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.     

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.     

Tin and Iron Content of Canned and Bottled Foods

The tin and iron content of 14 different types of canned foods and of 5 different types of bottled foods were determined. No tin was detected in most bottled foods, but tin was detected in all canned foods. Storage of foods on the shelf for 4 months or in open cans in the refrigerator for 1 wk resulted in increased amounts of tin and iron in some of the canned foods. Those foods which were packed in totally lacquered cans accumulated little tin or iron during storage; those foods which were packed in unlacquered or partially lacquered cans generally accumulated significant amounts of iron and tin during storage. The tin content of the canned foods was not statistically correlated to the pH of the foods.     

Chemical composition and volatile constituents of canned mango juice

The chemical composition of mango (Mangifera indica L.) pulp and canned mango juice were evaluated. Canned mango juice was characterized by a lower content of ascorbic acid, free amino nitrogen, reducing sugars and carotenoids than the mango pulp, while the latter was characterized by lower natural total soluble solids, higher pH, lower total sugars and lighter color. The volatile composition of canned mango juice was investigated by means of standard-controlled distillation-extraction, liquid-solid chromatography and gas chromatography-mass spectrometry. This combination led to the characterization of 64 volatiles, of them 21 hydrocarbons, 25 alcohols, 12 esters, 2 aldehydes, 2 lactons and 2 other compounds. The volatile components of canned mango juice were quantitatively determined in range of 2260 ppb to 10 ppb. Limonene, myrcene, cis and trans-ocimene, β-caryophellene and α-terpinolene were the major hydrocarbons of canned juice; meanwhile, methyl butanoate + ethyl 2-methyl butanoate, furfural, α-terpineol and γ-octalacton were the abundant oxygenated compounds.     

Preservation of mango juice by freezing and canning

In this work the preservation of mango juice by freezing and canning was compared. The following results were obtained: The loss of ascorbic acid during the preparation of canned mango juice is mainly due to the processing steps other than retorting which had the least harmful effect. The retention of ascorbic acid and carotene after canning and freezing was nearly the same. Both freezing and canning caused no marked changes in the pectin content. The inactivation of the pectin methylesterase was more obvious after canning than after freezing. Reducing sugars slightly increased after freezing and canning, while the acidity and pH showed no appreciable changes. The chemical constituents except the sugars of the commercial samples were lower than those of the experimental samples. During storage, the percentage retention of ascorbic acid and carotene were lower when pasteurization was not included, and in canned samples they were higher in the experimental juice than in the market samples. Pectin content showed no changes in all cases studied. The activity of pectin methylesterase slightly decreased in frozen samples, while it was a small increase in case of canned juices. During storage the microbial count of frozen and canned samples decreased when storage progressed. The addition of water and sugar during manufacturing of commercial samples did not help to obtain a product with good storage stability. There was a significant difference between the characteristics of frozen pasteurized and non pasteurized mango juice. It seems very important to pasteurize mango juice before storage in a frozen form.     

Effects of pH, Storage Time and Temperature on the Tin Content of Single Strength Canned Grapefruit Juice

Grapefruit juice modified to pH 3.0, 3.5 and 4.0 and stored at 4, 21, 27, 32 and 38°C manifested a consistent two-stage pattern for tin uptake. The first stage consisted of a rapid (3 wk) uptake of tin (from 12 to approximately 100 ppm) and was relatively independent of juice pH or storage temperature. In the second stage, the increase in tin concentrations was extremely temperature dependent and only slightly pH dependent. Canned grapefruit juice should be stored below 27°C to insure tin contents do not exceed the Codex maximum of 250 ppm. In a survey of 55 commercially canned grapefruit juice samples stored 1-8 months under commercial conditions, tin concentrations ranged from 34-180 ppm.     

藕汁牛奶饮料研制

以新鲜莲藕、脱脂奶粉、白砂糖为主要原料,配以稳定剂,制成一种营养丰富、气味芳香的藕汁乳饮 料。该饮料灌装后有良好的稳定性。     

柑橘汁胞生产过程中脱囊衣技术的研究进展

脱囊衣是柑橘罐头和橙汁生产过程中的关键环节,在柑橘汁胞分离过程中同样需要进行脱囊衣处理,文中概述了几种柑橘脱囊衣的方法,主要介绍了酶法脱囊衣,并对其发展和应用前景进行了展望。     

基于CFD技术的橙汁巴氏高温灭菌及冷却工艺研究

为了对橙汁灭菌及冷却工艺进行精确的研究,确保果汁品质的同时达到降低生产能耗、缩短生产时间的目的,在分析得到果汁中常见细菌灭杀温度及试验验证模型可靠性的基础上,对罐装橙汁高温灭菌及冷却工艺进行模拟计算。结果表明,在兼顾时间和能耗的原则下,最优灭菌工艺为95℃、1 020s,最优冷却工艺为10℃、720s。     

The effect of iron, tin, aluminium, and chromium on fading, discoloration, and precipitation in berry and red beet juices.

The effect of iron(II), tin(II), aluminium(III), and chromium(III) on the properties of red whortleberry, blackcurrant, and red beet juices was followed during storage for 10 months at 5 degrees C. The colour and pH changes were studied, and the precipitates formed were weighed and their metal contents assayed. Of the metals tested, only tin caused bluish discoloration in the berry juices. In the case of iron, aluminium, and chromium the low pH prevented this type of discoloration. In berry juices, some increases in colour intensity took place with the lowering of pH value, whereas in red beet juice the opposite change occurred. The colour changes due to storage appear to take place irrespective of the metals. Precipitation is enhanced in red whortleberry juice only by tin, and in blackcurrant juice by tin and iron. In red beet juice, precipitation is increased by the lowering of pH resulting from metal salt addition. In general, increase in the amount of metal added increased the metal content of the precipitate. Iron showed the greatest tendency to become bound in the precipitate, particularly in blackcurrant and red beet juice. The suitabilities of the metals for canning purposes are considered. Chromium, in particular, has interesting possibilities in view of the low degree of colour change associated with it.     

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%.     

荔枝果汁产品开发与市场策略分析

荔枝是我国岭南特色水果之一,其采收季节短,贮藏保鲜难度大,鲜果供应期集中,限制了荔枝产业的健康发展。荔枝加工产品主要包括荔枝干、荔枝罐头等。果汁加工具有原料消耗量大,市场需求高,对水果原有营养成分保存较多的特点,因此一直是水果加工的最主要形式,但目前荔枝果汁产品还鲜见于市场。本文探讨了以荔枝为原料,加工成为果汁系列产品的可行性和市场策略,以期为荔枝产业的持续发展提供有益的思路。     

Investigation of fish product–metal container interaction using scanning electron microscopy–X-ray microanalysis

Scanning electron microscopy (SEM) and X-ray microanalysis (EDS) were used to investigate metal can discoloration and lacquer adhesion failure in enameled food cans containing tuna in vegetable oil and octopus in brine, respectively. Black and brown spots on the internal surface of the can body were caused by the formation of FeS and SnS, respectively. The source of metal can discoloration was traced to inadequate lacquering of the tin plated steel, exposing both tin and iron to sulfur containing amino acids originating from the tuna product. Enamel adhesion failure in canned octopus was also traced to local defects in the lacquer coating enabling both NaCl and citric acid contained in the brine to cause enamel blisters on the can body leading to lacquer peeling and in turn to local detinning and steel corrosion. The first defect known as “sulfide staining” is harmless to human health and does not usually affect the product. The second defect may cause extensive detinning and steel corrosion possibly affecting the safety of the canned product. This postulation is supported by iron and tin concentrations both in the product and liquid medium carried out by atomic absorption spectroscopy.     

Nutritional value of some canned tomato juice and concentrates

Fresh tomatoes, juice and concentrate were analysed chemically. The canned tomato products were not a good source of vitamin C, but their niacin content was higher than that of the fresh tomatoes. Thiamin was not affected by the canning process, but riboflavin was, and vitamin A was slightly affected. Nine elements: Ca, Cu, Fe, Mg, Mn, Ni, K, Na and Zn, were determined in the fresh tomato and its products, but Pb was found only in the final products.     

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.     

Development and Validation of an ETAAS Method for the Determination of Tin in Canned Tomato Paste Samples

The determination of tin in canned food became very important in the last few years since it gives information about the contamination process helping to increase canned food quality and safety. The present work describes the development of a method for the determination of tin in canned tomato paste by electrothermal atomic absorption spectrometry in order to investigate the influents of (1) the industrial sample pretreatment procedure of canned tomato paste and (2) the type of materials used in packaging, on the total concentration of tin in canned tomato paste samples. For method validation, precision (repeatability and reproducibility) and accuracy (by recovery tests) have been assessed as performance criteria. The calculated recoveries ranged between 87.9% and 91.9%. The calculated expanded uncertainties based on the EURACHEM/CITAC Guidelines achieved from three different concentration levels were also calculated. The obtained results indicated that the method is efficiently and properly implemented. The validated method was applied for tin concentration determination in canned tomato paste purchased from the local market. In all analyzed samples, tin concentrations levels were lower than the maximum permissible value recommended by the European Regulation.     

Improved iron solubility in carrot juice fermented by homo- and hetero-fermentative lactic acid bacteria

To evaluate lactic acid fermentation as a means to increase the availability of iron in carrot juice, two strains (Lactobacillus pentosus FSC1 and Leuconostoc mesenteroides FSC2), two types of carrot juice and two modes of fermentation were compared. Fermentation improved iron solubility up to 30 fold. The total mineral content and the yield of soluble iron differed between the two types of juice. Addition of pectolytic enzyme and cellulase further improved iron solubility in fermented juice by about 10%. L. pentosus FSC1 yielded the largest improvement in soluble iron, which was not simply a result of a decrease in pH. The concentration of soluble iron in Ln. mesenteroides FSC2 fermentation was linearly related to the major acids produced. Besides, the mineral inhibitor phytate was completely degraded in all the fermentations.Lactic acid fermentation strongly improves iron solubility in carrot juice. The level of improvement was strain specific and related to the produced acids rather than a simple pH effect. Composition of carrot juice and addition of viscosity-reducing enzymes also contributed to this improvement. Our study suggests that carrot juice with high mineral availability may be achieved by fermentation using selected starter cultures, substrate and process.     

Inhibition of yeast growth in grape juice through removal of iron and other metals

Growth of microbial spoilage organisms requires an adequate supply of essential trace metals. Removal of iron and other metals from grape juice with chelating resins was studied with a view to obtaining microbiological stability without the addition of chemical preservatives. Several chelating resins were examined for their iron and other metal removal efficiencies. High affinity and selective removal of essential trace microbial nutrient metals was investigated for its effects on the growth of Saccharomyces cerevisiae in grape juice.
Iron removal from grape juice was studied in terms of removal kinetics and completeness. Iron removal was fast, and almost all of the iron was removed within 1  h. The chelating resins were able to easily remove the iron to a level below 5 p.p.b. in a batch process, and with a column process the iron concentration could be reduced to about 1 p.p.b. Other metals significantly removed by the resins in the treatment were Cu, Mn, Mg, Ca and Zn. Levels of Na and K were also significantly affected by the treatments.
Grape juice with an iron content below 3 p.p.b. could be prepared by using the chelating resins. Preliminary evaluation indicated that the growth of S. cerevisiae , a bottom wine yeast, was substantially inhibited in the treated grape juice. The inhibitory effect could be abolished by re-addition of the removed metals.     

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.     

Optimized Ultrasound-Assisted Temperature-Controlled Ionic Liquid Microextraction Coupled with FAAS for Determination of Tin in Canned Foods

A simple and rapid method based on ultrasound-assisted temperature-controlled ionic liquid microextraction combined with flame atomic absorption spectrometry (FAAS) has been developed for determination of tin. In this method, Sn(IV)-ammonium pyrrolidinedithiocarbamate (APDC) complex was extracted into a small volume of 1-hexyl-3-methylimidazolium hexafluorophosphate as ionic liquid and after phase separation, the enriched analyte in the final solution is determined by FAAS. Experimental design approaches were used to obtain the best conditions. The variables of interest were temperature, pH, buffer volume, extraction time, centrifugation time and volumes of ionic liquid, methanol, and APDC. The Plackett–Burman design was employed for screening to determine the variables significantly affecting the extraction efficiency. Then, the significant factors were optimized by using a central composite design. In the optimal conditions the calibration graph was linear in the range of 0.10–6.0 mg?L^?1 with a correlation coefficient of 0.997. The limit of detection and relative standard deviation (n?=?5 for determination of 1.0 mg?L^?1) were 42 μg?L^?1 and 1.6 %, respectively. The preconcentration factor was calculated to be 52.7. Finally, the method was successfully applied to the determination of tin in various canned products including peach, pineapple and aloe vera juice, canned pea, and canned cheese.