Inhibitory effect of onion extract on polyphenol oxidase and enzymatic browning of taro (Colocasia antiquorum var. esculenta)

The inhibitory effect of onion extract on polyphenol oxidase and enzymatic browning of taro was investigated. The polyphenol oxidase from taro was strongly inhibited by various reducing agents, such as l-ascorbic acid, l-cysteine, dithiothreitol, glutathione and sodium pyrosulfite. The enzyme was also inhibited by addition of onion extract. Regardless of substrates used, the addition of heated onion extract at 100 °C for 10 min, gave a stronger inhibitory effect on taro polyphenol oxidase activity than did fresh unheated extrtact. The inhibitory effect of onion extract was dependent on heating temperature and time. The addition of glucose, glycine, or both to the onion extract, during heating, stimulated the inhibitory effect of the onion extract, suggesting that non-enzymatic browning products, produced during heating, might be responsible for the stronger inhibitory action of the heated onion extract.     

Inclusion of the variability of model parameters on shelf-life estimations for low and intermediate moisture vegetables

Shelf-life is the time period during which products retain market-acceptable quality while meeting legal and safety requirements. Deterministic models yield single value estimations of shelf-life typically based on average or worst-case values for input parameters. In deterministic calculations, considering the input parameter variability can be challenging. In this study, a Monte Carlo procedure and the G.A.B. model for moisture sorption isotherms were used to predict shelf-life frequency distributions for intermediate moisture (IM) tomato slices, and low moisture (LM) onion flakes and sliced green beans. End of shelf-life for IM tomato slices (initial a_w = 0.8) was assumed to occur for a 10% moisture loss, and when a_w changed from 0.25 to 0.4 for LM onion flakes and LM sliced green beans. The estimated shelf-life for tomato slices, LM onion flakes, and LM sliced green beans based on the deterministic approach was 243, 86, and 79 days, respectively. The Monte Carlo procedures yielded shelf-life frequency distributions with values ranging 181–366, 76–95, and 71–90 days, respectively. Products would fail before the deterministic shelf-life value with an unacceptably high probability of 51.6, 48.6, and 53.0%, respectively. If 5% is an acceptable probability that the actual shelf-life is shorter than specified, the estimated values would be 211, 81, and 73 days, respectively. X_m and K were the most influential G.A.B parameters on the shelf-life of the three products. The package area, product amount, and water vapor transmission rate were high contributors and had the expected effect on shelf-life as demonstrated by deterministic estimations.     

RESIDUAL PECTINESTERASE ACTIVITY IN DEHYDRATED ONION AND GARLIC PRODUCTS

During the dehydration of onion and garlic products, use of high temperatures is undesirable due to the potential loss of aroma and flavor characteristics. As a consequence, residual pectinesterase (PE) activity may be found in these dehydrated spices. This study reports the presence of PE activity in raw onions and in dehydrated onion and garlic products. Pectinesterase activity is higher in the raw onion stem disks, and dehydrated products made from this tissue, than in the bulbs. Dehydrated onion products induced gelation of citrus pectin solutions and tomato purees. Although some inactivation of PE in dehydrated onion water suspensions and extracts was observed after 10 min at 50C, complete inactivation required 2 min at 82C. Commercial dehydration operations may require reevaluation to eliminate residual PE activity in dehydrated onion and garlic products.     

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.     

紫皮洋葱低聚糖的提取及分离研究

以新鲜紫皮洋葱为原料,采用热水浸提法提取洋葱低聚糖并对提取物进行分离研究。通过单因素实验及正交试验确定洋葱低聚糖的最佳提取工艺,利用薄层层析法(TLC检测)和质谱(MS)分析检测提取物,Bio gel P-2生物胶层析对糖分进行分离。结果表明:紫皮洋葱低聚糖的最佳提取工艺为料液比1:5 (g/mL)、提取温度70 ℃、提取时间80 min,在此提取工艺下,所提取到的低聚糖含量为3.92 mg/g。TLC检测分析和MS检测表明,紫皮洋葱提取物中有多种聚合度的糖类物质存在,HPLC分析显示,紫皮洋葱低聚糖主要组成为蔗果低聚糖,β-呋喃果糖苷酶能较好的对其水解,且凝胶层析结果表明Bio gel P-2凝胶可以对紫皮洋葱低聚糖进行初步分离。     

A rapid spectrophotometric method of determination of thiopropanal s-oxide (lachrymator) in onion (allium cepa l.) and its significance in flavour studies

The method depends upon rapid extraction of the lachrymator (thiopropanal S-oxide) into hexane at 0 °C and observation of the absorbance maximum at 254 nm as compared with that of the synthetic compound as a standard. Thiopropanal S-oxide was synthesised by dehydrochlorination of 1-propanesulphinyl chloride by a published method. Evidence that the observed absorbance was due to the presence of thiopropanal S-oxide was based mainly on agreement of the properties of the synthetic compound with those of hexane extracts of fresh onion juice with respect to λ_max values, reaction with L-cysteine reagent, and thin-layer chromatography. Further confirmation was afforded by the properties of alliinase fission products of synthetic (±)-S-l-propenyl-L-cysteine sulphoxide. A series of applications of the method in determination of onion flavour intensity, including non-destructive sampling, is described.     

影响洋葱泥红变的因素研究

洋葱作为传统的药食两用植物,其营养保健功能日益被人们所关注,同时也成为出口创汇的重要蔬菜之一。洋葱在加工时经破碎处理会发生红变现象,严重影响了洋葱产品的感官质量,给企业带来不小的经济损失。本文以新鲜洋葱泥为研究对象,分析了低温贮藏、加热时间、加热温度、pH值和O2对其红变的影响。结果表明,新鲜洋葱泥放置过夜促进红变,增幅超过200％;低温并不能明显促进红变;加热时间对红变影响不大,较对照组,最大增幅仅有53．33％;高温也可促进红变,90℃红变颜色最深;pH值对红变影响显著,pH值为5．0时红变最严重;与O2接触明显促进红变发生。因此在洋葱产品加工过程中,应对生产过程中的烫漂温度、护色剂选择和空气暴露时间严格控制,力求在加工中最大程度抑制洋葱红变的发生。     

The Impact of Pasteurisation and Sterilisation on Bioactive Compounds of Onion By-products

Onion (Allium cepa L.) waste disposal represents a worldwide environmental problem. A solution to this issue could be the use of onion waste as food-grade ingredients, which could be added to processed foods for their enrichment in bioactive compounds. For this purpose, onion waste should be adequately processed and stabilised. Thus, the objective of this work was to study the composition of processed onion waste, assessing the effects of processing and thermal stabilisation on onion waste bioactive compounds. Onion waste was triturated (‘Paste’) and triturated?+?pressed (‘Bagasse’, solid residue and ‘Juice’, liquid fraction). All by-products were stabilised by pasteurisation and sterilisation. Results indicated that bagasse was an enriched dietary fibre product (361–453 mg/g dry weight (DW)); paste showed high alkyl or alkenyl cystein sulphoxide (ACSO) content (5.6 mg/g DW); and juice showed large fructans concentration (205–221 mg/g DW). In paste and bagasse, pasteurisation and sterilisation improved soluble/insoluble fibre ratio, with no changes in total dietary fibre concentration in pasteurised products and a slight decrease (8 % on average) in the sterilised ones. In juice, thermal treatments produced fructans losses, more pronounced after sterilisation (59 % on average) than after pasteurisation (36 % on average). However, sterilisation provided by-products with better ACSO results than pasteurisation. As a conclusion, industrial processing has an important impact on the bioactive composition, generating products with different functional applications. Moreover, pasteurisation resulted to be the most suitable treatment to obtain safe products enriched in dietary fibre and fructans, while sterilisation could be used to produce products rich in ACSOs.     

Quantitative Evaluation of the Pyruvic Acid Content in Onion Samples with a Fully Validated High-Performance Liquid Chromatography Method

Onion cultivars with low pungency have been increasing in popularity because they are more attractive for fresh, uncooked use. The pyruvic acid amount is commonly used as a measure of onion pungency. For the first time the validation of a reversed-phase high-performance liquid chromatography method for the quantitative analysis of pyruvic acid in onion extracts was carried out. The established chromatography method based on the use of a 50 mM phosphate buffer (pH 2.5) eluent system provided good precision (RSD% in the range of 1.25–1.29, in the long-period) and accuracy (recovery% in the range of 97.70–111.62, in the long-period) as well as appreciably low limit of detection and limit of quantitation values (11.03 and 33.41 ng/mL, respectively). The validated method proved successful in the analysis of the onion extract from Dorata di Parma cultivar after a preliminary solid-phase extraction step. A significant adherence with results from previous spectrophotometric determinations turned out.     

Investigation of food products containing garlic or onion for a false positive sulphite response by LC-MS/MS

ABSTRACT

In the US, sulphites must be declared on the label if they are present in concentrations greater than 10 mg/kg (determined as) SO₂ because an allergic-like response has been reported in a small subset of the population upon consumption of sulphite-containing products. The most widely used method for sulphite determination, the optimised Monier-Williams (OMW), produces false positive results with vegetables from the Allium (garlic) and Brassica (cabbage) genera due to extraction conditions that are thought to cause endogenous sulphur compounds to release SO₂. Recently, an LC-MS/MS method was developed for sulphites but has only been tested with samples that are 100% Allium or Brassica. Since regulatory samples may contain these vegetables as ingredients, additional investigations were necessary to determine the potential extent of false positives. Four blank matrices, chips, phyllo shells, hummus, and quinoa were spiked with various concentrations of onion and garlic powders. The sulphite concentrations were determined using an LC-MS/MS method. The matrix is extracted with a buffered formaldehyde solution, converting free and reversibly bound sulphite to the stable formaldehyde adduct, hydroxymethylsulfonate (HMS). It was determined that even at concentrations up to 8% garlic powder or 2% onion powder, the measured sulphite concentration was below the 10 mg/kg SO₂ labelling threshold. Commercial dried garlic powders were evaluated to determine the variation in responses that might be encountered in future regulatory samples. Recovery studies were conducted to determine if these methods would detect added sulphite. The ability to eliminate false positives due to these ingredients will result in a greater reliability in the accurate determination of added sulphite to ensure compliance with labelling requirements.     

洋葱皮黄酮微胶囊技术研究

通过制备洋葱皮黄酮微胶囊,以提高洋葱皮黄酮的稳定性。实验以β-环糊精为壁材,研究了分子包埋法制备微胶囊工艺中不同因素对微胶囊化包埋率的影响。结果表明:芯材与壁材的最佳配比为1∶11.49,搅拌时间60.6min,搅拌温度61℃。在此条件下,产品微胶囊化效率达到41.26%。     

洋葱的活性成分药理功效及产品开发综述

分析了洋葱中主要活性成分,并对其药理功效研究进展进行了综述,通过对其营养和药用价值的探究阐述了洋葱产品开发的必要性和实用性,同时对其开发应用前景进行了展望.     

Phenolic compounds,microstructure and viscosity of onion and apple products subjected to in vitro gastrointestinal digestion

Microstructure, viscosity and their relationship with bioaccessibility of phenolic compounds in onion and apple products (untreated and HPP) and commercial quercetin supplement throughout a dynamic gastrointestinal digestion (GID) model were investigated. In non-digested (ND) samples, untreated and HPP-onion presented higher total phenolic and flavonol content (TFC-HPLC and TPC-FC) than apple counterparts. TFC-HPLC decreased throughout GID phases in all samples studied. TFC-HPLC bioaccessibility was higher in onion (~17.6%) than in apple (~10%) and in quercetin supplement (0.027%). HPP did not improve TFC-HPLC bioaccessibility. Throughout GID, onion and apple showed a significant decrease in both consistency (K) and apparent viscosity at 10 s⁻¹ but higher values were found in apple. These data agree with TFC-HPLC and TPC-FC decrease and with the lower bioaccessibilities of apple compared with onion. Food matrix had a more significant effect than HPP on TFC-HPLC bioaccessibility, which is related to the rheological behavior of the GID-phases.Industrial relevanceHigh-pressure processing (HPP) (400 MPa at 25 °C during 5 min) combined with freeze-drying enhanced significantly flavonols extractability (TFC-HPLC) in onion and apple and in some cases their bioaccessibility. Bioaccessibility of bioactive compounds in each food matrix is being required by industrials and consumers concerned to know the actual amount of bioactive compounds that are available for intestinal absorption. The change of the matrices viscosity studied throughout in vitro gastrointestinal digestion (GID) could predict the bioaccessibility of these bioactive compounds. HPP could be proposed as a strategy for increasing the extractability of bioactive compounds in vegetable derived products.     

Solubilization of onion with polysaccharide-degrading enzymes

For the selection of suitable enzymes for the solubilization of onion, degree of solubilization (DS) values were measured. The DS values of Pectinex and Viscozyme were 75.8 and 78.4%, respectively, which indicates they have higher specific activities than Cereflo and Celluclast. The enzyme mixture of Pectinex and Viscozyme (relative ratio of 1:3) had higher DS values and reducing sugar content than Pectinex alone. The enzyme mixture degraded onions with a synergistic effect, solubilizing 85% of the onion. The DS values and reducing sugar content at the optimal condition (pH 4.5 and 45 °C) reached a maximum of 85% and 494.8 mg g^–1 of onion, respectively. The DS values and reducing sugar content increased with increasing reaction time, reaching a maximum of 89% and 517.5 mg g^–1 of onion, respectively. When cooking pork, onion appeared to be preferable to onion hydrolysate, however there was no significant difference. The sweetness and preference of pork cooked with 3% addition of hydrolysate per gram of pork meat were the highest but those were not different significantly from those cooked with less than 10% addition of hydrolysate per pork meat.     

富黄酮洋葱酒中黄酮类化合物稳定性研究

目的研究不同因素对洋葱酒中总黄酮化合物的影响。方法以富黄酮洋葱为试验材料,分别测定温度、p H、氧化剂、还原剂、常用的食品添加剂及金属离子对洋葱发酵酒的黄酮含量影响。结果低温对洋葱黄酮影响不大,升高温度可能导致黄酮分解;p H对黄酮影响较大,应尽可能在酸性范围内贮存富黄酮洋葱酒;洋葱黄酮对氧化还原剂较稳定,具有良好的抗氧化能力,但还原剂可能导致黄酮含量减小,应避免接触;在不同浓度的食品添加剂中,黄酮含量较稳定,可以添加常见添加剂调整富黄酮洋葱酒风味;金属离子对其影响较大。结论本研究优化的储藏条件为富黄酮洋葱酒的开发与保存提供了方法与依据。     

Semi-quantitative estimation of the walnut content in fillings of bakery products using real-time polymerase chain reaction with internal standard material

A method for absolute quantification of walnuts in fillings of bakery products was developed. Macadamia nuts were used as an internal standard material. A duplex real-time polymerase chain reaction (PCR) with 5′-nuclease (TaqMan) probes labelled with FAM and JOE for walnuts and the internal standard, respectively, was used. Difference between threshold cycle values (Δc _T) for the analyte and the internal standard, plotted against logarithm of contents, was used to construct the calibration line. A level of 5?% (w/w) of the internal standard material was found to be suitable for quantification of walnuts in nut fillings, the calibration line being linear. The developed method was applied to bakery products from the market, and crucial factors for its routine applicability have been identified in sampling and sample preparation. The present study demonstrates that quantification of walnuts in the fillings of bakery products should be achievable by real-time PCR with an internal standard material when the reference filling, which is used for calibration, is comparable to the fillings of the samples, a calibration line of low variability is obtained, and the sample material is properly homogenized before weighing the analytical sample.     

Study of total fructan and fructooligosaccharide content in different onion tissues

The objective of this work was to determine the fructan and fructooligosaccharide (FOS) content of different onion tissues in order to evaluate the potential use of onion by‐products from the food industry as a source of FOS and fructans. Assays with two methods were carried out to optimise the extraction procedure. The main FOS, namely kestose (GF₂), nystose (GF₃) and fructofuranosylnystose (GF₄), were measured directly using standard sugars. The method for total fructans was based on enzymatic treatment (Novozym 230) of ethanolic/aqueous extract followed by determination of released fructose and glucose by HPLC. Data showed a clear predominance of GF₂ in every onion tissue and no occurrence of highly polymerised fructans. The tissues richest in fructans were the fleshy layers, so that the outer two fleshy layers turn out to be the best onion by‐product as a possible fructan source. © 2000 Society of Chemical Industry     

响应面法对洋葱酒发酵工艺的优化

目的：为充分利用洋葱资源,制得具有良好口感与保健功能的洋葱酒。方法：以黄皮洋葱为原料,选择不同的前处理方式对洋葱进行前处理并采用响应面法对洋葱酒的发酵工艺进行优化。结果：洋葱在539W微波条件下处理20min,按料液比1:3(g/mL)打浆,在发酵温度25.3℃、酵母菌接种量0.84%、发酵时间48.36h条件下发酵,制得洋葱酒乙醇体积分数9.7%,总黄酮的浸出率为65.12%。多元回归分析结果显示,发酵温度、酵母菌接种量、发酵时间与洋葱酒酒精含量和黄酮浸出率之间回归模型极显著,可用于实际生产预测。结论：微波处理可明显除去洋葱的葱臭味,并得出了洋葱酒发酵的最优条件。     

洋葱油的提取价值及其技术研究

综述了洋葱的开发价值,指出了洋葱油可以作为医疗保健药品,对防治动脉硬化、降血压、抗糖尿病、抵抗传染病等都具有良好的功效。并分别用蒸馏法和溶剂法研究了洋葱的提取技术,平均出油率在3‰左右。     

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.