S-sulfonate contents in raw and cooked meat products

S-Sulfonates (R-S-SO3-) are compounds formed by the reaction between the sulfites added to foodstuffs and the disulfide bonds of cystine, peptides, and proteins. The content of S-sulfonates has been determined in raw sausages and burgers (n = 62). The range of variation in the contents of the determined S-sulfonates is very wide and varies between 47 and 267 microg of SO2/g. The degree of formation of S-sulfonates with regard to the determined sulfite (total SO2 + S-sulfonates) is similar in all of the samples and does not seem to be conditioned by the meat compound (chicken or beef) or by the process of elaboration or type of product (burgers or sausages). In grilled burgers (n = 20) significant losses are produced in the levels of the additive in any of its forms. The value for the S-sulfonates is 31 +/- 9.8%, 29 +/- 6.6% corresponding to the free sulfite and a very similar percentage to the total sulfite (free + reversibly bound) 28 +/- 6.7%. It is possible that during the cooking process cleavages of some bound compounds occur, releasing SO2 and reacting to form new adducts.     

Voltammetric assay for the aging of beer

A new method for the evaluation of beer aging, based on a voltammetric analysis of beer distillates, is described. By measuring the current of both acetaldehyde and sulfite voltammetric peaks it is possible to distinguish between fresh, naturally aged, and artificially aged beers. The results obtained for the ratio of acetaldehyde and SO(2) currents correlate well with those given by an expert sensory panel. The kinetics of the combining reaction of sulfite with acetaldehyde was followed for different acetaldehyde/SO(2) molar ratios by using a programmed voltammetric procedure. The formation of an acetaldehyde-sulfite adduct is rapid, and the reaction equilibrium is reached after 30 min, which is in accordance with the results previously obtained by other methods. This voltammetric-based approach seems to be a new attractive tool for detecting chemical equilibria of the addition of sulfite to carbonyls in beer model systems.     

Single-drop and nanogram level determination of sulfite (SO3(2-)) in alcoholic and nonalcoholic beverage samples based on diffuse reflectance fourier transform infrared spectroscopic (DRS-FTIR) analysis on KBr matrix

The diffuse reflectance Fourier transform spectroscopic (DRS-FTIR) method, using potassium bromide matrix, has been developed for the one-drop microdetermination of sulfite in beverage samples. The present method is very simple, rapid, and precise for the determination of sulfite. The nanogram level of sulfite determination is based on the selection of a quantitative analytical peak at 495 cm (-1) among the three observed vibrational peaks obtained by diffuse reflectance Fourier transform infrared spectroscopy (DRS-FTIR). As little as a single drop of sample is sufficient for quantitative analysis of sulfite. The limit of detection (LOD) and the limit of quantification (LOQ) of the method are found to be 8 and 40 ng of SO 3 (2-) 0.1 g (-1) of KBr matrix, respectively. The linear range of the method (LR) as well as the LOD based on the concentration of sulfite in the solution are 5-500 and 0.8 microg/mL, respectively. The precision in terms of standard deviation and relative standard deviation value at a level of 100 ng of SO 3 (2-) 0.1 g (-1) of KBr for n = 10 are found to be 2 ng of SO 3 (2-) and 2.3%, respectively. The relative standard deviation ( n = 10) for the determination of sulfite in beverage samples available in the local market was observed to be in the range of 2.4-7.8%. The method is free from interionic effects of foreign species. No sample pretreatment is required in this method. The proposed method avoids the requirement of large numbers and bulk amounts of reagents. The method is well-suited to the need of green chemistry.     

Cholesterol oxidation in meat products and its regulation by supplementation of sodium nitrite and apple polyphenol before processing

The levels of cholesterol oxidation derivatives (OxChol) in eight commercial species of meat products were examined. These products contained more than 1 mg/100 g of OxChol, and 7beta-hydroxycholesterol + 5beta-epoxycholesterol (111-1092 microg/100 g), 5alpha-epoxycholesterol (80-712 microg/100 g), cholestanetriol (0-368 microg/100 g), and 7-ketocholesterol (708-1204 microg/100 g) were detected. To know the interaction of sodium nitrite supplementation against cholesterol oxidation in meat products, sausage was produced with or without varying levels of sodium nitrite and stored in the refrigerator for 15 days. As a result, cholesterol oxidation in sausage was inhibited by addition of sodium nitrite in a dose-dependent manner. This observation may be associated with inactivation of O(2)(-) radical and stabilization of polyunsaturated fatty acids (PUFAs). In fact, the levels of OxChol in sausage increased, accompanying the decrease of coexisting linoleic acid when sodium nitrite was not added to sausage meat. Thus, cholesterol oxidation in meat products seems to be considarably promoted by the oxidation of coexisting PUFAs. On the other hand, additive apple polyphenol also inhibited linoleic acid oxidation in sausage and then suppressed cholesterol oxidation through its radical scavenging effects. Therefore, apple polyphenol, having a large amount of an oligomer of catechin, may interfere with cholesterol oxidation in meat processing or storage of meat products through its antioxidative action and be useful as a new antioxitant for meat products when it is added to the original meat before processing.     

Determination of sulfites in foods by simultaneous nitrogen purging and differential pulse polarography

An improved technique has been developed for determination of sulfites in food by differential pulse polarography. A Teflon sleeve is fitted to the dropping mercury electrode capillary so that SO2 is purged from the sample and simultaneously detected at peak potential. Bound sulfite in the sample is released at room temperature by addition of base in the absence of oxygen. For some foods, the prepared sample was passed through a Sep-Pak C-18 cartridge to remove naturally occurring sulfur compounds so that only added sulfite is measured. The level of detection was approximately 1 microgram SO2/g. Results agreed with those obtained by the optimized Monier-Williams method for a variety of foods.     

Synergetic activity of catechin and other antioxidants.

The antioxidant synergy between (+)-catechin and other wine or biological antioxidants (Trolox, ascorbate, SO(2), uric acid) was measured in vitro using the Folin-Ciocalteu (FC) and metmyoglobin assays. Although the two assays are based on very different reagents (i.e., metal salts versus organic and biochemical reagents), the individual antioxidants showed similar relative activities in both systems. In addition, interaction studies showed simple additive effects in all cases except with the (+)-catechin/SO(2) mixture, which showed a remarkable synergetic effect in both assays.     

Ion chromatographic determination of sulfites in foods

Ion chromatography (IC) is shown to be a promising technique for the determination of sulfites (SO2, SO2/3-) in foods. Results of a 10 min flash distillation and 10 min IC determination compare favorably with the results from the conventional Monier-Williams method for total sulfite in a variety of food matrices. The IC technique also provides a wealth of additional information, such as (1) sulfite and sulfate (oxidized sulfite) content of the spiking or treatment solution, (2) residual sulfite applied to the food after oxidation losses in the treatment process, (3) free sulfite in foods, and (4) total sulfite in foods. As a further check on the Monier-Williams method, the sulfate content of the trapping solution can be determined by IC. Because the IC technique traps the liberated SO2 in a non-oxidizing rather than an oxidizing medium, it is considered free from interfering sulfides and organic sulfur-containing groups which can give false positives in the Monier-Williams method. IC thus offers a high speed, more sensitive, and cost-effective alternative to conventional techniques for the determination of sulfite in foods.     

Differential pulse polarographic determination of sulfites in foods: collaborative study

A differential pulse polarographic (DPP) method for the determination of "free" and "total" sulfite in foods was collaboratively studied by 8 laboratories. The collaborators analyzed blind duplicate samples of shrimp, orange juice, peas, dried apricots, and dehydrated potatoes. Collaborators also analyzed the same samples spiked with sulfites at 2 levels, which ranged from 10 to 1100 micrograms added SO2/g. The variability of free SO2 results was excessive for quantitative analysis, but the method can be used for qualitative detection of free SO2. The method for total SO2 determination was suitable for as low as approximately 10 micrograms/g. Recoveries are comparable to those for the official Monier-Williams method at high levels and are superior at low levels. The method has been adopted official first action for determination of total SO2 in the foods studied.     

超表达亚硫酸氧化酶基因对促进番茄果实亚硫酸盐氧化的研究

本研究以亚硫酸氧化酶基因（SO）超表达系（OE）、干扰系（Ri）及野生型（WT）的绿熟番茄果实为材料,经SO2熏蒸后,12℃低温贮藏,研究亚硫酸氧化酶基因的超表达,对番茄贮藏期间相对电导率、亚硫酸盐含量、番茄红素含量及成熟度的变化。结果表明,经SO2熏蒸后,Ri果实较WT果实表现为相对电导率增加,亚硫酸盐残留较多,番茄...     

Magnetic resonance imaging, rheological properties, and physicochemical characteristics of meat systems with fibrinogen and thrombin

Magnetic resonance imaging (MRI) and textural and physicochemical analyses were carried out to evaluate the effect of fibrinogen and thrombin (Fibrimex) addition to meat systems formulated with and without NaCl. For this purpose, different model systems were elaborated: fibrinogen and thrombin (FT), meat emulsion (ME), and meat emulsion with fibrinogen and thrombin (MEFT), with 0, 1, and 2% of NaCl. The addition of fibrinogen-thrombin to meat emulsions results in a gel network with modified physicochemical and textural characteristics, increasing the hardness and springiness. The addition of NaCl at 2% to FT and MEFT systems reduced the gel hardness. MRI parameters (T2, T1, and apparent diffusion coefficient) indicated that systems with fibrinogen and thrombin (FT and MEFT) presented a structure with many and large pores, bulk water, and higher translational motion of water. Significant correlations were found between MRI, texture, and physicochemical parameters.     

Glutathione peroxidase activity, TBARS, and alpha-tocopherol in meat from chickens fed different diets.

This study investigated the effect of feeding broilers with diets differing in dietary fat source (lard, sunflower oil, olive oil) and vitamin E (basal vs supplemented with 200 mg of alpha-tocopheryl acetate/kg) on meat lipid oxidative stability. The diets differed by their degree of unsaturation and included the natural antioxidant alpha-tocopherol (vitamin E). Glutathione peroxidase (GSHPx) activity was measured in raw meat and ranged from 3.62 to 8.06 nmol NADPH/min/mg protein. The enzyme activity was influenced by the degree of unsaturation of the diet. Capillary gas chromatography analyses showed that dietary alpha-tocopherol accumulated in the muscle tissue and contributed to a better oxidative stability of the raw and cooked meat. Thigh meat alpha-tocopherol levels ranged from 2.73 to 3.62 microg/g in unsupplemented chickens whereas levels from 8.69 to 13.37 microg/g were observed in the thigh meat from alpha-tocopherol supplemented animals. The inclusion of olive oil and alpha-tocopherol in the animal diet gave lower thiobarbituric acid reactive substance (TBARS) values and lower GSHPx activity. High correlations were found between the parameters studied. The results suggest that the glutathione peroxidase activity could be used as an indicator of the meat oxidative stability. A negative relationship was observed between GSHPx activity and tissue alpha-tocopherol levels, and a positive relationship was evidenced between TBARS and antioxidant enzyme activity.     

Stability of sterols in phytosterol-enriched milk under different heating conditions

Commercially available phytosterol-enriched milk was subjected to usual and drastic heating conditions to evaluate the stability of the sterols at different treatments. Products showed 422.2 mg of phytosterols/100 g of milk and 132 microg of sterol oxidation products (SOPs)/g of fat (277 microg of SOPs/100 g of milk). Schaal oven conditions (24 h/65 degrees C, equivalent to 1 month of storage at room temperature) reduced the phytosterol content by only 4%. Drastic heating treatments (2 min of microwave heating at 900 W or 15 min of electrical heating at 90 degrees C) led to a 60% decrease of total phytosterol content, with a significant increase of TBARs. The oxysterol amount under those conditions (which was higher in microwave-treated samples) was lower than expected, probably because of the degradation of the oxidation products. Usual heating conditions (1.5 min of microwaves) maintained phytosterol content on physiologically active values (301 mg/100 g of milk) with oxidation percentages around 0.12-0.40% for phytosterols and 1.13% for cholesterol.     

Influence of feeding soybean oil on conjugated linoleic acid content in beef

Forty-eight steers were used to study the influence of feeding soybean oil (SO) on the conjugated linoleic acid (CLA) content of beef. Steers were fed either a control diet containing 954 g/kg of dry matter (DM) corn-based concentrate (CTL) or a control diet supplemented with SO at 20 (SO2) or 40 g/kg (SO4) of diet DM for 105 days. Adipose tissue samples were collected from the M. longissimus dorsi (LD) and from the M. semitendinosus (ST) on days 0 and 63 of the experiment. Adipose and muscle tissue samples were collected from the LD and ST immediately after slaughter. Feeding 40 g/kg of DM as SO increased the proportions of trans-C(18:1) in beef lipid as compared to CTL and SO2 treatments. The C(18:2) cis-9, trans-11 isomer of CLA as a proportion of total fat was not different in adipose and muscle across treatments. Supplementing SO increased C(18:2) trans-10, cis-12 CLA in adipose tissue of the LD. Supplementing high-grain finishing diets with SO is not an effective strategy to enhance the C(18:2) cis-9, trans-11 isomer of CLA in beef.     

Determination of sulfite in foods and beverages by ion exclusion chromatography with electrochemical detection: collaborative study

A liquid chromatographic (LC) method for determination of total sulfite in foods and beverages by alkali extraction followed by ion exclusion chromatographic separation and electrochemical detection (IEC-EC) was collaboratively studied by 9 laboratories. Blind duplicate samples of starch, diluted lemon juice, wine cooler, dehydrated seafood, and instant mashed potatoes were analyzed without spiking and with added sulfite at 2 levels. The initial sulfite levels varied from 0 to 384 ppm SO2, and the levels added varied from 10 to 400 ppm. The initial sulfite levels determined by the IEC-EC method and the Monier-Williams method were in good agreement. Recovery of added sulfite by the IEC-EC method was generally higher than that by the Monier-Williams method. Within-laboratory repeatability (RSDr) for the IEC-EC method varied from 4.4 to 26.0%, and overall reproducibility (RSDR) varied from 8.5 to 39.3%. The collaborators found the method to be fast, sensitive, and easy to use, which makes it a useful alternative to the Monier-Williams method. The method has been adopted official first action.     

Determination of sulfite in food by flow injection analysis

A method is described for the determination of sulfite levels in food products by flow injection analysis (FIA). The method is based on the decolorization of malachite green by SO2, which is isolated from the flowing sample stream by means of a gas diffusion cell. The FIA method has a detection limit in food sample extracts of 0.1 ppm SO2 (3 times peak height of blank), which corresponds to 1-10 ppm SO2 in a food product, depending on the extraction procedure used. At the 5 ppm SO2 level in a food extract, the precision of replicate injections is +/- 1-2%. The method was tested on a variety of both sulfite-treated and untreated food products and the results compared favorably with those obtained by the Monier-Williams, colorimetric (pararosaniline), and enzymatic (sulfite oxidase) methods. The average differences from the FIA results were 19, 11, and 12%, respectively, for those samples (n = 12) above 50 ppm SO2. At lower levels the results were somewhat more erratic due to inaccuracies of the various methods at low concentrations.     

Determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis: collaborative study

A method for the determination of total sulfite in shrimp, potatoes, dried pineapple, and white wine by flow injection analysis (FIA) was collaboratively studied by 8 laboratories. In the method, the sample solution is reacted with sodium hydroxide to liberate aldehyde-bound sulfite. The sample stream is acidified to produce SO2 gas, which diffuses across a Teflon membrane in the gas diffusion cell into a flowing stream of malachite green. The degree of discoloration of the malachite green is proportional to the amount of sulfite in the sample solution. Red wine was included in the study but interlaboratory precision for these samples was not satisfactory and correlation with Monier-Williams results was poor. The present method is not recommended for use with these samples. For shrimp, potatoes, dried pineapple, and white wine, average reproducibility (RSDR) of results was 25% for samples at 10 ppm SO2 and 10% for samples at greater than 50 ppm. Overall average reproducibility was 14%. Recoveries of sulfite added to samples averaged 80%. Comparison of FIA with the Monier-Williams method indicated comparable results by the 2 methods. The FIA method has been adopted official first action for determination of greater than or equal to 5 ppm total sulfite in shrimp, potatoes, dried pineapple, and white wine.     

Antioxidant activity and characterization of volatile constituents of Taheebo (Tabebuia impetiginosa Martius ex DC)

Volatiles were isolated from the dried inner bark of Tabebuia impetiginosa using steam distillation under reduced pressure followed by continuous liquid-liquid extraction. The extract was analyzed by gas chromatography and gas chromatography-mass spectrometry. The major volatile constituents of T. impetiginosa were 4-methoxybenzaldehyde (52.84 microg/g), 4-methoxyphenol (38.91 microg/g), 5-allyl-1,2,3-trimethoxybenzene (elemicin; 34.15 microg/g), 1-methoxy-4-(1E)-1-propenylbenzene (trans-anethole; 33.75 microg/g), and 4-methoxybenzyl alcohol (30.29 microg/g). The antioxidant activity of the volatiles was evaluated using two different assays. The extract exhibited a potent inhibitory effect on the formation of conjugated diene hydroperoxides (from methyl linoleate) at a concentration of 1000 microg/mL. The extract also inhibited the oxidation of hexanal for 40 days at a level of 5 microg/mL. The antioxidative activity of T. impetiginosa volatiles was comparable with that of the well-known antioxidants, alpha-tocopherol, and butylated hydroxytoluene.     

Influence of different dietary doses of n-3- or n-6-rich vegetable fats and alpha-tocopheryl acetate supplementation on raw and cooked rabbit meat composition and oxidative stability

This study evaluates the effects of replacing beef tallow added to rabbit feeds (3% w/w) by different doses (0%, 1.5% and 3% w/w) of n-6- or n-3-rich vegetable fat sources (sunflower and linseed oil, respectively) and alpha-tocopheryl acetate supplementation (0 and 100 mg/kg) on the fatty acid composition, alpha-tocopherol content, and oxidation levels [assessed by analyzing thiobarbituric acid (TBA) and lipid hydroperoxide values] in rabbit meat. We also measured these parameters after cooking and refrigerated storage of cooked rabbit meat. Both dietary alpha-tocopheryl acetate supplementation and the dose and source of fat added to feeds influenced meat fatty acid composition, modifying the n-6/n-3 ratio, which was more nutritionally favorable when linseed oil was used. Furthermore, the addition of linseed oil and the supplementation with alpha-tocopheryl acetate enhanced long-chain PUFA biosynthesis. However, the addition of 3% linseed oil increased meat oxidation, and although it was reduced by dietary supplementation with alpha-tocopheryl acetate in raw meat, this reduction was not as effective after cooking. Therefore, dietary supplementation with 1.5% linseed oil plus 1.5% beef tallow and with alpha-tocopheryl acetate would be recommended to improve the nutritional quality of rabbit meat.     

Residues of spinosad in meat, milk, and eggs

Spinosad is an insect control agent that is derived from a naturally occurring soil bacterium and has a high level of activity against insects that infest a variety of crops. Dairy and poultry feeding studies were conducted to determine the magnitude of spinosad residues in animal products that would result from the consumption of typical feed commodities containing residues of spinosad. Dairy cows were dosed for 28 days with spinosad at rates equivalent to 0, 1, 3, and 10 microg/g in the diet. Chicken hens were dosed for 42 days with spinosad at rates equivalent to 0, 0.1, 0.3, 1, and 5 microg/g in the diet. Milk, eggs, and tissue samples were analyzed by high-performance liquid chromatography and/or immunoassay methods. Spinosad residues occurred in all of the sample types but were lowest in eggs, skim milk, and lean meat and were highest in the fat.     

Oxidation process affecting fatty acids and cholesterol in fried and roasted salmon.

Salmon was processed by three different culinary techniques: pan-frying with olive oil, pan-frying with soya oil, and roasting. Roasting did not modify the fat content from that of raw samples. Frying increased the fat content 2-fold, with no difference between samples fried with different oils. Total cholesterol oxidized products (COPs) were 0.74, 2.98, 3.35, and 7.38 microg/g fat in raw, fried with olive oil, fried with soya oil, and roasted salmon, respectively, which represent 0.01, 0.08, 0.09, and 0.15% of cholesterol. A significant correlation (r = 0.902, < or = 0.01) was found between acidity index and total COPs. The most abundant COPs were 7-ketocholesterol, which appeared in all the samples, and cholestanetriol (one of the most citotoxic COP), which appeared only in cooked samples (1.05-1.33 microg/g fat). All cooked samples supplied more omega-6 polyunsaturated fatty acids (PUFAs) than raw samples and showed higher omega-6/omega-3 ratios. Roasted salmon showed the lowest omega-3 content and the highest PUFAs/(SFAs)-C18:0 and MUFAs+PUFAs/(SFAs-C18:0) ratios.