Effect of oil marinades with garlic, onion, and lemon juice on the formation of heterocyclic aromatic amines in fried beef patties

Effects of the application of oil marinades with garlic, onion, and lemon juice on the formation of heterocyclic aromatic amines (HAAs) in fried beef patties were investigated. Two different statistical design models were used. In the screening experiment, a significant inhibition of formation of MeIQx was determined only by addition of garlic (p < 0.05). When the amount of garlic was changed from 2 to 20 g/100 g of marinade, the estimated MeIQx content in patties was reduced about 70%. MeIQx (0.38-1.22 ng/g), 4,8-DiMeIQx (n.d.-0.45 ng/g), PhIP (n.d.-0.09 ng/g), norharman (0.76-13.5 ng/g), and harman (2.9-21.5 ng/g) were found in fried patties. The results of two-level and three-level fractional factorial design experiments confirmed the first investigation. They showed a stronger reduction in MeIQx in patties with the addition of increasing amounts of garlic (p < 0.01) and onion (p < 0.05) in marinades. A higher content of lemon juice in marinades led to only a marginal reduction in MeIQx (p > 0.05). The optimum amounts of onion, garlic, and lemon juice that achieved a maximum reduction of HAAs were calculated as 31.2%, 28.6%, and 14.6% in marinade.     

Consequences of microwave heating and frying on the lipid fraction of chicken and beef patties

Two types of commercial meat patties were analyzed to evaluate the effect of two applied cooking methods on the lipid fraction and the cholesterol oxidation process during heating. Microwave heating hardly modified the fatty acid profiles of both chicken and beef patties, whereas frying in olive oil increased oleic and eicosapentaenoic acids and decreased linoleic and docosahexaenoic acids in both types of products. Frying improved the omega6/omega3 fatty acids ratio in beef patties from 10.67 (raw) to 5.37 (fried). Total cholesterol oxidation product (COP) increments were 5.3-6.1-fold with microwave heating and 1.5-2.6-fold with frying. Chicken patties, raw and cooked, had a COP content twice as high as the corresponding beef ones.     

Evaluation of oligosaccharide synthesis from lactose and lactulose using β-galactosidases from Kluyveromyces isolated from artisanal cheeses

The β-galactosidase activity of 15 Kluyveromyces strains isolated from cheese belonging to Kluyveromyces lactis and Kluyveromyces marxianus species was tested for the production of oligosaccharides derived from lactose (GOS) and lactulose (OsLu). All Kluyveromyces crude cell extracts (CEEs) produced GOS, such as 6-galactobiose and 3'-, 4'-, and 6'-galactosyl-lactose. At 4 h of reaction, the main trisaccharide formed was 6'-galactosyl-lactose (20 g/100 g of total carbohydrates). The formation of OsLu was also observed by all CEEs tested, with 6-galactobiose, 6'-galactosyl-lactulose, and 1-galactosyl-lactulose being found in all of the reaction mixtures. The synthesis of trisaccharides predominated over other oligosaccharides. K. marxianus strain O3 produced the highest yields of GOS and OsLu after 4 h of reaction, reaching 42 g/100 g of total carbohydrates (corresponding to 80% lactose hydrolysis) and 45 g/100 g of total carbohydrates (corresponding to 87% lactulose hydrolysis), respectively. Therefore, the present study contributes to a better insight into dairy Kluyveromyces β-galactosidases and shows the feasibility of these enzymes to transglycosylate lactose and lactulose, producing high yields of prebiotic oligosaccharides.     

Quantification of heterocyclic aromatic amines in fried meat by HPTLC/UV-FLD and HPLC/UV-FLD: a comparison of two methods

A recently developed HPTLC/UV-FLD method was compared to the routinely used HPLC/UV-FLD method for the quantification of heterocyclic aromatic amines (HAA) formed at trace levels during the heating process of meat. For formation of these process contaminants under normal cooking conditions, beef patties were fried in a double-contact grill at 230 degrees C for five different frying times and extracted by solid-phase extraction. The HAAs most frequently found, that is, 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5- f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5- f]quinoxaline (4,8-DiMeIQx), 9 H-pyrido[3,4- b]indole (norharman), and 1-methyl-9 H-pyrido[3,4- b]indole (harman), were quantified by two chromatographic methods, which were orthogonal to each other (normal versus reversed phase system). Both methods showed a similar performance and good correlation of the results ( R (2) between 0.8875 and 0.9751). The comparison of running costs and run time in routine analysis proved HPTLC/UV-FLD to be more economical (factor of 3) and faster (factor of 4) due to its capability of parallel chromatography. The HAA findings calculated by standard addition increased with the heating time from <1 to 33 microg/kg related to 3-6 min of frying time. The precision (RSD) was between 7 and 49% (HPTLC) and between 5 and 38% (HPLC) at these very low HAA levels formed.     

Plant extracts, spices, and essential oils inactivate Escherichia coli O157:H7 and reduce formation of potentially carcinogenic heterocyclic amines in cooked beef patties

Meats need to be heated to inactivate foodborne pathogens such as Escherichia coli O157:H7. High-temperature treatment used to prepare well-done meats increases the formation of carcinogenic heterocyclic amines (HCAs). We evaluated the ability of plant extracts, spices, and essential oils to simultaneously inactivate E. coli O157:H7 and suppress HCA formation in heated hamburger patties. Ground beef with added antimicrobials was inoculated with E. coli O157:H7 (10(7) CFU/g). Patties were cooked to reach 45 °C at the geometric center, flipped, and cooked for 5 min. Samples were then taken for microbiological and mass spectrometry analysis of HCAs. Some compounds were inhibitory only against E. coli or HCA formation, while some others inhibited both. Addition of 5% olive or apple skin extracts reduced E. coli O157:H7 populations to below the detection limit and by 1.6 log CFU/g, respectively. Similarly, 1% lemongrass oil reduced E. coli O157:H7 to below detection limits, while clove bud oil reduced the pathogen by 1.6 log CFU/g. The major heterocyclic amines 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) were concurrently reduced with the addition of olive extract by 79.5% and 84.3% and with apple extract by 76.1% and 82.1%, respectively. Similar results were observed with clove bud oil: MeIQx and PhIP were reduced by 35% and 52.1%, respectively. Addition of onion powder decreased formation of PhIP by 94.3%. These results suggest that edible natural plant compounds have the potential to prevent foodborne infections as well as carcinogenesis in humans consuming heat-processed meat products.     

In vitro investigation into the potential prebiotic activity of honey oligosaccharides

The effect of honey oligosaccharides on the growth of fecal bacteria was studied using an in vitro fermentation system. Prior to treatment, glucose and fructose (31.73 and 21.41 g/100 g of product, respectively) present in honey, which would be digested in the upper gut, were removed to avoid any influence on bacterial populations in the fermentations. Nanofiltration, yeast (Saccharomyces cerevisiae) treatment, and adsorption onto activated charcoal were used to remove monosaccharides. Prebiotic (microbial fermentation) activities of the three honey oligosaccharide fractions and the honey sample were studied and compared with fructooligosaccharide (FOS), using 1% (w/v) fecal bacteria in an in vitro fermentation system (10 mg of carbohydrate, 1.0 mL of basal medium). A prebiotic index (PI) was calculated for each carbohydrate source. Honey oligosaccharides seem to present potential prebiotic activity (PI values between 3.38 and 4.24), increasing the populations of bifidobacteria and lactobacilli, although not to the levels of FOS (PI of 6.89).     

Addition of various carbohydrates to beef burgers affects the formation of heterocyclic amines during frying

The influence of the addition of carbohydrates with different physicochemical properties on weight loss and formation of heterocyclic amines (HAs) during the frying of beef burgers was examined. Furthermore, the capability of carbohydrates to bind HAs was tested. Beef burgers containing 1.5% NaCl and 0.3% tripolyphosphate (reference), with the addition of 1.5% carbohydrate, were fried for 5 min at 200 degrees C in a double-sided pan fryer. The beef burgers were analyzed for HAs with solid phase extraction and liquid chromatography/mass spectrometry. 2-Amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP), and 9H-pyrido[3,4-b]indole (Norharman) were detected in all of the beef burgers. The addition of carbohydrates affected both the weight loss and the formation of HAs during cooking. The formation of HAs could be correlated to depend on both the weight loss and the type of the added carbohydrate. Of the 11 different carbohydrates tested, raw potato starch was most capable of inhibiting the formation of HAs, while potato fiber gave the lowest weight loss and a comparably low amount of PhIP. Wheat bran and potato fiber were found to reversibly bind HAs. It is concluded that adding small amounts of certain carbohydrates may be a simple and effective way of reducing the amount of HAs and can easily be applied in households and commercial preparations of beef burgers.     

Liquid chromatography-tandem mass spectrometry analysis of 2-amino-1-methyl-6-(4-hydroxyphenyl)imidazo[4,5-b]pyridine in cooked meats

Several cooked meats such as beef (fried, coated-fried), pork (fried, coated-fried), and chicken (fried, griddled, coated-fried, roasted) were analyzed for the heterocyclic amine 2-amino-1-methyl-6-(4-hydroxyphenyl)imidazo[4,5- b]pyridine (4'-OH-PhIP) not commonly determined in food and 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine (PhIP). The highest content of 4'-OH-PhIP was found in fried and griddled chicken breast, the concentration being 43.7 and 13.4 ng/g, respectively, whereas the corresponding PhIP concentrations were 19.2 and 5.8 ng/g. The estimated concentration of both pyridines in fried pork loin, in fried pork sausages, and in coated-fried chicken was below 2.5 ng/g. In the rest of the samples, 4'-OH-PhIP was not detected. The analyses were performed by solid-phase extraction and LC-MS/MS. The fragmentation of 4'-OH-PhIP in an ion trap mass analyzer was studied in order to provide information for the identification of 4'-OH-PhIP. Additionally, the effect of red wine marinades on the formation of 4'-OH-PhIP in fried chicken was examined, finding a notable reduction (69%) in the amine's occurrence.     

Formation of Oligosaccharides and Polysaccharides by Lactobacillus reuteri LTH5448 and Weissella cibaria 10M in Sorghum Sourdoughs

Gluten‐free breads, which are composed of gluten‐free flours, starch, and hydrocolloids, differ from wheat and rye breads in relation to texture, volume, and crumb structure. Moreover, the dietary fiber content is lower compared with wheat or rye breads. Cereal isolates of lactic acid bacteria frequently produce oligo‐ and homopolysaccharides from sucrose, which can improve the nutritional and technological properties of gluten‐free breads as prebiotic carbohydrates and hydrocolloids, respectively. Sorghum sourdough was fermented with Lactobacillus reuteri LTH5448 or Weissella cibaria 10M, which synthesize fructooligosaccharides (FOS) and levan, and isomaltooligosaccharides and dextran, respectively. The gluten‐free bread was produced with 14% sourdough addition. L. reuteri LTH5448 formed FOS and 1.5 g of levan/kg DM in quinoa sourdoughs. FOS were digested by the baker's yeast during proofing, and the levan could be qualitatively detected in the bread. W. cibaria 10M produced >60 g of isomaltooligosaccharides/kg DM and 0.6 g of dextran/kg DM, which could still be detected in the bread. Breads prepared with W. cibaria 10M were less firm compared with breads prepared with L. reuteri LTH5448 or a FOS and levan‐negative mutant of L. reuteri LTH5448. The addition of sourdoughs fermented with oligo‐ and polysaccharide forming starter cultures can increase the content of prebiotic oligosaccharides in gluten‐free breads.     

Particulate metmyoglobin reducing activity and its relationship with meat color

There is controversy about the effect of storage time on metmyoglobin (MetMb) reducing activity in the sarcoplasmic fraction of meat and the role of this reducing activity in maintaining the color of red meat. The presence of metmyoglobin reducing activity in the myofibrillar fraction of muscle extracts was investigated as a possible reason for this controversy. NADH-dependent MetMb reducing activity was found in the particulate fraction of meat following sedimentation of a meat homogenate at 35 000g. There was 5.8 times more MetMb reducing activity in the particulate fraction compared with that of the sarcoplasmic (supernatant) fraction. The presence of metmyoglobin reducing activity in the myofibrils (MMRA), defined as the activity in the sediment after centrifugation of a meat homogenate at 2 000g, was confirmed. The myofibrillar fraction contained 63% of the total MetMb reducing activity available in the meat. The relationship between muscle MetMb reducing activities and meat color parameters was investigated in a beef patties system. The particulate MetMb reducing activity (PMRA) in beef patties was found to be a good indicator of the total metmyoglobin reducing activity in meat and was positively correlated with the color parameters of the patties, suggesting that PMRA may be associated with red meat color of meat patties.     

Evaluation of 2-dodecylcyclobutanone as an irradiation dose indicator in fresh irradiated ground beef

Alkylcyclobutanones (2-ACBs) are radiolytic products formed when fatty acids are irradiated. These cyclobutanones are unique irradiation byproducts and therefore may serve as indicators of irradiation exposure. As only limited information exists about 2-ACB formation in retail meat products, reliable methods that can quantify 2-ACBs and thus estimate irradiation dose in commercial meat products are desired. The cyclobutanone studied in this experiment was 2-dodecylcyclobutanone (2-DCB), which is formed from palmitic acid. The formation of 2-DCB was evaluated in fresh irradiated ground beef patties at two fat levels. Patties containing 15% and 25% fat were irradiated by electron beam at 1.0, 2.0, 3.0, and 4.5 kGy. Commercially available 1-lb irradiated ground beef chubs with different fat levels were analyzed in order to estimate dose absorbed by these samples. The 2-DCB was extracted using supercritical fluid extraction (SFE) and analyzed by gas chromatography-mass spectroscopy (GC-MS) and was detected in all the irradiated samples. The concentration of 2-DCB increased linearly with dose with R2 = 0.9646 for 25% fat samples and R2 = 0.9444 for 15% fat samples. Further, there was no significant difference in 2-DCB concentrations between the two fat levels. The estimated doses applied to the commercial samples ranged between 1.38 and 1.55 kGy, values consistent with doses normally used in the industry (1.0-2.0 kGy). Our results show that 2-DCB can be used to monitor fresh irradiated beef and approximate the absorbed dose.     

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.     

Inhibition of lipid oxidation in cooked beef patties by hydrolyzed potato protein is related to its reducing and radical scavenging ability

Protein hydrolysates were prepared by limited alcalase hydrolysis (0.5, 1, and 6 h, corresponding to degrees of hydrolysis of 0.72, 1.9, and 2.3, respectively) of heat-coagulated potato protein. The hydrolysates were characterized for peptide composition, ferric reducing/antioxidant power (FRAP), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging activity, and Fe2+- and Cu2+-chelation capacity. Hydrolyzed and intact proteins were formulated (4%, w/w) into beef patties to determine in situ antioxidant efficacy. Thiobarbituric acid-reactive substances (TBARS) and peroxide value (PV) formed in cooked and PVC-packaged patties during storage (4 degrees C, 0-7 days) were analyzed. Hydrolysis increased the protein solubility by 14-19-fold and produced numerous short peptides (< 6 kDa). The FRAP values of the protein sample (23 micromol/g) increased markedly after hydrolysis but were similar between the three hydrolysates (597-643 micromol/g). Similarly, the ABTS radical-scavenging activity also was increased by hydrolysis and was the greatest for the 1-h hydrolysate. Hydrolysis increased the Cu2+-chelation activity but decreased the Fe2+-chelation ability of the protein. The production of PV in patties after 7 days of storage was lowered 44.9% and 74.5% (P < 0.05), and that of TBARS was reduced 40.9% and 50.3% (P < 0.05), by intact and hydrolyzed proteins, respectively.     

Metabolic profiling of potential probiotic or synbiotic cheeses by nuclear magnetic resonance (NMR) spectroscopy

To assess ripening of potential probiotic cheeses (containing either Lactobacillus casei -01 or Bifidobacterium lactis B94) or synbiotic cheeses with fructooligosaccharides (FOS) or a 50:50 mix of FOS/inulin, metabolic profiles have been obtained via classical biochemical analyses and by NMR spectroscopy. The addition of prebiotics to the cheeses resulted in lower proteolysis indices, especially in those synbiotic cheeses inoculated with B. lactis B94. Among synbiotic cheeses the combination of FOS and inulin resulted in an increase in lipolytic activity. The metabolic profiles of the cheeses analyzed by NMR spectroscopy, combined with multivariate statistics, allowed profiles to be distinguished by maturation time, added probiotic bacteria, or, in the case of B. lactis B94 cheese, added prebiotic. The NMR results are in agreement with the biochemical analyses and demonstrate the potential of NMR for the study of metabolic processes in probiotic/synbiotic food matrices.     

Effect of cooking on concentrations of β-estradiol and metabolites in model matrices and beef

Because beef food products are generally cooked prior to consumption, the behavior of chemicals in these cooked foods is important in estimating human exposure. The heat stability of the natural estrogen β-estradiol (β-E2) and its metabolites α-estradiol (α-E2), estrone (E1), and several catechol estrogens was examined in heated vegetable oil and aqueous solutions. The chemicals were also incorporated into regular and extra lean ground beef and subjected to cooking. E1 and E2 were stable in aqueous solutions at 100°C, whereas the catechol estrogens exhibited first-order decay curves with half-lives of 2-10 min. Their stability improved to the same level as the other test chemicals when an antioxidant was added to the solution, suggesting that their disappearance was due to oxidation rather than thermal degradation. E1 and E2 were also stable in heated vegetable oil (160-180°C), whereas catechol estrogen decreased 30-50% over the 2 h duration of the experiments. Chemical losses from cooked beef appear to be related to the fat content of the beef, with greater losses occurring in regular ground beef (25-30%), compared to extra lean ground beef (5-20%). This study shows that cooking reduces but does not eliminate the potential for dietary exposure to growth promoters in ground beef.     

Inhibitory effect of fruit extracts on the formation of heterocyclic amines

Natural extracts have attracted considerable attention for development into effective inhibitors against the formation of genotoxic heterocyclic amines (HAs) in processed foods. In this study, four fruit extracts (apple, elderberry, grape seed, and pineapple) were evaluated for their effects on HA formation in fried beef patties. Apple and grape seed extracts were found to be the most effective in both the degree of inhibition in the formation of individual HAs (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx), and 2-amino-1-methyl-6-henylimidazo [4,5-b]pyridine (PhIP)) and in the reduction of total HA content (approximately 70% relative to the control). Activity-guided analysis of apple extract using model systems (PhIP- and MeIQx-producing models) showed that the proanthocyanidins, phloridzin and chlorogenic acid were responsible for reducing the amount of HAs formed. Proanthocyanidins were identified as the dominant inhibitors because they were strongly active against HA formation in both the PhIP and MeIQx model systems. For phloridzin, the inhibitory effect was observed only on the formation of PhIP. In contrast, chlorogenic acid, although effective against the formation of MeIQx, significantly enhanced the formation of PhIP. This is the first report showing the inhibitory activities of apple phenolics on the formation of heterocyclic amines. The findings provide valuable information for the development of effective strategies to minimize HA content of cooked meats and to identify several new natural products that may have new applications in the food industry.     

2-alkylcyclobutanones as irradiation dose indicators in irradiated ground beef patties

Alkylcyclobutanones have been recognized as chemical markers of irradiated lipid-containing foods since 1970. They are important because they are produced solely as a result of irradiation and not any other processing method. This study investigated the formation of 2-dodecylcyclobutanone (2-DCB) and 2-tetradec-5'-enylcyclobutanone (2-TDCB) in irradiated ground beef patties from commercial and noncommercial sources. Patties were irradiated using a (60)C source (gamma-irradiation) and electron beam irradiation, at five targeted absorbed doses of 0.5, 1.0, 2.5, 5.0, and 7.0 kGy. Commercially available irradiated patties were also studied. A supercritical fluid extraction (SFE) procedure was optimized and used for the extraction and isolation of the alkylcyclobutanones. Samples can be used for extraction without a prior cleanup step, which makes this procedure rapid and convenient to use. Identification and quantitation of the cyclobutanones were done by gas chromatography-mass spectroscopy. 2-DCB was detected in all of the irradiated samples (including commercial patties), and its concentration increased linearly with the irradiation dose. Electron beam irradiation produced a greater amount of 2-DCB compared to gamma-irradiation at dose levels >2.5 kGy. 2-TDCB was detected only at the two higher irradiation doses, whereas both marker compounds were not detected in the non-irradiated samples.     

Simple and fast method for recognition of reducing and nonreducing neutral carbohydrates by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Negative-ion mode matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry (TOF-MS) was used for the characterization of storage, neutral oligosaccharides extracted from Jerusalem artichoke, red onion, and wheat. The oligosaccharides from the real samples were analyzed with 2,4,6-trihydroxyacetophenone as the most convenient matrix that was selected in advance with the standard carbohydrate samples (inulin and maltooligosaccharides). The oligosaccharides from Jerusalem artichoke and red onion (similarly as inulin) produced [M - H](-) peaks as the main distribution, which reflects their nonreducing composition. On the contrary, the cross-ring fragmentations [M - H - 120](-) formed the main distribution in the mass spectra of hydrolyzed wheat starch similarly to reducing maltooligosaccharides and dextrans. The negative-ion mode MALDI-TOF MS is capable of recognizing reducing and nonreducing oligosaccharides. Such a simple differentiation of malto or inulin type of oligosaccharides is not possible in the positive-ion mode.     

Quantitation of carnosine in humans plasma after dietary consumption of beef

Carnosine (beta-alanyl-L-histidine) is a dipeptide found in the muscle foods that has been postulated to be a bioactive food component. The objective of this research was to determine the concentration of carnosine in human plasma after ingestion of beef. Nine males and nine females were recruited for the study. Food devoid of meat products was given to the subjects so that they did not consume carnosine for 48 h prior to the test. Subjects fasted for 12 h and then had blood withdrawn prior to a meal containing 200 g of ground beef. Additional blood samples were collected over the following 24 h and carnosine concentrations were determined by HPLC. The cooked ground beef used in the study contained 52% water, 24% protein, 22% fat, and 124 mg of carnosine/100 g of beef. No plasma carnosine was detected in subjects before the consumption of the beef. Carnosine was detected in plasma 15 min after beef consumption. Plasma carnosine concentrations continued to increase with a maximum (32.7 mg of carnosine/L of plasma) being recorded 2.5 h after consumption. Carnosine concentrations then decreased until no carnosine could be detected at 5.5 h postconsumption. These results indicate that dietary carnosine is absorbed into human plasma after the consumption of beef. Since carnosine has several potential health benefits, evidence of its bioavailability suggests that it could be a bioactive food component.     

Inulin effects on bioavailability of soy isoflavones and their calcium absorption enhancing ability

The effect of inulin on isoflavone absorption and the effect of isoflavones and synergy with inulin on calcium absorption in rats was investigated. Rats (n = 48) were divided into three groups and fed inulin (50 mg/g), isoflavone (8 mg/g) or inulin + isoflavone (50 mg/g + 8 mg/g) diets for 21 days. After a 2-h fast, rats were given (45)Ca orally or intraperitoneally, together with 25 mg of calcium as calcium acetate. Blood and femurs were collected 4 days later. Sera were analyzed for isoflavones using HPLC-MS, femurs for (45)Ca by beta-scintillation counting, and total femoral calcium by atomic absorption spectroscopy. Both groups fed isoflavones had similar and significantly higher weight-adjusted total femoral calcium content compared to the inulin-fed group (p < 0.0001). (45)Ca absorption was significantly higher (p < 0.01) when isoflavones were added to the diet, and serum equol was significantly lower (p < 0.01) when inulin was added to the diet containing isoflavones. We conclude that isoflavones enhance calcium absorption, without synergy from inulin, and that inulin decreases equol production.