Stability studies of the metabolites of nitrofuran antibiotics during storage and cooking

Nitrofuran antibiotics cannot be used in food production within the European Union because of their potential health risks to consumers. The recent discovery of their widespread use in global food industries and the finding of semicarbazide in baby food as a result of packaging contamination have focused attention on the toxicity and stability of these drugs and their metabolites. The stability of the nitrofuran marker residues 3-amino-2-oxazolidinone (AOZ), 3-amino-5-morpholinomethyl-2-oxazolidone (AMOZ), 1-aminohydantoin (AHD) and semicarbazide (SEM) were tested. Muscle and liver of nitrofuran treated pigs were cooked by frying, grilling, roasting and microwaving. Between 67 and 100% of the residues remained after cooking, demonstrating that these metabolites are largely resistant to conventional cooking techniques and will continue to pose a health risk. The concentration of metabolites in pig muscle and liver did not drop significantly during 8 months of storage at -20 degrees C. Metabolite stock and working standard solutions in methanol were also stable for 10 months at 4 degrees C. Only a 10 ng ml(-1) solution of SEM showed a small drop in concentration over this extended storage period.

Stability during cooking of anthelmintic veterinary drug residues in beef

Anthelmintic drugs are widely used for treatment of parasitic worms in livestock, but little is known about the stability of their residues in food under conventional cooking conditions. As part of the European Commissionfunded research project ProSafeBeef, cattle were medicated with commercially available anthelmintic preparations, comprising 11 active ingredients (corresponding to 21 marker residues). Incurred meat and liver were cooked by roasting (40 min at 190°C) or shallow frying (muscle 8-12 min, liver 14-19 min) in a domestic kitchen. Raw and cooked tissues and expressed juices were analysed using a novel multi-residue dispersive solid-phase extraction method (QuEChERS) coupled with ultra-performance liquid chromatography-tandem mass spectrometry. After correction for sample weight changes during cooking, no major losses were observed for residues of oxyclozanide, clorsulon, closantel, ivermectin, albendazole, mebendazole or fenbendazole. However, significant losses were observed for nitroxynil (78% in fried muscle, 96% in roast muscle), levamisole (11% in fried muscle, 42% in fried liver), rafoxanide (17% in fried muscle, 18% in roast muscle) and triclabendazole (23% in fried liver, 47% in roast muscle). Migration of residues from muscle into expressed cooking juices varied between drugs, constituting 0% to 17% (levamisole) of total residues remaining after cooking. With the exception of nitroxynil, residues of anthelmintic drugs were generally resistant to degradation during roasting and shallow frying. Conventional cooking cannot, therefore, be considered a safeguard against ingestion of residues of anthelmintic veterinary drugs in beef. © 2011 Taylor & Francis.

Arsenic speciation in Japanese rice drinks and condiments

Rice has been demonstrated to be one of the major contributors to inorganic arsenic (i-As) intake in humans. However, little is known about rice products as additional source of i-As exposure. In this study, misos, syrups and amazake (a fermented sweet rice drink) produced from rice, barley and millet were analysed for total arsenic (t-As) and a subset of samples were also analyzed for As speciation. Rice based products displayed a higher i-As content than those derived from barley and millet. Most of the t-As in the rice products studied was inorganic (63-83%), the remainder being dimethylarsinic acid. Those who regularly consume rice drinks and condiments, such as the Japanese population and those who follow health conscious diets based on the Japanese cuisine, could reach up to 23% of the World Health Organization's Provisional Tolerable Daily Intake of i-As, by only consuming these kinds of products. This study provides a wide appreciation of how i-As derived from rice based products enters the human diet and how this may be of concern to populations who are already exposed to high levels of i-As through consumption of foods such as rice and seaweed.

Cooking rice in a high water to rice ratio reduces inorganic arsenic content

Total arsenic and arsenic speciation was performed on different rice types (basmati, long-grain, polished ([white] and wholegrain [brown]) that had undergone various forms of cooking. The effect of rinse washing, low volume (2.5 : 1 water : rice) and high volume (6 : 1 water : rice) cooking, as well as steaming, were investigated. Rinse washing was effective at removing circa. 10% of the total and inorganic arsenic from basmati rice, but was less effective for other rice types. While steaming reduced total and inorganic arsenic rice content, it did not do so consistently across all rice types investigated. Low volume water cooking did not remove arsenic. High volume water : rice cooking did effectively remove both total and inorganic arsenic for the long-grain and basmati rice (parboiled was not investigated in high volume cooking water experiment), by 35% and 45% for total and inorganic arsenic content, respectively, compared to uncooked (raw) rice. To reduce arsenic content of cooked rice, specifically the inorganic component, rinse washing and high volume of cooking water are effective.

Survey of arsenic and its speciation in rice products such as breakfast cereals, rice crackers and Japanese rice condiments

Rice has been demonstrated to be one of the major contributors to arsenic (As) in human diets in addition to drinking water, but little is known about rice products as an additional source of As exposure. Rice products were analyzed for total As and a subset of samples were measured for arsenic speciation using high performance liquid chromatography interfaced with inductively coupled plasma-mass spectrometry (HPLC-ICP-MS). A wide range of rice products had total and inorganic arsenic levels that typified those found in rice grain including, crisped rice, puffed rice, rice crackers, rice noodles and a range of Japanese rice condiments as well as rice products targeted at the macrobiotic, vegan, lactose intolerant and gluten intolerance food market. Most As in rice products are inorganic As (75.2-90.1%). This study provides a wider appreciation of how inorganic arsenic derived from rice products enters the human diet. (C) 2008 Elsevier Ltd. All rights reserved.

Arsenic Bioaccessibility in Cooked Rice as Affected by Arsenic in Cooking Water

Rice can easily accumulate arsenic (As) into its grain and is known to be the highest As-containing cereal. In addition, the As burden in rice may increase during its processing (such as when cooking using As-polluted water). The health risk posed by the presence of As in cooked rice depends on its release from the matrix along the digestive system (bioaccessibility). Two types of white polished long-grain rice, namely, nonparboiled and parboiled (total As: 202 and 190 mu g As kg(-1), respectively), were cooked in excess of water with different levels of As (0, 10, 47, 222, and 450 mu g As L-1). The bioaccessibility of As from these cooked rice batches was evaluated with an in vitro dynamic digestion process. Rice cooked with water containing 0 and 10 mu g As L-1 showed lower As concentrations than the raw (uncooked) rice. However, cooking water with relatively high As content (>= 47 mu g As L-1) significantly increased the As concentration in the cooked rice up to 8- and 9-fold for the nonparboiled and parboiled rice, respectively. Parboiled rice, which is most widely consumed in South Asia, showed a higher percentage of As bioaccessibility (59% to 99%) than nonparboiled rice (36% to 69%) and most of the As bioaccessible in the cooked rice (80% to 99%) was released easily during the first 2 h of digestion. The estimation of the As intake through cooked rice based on the As bioaccessibility highlights that a few grams of cooked rice (less than 25 g dry weight per day) cooked with highly As contaminated water is equivalent to the amount of As from 2 L water containing the maximum permissible limit (10 mu g As L-1).

Effect of cooking method and rice type on arsenic concentration in cooked rice and the estimation of arsenic dietary intake in a rural village in West Bengal, India

Arsenic (As) contamination of rice plants can result in high total As concentrations (t-As) in cooked rice, especially if As-contaminated water is used for cooking. This study examines two variables: (1) the cooking method (water volume and inclusion of a washing step); and (2) the rice type (atab and boiled). Cooking water and raw atab and boiled rice contained 40 g As l-1 and 185 and 315 g As kg-1, respectively. In general, all cooking methods increased t-As from the levels in raw rice; however, raw boiled rice decreased its t-As by 12.7% when cooked by the traditional method, but increased by 15.9% or 23.5% when cooked by the intermediate or contemporary methods, respectively. Based on the best possible scenario (the traditional cooking method leading to the lowest level of contamination, and the atab rice type with the lowest As content), t-As daily intake was estimated to be 328 g, which was twice the tolerable daily intake of 150 g.

Determination of the persistence of dimetridazole, metronidazole and ronidazole residues in black tiger shrimp (Penaeus monodon) tissue and stability during cooking

The depletion of three banned nitroimidazole drugs (dimetridazole (DMZ), metronidazole (MNZ) and ronidazole (RNZ)) was investigated in black tiger shrimp (Penaeus monodon) following in-water medication. The highest concentrations of residues were measured immediately after the 24 h immersion (day 0). At this time, MNZ and MNZ-OH residues were measured in shrimp tissue samples at concentrations ranging from 361–4189 and 0.28–6.6 μg kg−1, respectively. DMZ and its metabolites HMMNI ranged in concentration between 31509–37780 and 15.0–31.9 μg kg−1, respectively. RNZ and HMMNI concentrations ranged 14530–24206 and 25.0–55 μg kg−1, respectively. MNZ, DMZ and RNZ were the more persistent marker residues and can be detected for at least eight days post-treatment. MNZ-OH was only detectable on day 0 following treatment with MNZ. HMMNI residues were only detectable up to day 1 (0.97–3.2 μg kg−1) or 2 (1.2–4.5 μg kg−1) following DMZ and RNZ treatment, respectively. The parent drugs, MNZ, DMZ and RNZ were still measureable on day 8 at 0.12–1.00, 40.5–55 and 8.8–18.7 μg kg−1, respectively. The study also investigated the stability of nitroimidazole residues under various cooking procedures (frying, grilling, boiling and boiling followed by microwaving). The experiments were carried out in shrimp muscle tissue containing both high and low concentrations of these residues. Different cooking procedures showed the impact on nitroimidazole residue concentration in shrimp tissuetheir concentration depleted significantly, but partially, by boiling and/or microwaving but the compounds were largely resistant to conventional grilling or frying. Cooking cannot therefore be considered as a safeguard against harmful nitroimidazole residues in shrimp.

Hydroprocessing of waste cooking oil over a dispersed nano catalyst: Kinetics study and temperature effect

The kinetics of hydrodeoxygenation of waste cooking oil (WCO) is investigated with unsupported CoMoS catalysts. A kinetic model is established and a comprehensive analysis of each reaction pathway is carried out. The results show that hydrodecarbonylation/decarboxylation (HDC) routes are the predominant reaction pathways in the elimination of oxygen, with the rate constant three times as high as that of hydrodeoxygenation (HDO). However, the HDC activity of the CoMoS catalyst deactivates due to gradual loss of sulfur from the catalyst. HDO process is insensitive to the sulfur deficiency. The kinetic modeling shows that direct hydrodecarbonylation of fatty acids dominates the HDC routes and, in the HDO route, fatty acids are transferred to aldehydes/alcohols and then to C-18 hydrocarbons, a final product, and the reduction of acids is the rate limiting step. The HDO route via alcohols is dominant over aldehydes due to a significantly higher reaction rate constant. The difference of C-18/C-17 ratio in unsupported and supported catalysts show that a support with Lewis acid sites may play an important role in the selectivity for the hydrodeoxygenation pathways and promoting the final product quality