Iron and tin content of canned fruit juices and nectars

A survey of the iron and tin content of twelve different types of canned fruit juices and nectars revealed that, of the 122 cans examined, 23 (or 18·9%) contianed iron in excess of 15 mg kg^?1 and 16 (or 13·1%) contained tin in excess of 250 mg kg^?1. Apple juice and tomato juice were found to contain particularly high levels of iron, the maximum level recorded being 42·6 mg kg^?1. Mango juice and orange juice exhibited significant non-compliance with recommended Codex tolerance limits for tin. Statistical analysis showed that, at the 5% probability level, the mean iron contents of products packed in completely unlacquered and end-lacquered cans were not significantly different from each other, but were significantly lower than the mean iron content of products packed in fully lacquered cans. The mean tin content fell in the order unlacquered > end-lacquered > fully lacquered cans.     

Lead, chromium, tin, iron and cadmium in foods in welded cans

The levels of lead, chromium, tin, iron and cadmium in fruit and vegetables in welded tinplate cans were determined by atomic absorption spectrophotometry. The levels found were compared with those in foods in soldered tinplate cans and fresh foods. The results show that the lead levels in foods in welded cans were much lower than those in similar foods in soldered cans. Foods in unlacquered welded cans contain much more lead, chromium and tin than foods in lacquered welded cans. The cadmium and iron levels in canned fruit and vegetables in welded cans were similar to those found in the corresponding fresh foods.     

COLOR OF PROCESSED SWEET POTATOES: EFFECTS OF CAN TYPE

Sweet potatoes packed in four types of enamel-lined cans were darker in color and less attractive than those packed in tin-coated cans. The differences in color among can types was more pronounced after opening the canned product and exposure to air for an hour. The tin content of the product from the tin-coated cans was much greater than that from the enamel-lined cans. The brighter color of the product from the tin-coated cans is assumed to result from the substitution of tin for iron or other metals in the complex formed in the pheno-lase reactions.     

Storage stability of a high protein food beverage powder prepared from the Nigerian ‘red skin’ groundnut (Arachis hypogaea) protein concentrates

A high protein, groundnut-based powder reconstitutable into a milk-like beverage was packed in polyethylene bags and in lacquered tin cans, and stored at both room temperature (25 ± 2°C) and in a domestic refrigerator (5 ± 2°C) for 60 days. Storage stability was evaluated by analysing periodically for changes in physical characteristics, proximate composition, and development of browning and rancidity, and assessing moisture sorption characteristics. Protein, lipid, total soluble sugars, peroxide value, total carbonyls and extinction values of the ethanolic extract remained practically constant during storage. The isotherm curves exhibited the characteristic sigmoidal shape typical of high protein foods. There was a greater increase in density, hygroscopicity and wettability in polyethylene-packed samples at both temperatures suggesting that the lacquered tin can leads to better keeping quality for this product.     

Internal corrosion and shelf‐life of food cans and methods of evaluation

Internal corrosion in food cans is characterized by metallic dissolution which is an electrochemical reaction. In lacquered cans, corrosion may also cause disruption in the continuity of the lacquer film. These reactions may cause organoleptic changes in the product, loss of vacuum, swelling, and leaking in extreme cases. In some instances the metal dissolution (i.e., lead) may give rise to toxicological problems. Therefore, these phenomena are often the limiting factor in the shelf life of canned products. Changes in color, texture, and sensoric properties of the foods, which take place simultaneously, affect the aesthetic and nutritional value of the product and thus its shelf life. These changes are often related to interactions with the container. For example, tin dissolution prevents browning and loss of ascorbic acid. Shelf life of canned foods is governed by the quality of the raw materials, the processing technology, quality of the container and storage conditions which will be reviewed in this paper. Can manufacturing technologies, mechanisms of electrochemical corrosion, methods of their measurement and prediction of shelf life will be discussed.     

Changes in individual carotenoids on processing and storage of mango (Mangifera indica) slices and purée

Susceptibility of different carotenoids to degradation during thermal processing and storage of two mango cultivars was investigated. The carotenoid composition was practically maintained on processing mango (cultivar Tommy Atkins) slices. The only significant change was the increase in luteoxanthin, compatible with the conversion of 5,6- to 5,8-epoxide. More evident transformations occurred on processing mango (cultivar Golden) purée. The major pigment β-carotene decreased 13%, resulting in a corresponding reduction of the vitamin A value. Auroxanthin, not found in the fresh fruit, appeared while violaxanthin and luteoxanthin decreased. During storage of mango slices in lacquered (epoxy) or plain tin-plate cans, no appreciable loss of β-carotene was observed during 10 months. Between the tenth and fourteenth month, about 50% reduction of β-carotene occurred. The degradation continued, resulting in a total loss of 84% after 24 months. A tendency of violaxanthin to decrease, and auroxanthin to increase, during storage was also noted. β-carotene showed a greater susceptibility to degrade in bottled mango purée (18% loss after 10 months) than in the canned product. As in the case of mango slices, however, both bottled and canned purée suffered 50% loss of β-carotene after the tenth month, and a total loss of 83% after 24 months. Violaxanthin and luteoxanthin tended to decrease while auroxanthin maintained a comparatively high level throughout storage. The vitamin A values reflected the degradation trend of β-carotene, a pattern that appears to agree with a free radical mechanism.     

马口铁包装水果罐头中锡的浓度变化和形态分布研究

目的 研究马口铁包装水果罐头中锡的浓度变化和形态分布。方法 采用电感耦合等离子体串联质谱法(inductively coupled plasma tandem mass spectrometry, ICP-MS/MS)测定马口铁包装水果罐头的锡含量,并分析锡浓度随储存时间、加热次数的变化特点;采用高效液相色谱电感耦合等离子体串联质谱法(high performance liquid chromatography-inductively coupled plasma tandem mass spectrometry, HPLC-ICP-MS/MS)测定并分析罐头中锡的形态分布。结果 镀锡马口铁包装水果罐头中锡含量在生产日期3个月内为27.17~183.81 mg/kg,生产日期12个月时为54.56~265.44 mg/kg,锡浓度随储存时间、加热次数而明显增加,溶出锡为无机形态,以二价锡Sn[II]为主,未检测到锡的有机形态。结论 马口铁包装水果罐头中锡随储存时间和加热次数而大量增加,但都以无机锡的形态存在,因吸收利用率低,毒性较低;尽量选择靠近生产日期的产品,且不要罐内加热食用。     

High Vacuum Flame Sterilized Fruits: Influence of Can Type on Storage Stability of Vacuum Packed Peach and Pear Slices

The feasibility of using enameled tin and tin-free steel (TFS) cans for processing oxygen sensitive fruits by high vacuum flame sterilization was evaluated. Through 18 months storage at ambient temperatures, the appearance and quality of the HVFS peaches and pears remained acceptable for all can types. Fruits packed into plain tin cans appeared brighter and tasted tangier than those packed into TFS or inside-enameled tin cans. Texture, pH and titratable acidity of fruit were not measurably affected by variation in can types. Mechanical deaeration followed by flame sterilization, produced a product with quality comparable to that achieved in flame deaerated packs.     

Corrosion behaviour of tinplate cans in contact with tomato purée and protective (inhibiting) substances

The dissolution of iron and tin from tinplate cans filled with tomato purée (pH 4.34) and dioctyl sebacate oil (DOS), essential onion oil (EOO) or potassium nitrate was studied using atomic absorption spectroscopy (AAS), while nitrate was determined using high-performance liquid chromatography (HPLC). The maximum values found in cans were up to 284 mg kg^?1 for tin and 513 mg kg^?1 for iron at elevated storage temperature. Results indicated that the addition of EOO to tomato purée prevents the corrosion process in the case of tin, where concentrations were lowered from 223 to 28 mg kg^?1 for cans with DOS oil and EOO at 20°C, respectively (inhibition rate of 87%). On the other hand, the presence of EOO enhanced the corrosion process for iron increasing the concentration from 15 to 46 mg kg^?1 during 7 months of storage, although this value did not exceed maximum permitted value (50 mg kg^?1). In cans with tomato purée and potassium nitrate, dissolution of tin started after 30 (36°C) and 60 (20°C) days of storage as a consequence of nitrate action, which act as a corrosion accelerator. Since the addition of EOO improves the taste of canned tomato purée, its potential use as a corrosion inhibitor would be of interest.     

Shelf life of canned grapefruit juice - methods for evaluation and factors affecting it

Summary. Dissolved tin content was used as a criterion of shelf life for both can and content. Several methods for determining the dissolved tin content are available, but most of them are destructive and involve time-consuming digestion of the samples. A non-destructive In-Can measuring device, which permits the changes in dissolved tin content to be followed in sealed plain tin cans during storage, was found to be highly reliable as a shelf life indicator. Using those methods, the effect of several processing variables on the shelf life of canned grapefruit juice were studied. the detrimental effect of large headspace and slow cooling and the benefit of de-aeration were shown.     

Bisphenol A (BPA) and its source in foods in Japanese markets

The determination of bisphenol A (BPA) and/or bisphenol A diglycidyl ether (BADGE) in foods sold in Japanese markets and in water leached from six epoxy resin cans with similar diameters was carried out using high-performance liquid chromatography (HPLC) with electrochemical detection (LC/ECD), LC-mass spectrometric detection (LC/MS) and LC-tandem mass spectrometric detection (LC/MS/MS). BPA concentrations were 0-842 ng g^-1 for 48 canned foods, 0-14 ng g^-1 for 23 foods in plastic containers, and 0-1 ng g^-1 for 16 foods in paper containers. No BADGE was detected in three canned foods. There was no difference in leaching concentrations of BPA into glycine buffers at pHs 8 and 11, and water. The amounts of BPA leached into water from six epoxy resin cans held at 121°C for 20 min were almost the same as the cans' contents and were much higher than the amounts leached from cans held at or below 80°C for 60 min. The amount leached depended on the type of can, but not on the amount of BADGE leached from the cans. Considerably more BPA than BADGE leached to water from six cans. Two cans whose contents had high concentrations of BPA showed no BADGE leaching even at 121°C, suggesting the different kinds of epoxy resin can linings from others. The results imply that the main source of human exposure to BPA is food from cans with linings that contain high percentages of BPA as an additive or an unforeseen contaminant.     

LEAD CONTENT OF FOODS STORED IN CANS AFTER OPENING

A study was conducted of the effect on the concentration of lead in canned foods when they are stored in their lead-soldered cans after opening. Lead concentrations were periodically monitored during 5 days or 14 days after can opening. Fruit juices had the greatest increases in lead concentration during storage. Low-acid foods did not exhibit a significant increase in lead concentration. Recommendations against storing acidic foods and juices in their opened cans are supported by the results of the study.     

Lead and tin in canned foods: results of the UK survey 1983-1987.

Concentrations of tin and lead in canned foods have been monitored since 1983 to determine the effects of recent changes in can-making technology. In the sample studied the proportion of foods contained in non-soldered as opposed to soldered cans has risen consistently during the survey and now accounts for 83% of all samples (excluding sardines). Foods contained in non-soldered cans have lower lead concentrations than those contained in soldered cans and this changeover is likely to result in a decrease in dietary lead intakes in the UK.     

Analysis of fruit juice by atomic absorption spectrophotometry. I. The determination of iron and tin in canned juice

Atomic absorption spectrophotometry has been used to compare the concentrations of iron and tin in canned fruit juice with those in juice not stored in cans. No significant difference was found in the level of iron, but the amount of tin was considerably higher in canned samples. The determination is rapid, and no ashing procedure is required.     

Estimates of per capita exposure to substances migrating from canned foods and beverages.

A study was undertaken by European industry to estimate the consumption of canned beverages and foodstuffs. European can production data were used with adjustments for imports into and out of the EU. It was further assumed that can production, with adjustments, equalled consumption. Owing to the lack of actual consumption country-by-country or household-by-household data throughout Europe, only per capita estimates of consumption were possible. Data were compiled country-by-country for seven major can-producing EU Member States and for eight different types of canned food and two types of canned beverage (beer and soft drinks). The per capita consumption of canned foods was 1.1 cans/person/week, and consumption of canned fish was estimated as 2.2 kg/person/year. The estimate of per capita consumption of canned food was 62 g/person/day or 22.6 kg/person/year. Canned beverages account for about 60% of the consumption of canned foodstuffs. The usefulness of per capita consumption of beverages is questionable because consumption habits may vary more widely than those for canned foods. However, as the migration into beverages is insignificant, these data were added for completeness. Per capita consumption of canned beverages is 67 cans/person/year or 61 g/person/day. From the average can sizes, the surface area of the cans consumed was estimated. The per capita surface area exposure was 0.55 dm(2)/person/day for canned foods and 0.55 dm(2)/person/day for canned beverages, giving 1.1 dm(2)/person/day. Migration of a substance at 0.02 mg dm(2) gives an exposure of 0.01 mg/person/day assuming a per capita consumption, using a surface area model. Migration at 0.12 mg kg(-1) in food gives an exposure of 0.007 mg/person/day using a weight model. Both models assumed migration into all food types at the same level, which is highly unrealistic. Exposure to BADGE from canned foods has been used as a case study. The best estimate for a worst case per capita exposure to BADGE and relevant derivatives was between 6 and 10 micro g/person/day, depending upon the approach and assumptions used.     

DETINNING IN CANNED TOMATOES CAUSED BY ACCUMULATIONS OF NITRATE IN THE FRUIT

ABSTRACT— The 1965 experimental crop of Floradel variety tomatoes accumulated no nitrate and removed only about 15% of the tin from their containers in a 2-yr storage period. The 1966 Florida crop of Homestead 24 variety tomatoes accumulated from about 50–80 ppm in the fruit and removed about 70% of the tin from their cans. All fertilizer application variables except the lowest resulted in about the same level of nitrate accumulation. The nitrate in most of these variables was exhausted in about 6 mo and the rate of detinning leveled off soon after. The correlation between loss of nitrate and tin removal was significant at the 5% level. Detinning in these cans approached a "problem level' in that about 70% of the tin was removed in 18 mo. In the 1965 tomato crop at Ohio State University there was no apparent connection between the levels of applied nitrogen and the nitrate accumulated in the fruit. In the 1966 Ohio tomatoes, the treatments with no applied nitrogen accumulated less nitrate in the fruit than the other treatments with varying levels of nitrate fertilization. The differences among the detinning histories of the various treatments followed in a general way the differences in nitrate accumulation. Detinning in individual cans varied between extremely wide limits. There were no differences apparent among the treatment variables in the 1965 crop. In the 1966 tomatoes the zero applied nitrogen treatment consistently showed less detinning than the others. In both the 1965 and 1966 crops the nitrate in the canned samples was exhausted after about 2 mo of storage. Essentially all of the detinning in these tomatoes occurred during the first 6 mo. Regression equations from pooled results of field studies and work on nitrate fortification of non-aggressive tomatoes suggest that an initial nitrate concentration of the order of 100 ppm can constitute a rapid detinning problem in tomatoes in a 303 can having a tin coating weight of 1.00 Ib/bb.     

Essential Elements in Fresh and Canned Tomatoes

The content of 16 essential elements was determined in fresh and canned tomatoes by atomic absorption spectrophotometry. The elemental content of fresh tomatoes was compared with that of canned tomatoes. All data were analyzed statistically. There were significantly higher amounts of calcium, chloride, cobalt, copper, nickel, sodium, tin, and zinc in canned tomatoes than in fresh tomatoes. There were significantly lower amounts of magnesium, manganese, phosphorus, potassium, and silicon in canned tomatoes than in fresh tomatoes. No significant difference in iron was found between fresh and canned samples. Percentages of the established and estimated RDA's show that fresh and canned tomatoes are relatively good sources of potassium and relatively fair sources of iron. Canned tomatoes are a relatively good source of sodium. Element retention in the canned tomatoes was 77–7,651%.     

食品金属罐中14种双酚类物质迁移量的同时测定及杀菌过程对其迁移的影响

为了调查国内食品金属罐中双酚类物质的迁移水平,本文建立了同时测定食品金属罐中14种双酚类物质迁移量的高效液相色谱法,并研究了杀菌过程对双酚类物质迁移的影响及食品金属罐中双酚类物质的迁移规律.结果表明,14种双酚类物质在4种食品模拟物(4％体积乙酸、10％体积乙醇、50％体积乙醇和异辛烷)中线性关系良好,加标回收率为83...     

A Rapid Gas Chromatographic Method for the Identification of Sporeformers and Nonsporeformers in Swollen Cans of Low-Acid Foods

A rapid gas-liquid chromatographic method for the identification of sporeformers and nonsporeformers as the probable cause of swollen cans of low-acid foods was developed and evaluated. Cans of five types of food were inoculated with cultures of seven sporeforming organisms and three nonsporeformers. The supernatant from the can content was assayed on two packed columns designed for the assay of aqueous solutions of volatile free acids using flame ionization detectors. A statistical discriminant analysis was conducted on selected peak areas. Overall, 88% of 120 cans were correctly identified in the standard data set and 80% of 110 cans analyzed as unknowns. Sporeformers were detected in 62% of 30 cans inoculated with three mixtures of sporeformers and nonsporeformers.