Levels of selected heavy metals in canned tomato paste sold in Ghana

Sixty-one samples of canned tomato paste comprising seven brands originating from three countries and sold in local markets in the Kumasi Metropolis of Ghana were analysed for levels of iron (Fe), zinc (Zn), manganese (Mn), cadmium (Cd) and lead (Pb) by flame atomic absorption spectrophotometry and for levels of mercury (Hg) by direct mercury analyzer. Mean heavy metal concentrations varied by brand, ranging from below the limit of detection (Cd) to a maximum concentration range of 1.68?±?1.63 to 58.6?±?14.5?µg?g?^?1 (Fe). Estimated mean ranges of other heavy metals are 2.06?±?0.62 to 8.52?±?0.68?µg?g?^?1 (Zn), 2.62?±?0.33 to 5.75?±?0.47?µg?g?^?1 (Mn), 0.070?±?0.003 to 0.116?±?0.012?µg?g?^?1 (Pb) and 0.011?±?0.001 to 0.102?±?0.001?µg?g?^?1 (Hg). Assessed metal levels in five brands were below the WHO/FAO permissible levels. Results of the one-way analysis of variance (ANOVA) conducted on the data suggested no significant variations (P?>?0.05) in the concentrations of the metals in the same brands of canned tomatoes.     

三明治贮藏过程中的水分迁移特性研究

三明治面包属于多组分食品,在其贮藏过程中水分从水分含量较高的馅中迁移到水分含量相对较低的面包中,导致了各部分感官质地的变化。水分迁移的发生主要是由于不同部位之间水分活度梯度的存在而引起的。影响水分迁移的因素有:水分活度梯度大小、贮藏温度、油脂含量等。水分活度梯度越大,水分迁移量及其速率越大;低温贮存4℃可以延缓水分的迁移速率;而面包部分中油脂的含量对水分迁移几乎没有影响,但在馅中添加油脂可以在一定程度上减少水分的迁移。      

番茄果实采后贮藏的颜色动力学研究

研究了番茄采后成熟过程中果皮颜色的变化规律,建立了多种颜色指标的动力学模型。认为番茄采后成熟过程中色泽角(H0)、色泽比(a/b)、色泽总量(La/b)和a值、明度等颜色参数的动力学变化模型符合一级动力学方程。番茄采后成熟过程中最佳颜色指标是色泽角(H0)。根据实验数据采用数理统计的方法分别确定了各颜色模型的参数：参考变化速率常数(Kref)和反应活化能(Ea)。     

Problems during processing and storage of meat in cans. II. Chemical changes in canned meat with long storage time (author's transl)]

By sensory analysis and according to results of objective chemical investigations meat cans sterilized at 120 degrees C for long storage times were at best evaluated, if they were processed after the 4th and 7th day after slaughter. At first the 4th day; after 2 days the 7th day were preferred. 2. For comparison meat cans with long storage time of 5 and 9 years were analyzed in the same manner. In taste these were empty, strawy, and partly bitter. Frozen meat which was processed according to old procedures (long stored without any shock freezing), was regarded, extremely unagrellable. The attributs were adstringend and soapy. 3. Gelfiltration of diffusates showed a separation in 2 main peaks. The first from fractions 90--130 had a typical aroma of a heated meat, after hydrolysis glucose was detected as main sugar component. The 2th peak from fractions 170--230 tasted more sweet with parfumlike odor, after hydrolysis ribose was detected besides other substances stained by anisidine phthalate. 4. During storage substances of peak 1 were reduced in contrast to peak 2 substances. The latter seemed to be responsible for the aroma and taste at beginning of eating, but no fixation at the tongue could be observed in contrast to the substances of the peak 1. 5. Staining of separated peptides--by electrochromatography--with ninydrin received from the diffusates of the meat cans showed some brown coloured peptides, which disappeared during storage. This was in good correlation with the results of sensory analysis.     

油浸鲣鱼罐头贮藏过程中挥发性成分的变化规律研究

运用电子鼻和顶空固相微萃取气质联用（headspace solid phase micro extraction gas chromatograph-mass spectrometer,HS-SPME-GC-MS）技术,分析不同贮藏时间的油浸鲣鱼罐头的挥发性成分的变化。结果表明:电子鼻能够快速、灵敏地检测到油浸鲣鱼罐头在贮藏过程中的气味变化。利用气质联用仪在油浸鲣鱼罐头贮藏过程共鉴定出47种可挥发性化合物,呋喃类化合物、含氮类化合物为主要挥发性成分,其中呋喃类化合物相对含量随着贮藏时间的延长,含量不断降低,从刚出厂罐头的51.42%减少到贮藏第4年的41.20%。电子鼻可以用来区分罐头的贮藏时间,超过保质期的罐头挥发性风味物质变化较大。      

壳聚糖处理对梅杏采后品质的影响

以梅杏为试材,用浓度为0.5、0.75、1.0g/L壳聚糖浸果实1min后进行冷藏,研究壳聚糖处理对梅杏采后贮藏品质的影响。结果表明,以0.75g/L壳聚糖处理效果较好,可降低梅杏的呼吸强度和失重率,抑制细胞膜透性和丙二醛含量的增加,保持较高的硬度、可溶性固形物、可滴定酸、Vc含量,减少梅杏腐烂发生,从而延长贮藏期。     

1-MCP在果品贮藏上的研究进展

1-MCP是一种新型乙烯作用抑制剂,可以延缓采后果实的衰老,延长果实的贮藏保鲜期。对1-MCP的作用机理及其对采后果品保鲜效果的影响进行了初步探讨,并综述了近年来1-MCP在果品贮藏保鲜上的应用研究进展。     

水杨酸处理对梅杏采后贮藏品质的影响

以梅杏为试材,用浓度为0.3、0.5、1.0g/L水杨酸（SA）溶液（清水为对照）浸果实20min后进行冷藏,研究水杨酸处理对梅杏采后贮藏品质的影响。结果表明,0.5g/L水杨酸处理能够较好地降低梅杏的呼吸强度和失重率,抑制细胞膜透性和丙二醛含量的增加,保持较高的硬度、可溶性固形物、可滴定酸、VC含量,减少梅杏腐烂发生,从而延长贮藏期。     

Lipid changes during long-term storage of canned tuna (Thunnus alalunga)

 In previous studies fluorescence detection at different excitation/emission maxima during common fish processing has been used. A bathochromic shift towards higher wavelength maxima was observed and measured as the ratio between absorption at two of the maxima tested. This fluorescence ratio (δF) value correlates positively with fish damage. In the present work, the influence of formaldehyde (FA) on the value δF was studied. A model system was set up in which FA reacted at 30°C for 25 days with propylamine and fish muscle. It was observed that FA was less able to produce fluorescent compounds compared with common fish oxidation products that were also tested, i. e. propanal and hexanal. However, in the presence of both lipid oxidation aldehydes, the FA-containing mixtures led to a higher δF value. Model systems consisting of FA and fatty fish (sardine) muscle produced more fluorescence than FA and lean fish (cod), because of the formation of lipid oxidation compounds under the reaction conditions of the former systems. It is thus concluded that the presence of FA in a reacting medium enhances fluorescence formation, such that δF be can used as an accurate measure of fish damage. It is thought that measurement of δF in processes such as the freezing of gadoid fish, in which both FA and lipid oxidation are produced, could be of benefit. Received: 23 June 1997     

干装苹果罐头贮藏过程中质地与细胞壁组分的变化

以干装苹果罐头为研究对象,采用TPA质构分析和乙醇不溶物（AIR）法,研究干装苹果罐头（4±1） ℃和常温贮藏过程中质地和细胞壁组分的变化,并探讨其质地参数和细胞壁组分变化的相关性。结果表明,低温贮藏能延缓干装苹果罐头质地和细胞壁组分的变化,（4±1） ℃贮藏的在24个月时硬度、回复性、咀嚼性、内聚性的变化率分别为0.74%、1.92%、0.25%、0,水溶性果胶（WSF）降低率为5.45%、螯合剂溶性果胶（CSF）和碳酸钠溶性果胶（NSF）升高8.88%和24.49%、半纤维素组分（HF）降低14.15%;常温贮藏的在12个月时硬度、回复性、咀嚼性、内聚性的降低率分别为3.93%、3.85%、11.36%、3.45%,WSF降低率为7.27%、CSF和NSF升高0.58%和4.08%、HF降低14.41%,质地参数与WSF呈负相关,与CSF、NSF、HF呈显著正相关。     

Lipid changes during long-term storage of canned tuna (Thunnus alalunga)

 Lipid damage during prolonged storage of canned fish was studied. Albacore tuna was processed under two sterilization conditions (115°C, 74 min; 120°C, 40 min) and then stored for up to 6 years. Analyses (lipid oxidation and hydrolysis, browning and formation of fluorescent compounds) of the lipids extracted from the white muscle of the fish and the packing oils were carried out. Muscle lipids were partially extracted by the packing oil, so that an increase in the storage time produced higher levels of free fatty acids, browning and fluorescence development in the packing oils. As regards the types of muscle, little difference between them throughout the canned storage was detected. Received: 17 February 1997 / Revised version: 12 May 1997     

间歇升温对香蕉李贮藏中营养成分的影响

以香蕉李为试材,研究了不同的间歇升温对低温下贮藏的李果实营养成分的影响.结果表明,对照果在冷藏30d时,可滴定酸、蛋白质、VC含量都呈现快速下降的趋势,还原糖、总糖含量异常上升,说明此时冷害已经发生.而经过间歇升温的果实,蛋白质、还原糖、总糖含量都呈现缓慢上升、下降的趋势,VC和可滴定酸含量呈现逐渐下降的趋势,冷害指数明显降低,说明间歇升温明显地抑制了李果实冷害的发生,尤其间歇升温到18℃抑制冷害的效果更好,保持了李果较好的营养品质.     

二氧化氯处理对贡柑采后贮藏品质的影响

为探究二氧化氯(ClO_2)处理在贡柑果实采后贮藏中的防腐保鲜作用,设计不处理、水处理及5、10、15、L ClO_2溶液分别浸果处理5 min,装入塑料薄膜保鲜袋中在自然室温下贮藏90 d,期间于0、15、30、45、60、75、90 d时分别测试分析了各处理果实贮藏品质的响应与差异。结果表明,不同浓度ClO_2溶液浸果处理,均可不同程度地抑制贮藏期间贡柑果实可溶性糖、可滴定酸及维生素C(Vc)含量的下降,对贮藏中贡柑果实的失重和腐烂尤其具预防和抑制作用,其中ClO_2浓度达15 mg/L及其以上的处理,各项指标均与不处理、水处理有显著性差异(P<0.05)。该研究结果为贡柑果实绿色防腐保鲜提供了技术参考,可在采后商品化实践中应用。     

微波条件下陶瓷食品接触材料中有害重金属迁移行为的研究

目的 研究微波条件下陶瓷食品接触材料中有害重金属的迁移行为。方法 向陶瓷餐具中装入乙酸溶液, 进行常规处理和微波加热处理, 最后用火焰原子吸收分光光度计检测, 研究微波功率、加热时间和迁移液pH值对陶瓷餐具中铅、镉向乙酸溶液迁移的影响, 并将该方式与常规方式作对比。结果 铅、镉的迁移量随微波功率和加热时间的增加而增大, 并基本在加热15 min后达到迁移平衡; 微波功率不但影响铅、镉的迁移速度, 还影响其达到迁移平衡时的浓度; 铅、镉的迁移量随迁移液pH值的降低而增大。结论 通过短时间的微波加热, 即可使铅、镉的迁移量达到甚至显著超出(22?2)℃温度下浸泡24 h?20 min的迁移量。     

Composition of the surface waxes of apple fruits and changes during storage

The hydrolysed surface waxes of Dougherty, Granny Smith and Sturmer apples at harvesting consisted of 57 to 62% acids, 21 to 26% hydrocarbons, 7% primary alcohols, 3 to 5% secondary alcohols and 4 to 7% of other constituents. The hydrocarbon homologues ranged from C₁₈ to C₃₁ with n-nonacosane comprising 84 to 92% of the total hydrocarbons. The primary alcohols (C₁₄ to C₂₈) were mainly n-hexacosanol in Sturmer and n-tetracosanol in Dougherty and Granny Smith cultivars, the amounts of these alcohols being, respectively, 53.4, 32.4 and 35.6% of the total alcohols. In all three cultivars the secondary alcohols consisted almost entirely of one component, possibly nonacosan-10-ol. The Sturmer waxes were distinguished from those of the Dougherty and Granny Smith by a lower content of linoleic and by a generally higher content of palmitic acid. During storage the amount and composition of the waxes of Sturmers did not change appreciably. The wax content of the Granny Smith cultivar increased up to 268 days and that of the Dougherty up to 70 days of storage. Changes in fatty acid composition also occurred during storage, the most remarkable being the up to 11-fold elevation of the linolenic acid content of the Granny Smith apples.     

芒果贮藏保鲜技术的研究

以"瓦橙"芒果果实为实验材料,研究其采后生理特性和贮藏保鲜技术.测定了腐烂指数、失重率、呼吸强度、过氧化物酶等芒果果实采后理化指标,结果表明:瓦橙的最佳贮藏温度是8℃,最佳保鲜药剂是扑海因,贮藏温度是影响芒果采后生理的重要因素.     

Determination of trace metals in canned fish marketed in Turkey

The levels of trace metals of canned fish samples collected from markets in Turkey were determined by flame and graphite furnace atomic absorption spectrometry after microwave digestion. The accuracy of the method was corrected by standard reference material (NRCC-DORM-2 Dogfish Muscle). The contents of investigated trace metals in canned fish samples were found to be in the range 1.10–2.50 μg/g for copper, 7.57–34.4 μg/g for zinc, 0.90–2.50 μg/g for manganese, 10.2–30.3 μg/g for iron, 0.96–3.64 μg/g for selenium, 0.45–1.50 μg/g for aluminium, 0.97–1.70 μg/g for chromium, 0.42–0.85 μg/g for nickel, 0.09–0.40 μg/g for lead and 0.06–0.25 μg/g for cadmium. The results were compared with the literature values.     

Effect of processing on galactose in selected fruits.

PURPOSE: The impact of consuming processed versus fresh fruits and vegetables on the galactose intake of galactosemic patients was compared. METHODS: The galactose content of processed fruits was determined when the following processing methods were used: freezing, drying, blanching, microwaving, canning, and a combination of blanching and freezing. Then three-day food intakes of five subjects with galactosemia were recorded. The records were used to estimate galactose intake, according to previously reported galactose levels for fresh fruits and vegetables and the potential reduction in galactose intake when only processed fruits and vegetables are consumed. RESULTS: The average galactose reduction was approximately 45% for all the fruits and all processing methods, excluding drying. Intakes varied from 17 to 108 mg/day when fresh values were used and 11 to 103 mg/day when only processed fruits and vegetables were consumed. This reduction was statistically significant for four out of five patients. CONCLUSIONS: When the reduction is compared with reported daily fluctuations in galactosemic patients' endogenous galactose production, the clinical significance of reduced free galactose consumption on long-term outcome is unclear. However, metabolic dietitians now have objective data that the processing methods described will lower the free galactose content of the fruits analyzed.     

影响冷藏荔枝货架期因素的研究

状元红荔枝果实经保鲜剂处理，在低温2－4℃下贮藏60d后，然后采用出库复色剂处理和出库复色并加固色剂处理2种出库方式。结果表明，贮藏期间荔枝果实呼吸强度明显下降，但出库后呼吸强度显著上升；冷藏期荔枝果皮PPO酶活性下降，出库后稍微上升，其b处理60d后好果率为90．1％，采用抗氧化剂出库的果实货架期常温72h后好果率为85．7％。