Storage and ultraviolet‐induced tissue stress effects on fresh‐cut pineapple

The effect of UV‐induced stress on the volatile aroma compounds in cut pineapple was compared with that of storage at 4 °C for 24 h. Eighteen volatile compounds were identified by solid‐phase microextraction (SPME) in fresh‐cut pineapple. Methyl‐2‐methylbutanoate, methyl hexanoate, methyl 5‐hexenoate, ethyl hexanoate and ethyl 5‐hexenoate were the major aroma compounds. Storage at 4 °C for 24 h, and exposure of cut fruit to UV radiation for 15 min caused a considerable decrease in the concentration of esters and increase in the relative amount of copaene. This sesquiterpene, when added to crushed cantaloupe melon (0.1 mg g^?1), inhibited microbial growth in the fruit over a period of 24 h at 20 °C. Cis‐ and trans‐ocimene were present in the fruit but their production was not photo‐induced by UV irradiation. Ocimene, however, was a potent antimicrobial agent that killed microorganisms when added to the crushed fruit and stored at 20 °C for 24 h. The results indicate that sesquiterpene phytoalexins could contribute to the defense mechanism in wounded pineapple tissue. Published in 2004 for SCI by John Wiley & Sons, Ltd.     

Changes in wheat lipids during mixing and resting of flour-water doughs

Lipids extracted with water-saturated n-butanol from flour and flour-water doughs were examined to determine the extent of oxidations and other changes which occurred in mixing and resting dough. Extracted lipids were converted to fatty acid methyl esters (FAME) and quantified by gas-liquid chromatography (g.l.c.) using heptadecanoic acid (17 : 0) as internal standard. The original flour or dough and the corresponding solvent-extracted residues were acid hydrolysed, and the hydrolysate lipids converted to FAME for g.l.c. determination of the total lipid and residual unextracted lipid contents. The total flour or dough lipids equalled the extracted lipids + unextracted lipids, except where there were unavoidable autoxidative losses of linoleate (18 : 2) and linolenate (18 : 3). The unextracted flour lipids (13% of total lipids) were not oxidised during dough mixing. There were no changes in any of the extracted lipid classes other than free fatty acids (FFA) and monoglycerides (MG) which showed losses of 18 : 2 and 18 : 3 after aerobic dough mixing. Losses of FFA and MG are attributed to lipoxygenase activity during dough mixing and the period immediately after. The small amount of 18 : 2 in the “free” petroleum ether-extracted FFA appeared to be unaffected by lipoxygenase. Recoveries of FFA other than 18 : 2 or 18 : 3 were constant, indicating no lipolysis of glycerolipids and no general oxidation or degradation of FFA. Experiments with [U-¹⁴C]palmitic acid confirmed that there was no oxidation, degradation or re-esterification of FFA. Much of the non-polar lipids (steryl ester, triglyceride, diglyceride, FFA, MG) and almost all of the polar lipids were bound on dough mixing. Binding was non-selective with regard to fatty acid composition. Triglyceride was the only lipid class bound to a greater extent in anaerobic dough than in aerobic dough. Some selectivity of binding between lipid classes was indicated.     

Evolution of aroma compounds of murtilla fruits (Ugni molinae Turcz) during storage

BACKGROUND: ‘Murtilla’, ‘mutilla’ or ‘murta’ (Ugni molinae Turcz) is a native Chilean species that produces a small berry fruit with a special aroma, whose volatile compounds have not yet been identified. The fruit may be consumed raw and also as jams, juice, canned products, confections and liquor. RESULTS: At the beginning and end of the storage, 24 volatile compounds were identified in murtilla fruit aroma and the concentration of these compounds in murtilla fruit ranged from 1.2 to 250.5 µg kg^?1 fresh weight. Methyl 2‐methyl butanoate, ethyl butanoate, ethyl 2‐methyl butanoate, methyl hexanoate, ethyl hexanoate, methyl benzoate and ethyl benzoate were the major components, all of which have been reported as potent odors in other aromatic fruits. Based on estimated odor activity value, the most potent compound in the murtilla fruit aroma were ethyl hexanoate and 4‐methoxy‐2,5‐dimethyl‐furan‐3‐one. The statistical analysis showed that the storage produced a distinct effect on the same volatile compounds released from the murtilla ecotypes. CONCLUSION: The volatile compounds identified in murtilla fruit aroma, which may be described as fruity, sweet and floral, have been found in other aromatic fruits. Concerning the aroma, the murtilla fruit from ecotype 19‐1 was shown to be the best in cooled storage. Copyright © 2007 Society of Chemical Industry     

In vivo incorporation of C14-1-acetate into liver and plasma lipids of postnatally overfed rats

Postnatal overnutrition due to breeding of rats in small nests (4 pups per dam) leads to distinct metabolic changes in later life stages even in conditions of ad libitum feeding. At an age of 5 months rats from small nests differ from those of large nests (14 pups per dam) in a significant higher level of liver triglycerides and cholesterol esters, whereas changes in plasma lipids concern only the increased cholesterol ester fraction. The relative distribution of in vivo incorporated C¹⁴-l-acetate into liver lipids shows a higher moiety in the triglyceride fraction of animals from small nests but no changes of the relative distribution of activity among lipid fractions of plasma. These changes of lipid metabolism are discussed in relation to the development of an obese state of postnatally overfed animals.     

生物柴油酯基结构优化及其对低温性能研究

在自行设计的反应装置中,以自制吡啶硫酸氢盐离子液体为催化剂,采用酯交换法制得了硬脂酸类脂的8种酯。通过条件优化分析,找出了硬脂酸甲酯、乙酯、丙酯、异丙酯、丁酯、异丁酯、戊酯、异戊酯的最佳反应条件,转化率均在97%以上;对8种酯进行了IR分析,制备的8种酯主要官能团和化学键均与标准符合;最后对5种直链酯和3种支链酯进行了低温性能测验,结果表明,直链酯、支链酯碳链长度越长,低温性能越好;同一碳链长度下,支链酯比直链酯的低温性能要好。     

Fractionation of lipids and purification of γ-linolenic acid (GLA) from Spirulinaplatensis

The microalgae, Spirulinaplatensis, is an excellent source of γ-linolenic acid (GLA), an essential polyunsaturated fatty acid and a potent nutraceutical. The fatty acid composition of S.platensis ARM 740 was determined after transmethylation by gas chromatography (GC). Lipid fractionation was achieved on silica gel column chromatography and preparative TLC. Neutral lipids, glycolipids and phospholipids accounted for 77.0%, 15.6% and 7.4%, respectively, of the total lipid fraction. S.platensis ARM 740 was found to contain 94% of the total GLA in the glycolipid fraction. Attempts were made to purify GLA methyl ester by using urea to form inclusion complexes with the saturated and the less unsaturated FAMEs (fatty acid methyl esters), which enhanced the purity of GLA methyl ester to 84%. A further approach to isolate GLA methyl ester with higher purity involved the use of argentated silica gel chromatography. An initial PUFA concentration step frequently adopted by most researchers to increase GLA purity was not necessary in the isolation of GLA from S.platensis. A GLA methyl ester with a purity of >96% and a recovery of 66% was obtained. Purity of the isolated GLA methyl ester was confirmed by GC and IR analysis with respect to authentic standard.     

Ursolic acid and its esters: occurrence in cranberries and other Vaccinium fruit and effects on matrix metalloproteinase activity in DU145 prostate tumor cells

BACKGROUND: Ursolic acid and its cis‐ and trans‐3‐O‐p‐hydroxycinnamoyl esters have been identified as constituents of American cranberries (Vaccinium macrocarpon), which inhibit tumor cell proliferation. Since the compounds may contribute to berry anticancer properties, their content in cranberries, selected cranberry products, and three other Vaccinium species (V. oxycoccus, V. vitis‐idaea and V. angustifolium) was determined by liquid chromatography‐mass spectroscopy. The ability of these compounds to inhibit growth in a panel of tumor cell lines and inhibit matrix metalloproteinase (MMP) activity associated with tumor invasion and metastasis was determined in DU145 prostate tumor cells. RESULTS: The highest content of ursolic acid and esters was found in V. macrocarpon berries (0.460–1.090 g ursolic acid and 0.040–0.160 g each ester kg^?1 fresh weight). V. vitis‐idaea and V. angustifolium contained ursolic acid (0.230–0.260 g kg^?1), but the esters were not detected. V. oxycoccus was lowest (0.129 g ursolic acid and esters per kg). Ursolic acid content was highest in cranberry products prepared from whole fruit. Ursolic acid and its esters inhibited tumor cell growth at micromolar concentrations, and inhibited MMP‐2 and MMP‐9 activity at concentrations below those previously reported for cranberry polyphenolics. CONCLUSION: Cranberries (V. macrocarpon) were the best source of ursolic acid and its esters among the fruit and products tested. These compounds may limit prostate carcinogenesis through matrix metalloproteinase inhibition. Copyright © 2011 Society of Chemical Industry     

Selective extraction and quantitative analysis of non-starch and starch lipids from wheat flour.

Wheat flour non-starch lipids (lipids not bound to starch) were quantitatively extracted with water-saturated n-butanol (WSB), benzene-ethanol-water (10:10:1, by vol.) or ethanol-diethyl ether-water (2:2:1, by vol.) in 10min at 20 °C. Starch lipids (lipids bound to starch) were subsequently extracted with WSB at 90–100 °C. Carotenoid pigments were quantitatively extracted with the non-starch lipids. There was no significant hydrolysis of esterified fatty acids and no detectable autoxidation of unsaturated acids in the hot solvent extracts. Non-starch and starch lipids from a high grade spring wheat flour and three grades of winter wheat flour were separated by thin-layer chromatography and quantified as fatty acid methyl esters (FAME) by gas-liquid chromatography (g.l.c.) using heptadecanoic acid (or its methyl ester) as internal standard. Total flour and starch lipids after acid hydrolysis were also converted to FAME for quantitation by g.l.c. Non-starch lipids consisted of 59–63% non-polar (neutral) lipids, 22–27% polar glycolipids and 13–16% phospholipids. Steryl esters, triglycerides, and all the diacyl galactosylglycerides and phosphoglycerides were present only in non-starch lipids. Starch lipids consisted of 6–9% non-polar (neutral) lipids (mostly free fatty acids), 3–5 % polar glycolipids and 86–91 % phospholipids (mostly lysophosphatidyl choline). Starch lipids were almost exclusively monoacyl lipids. Factors are given for converting weight of FAME into weight of original lipid for all individual lipid classes in wheat which contain O-acyl groups. Factors for total lipids are: total starch lipids = FAME × 1.70, total non-starch lipids = FAME × 1.20, and total flour (non-starch + starch) lipids = FAME × 1.32. Similar factors could be used to convert weight of lipids obtained by conventional acid hydrolysis methods into weight of unhydrolysed lipids. Phospholipid contents are given by: total starch phospholipids = P × 16.51, total non-starch phospholipids = P × 23.90, total flour phospholipids = P × 17.91.     

Aroma profile and volatiles odor activity along gold cultivar pineapple flesh

Physicochemical attributes, aroma profile, and odor contribution of pineapple flesh were studied for the top, middle, and bottom cross-sections cut along the central axis of Gold cultivar pineapple. Relationships between volatile and nonvolatile compounds were also studied. Aroma profile constituents were determined by headspace solid-phase microextraction at 30 °C, followed by gas chromatography/mass spectrometry analysis. A total of 20 volatile compounds were identified and quantified. Among them, esters were the major components which accounted for 90% of total extracted aroma. Methyl butanoate, methyl 2-methyl butanoate, and methyl hexanoate were the 3 most abundant components representing 74% of total volatiles in pineapple samples. Most odor active contributors were methyl and ethyl 2-methyl butanoate and 2,5-dimethyl 4-methoxy 3(2H)-furanone (mesifuran). Aroma profile components did not vary along the fruit, but volatile compounds content significantly varied (P < 0.05) along the fruit, from 7560 to 10910 μg/kg, from the top to the bottom cross-sections of the fruit, respectively. In addition, most odor-active volatiles concentration increased from the top to the bottom 3rd of the fruit, concurrently with soluble solids content (SSC) and titratable acidity (TA) differences attributed to fruitlets distinct degree of ripening. Large changes in SSC/TA ratio and volatiles content throughout the fruit found through this study are likely to provoke important differences among individual fresh-cut pineapple trays, compromising consumer perception and acceptance of the product. Such finding highlighted the need to include volatiles content and SSC/TA ratio and their variability along the fruit as selection criteria for pineapples to be processed and quality assessment of the fresh-cut fruit.     

THE INFLUENCE OF LIPIDS DERIVED FROM MALT SPENT GRAINS ON YEAST METABOLISM AND FERMENTATION

The addition to wort of lipids derived from malt spent grains had a pronounced effect on yeast metabolism. The lipids allowed the fermentation of de-oxygenated wort and also stimulated yeast growth and the corresponding rate and extent of fermentation of air-saturated wort by yeast strains having a high oxygen requirement. The lipids increased the fusel alcohols content of beer and decreased the content of esters and medium chain-length fatty acids. The yeast incorporated sitosterol and unsaturated fatty acids from the spent grain lipids and the unsaturated fatty acids changed the pattern of fatty acids and sterols synthesized by the yeast. The fatty acids were present in the spent grain lipids mainly as triglycerides, free fatty acids and phospholipids. Using pure lipid compounds it was shown that the triglycerides were inactive and that the spent grain lipids exerted their effect on fermentation through the synergistic action of free unsaturated fatty acids, sitosterol and phospholipid. Phospholipid could be replaced by the detergent, Triton X-100. The effect of the lipids on the synthesis of esters, fusel alcohols and medium chain fatty acids could be explained solely by their content of unsaturated fatty acids.     

三种水果韭花酱香气成分分析

采用顶空固相微萃取(HS-SPME)与气相色谱-质谱联用(GC-MS)法分析对照韭花酱及加入3种不同水果(苹果、梨、菠萝)韭花酱的香气成分。在温度20℃、萃取时间30min 的条件下,对3 种水果韭花酱香气成分测定。结果：从苹果韭花酱、梨韭花酱、菠萝韭花酱中分别鉴定出7、7、11 种香气成分;4 种韭花酱的共有成分为甲硫醇、二甲基二硫醚、一硫二丙烯、二甲基三硫醚,其中苹果韭花酱中特有成分为1- 甲硫基-1- 丙烯-(E),菠萝韭花酱中特有成分为丁酸甲基酯、2-甲基-丁酸-甲基酯、甲基酯己酸、甲基丙基二硫醚、二噻烷。     

Structures and pesticidal activities of derivatives of dinitrophenols. 8. Effects of substitution with C5 to C13-s-alkyl groups and of esterification on the acaricidal activity of dinitrophenols

38 methyl-, 37 ethyl- and 19 other alkyl-carbonates, 37 crotonates, 10 acrylates and 17 other esters, and 15 methyl ethers of 2-(C₅ to C₁₃-s-alkyl)-4,6-dinitro- and 4-(C₄ t4 to C₁₃-s-alkyl)-2,6-dinitrophenols were synthesised, and their activities against Tetranychus telarius (greenhouse red spider mite) were investigated. 2-s-Alkyl-4,6-dinitrophenols and esters were more active than their 4-s-alkyl-2,6-dinitro- analogues, acaricidal activity remaining high with the 4,6-dinitrophenols up to 2-(C₁₁-s-alkyl). Generally compactness of the 2-s-alkyl group aided activity. Methyl ethers had very low activity. Esters of 2-(C₃ to C₇-s-alkyl)-4,6-dinitrophenols were more acaricidal than the parent phenols, but the reverse was the case with C₈ to C₁₃-s-alkyl compounds. Crotonates and other esters were generally less active than methyl carbonates. The methyl carbonates of 2-(1-ethylhexyl)- and 2-(1-propylpentyl)-4,6-dinitrophenols were found to be of particular economic interest as acaricides.     

Investigation on the role played by fermentation esters in the aroma of young Spanish wines by multivariate analysis

The role played by ethyl esters of fatty acids and by acetates of higher alcohols on the aroma of young wines from neutral grape varieties has been investigated. The statistical methods used have been stepwise linear regression and principal components analysis. Very significant conclusions have been reached. The role played by these compounds depends on the type of wine. In white wines their main role is in the perception of tree fruit and tropical fruit notes. It has been demonstrated that the former notes are linked to ethyl esters, while the latter are linked mainly to acetates of higher alcohols. In rose wines the intensity of tree fruit aroma was correlated with ester content, however no clear conclusion was reached about the role of various compounds on the perception of quality. Finally, in red wines these compounds do not determine the intensity of fruit aromas, and they only play a modulating role on aroma quality. This indicates that red grape varieties must have other aroma compounds which are responsible for the fruity characteristics of wines.     

Effect of nitrogen fertilization on quality markers of strawberry (Fragaria × ananassa Duch. cv. Aromas)

BACKGROUND: Nitrogen is an indispensable element for fruit metabolism and low or excessive N levels can affect the accumulation of the most important components that contribute to the flavour and aroma of the fruit. Among them, sugars, acids and volatile compounds can be considered quality markers. The objective of this study was to evaluate the effect of N fertilization on these quality markers of the fruit at two harvest dates. RESULTS: Strawberry plants were grown in a hydroponic system and N was applied as Ca(NO₃)₂ at concentrations of 0.3, 3 and 6 mmol L^?1 in the nutrient solution. Total soluble solids, soluble carbohydrates, amino acids and organic acids and volatile compounds of the fruit were analyzed. The fruits produced at 3 and 6 mmol L^?1 N had higher contents of esters, soluble carbohydrates and amino acids. The hexanal content increased with the 6 mmol L^?1 dose. The effect of fertilization was more marked at the second harvest date. CONCLUSION: The availability of N in strawberry plants affected the accumulation of quality markers. The fruits expected to have the best flavour and aroma, with both high levels of soluble carbohydrate and esters and low levels of hexanal, were obtained with 3 mmol L^?1 nitrate in the solution. Copyright © 2009 Society of Chemical Industry     

REDUCTION IN MICROBIAL GROWTH AND IMPROVEMENT OF STORAGE QUALITY IN FRESH-CUT PINEAPPLE AFTER METHYL JASMONATE TREATMENT

Maintaining the quality of a fresh‐cut fruit or vegetable product is a major concern and a priority in the development and in the production of fresh‐cut produce products of the industry. The industry has been searching for alternative methods to protect fresh‐cut produce from decay and to prolong shelf life. The objective of this research is to enhance the quality and the shelf life of fresh‐cut pineapple by exposure to methyl jasmonate (MJ). The exposure of the diced pineapple to a MJ emulsion at a concentration of 10 ^?4 M for 5 min in a sealed container decreased microbiological growth by 3 logs after 12 days of storage at 7C, compared with the control pineapple. Methyl jasmonate as vapor or as dip did not affect the firmness or the color of the fruit. Methyl jasmonate may be a practical treatment to ensure the safety and the quality of fresh‐cut pineapple and other fruits and vegetables.     

Oxidation of free and esterified linoleic and linolenic acids in bread doughs by wheat and soya lipoxygenases

Lipids containing ¹⁴C-labelled linoleic and linolenic acids were added to flour which was then made into bread doughs with or without 2% enzyme-active soya flour. The ¹⁴C-labelled lipids and their oxidation products were analysed as intact lipids or as ¹⁴C fatty acid methyl esters by thin-layer chromatography. In the control doughs wheat lipoxygenase oxidised free fatty acids and monoglycerides. In doughs containing soya flour, steryl esters, triglycerides, diglycerides, mono-galactosyl diglycerides, digalactosyl diglycerides and phosphatidyl choline were also oxidised, and the oxidation of these lipids is attributed to soya lipoxygenase.     

Methyl jasmonate in conjunction with ethanol treatment increases antioxidant capacity,volatile compounds and postharvest life of strawberry fruit

The antioxidant capacity, total anthocyanins, total phenolics, volatile compounds, and postharvest quality of strawberry fruit were evaluated after treatment with natural antimicrobial compounds and during storage at 7.5 °C. Strawberries treated with methyl jasmonate (MJ) in conjunction with ethanol (MJ-ETOH) showed higher antioxidant capacity, total phenolics, and anthocyanins than those treated with ethanol or control (non-treated). MJ-ETOH and ethanol treatments also increased volatile compounds during storage period. However, individual volatile compounds were affected differently. Methyl acetate, isoamyl acetate, ethyl hexanoate, butyl acetate, and hexyl acetate increased, while ethyl butanoate, 3-hexenyl acetate, and methyl hexanoate decreased during storage. The postharvest life was longer for those berries treated with MJ-ETOH and MJ than for those treated with ethanol or control fruit. In conclusion, strawberries treated with MJ-ETOH maintained an acceptable overall quality for the longest storage duration and retained higher levels of volatile compounds; also, berries treated with MJ showed the highest antioxidant capacity compared with other treatments during the postharvest period.     

MODIFICATION OF FISH OIL BY LIPOZYME TL IM TO PRODUCE STRUCTURED LIPID

Stearic acid methyl esters was enzymatically interesterified with fish oil (EPAX 5500) containing 44.5 and 32.6 mol% eicosapentaenoic acid (EPA, C20:5n-3) and docosahexaenoic acid (DHA, C22:6n-3), respectively. Lipozyme TL IM from Thermomyces lanuginosus was used to produce structured lipids (SL) that may be suitable for margarine or shortening application. Interesteri-fication was performed in hexane. Fish oil: stearic acid methyl ester levels ranging from 1 to 5 mole ratio was used. The effect of incubation time, substrate ratio and incubation temperature were also studied. Generally, as incubation time and substrate ratio increased, so did the mol % incorporation of stearic acid. After 24 h incubation in hexane, there was a 49.4 mol% incorporation of stearic acid into fish oil, while the mol% of EPA and DHA were reduced to 15.0 and 13.0 mol%, respectively. Time course studies also indicated that the highest stearic acid incorporation occurred at 72 h while 1:Sjish oil to stearic acid mole ratio gave the highest stearic acid incorporation. The data suggests that Lipozyme Ti5 IM could be used to produce SL.     

A METHOD TO QUANTIFY BUTTEROIL ADDED TO BUTTER-MARGARINE BLENDS

Table spreads containing various amounts of butteroil blended with vegetable oils are now commercially available. The butter fat percentages in these blends range from 2–40% according to the label information. This research was designed to determine the efficacy of a gas chromatographic procedure for monitoring the quantity of butteroil in the blend. Methyl esters were formed using potassium methoxylate as a catalyst and a heating interval of 2 min at 65°C in a closed vial under a nitrogen atmosphere. Carbon disulfide was used to extract the fatty acid methyl esters which were then separated by capillary gas chromatography. Retention times, peak areas and relative concentrations were determined by an integrator connected to the chromatograph. Changes in chromatographic patterns were monitored as known weights of butteroil were added to melted margarine. Dodecanoic, tetradecanoic, and pentadecanoic acids increased proportionately as butteroil was added to margarine. Commercial butter-margarine blends were prepared using the same procedure and the quantity of butteroil present was predicted by regression analysis.     

A comparative study on the effect of some antioxidants on the lipid and pigment oxidation in dry-fermented sausages

A comparative study on the effect of antioxidants on the lipid and pigment oxidation in Bulgarian dry‐fermented sausage type lukanka is described. A commercial mix of antioxidants, called ‘grindox 1021’ (GR), restricted the development of the peroxidation processes in dry‐fermented sausages (type lukanka) to a greater extent than either rosemary (RS), rutine (RT), sodium erythrobate (SE) or l ‐ascorbic acid, when applied at the same concentration. The latter compounds did not effectively stabilize lipids in sausages against oxidation; they only slowed down the lypolysis and did not greatly change the colour of the cross‐sectional surface. However, the sausage lipids were best stabilized when 1 g kg^?1 GR, RS or RT was added. The addition of 1 g kg^?1 RS and GR most efficiently suppressed the hydroperoxides – primary derivatives of lipid peroxidation, while the secondary derivatives in the final product were most reduced when 1 g kg^?1 GR and SE were added.