Behavior of flavonols and carotenoids of minimally processed kale leaves during storage in passive modified atmosphere packaging.

Minimally processed kale leaves were packed in passive modified atmosphere and stored at 3 conditions: 1 °C in the dark and 11 °C with or without light exposure. The products were evaluated during storage in terms of headspace gas composition, sensory attributes, flavonol, and carotenoid contents. The sensory quality decreased slightly during 17 d at 1 °C in the dark. At 11 °C, the vegetable shelf life was predicted to be 6 d in the dark and 3 d with light. Quercetin and kaempferol were stable during storage for 15 d at 1 °C in the absence of light. At 11 °C in the dark, quercetin was stable during 10 d, increasing slightly on the 8th day. Kaempferol decreased up to the 5th day but increased on the 8th day, decreasing again on the 10th day. After 5 d at 11 °C under light, the flavonol levels were significantly higher than those of the initial values. Neoxanthin and violaxanthin did not change significantly after 15 d at 1 °C in the dark. Lutein and ß-carotene, however, decreased 7.1% and 11.3%, respectively. At 11 °C in the dark, neoxanthin, violaxanthin, lutein, and ß-carotene decreased 16.1%, 13.2%, 24.1%, and 23.7% after 10 d, respectively. At 11 °C under light, neoxanthin and lutein had a slight increase while violaxanthin and ß-carotene decreased 23.1% and 16.5% after 5 d. Practical Application: Passive modified atmosphere packaging together with refrigeration can extend the shelf life of minimally processed kale, retaining the health-promoting compounds, flavonols and carotenoids. Quercetin, kaempferol, neoxanthin, and violaxanthin are stable and lutein and ß-carotene slightly reduced.

Degradation of lycopene and beta-carotene in model systems and in lyophilized guava during ambient storage: kinetics, structure, and matrix effects.

Being highly unsaturated, carotenoids are susceptible to isomerization and oxidation during the processing and storage of food. In the present study, the degradation of acyclic lycopene and dicyclic beta-carotene in low-moisture and aqueous model systems, as well as in lyophilized guava, during storage at ambient temperature, in the absence or presence of light, was investigated. Both carotenoids followed first order kinetics under the various conditions investigated. Lycopene degraded much faster than beta-carotene in all the model systems. In a comparison of lycopene isolated from guava, tomato, and watermelon, greater losses were observed with lycopene from tomato. Since the model system was identical in the 3 cases, these results indicated that other compounds from the food sources, co-extracted with lycopene, might have influenced the oxidation. Light consistently and strongly promoted degradation under all conditions studied. The susceptibility of lycopene to degradation was much less in lyophilized guava than in the model systems, showing the marked protective influence of the food matrix. Loss of beta-carotene, found at a concentration of about 18 times lower than lycopene, was only slightly lower than that of lycopene in lyophilized guava, indicating that the effect of matrix and/or the initial concentration overshadowed the structural influence.

Aflatoxin M(1) and ochratoxin A in a human milk bank in the city of São Paulo, Brazil.

Because infants are more susceptible to the adverse effects of mycotoxins, this work was carried out to determine aflatoxin M(1) (AFM(1)) and ochratoxin A (OA) in milk from the Human Milk Bank of the Southern Regional Hospital, São Paulo, Brazil. Analytical methods were first established and evaluated. The methods involved the extraction of AFM(1) with methanol and OA with 1% aqueous sodium bicarbonate solution and methanol, clean-up with immunoaffinity columns having antibodies specific for each mycotoxin and quantification by high performance liquid chromatography (HPLC) with fluorescence detection. The method established for AFM(1) had mean recovery percentages of 94, 77 and 82% and coefficients of variation of 17.5, 3.4 and 4.2% at 0.01, 0.03 and 0.05 ng ml(-1), respectively. For the OA method, the corresponding values were 84, 84 and 75% for recovery and 14.1, 3.7 and 4.0% for the coefficient of variation. The limit of quantification for both methods was 0.01 ng ml(-1). Of a total of 50 samples analysed, only one was contaminated with AFM1, at 0.024 ng ml(-1), and two with OA, at 0.011 and 0.024 ng ml(-1). Although the incidence observed was low, it is recommended that the study be extended to other milk banks of the city of São Paulo.

New data on the total lipid, cholesterol and fatty acid composition of raw and grilled beef longissimus dorsi

Simultaneous analyses of total lipids, cholesterol and fatty acids were carried out on raw and grilled beef longissimus dorsi trimmed of external fat. Cholesterol was determined by high performance liquid chromatography and the fatty acids by gas chromatography. Mean total lipid (g/100 g) ranged from 2.1 to 2.6 for raw beef and 3.5 to 4.0 for grilled beef steaks. Cholesterol levels (mg/100 g) ranged from 40 to 43 for raw beef and 67 to 70 for grilled beef steaks. The main intramuscular fatty acids of the raw and grilled meat were 14:0, 16:0, 16:1n7, 18:0, 18:1n9, 18:1n7 and 18:2n6. Grilled lean beef steaks had significantly higher contents of the principal fatty acids and most of the minor fatty acids. The higher values for the three components in the grilled meat were due to loss of moisture during grilling. There was no significant difference between the apparent and true retentions values, both indicating no significant loss or degradation of total lipids, cholesterol and fatty acids during grilling.

Incidence of patulin in fruits and fruit juices marketed in Campinas, Brazil.

One hundred and eleven samples of processed fruit juices (apple, grape, pineapple, papaya, guava, banana and mango) and 38 samples of sound fruits (apple, papaya, mango, pear and peach) produced and marketed in Brazil, were analysed for patulin by HPLC. Only one out of 30 samples of apple juice was found positive at 17 micrograms/l. Patulin was not detected in the other foodstuffs. It was found in 14 samples of spoiled fruit samples of apple (150-267 micrograms/kg), pear (134-245 micrograms/kg) and peach (92-174 micrograms/kg). Confirmation of the identity of patulin was based on the UV spectrum obtained by the HPLC diode array detector, compared with that of standard patulin, TLC developed by several solvent systems and sprayed with 3-methyl-2-benzothiazolinone hydrazone, and by acetylation with acetic anhydride.

Changes in carotenoids during processing and storage of foods.

Being highly unsaturated, carotenoids are susceptible to isomerization and oxidation during processing and storage of foods. Isomerization of trans-carotenoids to cis-carotenoids, promoted by contact with acids, heat treatment and exposure to light, diminishes the color and the vitamin A activity of carotenoids. The major cause of carotenoid loss, however, is enzymatic and non-enzymatic oxidation, which depends on the availability of oxygen and the carotenoid structure. It is stimulated by light, heat, some metals, enzymes and peroxides and is inhibited by antioxidants. Data on percentage losses of carotenoids during food processing and storage are somewhat conflicting, but carotenoid degradation is known to increase with the destruction of the food cellular structure, increase of surface area or porosity, length and severity of the processing conditions, storage time and temperature, transmission of light and permeability to O2 of the packaging. Contrary to lipid oxidation, for which the mechanism is well established, the oxidation of carotenoids is not well understood. It involves initially epoxidation, formation of apocarotenoids and hydroxylation. Subsequent fragmentations presumably result in a series of compounds of low molecular masses. Completely losing its color and biological activities, the carotenoids give rise to volatile compounds which contribute to the aroma/flavor, desirable in tea and wine and undesirable in dehydrated carrot. Processing can also influence the bioavailability of carotenoids, a topic that is currently of great interest.

Sources of errors in the quantitative analysis of food carotenoids by HPLC.

Several factors render carotenoid determination inherently difficult. Thus, in spite of advances in analytical instrumentation, discrepancies in quantitative results on carotenoids can be encountered in the international literature. A good part of the errors comes from the pre-chromatographic steps such as: sampling scheme that does not yield samples representative of the food lots under investigation; sample preparation which does not maintain representativity and guarantee homogeneity of the analytical sample; incomplete extraction; physical losses of carotenoids during the various steps, especially during partition or washing and by adsorption to glass walls of containers; isomerization and oxidation of carotenoids during analysis. On the other hand, although currently considered the method of choice for carotenoids, high performance liquid chromatography (HPLC) is subject to various sources of errors, such as: incompatibility of the injection solvent and the mobile phase, resulting in distorted or split peaks; erroneous identification; unavailability, impurity and instability of carotenoid standards; quantification of highly overlapping peaks; low recovery from the HPLC column; errors in the preparation of standard solutions and in the calibration procedure; calculation errors. Illustrations of the possible errors in the quantification of carotenoids by HPLC are presented.

Latin American food sources of carotenoids.

Latin America has a wide variety of carotenogenic foods, notable for the diversity and high levels of carotenoids. A part of this natural wealth has been analyzed. Carrot, red palm oil and some cultivars of squash and pumpkin are sources of both beta-carotene and alpha-carotene. beta-carotene is the principal carotenoid of the palm fruits burití, tucumã and bocaiuva, other fruits such as loquat, marolo and West Indian cherry, and sweet potato. Buriti also has high amounts of alpha-carotene and gamma-carotene. beta-Cryptoxanthin is the major carotenoid in caja, nectarine, orange-fleshed papaya, orange, peach, tangerine and the tree tomato. Lycopene predominates in tomato, red-fleshed papaya, guava, pitanga and watermelon. Pitanga also has substantial amounts of beta-cryptoxanthin, gamma-carotene and rubixanthin. Zeaxanthin, principal carotenoid of corn, is also predominant only in piquí. delta-Carotene is the main carotenoid of the peach palm and zeta-carotene of passion fruit. Lutein and beta-carotene, in high concentrations, are encountered in the numerous leafy vegetables of the region, as well as in other green vegetables and in some varieties of squash and pumpkin. Violaxanthin is the principal carotenoid of mango and mamey and is also found in appreciable amounts in green vegetables. Quantitative, in some cases also qualitative, differences exist among cultivars of the same food. Generally, carotenoids are in greater concentrations in the peel than in the pulp, increase considerably during ripening and are in higher levels in foods produced in hot places. Other Latin America indigenous carotenogenic foods must be investigated before they are supplanted by introduced crops, which are often poorer sources of carotenoids.

Occurrence of aflatoxin M1 in milk and dairy products commercialized in Campinas, Brazil.

One hundred and fifty-two samples of pasteurized milk, powdered milk, cheese and yoghurt, marketed in Campinas, Brazil in 1989-1990, were analysed for aflatoxin M1 by the AOAC TLC method (visual quantitation) 980.21. Fifty-two pasteurized milk samples were also analysed in 1992 by the AOAC HPLC method 986.16. Aflatoxin M1 was not detected in the 1989-1990 samples. Four milk samples of the 1992 batch were contaminated at 73-370 ng/1. Except for the sample with 370 ng/l, which would have been also found positive by the TLC method, the detection of aflatoxin M1 in 1992 reflects the higher sensitivity of the HPLC method, not a greater occurrence of the toxin. Contamination of milk and milk products with aflatoxin M1 does not appear to be a serious public health problem in the city of Campinas at the moment.

[Current status of analytical methods for measuring provitamin A]. / Estado actual de los métodos analíticos para determinar provitamina A.

The difficulties inherent to provitamin A determination and the present state of development of the analytical methodologies are appraised. The procedures, the advantages and disadvantages and the possible sources of error of the methods involved are discussed. Open-column methods are still the most viable option in developing countries but the efficiency and reproducibility of the chromatographic separation depend largely on the analysts skill and experience. Although HPLC chromatograms are highly reproducible, the problem is to transform the peak areas to provitamin A concentrations because of the instability, varying purity and unavailability of provitamin standards. Internal standardization with the stable Sudan appears to be a promising solution. Separation of cis-isomers requires rechromatography in open-column systems. For HPLC, this problem still remains to be solved. Confirmation of the identity of the provitamins and prevention of degradation during the analysis are also dealt with. Notwithstanding the obstacles involved, reliable data can be obtained with adequate application of the analytical techniques and proper interpretation of the results.

Carotenoid composition and vitamin A value of a squash and a pumpkin from northeastern Brazil.

The carotenoid composition of a squash and a pumpkin from Northeastern Brazil was determined. Nineteen carotenoids were detected in Cucurbita moschata variety "Baianinha"; beta-carotene was the principal carotenoid, contributing about 74% of an average total carotenoid content of 317.8 micrograms/g. In C. maxima variety "Jerimum Caboclo", 11 carotenoids were found with lutein, and beta-carotene as the major pigments accounting for about 60% and 27%, respectively, of an average total carotenoid content of 78.4 micrograms/g. The abundance of beta-carotene in the C. moschata variety "Baianinha" makes this squash one of the richest sources of provitamin A. The average vitamin A value was 43,175 IU (International Units) per 100 g or 4,317 RE (retinol equivalents) per 100 g. Its vitamin A values is more than 11 times that of C. maxima variety "Jerimum Caboclo" and five times that of C. moschata cultivar "Menina Verde", the squash found previously to be highest in provitamin A among the Cucurbita vegetables most commercialized in São Paulo (Southeastern Brazil).

Survey of aflatoxins, ochratoxin A, zearalenone, and sterigmatocystin in some Brazilian foods by using multi-toxin thin-layer chromatographic method.

A previously published method for ochratoxin A was evaluated and proved appropriate for simultaneous determination of aflatoxins, ochratoxin A, sterigmatocystin, and zearalenone, with considerable savings in time and reagent costs. The detection limits were 2, 5, 15, and 55 micrograms/kg, respectively. The recoveries and coefficients of variation obtained with artificially contaminated samples were 91-101% and 0-16% for aflatoxin B1, 98-117% and 0-17% for sterigmatocystin, and 96-107% and 0-17% for zearalenone, respectively. The coefficients of variation for naturally contaminated samples (aflatoxins in rice and ochratoxin A in beans) ranged from 0 to 8%. The method was used to survey 296 samples that included 10 cultivars of dried beans, 8 types of corn products, 3 types of cassava flour, and both polished and parboiled rice between May 1985 and June 1986 in Campinas, Brazil. Only aflatoxin B1 (9 samples, 20-52 micrograms/kg), aflatoxin G1 (4 samples, 18-31 micrograms/kg), and ochratoxin A (5 samples, 32-160 micrograms/kg) were found. The average contamination percentage was 4.7%; beans showed the highest (6.6%) and rice showed the lowest (3.3%) incidence rates. Zearalenone and sterigmatocystin were not detected. Positive samples were confirmed by chemical derivatization, corroborated by development in 3 solvent systems.

Assessment of provitamin A determination by open column chromatography/visible absorption spectrophotometry.

Determination of provitamin A content by open column chromatography/visible absorption spectrophotometry is assessed using food samples of varying carotenoid composition. A general method consisting of extraction with acetone, transfer to petroleum ether, saponification (optional), concentration, separation on activated MgO:Hyflo Supercel column developed with 1 to 15% acetone in petroleum ether, and quantitation of individual provitamins spectrophotometrically demonstrates repeatability comparable with that of high-performance liquid chromatographic (HPLC) methods. Overnight saponification (10% methanolic KOH, ambient temperature) does not degrade the provitamins and is unnecessary for kale, tomato, and squash; however, it is required for good separation of papaya carotenoids due to the presence of carotenol esters. The current Association of Official Analytical Chemists (AOAC) method is found to be inappropriate because (1) the volume of extracting solvent is not adjusted to the type of sample; (2) the less active alpha- and gamma-carotene, alpha- and beta-cryptoxanthin, and 5,6-monoepoxy-beta-cryptoxanthin (50% active) are quantified as beta-carotene (100% active); (3) inactive carotenoids such as xi-carotene and zeinoxanthin are also quantified as beta-carotene.

Screening and quantitation of ochratoxin A in corn, peanuts, beans, rice, and cassava.

To answer the need for simple, economical, rapid methods for mycotoxins, a procedure for screening and quantitation of ochratoxin A was developed. A methanol-aqueous KCl extraction is used, followed by cleanup with clarifying agents and partition into chloroform. Part of the chloroform extract is used for screening and the other part for quantitation by thin layer chromatography (TLC). The screening procedure takes 40 min, using a silica gel/aluminum oxide minicolumn developed for this purpose. The limits of detection are 80 and 10 micrograms/kg, respectively, for minicolumn screening and TLC quantitation. Ammonium sulfate is efficient in cleaning samples of corn and cassava; cupric sulfate is better with peanuts, beans, and rice. Tests were conducted on triplicate spiked samples of yellow corn meal, raw peanuts, dried black beans, polished rice, and cassava flour at different levels (400, 200, 80, 40, and 10 micrograms/kg). Recoveries ranged from 86 to 160% and the coefficients of variation ranged from 0 to 26%.