPH free radical scavenging assay and cupric ion reducing antioxidant capacity assay decreased by 50.0%, 45.2% and 45.8%, respectively. Levels of phenolic compounds in the apricot peels were approximately 2–4 times higher than those of the pulps. Quercetin‐3‐rutinoside may be substantially responsible for the antioxidant capacities of the peels. The late‐maturing varieties tended to have higher levels of phenolic compounds and higher antioxidant capacities than the early‐maturing varieties. The antioxidant capacities in green mature apricots were much higher than those of full mature apricots.     

Rheological properties of Josapine pineapple juice at different stages of maturity

The rheological behaviour of Josapine pineapple juice with at various maturity stages was studied at a wide range of temperature (5–65 °C) and concentration (4–14 °Brix) using a rotational rheometer as the measuring system. The results show that josapine pineapples juice demonstrated a Newtonian behavior and is influenced by maturity stage, temperature and concentration. The Arrhenius typed equation successfully describe the effect of temperature on the viscosity, on the other hand, the effect of concentration can be described better using exponential equation. Finally, an equation describing the combined effect of temperature and concentration on viscosity at different stages of maturity was successfully developed.     

不同成熟期番石榴果实品质特征与评价

目的 比较不同品种、不同成熟期的番石榴（Psidium guajava Linn.）果实品质特征。方法 采用国家标准方法,对不同品种不同成熟期番石榴果实的食用品质、外观品质和营养品质进行测定和分析。结果 番石榴各品种食用品质随果实发育成熟而明显提高,始熟期均表现出质地硬、汁液少、涩味重等共性,至完全成熟期食用状态最佳,‘水蜜’番石榴食用品质最好,‘珍珠’次之。不同成熟期红宝石的纵径、横径、单果重均显著高于相同成熟期的其它品种(P<0.05)。同一品种不同成熟期果实的纵径、横径和单果重,从始熟期至成熟期再至完全成熟期,均表现出显著上升的趋势(P<0.05),‘水蜜’的果形指数维持在<1.0,其余3个品种果形指数均维持在≥1.0。从始熟期至完全成熟期,4个品种番石榴果实含水量显著提高(P<0.05),淀粉、粗纤维含量均显著下降(P<0.05)。4个番石榴品种的总糖均主要由还原糖和蔗糖组成,且对于每个品种每个成熟期还原糖含量均高于蔗糖,还原糖、蔗糖、总糖含量随着果实成熟度的提高显著上升。在果实完全成熟期,还原糖、蔗糖、总糖均以 ‘红宝石’的含量最高,分别为32.74%、28.97%、63.16%,4个品种果糖含量范围为9.77~12.05%,葡萄糖为3.70~10.17%,每个品种的果糖含量均高于葡萄糖,品种之间葡萄糖含量差异较大。不同成熟期总酸含量均以‘珍珠’最高,其含量范围为5.32~7.58 g/kg。 结论 各成熟期‘水蜜’食用品质均最好,但外观差,‘西瓜’食用品质最差、含糖量最低。完全成熟期,‘珍珠’食用品质仅次于‘水蜜’,含糖量仅次于‘红宝石’,蛋白质含量最高,果实综合品质最佳,适于鲜食、制果汁,‘红宝石’含糖量高、个大,适于果茶、果酒加工。     

Volatile compounds, odor, and aroma of La Serena cheese high-pressure treated at two different stages of ripening

La Serena cheeses made from raw Merino ewe's milk were high-pressure (HP) treated at 300 or 400 MPa for 10 min on d 2 or 50 after manufacture. Ripening of HP-treated and control cheeses proceeded until d 60 at 8°C. Volatile compounds were determined throughout ripening, and analysis of related sensory characteristics was carried out on ripe cheeses. High-pressure treatments on d 2 enhanced the formation of branched-chain aldehydes and of 2-alcohols except 2-butanol, but retarded that of n-aldehydes, 2-methyl ketones, dihydroxy-ketones, n-alcohols, unsaturated alcohols, ethyl esters, propyl esters, and branched-chain esters. Differences between HP-treated and control cheeses in the levels of some volatile compounds tended to disappear during ripening. The odor of ripe cheeses was scarcely affected by HP treatments on d 2, but aroma quality and intensity scores were lowered in comparison with control cheese of the same age. On the other hand, HP treatments on d 50 did not influence either the volatile compound profile or the sensory characteristics of 60-d-old cheese.     

Volatile constituents of horseradish roots

Essences of the volatile components of five samples of horseradish root, three fresh and two of dried flakes, have been prepared and examined by gas chromatography (g.c.) and combined gas chromatography-mass spectrometry (g.c.-m.s.). At least 17 compounds are involved. Five of these have been rigorously identified by comparison with authentic compounds, synthesised where necessary, through mass spectra and retention data and the identities of three others have been tentatively established. The compounds concerned are methyl, ethyl, isopropyl, 2-butyl, allyl, 4-pentenyl and 2-phenethyl isothiocyanate and allyl thiocyanate. The constituents of the five essences were assessed semi-quantitatively by g.c. and definite differences found. These were reinforced by examination of the headspace vapours over the coarsely grated root. Additional attention was devoted to the allyl isothiocyanate-thiocyanate interconversion and to the odour assessment of the volatile horseradish components.     

Aroma components at various stages of litchi juice processing

BACKGROUND: Considering the importance of flavour on the quality of litchi juice, a study was conducted on how processing and operating stages influence the aroma components of clear litchi juice during processing. RESULTS: The aroma fractions isolated by solid‐phase micro‐extraction were analysed by capillary gas chromatography–mass spectrometry. According to statistical analyses, the amount of total and seven characteristic aroma compounds (geraniol, citronellol, phenylethyl alcohol, D ‐limonene, nonanal, geranial and linalool) increased significantly after enzyme hydrolysis, but decreased significantly during the process of enzyme inactivation, ultra‐filtration and sterilisation. CONCLUSION: The aromatic fraction of litchi juice decreased greatly during processing. The major losses in aromatic composition of clear litchi juice were related to the ultra‐filtration and sterilisation processes. With regard to the retention of aroma, an ultra‐filtration membrane with a larger pore size is better than a membrane with a smaller pore size, and a high‐voltage pulsed electric field was better than thermal sterilisation. Copyright © 2009 Society of Chemical Industry     

Tannin levels in leaves of some oak species at different stages of maturity

Total phenolics, condensed tannins, degree of polymerisation, protein precipitation capacity, protein precipitable phenolics and specific activity (protein bound per unit tannins) were determined in the leaves of four oak species at different stages of maturation (4 days old to 1 year old). The content of total extractable phenols was higher in younger leaves in Quercus ilex Linn, Quercus semecarpifolia Sm and Quercus serrata Roxb, whereas in Quercus glauca Thumb the content was higher in the mature leaves. In all species studied, condensed tannins increased with maturation. Protein precipitation capacity had a trend similar to that of total phenols. In Q serrate and Q semecarpifolia the apparent degree of polymerisation increased, and the content of protein precipitable phenolics and specific activity decreased as the leaves matured. The decrease in protein precipitation capacity with maturation in these two species may be explained by both the decrease in the content and the change in the nature of phenols capable of binding proteins. Protein precipitation capacity was not detectable in Q ilex leaves. Protein precipitation capacity in the mature leaves decreased in the order of Q serrata > Q semecarpifolia > Q glauca > Q ilex.     

Volatile flavour compounds of yoghurt

The volatile flavour compounds of three samples of Egyptian yoghurt were analysed over a two-week period at 8°C using a simple headspace gas chromatography technique in order to study the changes and relate them to flavour acceptability.
Volatile compounds present were acetaldehyde, diacetyl, acetoin, acetone, butanone, and acetic acid. Acetone and butanone disappeared within the first week of storage, whereas acetaldehyde, diacetyl and acetoin declined steadily but were still present after two weeks. Acetic acid increased to about twice its original level after 10d of storage.
The decreases in acetaldehyde, diacetyl, acetoin, and the increase of acetic acid were closely related to the rapid decrease in product acceptability after 8–10d storage.