A comparison of the quality of whole corn tortillas made from instant corn flours by traditional or extrusion processing

Summary The nutritional quality (chemical and biological assays) was evaluated for tortillas made with two samples of instant corn flour prepared with 0.15 and 0.25% calcium hydroxide and processed either by extrusion or by the traditional process (nixtamalization). Both raw corn and the tortillas made from instant whole corn flours prepared by extrusion (TEP) had higher Protein Efficiency Ratio (PER), and Net Protein Utilization (NPU) values ( p < 0.05) than tortillas prepared from traditional nixtamalization process. The Ca assimilation in the femurs bones of rats fed with raw corn, TEP (with 0.25% lime), and tortillas prepared from the nixtamal process, yielded lower values ( p < 0.05) as compared with those shown by the rats fed with the other treatments of TEP (with 0.15% lime). The Ca, Mg, and P contents and protein quality of the treatments used in the feed affected some physical characteristics rat femurs (length, diameter, weight, breaking force, volume and density). The force required to break the femurs of rats fed diets of raw corn, tortillas prepared using the traditional process and without added protein, was measured and compared with the force required to break the femurs of rats fed with diets contain casein and TEP with either 0.15 and 0 0.25% lime. Those animals assimilating the lowest content of lime had the weakest femurs.     

Studies and Biological Assays in Corn Tortillas Made From Fresh Masa Prepared by Extrusion and Nixtamalization Processes

ABSTRACT: :
The nutritional composition and protein efficiency ratio (PER) of raw corn meal and of tortillas prepared by extrusion and nixtamalization processes were determined. Rats were fed with diets containing unprocessed raw corn meal (RCM), tortillas prepared from extruded fresh masa without lime (ET), tortillas made from extruded fresh masa with 0.25% lime content (ETWL), and tortillas made with the traditional nixtamalization method (NT). The ETWL had higher protein (8.50%) and dietary fiber (14.52%) contents than did the NT (8.15% protein and 7.39% dietary fiber). The PER value of the ETWL diet was 14.65% higher (P ≤ 0.05) than that of the RCM diet and equivalent to that of the NT diet.     

Aflatoxin‐detoxification achieved with Mexican traditional nixtamalization process (MTNP) is reversible

To evaluate the effectiveness of maize detoxification achieved with the Mexican traditional nixtamalization process (MTNP), grain contaminated with 678.3 µg/kg of total aflatoxins was processed into tortillas. The MTNP caused an apparent 93.2% decrease in aflatoxin content in tortillas. However, extracts acidification prior to mycotoxin quantification caused in maize dough (masa) a 57.2% reformation of the original aflatoxin and 33.9% in tortillas. According to these results, the MTNP seems not to be safe for total detoxification, since a high percentage of the original aflatoxin content can be reverted to the original fluorescent form by the acidic medium. Acidification of the aflatoxin extracts, as occurs during digestion, would lead to a rebuilding of the aflatoxin molecule. Copyright © 2004 Society of Chemical Industry     

Aflatoxins’ fate during the nixtamalization of contaminated maize by two tortilla-making processes

The fate of aflatoxin B₁ and B₂ was studied during maize nixtamalization by two tortilla-making processes. High-quality maize seed (AS-900) was used, as well as a toxigenic strain of Aspergillus flavus. The grain moisture content was adjusted to 18%, and the incubation temperature was 27°C. One lot of grain served as the control and so was not inoculated with the fungus. At the end of the 13 d incubation period, this control lot was aflatoxin free (aflatoxin level 1). Two other lots were inoculated with the fungus and incubated for 12 and 14 d. They then had aflatoxin contamination of 29 and 93 ppb, respectively (aflatoxins levels 2 and 3). The quantification of aflatoxins was undertaken according to the AOAC Official Method 991.31 and their identification confirmed by HPLC. The maize grain was processed by the traditional (TNP) and the ecological (ENP) nixtamalization processes. Aflatoxins were quantified at all steps of the tortilla-making processes. The research was conducted under a completely randomized factorial design (2×3). In the case of tortillas processed with TNP, the total aflatoxin content was 2 and 9 ppb corresponding to aflatoxin levels 2 and 3 with a degradation rate of 92% and 90%, respectively. In tortillas obtained through the ENP, the aflatoxin content was 6 and 36 ppb for aflatoxin levels 2 and 3, with degradation rates of 78% and 61%, respectively. The TNP produced higher aflatoxin degradation rates than the ENP.     

Effects of Processing on Aflatoxin Levels and on Mutagenic Potential of Tortillas made from Naturally Contaminated Corn

Naturally contaminated corn containing 127 μ total aflatoxin per kg was divided into kg samples and treated with Ca(OH)2 for making tortillas. The treatments varied in % Ca(OH)2, boiling time, and holding time. Samples were taken after each processing step. Afla-toxin levels and mutagenic activity of acetone extractions of alka-line and reacidified products were measured. All treatments caused a decrease of aflatoxin (up to 46%); however, acidifying products prior to analysis caused reformation of much of the original aflatoxin. All treatments also effected a decrease in the mutagenic potential of the products, except for that of the acidified tortillas which was higher than that of the control corn. The tortilla manufacturing process may not be as effective in aflatoxin destruction as originally surmised.     

Effectiveness of modified yeast cell wall extracts to reduce aflatoxin B1 absorption in dairy ewes

This study investigated the effect of a modified yeast cell wall extract preparation (YCW) on the excretion of aflatoxin B1 (AFB1) and aflatoxin M1 (AFM1) in feces, urine, and milk of dairy ewes fed an aflatoxin-contaminated diet. Sixteen ewes in mid-lactation were assigned to 4 treatment groups: control, AF (60 μg of AFB1/kg of feed), YCW (2 g/kg of feed), and AF+YCW. The trial consisted of a short-term (3-d) exposure period followed by a long-term (21-d) exposure period. At the end of each exposure period, milk, urine, and feces were collected over 72 h. The treatments did not affect feed intake, milk production, milk composition, or body weight. The presence of AFM1 was detected in all matrices, whereas AFB1 was only present in feces. Daily excretion was higher following long-term exposure and reached 26.9 μg of AFB1/d in feces, 37.2 μg of AFM1/d in feces, and 10.7 μg of AFM1/d in urine. Supplementation with YCW was effective in increasing aflatoxin excretion in feces in the long-term exposure (up to 156% increase). The effect was accompanied by a trend of decreasing urinary excretion of AFM1. In contrast, the addition of YCW to the contaminated diet did not affect the transfer of aflatoxins from feed to milk under the present experimental conditions with low-producing ewes. The transfer rates of AFM1 in milk ranged from 0.24 to 0.54%. In conclusion, feed supplementation with YCW reduced the absorption of AFB1 and increased the elimination of AFB1 and AFM1 in ewe feces. Yeast cell wall extract could be used to protect ruminants from chronic exposure to aflatoxins present in feeds.     

Enhancement of Corn Nixtamalization by Power Ultrasound

Nixtamalization, a key production step for masa flour used for tacos, corn tortillas, and chips, traditionally involves corn kernel cooking for 1 h and a lengthy process of steeping (16–18 h) in a lime solution. This study aimed at accelerating the traditional nixtamalization (TN) process using power ultrasound with acoustic energy density around 1.85 W/g for 1 h during cooking followed by brief steeping for 1 h. The cooked kernels (nixtamal) were evaluated for texture and color, while the cooking liquor (nejayote) was evaluated for solid losses. The power ultrasound-assisted nixtamalization resulted in significantly (p?≤?0.05) reduced process time and softer nixtamal with less solid losses in nejayote than control (TN). Response surface methodology established significant relationships of sonication duration and cooking temperature to texture, color of nixtamal, and dry matter loss in nejayote. This study indicates that power ultrasound ameliorated traditional nixtamalization in terms of quality and operation time.     

Long-term administration of low doses of mycotoxins to poultry. 1. Residues of aflatoxin B1 and its metabolites in broilers and laying hens

A study was performed to determine aflatoxin residues in tissues and organs of male broilers and hens that had been fed a diet contaminated with 50 micrograms/kg aflatoxin B1 (AFB1). Residue levels of AFB1, aflatoxicol (Ro), aflatoxin M1 (AFM1) and aflatoxin B2a (AFB2a) were determined by an HPLC method and, with the exception of AFB2a, were detected in the liver, kidney and thigh of both male broilers and hens. The highest levels found were for Ro in liver (1.10 and 0.60 micrograms/kg for male broilers and hens, respectively). On the other hand no detectable amounts of aflatoxins were found in any tissue after withdrawal periods of 14 and 33 days for male broilers and laying hens respectively.     

Determination of aflatoxin M1 in breast milk as a biomarker of maternal and infant exposure in Colombia

Chronic exposure to aflatoxins, and especially to aflatoxin B₁ (AFB1), causes hepatocellular carcinoma with prevalence 16–32 times higher in developing compared with developed countries. Aflatoxin M₁ (AFM1) is a monohydroxylated metabolite from AFB1 that is secreted in milk and which can be used as a biomarker of AFB1 exposure. This study aimed to determine AFM1 levels in human breast milk using immunoaffinity column clean-up with HPLC and fluorescence detection. Breast milk samples were obtained from 50 nursing mothers. Volunteers filled in a questionnaire giving their consent to analyse their samples as well as details of their socioeconomic, demographic and clinical data. The possible dietary sources of aflatoxins were assessed using a food frequency questionnaire. A total of 90% of the samples tested positive for AFM1, with a mean of 5.2 ng l^?1 and a range of 0.9–18.5 ng l^?1. The study demonstrated a high frequency of exposure of mothers and neonates to AFB1 and AFM1 in Colombia, and it points out the need to regulate and monitor continuously the presence of aflatoxins in human foods. Further research is needed in order to determine the presence of other mycotoxins in foods and in human samples as well as to devise protection strategies in a country where mycotoxins in human foods are commonly found.     

Aflatoxin residues in eggs of laying Japanese quail after long-term administration of rations containing low levels of aflatoxin B1.

The aim was to evaluate the excretion of residues of aflatoxin B(1) (AFB(1)), aflatoxin M(1) (AFM(1)), aflatoxin B(2a) (AFB(2a)) and aflatoxicol (AFL) in eggs of laying Japanese quail fed rations with low levels of aflatoxin B(1) for 90 days. The quail were randomly assigned into four experimental groups and given prepared rations containing either 0 (controls), 25, 50 or 100 microg AFB(1) kg(-1) feed. Thirty-two eggs per treatment were collected on days 1-7, 10, 20, 30, 60 and 90 of the aflatoxin treatment period, and submitted to aflatoxin analysis by high-performance liquid chromatography. Average egg production and feed consumption were not affected ( p > 0.05) by AFB(1). Egg weight was significantly lower ( p<0.05) only for groups exposed to 100 microg AFB(1) kg(-1). Residues of aflatoxins were detected in eggs at levels that ranged from 0.01 to 0.08 microg kg(-1) (AFB(1)), 0.03-0.37 microg kg(-1) (AFM(1)), 0.01-1.03 microg kg(-1)(AFB(2a)) and 0.01-0.03 microg kg(-1) (AFL). Results indicate that the excretion of aflatoxin residues in quail eggs might occur at relatively low concentrations under conditions of long-term exposure of quail to low levels of AFB(1).     

Effect of microwave heating during alkaline-cooking of aflatoxin contaminated maize

To evaluate the effectiveness of maize detoxification achieved with a modified tortilla-making process (MTMP), maize contaminated with aflatoxin B(1) (AFB(1)) and aflatoxin B(2) (AFB(2)) at levels of 22.46, 69.62, and 141.48 ng/g (AFB(1)+ AFB(2)) was processed into tortillas. Aflatoxin content was determined according to the 991.31 AOAC official method. Based on the results obtained with spiked samples (0.78 to 25 ng/g), the mean recovery was 92%, with a standard error of 1.2, and a coefficient variation value of 4.4%. The MTMP caused 68, 80, and an 84% decrease in aflatoxin content, respectively. Extract acidification (as occurs during digestion) prior to mycotoxin quantification caused some reformation of the aflatoxin structure in tortillas (up to 3%). According to these results, the MTMP seems to be safe for decontamination since a low percentage of the initial aflatoxin concentration can be reverted to the original fluorescent form upon acidification. PRACTICAL APPLICATION: The potential presence of aflatoxins in maize destined for human consumption is a serious problem to the Mexican food supply, as these toxic compounds may persist during the traditional alkaline-process for tortilla elaboration. Consequently, new detoxification procedures are needed that eliminate or at least minimize the aflatoxin risk, through lowering aflatoxin concentration in maize-based products. Under these considerations, the use of MTMP is recommended, since it has definite advantages including non-production of wastewater and reduced energy/time consumption.     

Immunoaffinity clean-up and direct fluorescence measurement of aflatoxins B1 and M1 in pig liver: comparison with high-performance liquid chromatography determination.

An improved analytical method for aflatoxin B1 (AFB1) and aflatoxin M1 (AFM1) determination in pig liver is described, using an aqueous methanol extraction, an immunoaffinity column clean-up step and a direct fluorometric measurement for toxin detection and quantification. A detection limit of 1.0 microg kg-1 was achieved for AFB1 and AFM1. Mean recoveries of 80.7+/-9.0% for AFB1 spiked at 1.0-9.7 microg kg-1 levels and of 76.7+/-6.6% for AFM1 spiked at 1.0-5.5 microg kg-1 levels were obtained. Recovery data for spiked samples were statistically compared with those obtained by the same extract using classical reversed-phase high-performance liquid chromatography (RP-HPLC) with fluorescence detection, showing a significant correlation (p相似文献   

Excretion pattern of aflatoxin M1 in milk of goats fed a single dose of aflatoxin B1

The feedstuffs used in dairy animals must be able to give consumers confidence about the wholesomeness of milk with regard to aflatoxin contamination. The aim of this study was to determine the excretion patterns of aflatoxin M(1) (AFM1) in the milk of dairy goats fed a single dose of pure aflatoxin B(1) (AFB1), which can occasionally occur if feeds are infected by hot-spot growth of molds that produce aflatoxins. Five dairy goats in midlactation were administered 0.8 mg of AFB1 orally. Individual milk samples were collected for 84 h after AFB1 dosage. Aflatoxin M(1) was found in milk in the highest concentration. In all goats, AFM1 was not detected in milk before AFB1 administration, but was detected in the first milking following AFB1 administration. The excretion pattern of AFM1 concentration in milk was very similar in all goats even if the values of the concentration differed between animals. The peak values for AFM1 concentration in milk was observed in milk collected during the milking at 3 and 6h. After the peak, the AFM1 in milk disappeared with a trend that fitted well a monoexponential decreasing function, and the toxin was not detected after 84 h. Only about 0.17% of the amount of AFB1 administered was detected as AFM1 in milk, and about 50% of this was excreted in the first liter of milk yielded after AFB1 intake. Correct procedures to prevent growth of molds, and consequent AFB1 contamination, on the feedstuffs for lactating goats represent the key to providing consumers a guarantee that milk is not contaminated by AFM1.     

Milling and Processing Parameters for Corn Tortillas from Extruded Instant Dry Masa Flour

A continuous extrusion process to provide instant corn flour for tortillas was evaluated. Variables investigated included two types of mill (knives and hammer) with screens with two diameters (0.5 and 0.8 mm), two types of corn (hard endosperm or normal and soft endosperm or cacahuazintle), lime concentration (0.15 and 0.25% w/w), processing moisture (45 and 48% w/w) and temperature (70,80 and 90°C). The water absorption capacity, water solubility index, color of instant corn flour, adhesiveness of masa, tensile strength, cutting force, rollability and puffing of tortillas, were compared. Based on textural data the hammer mill with 0.8 mm sieve, normal corn type, 0.15% lime, 48% moisture and 90°C processing temperature, produced the highest quality tortillas.     

Determination of the aflatoxin AFB1 from corn by direct analysis in real time-mass spectrometry (DART-MS)

Direct analysis in real time (DART) ionisation coupled to a high-resolution mass spectrometer (MS) was used for screening of aflatoxins from a variety of surfaces and the rapid quantitative analysis of a common form of aflatoxin, AFB1, extracted from corn. Sample preparation procedure and instrument parameter settings were optimised to obtain sensitive and accurate determination of aflatoxin AFB1. 84:16 acetonitrile water extracts of corn were analysed by DART-MS. The lowest calibration level (LCL) for aflatoxin AFB1 was 4 μg kg^–1. Quantitative analysis was performed with the use of matrix-matched standards employing the ¹³C-labelled internal standard for AFB1. DART-MS of spiked corn extracts gave linear response in the range 4–1000 μg kg^–1. Good recoveries (94–110%) and repeatabilities (RSD = 0.7–6.9%) were obtained at spiking levels of 20 and 100 μg kg^–1 with the use of an isotope dilution technique. Trueness of data obtained for AFB1 in maize by DART-MS was demonstrated by analysis of corn certified reference materials.     

Occurrence of aflatoxins in peanuts, milk, and animal feed in Trinidad

The prevalence of aflatoxin B1 (AFB1) in 186 peanut products (140 peanuts, 32 peanut butter, and 14 nut cakes) from supermarkets, road vendors, and sale outlets, and 40 feed samples from dairy farmers was determined using the radioimmunoassay method (Charm II) test for aflatoxins. The frequency of aflatoxin M1 (AFM1) was also determined in 175 raw milk samples from milk collection centers and 37 pasteurized milk samples obtained from supermarkets and sale outlets. Overall, from a total of 438 samples tested, 18 (4.1%) were positive for aflatoxin comprising 5 (2.2%) of 226 peanut products and feeds positive for AFB1, and 13 (6.1%) of 212 milk samples positive for AFM1. All 186 peanuts and peanut products were negative (0.0%) for AFB1 while 5 (7.4%) of 40 dairy feed samples were positive. Of the 175 raw milk samples tested, 13 (7.4%) were contaminated with AFM1 while all pasteurized milk samples were negative. The detection of AFB1 in feed and AFM1 in milk is of public health importance considering the practice of raw milk consumption by the farmers and their families in the country.     

Occurrence of Aflatoxins in Ground Red Chili Pepper and Pistachio Nut

In total, 240 samples were randomly collected from different locations in Gaziantep Turkey, 120 of which were unpacked and packed ground red chili pepper and 120 of which were unpacked and packed pistachio nuts. All samples of the unpacked and packed ground red chili pepper were found to be contaminated with aflatoxins and aflatoxin B1. Three (9.4%) of the packed ground red chili pepper samples were over the legal limit of aflatoxin B1 while 55 (62.5%) of the unpacked samples were over the legal limit. Thirty four (36.2%) of the unpacked pistachio nut samples were contaminated with aflatoxins. There is a need to strictly prohibit the use of batches of ground red chili pepper and pistachio nuts containing aflatoxins.     

Dietary intake of aflatoxins in the adult Malaysian population – an assessment of risk

Exposure to aflatoxins in the adult Malaysian diet was estimated by analysing aflatoxins in 236 food composites prepared as “ready for consumption”. Dietary exposure to aflatoxin B1 (AFB1) ranged from 24.3 to 34.00?ng/kg?b.w./day (lower to upper bound), with peanuts being the main contributor. Estimated liver cancer risk from this exposure was 0.61–0.85 cancers/100,000 population/year, contributing 12.4%–17.3% of the liver cancer cases. Excluding AFB1 occurrence data higher than 15?µg/kg reduced exposure by 65%–91% to 2.27–11.99?ng/kg?b.w./day, reducing the cancer risk to 0.06–0.30 cancers/100,000 population/year (contributing 1.2%–6.1% liver cancer cases). Reducing further the ML of AFB1 from 15 to 5?µg/kg yielded 3%–7% greater drop in the exposure to 0.47–10.26?ng/kg?b.w./day with an estimated risk of 0.01–0.26 cancers/100,000 population/year (0.2%–5.1% liver cancer cases attributed to dietary AFB1). These findings indicate that current MLs are adequate in protecting Malaysians’ health.     

Determination of aflatoxins in eggs,milk, meat and meat products using HPLC fluorescent and UV detectors

Raw and pasteurised sheep’s, cow’s and goat’s milk, eggs, and beef samples from different local markets in Jordan were collected during a period of 5 months (January through May 2007) and examined for aflatoxins B1(AFB1), B2(AFB2), G1(AFG1), G2(AFG2), M1(AFM1) and M2(AFM2). The samples were analysed with high performance liquid chromatography (HPLC) using UV and Fluorescent detectors. The analysed samples of milk collected in January were found to contain 0.56 μg L⁻¹ AFM1 and 0.1 μg L⁻¹ AFM2 whilst, the concentration of AFM1 and AFM2 was < 0.05 μg L⁻¹ for milk samples collected between March and May. The AFB1, AFB2, AFG1 and AFG2 contents in the analysed food products ranged from 1.10 to 8.32 μg L⁻¹ and 0.15 to 6.36 μg L⁻¹ in imported and fresh meat samples collected during March, respectively. The mean recovery for the HPLC method was 92% to 109% and the quantification levels were 50 ng L⁻¹ for AFM1 and AFM2. The AFM1 was found in 10% of the tested samples with concentrations between 0.08 and 1.1 μg kg⁻¹ and AFM2 was only found in 1.82% of the tested samples with a level of 0.1 μg kg⁻¹. The AFM1 levels in the examined foods were higher than the maximum level of AFM1 in liquid milk set by the European Community and Codex Alimentarius of 50 ng L⁻¹.     

臭氧熏蒸对玉米胚中真菌毒素的降解消除作用

为探究臭氧熏蒸对玉米胚中真菌毒素消除效果,固定臭氧质量浓度为150 mg/L,以蒸馏水调节玉米胚水分至不同质量分数(5％、10％、15％、20％、25％、30％),并熏蒸不同时间(20、30、40、50、60、80min),分析熏蒸处理后玉米胚中真菌毒素含量以及玉米胚和玉米油品质的变化.结果表明:玉米胚水分质量分数为2...