Changes in antioxidant activity of dehydrated onion and garlic during storage

The effect of the Maillard reaction evolution on the overall antioxidant activity (AA) of stored dehydrated onion and garlic has been studied. Extent of the reaction was followed through the determination of the Amadori compounds, measured as 2-furoylmethyl-amino acids (2-FM-AA), and colour development whereas AA was evaluated by the ORAC_FL assay. Dehydrated garlic exhibited a very slow progress of the Maillard reaction which did not lead to any noticeable change in its AA upon storage. However, a substantial increase of AA was observed in dehydrated onion samples, in agreement with a major Maillard reaction evolution. Moreover, a positive correlation between colour and antioxidant properties was observed during the storage of dehydrated onion at 50 °C, suggesting the predominant role of the advanced stages of the Maillard reaction over the AA. In conclusion, this study demonstrated that, although the Amadori compounds might exert a moderate effect on the AA, the advanced Maillard reaction products are the major contributors to this property.     

羊栖菜干燥技术及其即食汤料包的研究

文章以羊栖菜为原料,通过对羊栖菜干制技术及调味配方的研究,制成一种方便营养的鸡肉味即食羊栖菜调味包。实验结果表明,干燥羊栖菜的最佳工艺为:在95℃下漂烫90s后热风干燥70℃下3.5h,脱水羊栖菜的复水形态、色泽等质量较好。最佳菜包配方为脱水红胡萝卜1.5g、脱水羊栖菜6g、脱水香葱0.6g;最佳调味粉配方为:4.5g、I+G 0.03g、味精0.5g、大蒜粉0.125g、生姜粉0.1g、葱粉0.15g、白胡椒粉0.1g;最佳鸡汤味酱包为:棕榈油在3.5g、食盐1.0g、酱油1.6g、鸡骨油1.5g。     

Thermal processing enhances anti‐radical activity and reduces pro‐oxidant activity in water‐soluble fraction of selected Allium vegetables

Both the pro‐ and antioxidant activities were found in water‐soluble components contained in onion, leek and garlic samples, and effects of thermal treatment on such activities were investigated. Raw vegetable extracts were prepared by squeezing vegetable homogenates followed by centrifugation at 4 °C. The extracts were subjected to thermal treatment at 75 or 100 °C for 30 and 60 min. The water‐soluble extracts were assayed for antiradical activity using both a chemical and a cellular system. Heating onion and leek extracts at 100 °C for 60 min, and garlic extract at 100 °C for 30 min, yielded strong antioxidant components that are able to scavenge free radicals, in either system, significantly. Measuring total phenolic content by the Folin–Ciocalteu method, we observed that thermal treatment significantly decreased the phenolic contents in leek and garlic extract. In addition, we estimated pro‐oxidant activities in the vegetable extracts, using reactive oxygen species (ROS)‐sensitive 2′,7′‐dichlorofluorescin diacetate; we found that extracts of raw alliums have strong ROS activity, and that thermal treatment destroyed most of the ROS activity present in the raw extracts. These findings indicate that thermal processing enhanced the nutritional value of alliums by increasing the total antioxidant activity, and reducing the pro‐oxidant elements. Copyright © 2007 Society of Chemical Industry     

Death of Salmonella,Escherichia coli O157:H7, and Listeria monocytogenes in garlic butter as affected by storage temperature

Garlic is known to have antimicrobial activity against several spoilage and pathogenic bacteria. However, the fate of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes in garlic butter has not been reported. This study was undertaken to determine the viability of these organisms in garlic butter as affected by the type of raw minced garlic added to the butter, storage temperature, and storage time. Unsalted butter at 40 degrees C was combined with raw minced jumbo, elephant, or small-cloved garlic at a 4:1 butter/garlic ratio (wt/wt), inoculated with mixed-strain suspensions of Salmonella, E. coli O157:H7, or L monocytogenes, and stored at 4.4, 21, or 37 degrees C for up to 48 h. All pathogens retained their viability at 4.4 degrees C, regardless of the presence of garlic. The addition of garlic to butter enhanced the rates of inactivation of all three pathogens at 21 and 37 degrees C. The most rapid decline in pathogen populations was observed at 37 degrees C. The inactivation of L. monocytogenes occurred more slowly than did that of Salmonella or E. coli O157:H7. The inactivation of Salmonella and L. monocytogenes was more rapid in jumbo garlic butter than in elephant or small-cloved garlic butter. It is concluded that Salmonella, E. coli O157:H7, and L. monocytogenes did not grow in unsalted butter, with or without garlic added (20%, wt/wt), when inoculated products were stored at 4.4, 21, and 37 degrees C for up to 48 h.     

ENHANCEMENT OF PYRUVIC ACID RELEASE AND FLAVOR IN DEHYDRATED ALLIUM POWDERS BY GAMMA GLUTAMYL TRANSPEPTIDASES

SUMMARY —The transpeptidase of sprouted onion, in conjunction with both endogenous and exogenous cysteine (sulfoxide) lyases, catalyzes the liberation of pyruvic acid from γ-L-glutamyl-L-cysteine (sulfoxide) dipeptides (precursors to flavor precursor) and increases the rate and extent of pyruvic acid formation and flavor in reconstituted samples of commercially dehydrated garlic and onion bulbs as well as in experimentally dehydrated onion roots and skins. Effects of enzyme concentration, time, pH, exogenous lyase and protease, as well as sample source have been investigated. The application of these enzymes may constitute a rapid and simple means for estimation in plants of the above mentioned dipeptides which appear, from such an analysis, to concentrate in the inner part of the onion bulb. Transpeptidases may be useful in enhancing the value and quality of dehydrated onion and garlic and other Allium species, improving the flavor of Allium-containing foods, as well as providing a use for a waste product, cull-sprouted onions. Other sources of transpeptidase such as mammalian kidney may also be suitable for enhancing onion flavor.     

Effect of garlic, onion, and their combination on the quality and sensory characteristics of irradiated raw ground beef

Irradiated raw ground beef had lower a*- and b*-values than nonirradiated ones regardless of garlic or onion treatment at 0 d. Irradiation increased TBARS values of control ground beef, but addition of 0.5% onion or 0.1% garlic+0.5% onion reduced oxidative changes during storage. Addition of garlic or onion greatly increased the amounts of sulfur compounds, but the increase was greater with garlic. With irradiation, the profiles and amounts of S-volatiles in raw ground beef changed significantly. However, the intensity of irradiation aroma in irradiated raw ground beef with garlic or onion was similar to that of the nonirradiated control. This indicated that some of the sulfur compounds unique to garlic or onion interacted with common sulfur compounds detected in irradiated meat and masked or changed the odor characteristics of irradiated raw ground beef. It was concluded that >0.5% onion or <0.01% garlic would be needed to mask or prevent irradiation aroma in irradiated raw ground beef.     

Effects of drying process on antioxidant activity of purple carrots

Purple carrot was analysed for its antioxidant activity by measuring its scavenging effect on 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical. The amount of purple carrot necessary to decrease by 50% the initial DPPH concentration (EC50) was found 30.23 +/- 5.17 (mg sample/mg DPPH). Effects of the dehydration process on the antioxidant activity of purple carrots were also determined after dehydration by using tray drier and microwave+tray drier combination. Purple carrots were cleaned, washed, sorted, sliced, and blanched in water at 98 +/- 1 degree C for 2 min. Then half of the samples were dehydrated in microwave (45 min) and tray drier (105 min) combination, and others were dehydrated in tray drier (150 min) until reaching the constant weight. Raw, blanched and dehydrated purple carrots were compared for their antioxidant activity and total anthocyanin contents, color values (L*, a*, b*, C*, H degrees) and dry matter contents. The antioxidant activity as measured by DPPH, EC50 value ranged from 7.80 to 30.23 of processed and raw carrots where the H degrees values were changed from -3.68 to -23.96 corresponding to a bluish hue.     

Fructo-oligosaccharide changes during the storage of dehydrated commercial garlic and onion samples

The composition of fructo-oligosaccharides (FOS), together with glucose, fructose and sucrose, has been determined in commercial dehydrated samples of onion ( Allium cepa L.) and garlic ( Allium sativum L.). No qualitative differences were detected among the FOS identified in both onion and garlic. Results show a lower FOS content in garlic than in onion in all samples analysed. In garlic samples, FOS with degree of polymerisation from 3 to 7 were identified and quantified for the first time. In addition, a study on the effect of the storage in these carbohydrates has been carried out under controlled conditions (50 °C, a _w 0.44). The storage seemed to promote important changes in the content of glucose and fructose, which could participate in the Maillard reaction and in the composition of sucrose and FOS, whose hydrolysis was noticeable during the storage time. Therefore, all these chemical changes should be considered to evaluate the quality of these foods.     

Physicochemical Properties,and Antioxidant and Antimicrobial Effects of Garlic and Onion Powder in Fresh Pork Belly and Loin during Refrigerated Storage

ABSTRACT: Pork loin and belly cuts were pumped to 110% of their original weight with solutions containing 5% of various ingredients (sodium ascorbate, garlic, and onion powder), and evaluated the physicochemical properties, and antioxidant and antimicrobial activities during refrigerated storage at 8 °C. The addition of garlic and onion powder tended to increase redness (a) and yellowness (b) in both the belly lean and loin with the exception of a few cases. Free fatty acid values in both pork belly and loin cuts were reduced with the addition of these ingredients, as compared to the control. Significant differences in peroxide values were observed in sodium ascorbate and garlic‐injected belly, and in sodium ascorbate and onion‐injected loin, as compared to the control. Thiobarbituric acid reactive substance values in the pork belly with garlic or onion powder were significantly lower than in the belly without these ingredients or with sodium ascorbate (P < 0.05). Total plate counts were lower in both the belly and loin containing garlic and onion powder, as compared to the control. In both the belly and loin cuts, the content of oxidative products (volatile compounds) was reduced with the addition of garlic and onion powder, particularly the aldehydes (hexanal). Overall, garlic and onion in enhanced meats showed an antioxidant activity as effective as that of sodium ascorbate and also an antimicrobial effect to inhibit the growth of total bacteria and Enterobacteriaceae.     

亚硫酸钠浸泡预处理对脱水蒜片主要品质指标的影响

蒜片在干制过程中,会发生褐变反应导致产品品质下降,考察亚硫酸钠溶液处理质量浓度、处理时间及温度对脱水蒜片色泽、硫代亚磺酸酯含量、SO2残留量、体外抗氧化活性等品质指标的影响。结果表明：亚硫酸钠溶液浸泡处理可有效地保持脱水蒜片品质,浸泡时间及浸泡温度对蒜片品质总体影响较小。500?mg/L亚硫酸钠溶液浸泡30?min时,蒜片色泽较优;不同条件浸泡所得蒜片,SO2残留量随处理质量浓度的增大及处理时间的延长而增大;亚硫酸钠溶液浸泡处理后,蒜中主要功能性成分硫代亚磺酸酯含量最高可达0.115?mmol/g,显著高于对照组0.077?1?mmol/g。     

Occurrence of furosine and hydroxymethylfurfural as markers of thermal damage in dehydrated vegetables

The presence of furosine and hydroxymethylfurfural (HMF) as markers of thermal damage in commercial dehydrated vegetables has been studied. Furosine was measured in all the analysed samples whereas HMF was detected only in garlic, onion, and tomato groups and some other individual vegetables. Furosine, as indicator of the first steps of the Maillard reaction, ranged from 1.12 to 923 mg/100 g protein (depending on the vegetable species and thermal treatment applied) and was well correlated with the browning development in not severely heat-treated samples. In addition, the results seem to indicate that reducing sugars play an important role in the formation of furosine in some vegetable species but not HMF at the conditions used for the dehydration process. The findings of this study show the usefulness of furosine as a quality indicator for sensitive control of the dehydration process in vegetables.     

THERMOSTABLE AND THERIVIOLABILEISOFORMS IN COMMERCIAL ORANGE PEEL PECTINESTERASE1

Thermostable and thermolabile pectinesterase isoforms in commercial Valencia orange peel pectinesterase (Sigma Chemical Co., St. Louis, MO) were separated by affinity chromatography on a Heparin‐Sepharose CL‐6B column. Among the seven putative PE isoforms separated, three (P1, P2 and P3 with 70 kDa, 60 kDa and 27 kDa, respectively)‐were thermostable and four [P4, P5, P6 (35 kDa) and P7 (35 kDa)]‐were thermolabile, according to the qualitative and quantitative studies of thermal stability. The commercial PE showed 83.4% and 98.3% inactivation after heat treatment at 70C for 5 min and at 90C for 1 min, respectively. P2 was the most heat stable, with 85.5% inactivation at 70C for 5 min and 93.0% inactivation at 90C for 1 min. The thermolabile P6 and P7 could be inactivated at 70C for 5 min or at 90C for 1 min. Thermostable PE activity was 16.6% of total activity of the commercial PE based on heat treatment at 70C for 5 min, but only 1.5% based on heating at 90C for 1 min. The 90C for 1 min heat treatment might be better than the 70C for 5 min heat treatment to distinguish thermostable PE and thermolabile PE isoforms in Valencia oranges.     

Estimation of volatile onion aroma and flavour compounds

Summary. The Chemical Oxygen Demand (COD) method was used for the evaluation of onion aroma components. the method was found to be reliable and to correlate well with odour threshold values for raw onions and with taste scores for dehydrated onion products. Odour threshold values could not be used for the latter products due to the development of undesirable off-odour after exposure to high temperature or prolonged storage.     

Garlic (Allium sativum L.) and ready-to-eat garlic products: In vitro antioxidant activity

Garlic contains polyphenol and sulphur compounds, which are responsible for its antioxidant activity (AA). This study aimed at evaluating the AA of fresh garlic and its commercialised products and their shelf life. Fresh garlic (FG) and its products, i.e. chopped with salt (CGS), chopped without salt (CG), fried (FRG) and mixed garlic (FG with dehydrated garlic; MG) antioxidant activity was evaluated by three different methods: DPPH (1,1-diphenyl-2-picrylhydrazyl) assay, β-carotene/linoleic acid assay and Rancimat^® method. Amongst all the analysed products, fried garlic presented the highest antioxidant activity. The free radical-scavenging activity decreased during the shelf life of all analysed products that correlated with the decrease in the total polyphenol content. Our findings suggest that some compounds other than phenol may have contributed towards this outcome.     

Effects of dehydration temperatures on colour and polyphenoloxidase activity of Amasya and Golden Delicious apple cultivars

During dehydration at different temperatures (60, 70 and 80 °C) of Amasya and Golden Delicious apple cultivars, changes in colour, polyphenoloxidase activity (PPO), browning index and hydroxymethylfurfural (HMF) content were studied. Effects of dehydration time on the L* values of both cultivars were not significant. Only Amasya samples dehydrated at 80 °C were found to have significantly higher L* values than the remaining samples. In all cases, Golden Delicious samples had higher L* values than those of the Amasya cultivar. a* values of samples increased within the first hour of dehydration and then remained almost unchanged. The enzyme activity showed a rapid decrease in the first hour of dehydration and residual enzyme activities (%) reached 9.8%, 5.3% and 4.5% for Amasya, and 17.4%, 10.3% and 4.6% for the Golden Delicious cultivar at 60, 70 and 80 °C, respectively. In all final samples the residual enzyme activities were around 1%. The highest browning values were observed at the second hour of dehydration at 60 and 70 °C and the first hour of dehydration at 80 °C. In all conditions Amasya apples had a higher browning tendency. The presence of HMF was detected only at the 4th hour of dehydration at 80 °C for both cultivars. Effects of dehydration temperature on colour and PPO of the final product were insignificant. However, an important effect of temperature was determined on the browning index of Golden Delicious samples. The lowest browning tendency was measured on samples dehydrated at 80 °C. The results showed that cultivar and dehydration temperature had considerable effect on the browning of apple slices. Copyright © 2006 Society of Chemical Industry     

Effect of minimal processing operations on the quality of garlic,green onion,soybean sprouts and watercress

The effect of unit operational procedures on the quality of minimally processed vegetables was investigated. Peeling methods were studied for garlic, while different preparation forms were tried for garlic, green onion and soybean sprouts. Washing and a mild heat treatment, at 60°C for 30 s, were investigated as measures to reduce microbial populations of minimally processed vegetables. With garlic it was found that dry peeling was better than wet peeling in reducing microbial populations and preserving ascorbic acid content. Removal of the root, a potential source for microbial contamination, reduced microbial load in garlic. For garlic and green onion, microbial quality deteriorated with severity of cutting. Washing reduced microbial counts of prepared vegetables. Repeated washing and use of chilled water further reduced the counts. A mild heat treat-ment markedly reduced microbial counts in soybean sprouts and watercress, which were highly loaded with microorganisms. Sensitivities of vegetables to heat treatment differ and may limit the usefulness of heat treatment for some products. © 1998 SCI.     

Control of Some Filamentous Fungi and Yeasts by Dehydrated Allium Extracts

The antifungal activities of dehydrated garlic (Allium sativum L.), onion (Allium cepa L.) and leek (Allium porrum L.) against Aspergillus niger, Fusarium oxysporum, Candida albicans ATCC 10231 and Metschnikowia fructicola were investigated. Inhibition activities of the ethyl alcohol or acetone extracts of dehydrated Allium species were studied by disc-diffusion and broth dilution methods. The Minimum Inhibitory Concentration (MIC) and the Minimum Fungicidal Concentration (MFC) were found in the range of 75 and 100 mg/mL (w/v). Ethyl alcohol extracts of dehydrated onion (Allium cepa L.) in the range of 75 and 175 mg/mL were determined as the most inhibitory MIC and MFC for A. niger, F. oxysporum and C. albicans respectively. The extracts possess antifungal activity against some of the tested filamentous fungi and yeasts at various concentrations.     

蒜制品中二氧化硫4种检测方法的比较研究

目的研究比较蒜制品中二氧化硫的检测方法。方法通过应用碘量法、比色法、柱后衍生-高效液相色谱法以及离子色谱法检测蒜制品中二氧化硫的结果进行比较分析。结果鲜蒜和脱水蒜制品的比色法检测结果差异较大。采用比色法(盐酸副玫瑰苯胺法)检测鲜蒜和脱水蒜制品中二氧化硫的结果普遍较高,蒜罐头类的检测结果与其他检测方法的值接近。采用滴定法、高效液相色谱法和离子色谱法的检测结果都较为接近。结论 4种方法都可用于蒜制品中二氧化硫的检测,但比色法不适用于鲜大蒜及脱水蒜制品中二氧化硫的检测。     

Control of Some Filamentous Fungi and Yeasts by Dehydrated Allium Extracts

The antifungal activities of dehydrated garlic (Allium sativum L.), onion (Allium cepa L.) and leek (Allium porrum L.) against Aspergillus niger, Fusarium oxysporum, Candida albicans ATCC 10231 and Metschnikowia fructicola were investigated. Inhibition activities of the ethyl alcohol or acetone extracts of dehydrated Allium species were studied by disc-diffusion and broth dilution methods. The Minimum Inhibitory Concentration (MIC) and the Minimum Fungicidal Concentration (MFC) were found in the range of 75 and 100 mg/mL (w/v). Ethyl alcohol extracts of dehydrated onion (Allium cepa L.) in the range of 75 and 175 mg/mL were determined as the most inhibitory MIC and MFC for A. niger, F. oxysporum and C. albicans respectively. The extracts possess antifungal activity against some of the tested filamentous fungi and yeasts at various concentrations. Received: July 8, 2008; accepted: July 30, 2008