Melanoidins from Coffee, Cocoa, and Bread Are Able to Scavenge α-Dicarbonyl Compounds under Simulated Physiological Conditions.

Free amino residues react with α-dicarbonyl compounds (DCs) contributing to the formation of advanced glycation end products (AGEs). Phenolic compounds can scavenge DCs, thus controlling the dietary carbonyl load. This study showed that high-molecular weight cocoa melanoidins (HMW-COM), HMW bread melanoidins (HMW-BM), and especially HMW coffee melanoidins (HMW-CM) are effective DC scavengers. HMW-CM (1 mg/mL) scavenged more than 40% DCs within 2 h under simulated physiological conditions, suggesting some physiological relevance. Partial acid hydrolysis of HMW-CM decreased the dicarbonyl trapping capacity, demonstrating that the ability to react with glyoxal, methylglyoxal (MGO), and diacetyl was mainly because of polyphenols bound to macromolecules. Caffeic acid (CA) and 3-caffeoylquinic acid showed a DC-scavenging kinetic profile similar to that of HMW-CM, while mass spectrometry data confirmed that hydroxyalkylation and aromatic substitution reactions led to the formation of a stable adduct between CA and MGO. These findings corroborated the idea that antioxidant-rich indigestible materials could limit carbonyl stress and AGE formation across the gastrointestinal tract.

Mrakia gelida in brewing process: An innovative production of low alcohol beer using a psychrophilic yeast strain.

Due to the increasing consumer demand, the production of low alcoholic and non alcoholic beer is the new goal of the present brewing producers. Although the beer with reduced alcohol content is currently obtained by physical methods, the use of non-Saccharomyces yeast, with low fermentations capacities, may represent an interesting biological approach. In this study the ethanol content and the volatile profile of a beer obtained using the basidiomycetous psychrophilic yeast strain Mrakia gelida DBVPG 5952 was compared with that produced by a commercial starter for low alcohol beers, Saccharomycodes ludwigii WSL17. The two beers were characterized by a low alcohol content (1.40% and 1.32% v/v) and by a low diacetyl production (5.04 and 5.20 µg/L). However, the organoleptic characteristics of the beer obtained using M. gelida are more appreciated by the panelists, in comparison to the analogous produced with the commercial strain of S. ludwigii.

Free α-dicarbonyl compounds in coffee, barley coffee and soy sauce and effects of in vitro digestion.

α-Dicarbonyl (α-DC) compounds were characterised in roasted (coffee, barley coffee) and in fermented (soy sauce) food matrices. Glyoxal (GO), methylglyoxal (MGO), diacetyl (DA) and 3-deoxyglucosone (3-DG) were found in all samples, and hydroxypyruvaldehyde and 5-hydroxypentane-2,3-dione in barley and soy. Cis and trans 3,4-dideoxyglucosone-3-ene (3,4-DGE) isomers and 4-glucosyl-5,6-dihydroxy-2-oxohexanal (4-G,3-DG) were found only in barley, and 3,4-DGE only in soy sauce with molasses. GO, MGO, and DA were quantified. Findings indicate that i) α-DC profiles depend on the food matrix and any technological treatments applied; ii) α-DC quantitation by HPLC requires matrix-specific, validated methods; iii) GO and MGO were the most abundant α-DCs; and iv) barley coffee was the matrix richest in α-DCs both qualitatively and quantitatively. In vitro simulated digestion reduced (coffee) or strongly increased (barley, soy sauce) free α-DC content. These findings suggest that α-DC bioavailability could actually depend not on food content but rather on reactions occurring during digestion.

Influence of valine and other amino acids on total diacetyl and 2,3-pentanedione levels during fermentation of brewer's wort.

Undesirable butter-tasting vicinal diketones are produced as by-products of valine and isoleucine biosynthesis during wort fermentation. One promising method of decreasing diacetyl production is through control of wort valine content since valine is involved in feedback inhibition of enzymes controlling the formation of diacetyl precursors. Here, the influence of valine supplementation, wort amino acid profile and free amino nitrogen content on diacetyl formation during wort fermentation with the lager yeast Saccharomyces pastorianus was investigated. Valine supplementation (100 to 300 mg L(-1)) resulted in decreased maximum diacetyl concentrations (up to 37 % lower) and diacetyl concentrations at the end of fermentation (up to 33 % lower) in all trials. Composition of the amino acid spectrum of the wort also had an impact on diacetyl and 2,3-pentanedione production during fermentation. No direct correlation between the wort amino acid concentrations and diacetyl production was found, but rather a negative correlation between the uptake rate of valine (and also other branched-chain amino acids) and diacetyl production. Fermentation performance and yeast growth were unaffected by supplementations. Amino acid addition had a minor effect on higher alcohol and ester composition, suggesting that high levels of supplementation could affect the flavour profile of the beer. Modifying amino acid profile of wort, especially with respect to valine and the other branched-chain amino acids, may be an effective way of decreasing the amount of diacetyl formed during fermentation.

Sensorically and antimicrobially active metabolite production of Lactobacillus strains on Jerusalem artichoke juice.

BACKGROUND: In the tubers of Jerusalem artichoke (Helianthus tuberosus L.) the main carbohydrate is the well-known prebiotic inulin, which is a good growth substrate for gut microorganisms. Jerusalem artichoke tuber is traditionally consumed boiled or pickled rather than in fermented form. Lactic acid bacteria are traditionally used in the production of fermented foods; nevertheless their behavior and metabolite production are considerably influenced by the substrate. The purpose of this study was to investigate the growth and production of the most important sensorically and antimicrobially active metabolites of different Lactobacillus strains on Jerusalem artichoke juice. RESULTS: All investigated strains grew well (in the range 10(9) cfu mL(-1) ) in the media. The organic acids (lactic acid, 110-337 mmol L(-1) ; acetic acid, 0-180 mmol L(-1) ; and succinic acid, 0-79 mmol L(-1) ), hydrogen peroxide (0.25-1.77 mg L(-1) ), mannitol (0.06-3.24 g L(-1) ), acetoin and diacetyl production of strains varies not only according to the species but also from strain to strain, which will be demonstrated and discussed in the paper. CONCLUSION: Our results showed that lactobacilli can be used for the fermentation of Jerusalem artichoke, which in this form could be used, alone or mixed with other raw food material, as a new synbiotic functional food.

Block of delayed rectifier (DRK1) K+ channels by internal 2,3-butanedione monoxime in Xenopus oocytes.

Inhibition of delayed rectifier (DRK1) potassium channels by 2,3-butanedione monoxime (BDM) was investigated in inside-out membrane patches from Xenopus oocytes previously injected with in vitro transcribed DRK1 cRNA. Internally applied BDM (20 mM) rapidly and reversibly reduced peak macroscopic DRK1 current. 20 mM internal BDM increased the time constant of activation at all voltages (from 8.0 +/- 0.9 ms to 19.8 +/- 2.0 ms at zero mV, n = 6). Fluctuation analyses, and direct measurement of single channel currents, indicated that BDM reduced open probability (P0), and single channel current, at all voltages. The peak P0-voltage (V) relationship (estimated with a Boltzman equation) was shifted (from V0 = -29.3 +/- 4.6 to -9.4 +/- 2.7 mV) and shallowed (from Z = 2.8 +/- 0.2 to 1.8 +/- 0.15, n = 4) by BDM. In a simple sequential kinetic model of DRK1, the peak P0-V relationship, both in control and in BDM, was well fitted with the same V0 and Z (1.51 +/- 0.1 and -37.1 +/- 4 mV, respectively; n = 4) but with different voltage-independent rate constants. Thus, the effects of BDM on the kinetics of activation, the voltage-dependence of activation, and the rate of inactivation could be accounted for by assuming changes only in voltage-independent parameters.

Nutritional and physiological effects of casein modified by glucose, diacetyl, or hexanal.

Casein was modified by glucose, diacetyl, or hexanal at 50 degrees C, RH 75% for 1, 7, or 11 days. The chemical changes and digestibility in vitro of these nondialyzable caseins were investigated. The effects of these nondialyzable caseins supplemented with lost amino acids, on rats were studied by pair-feeding for 2 months. It was observed that internal organs such as liver, spleen, kidney, stomach, small intestine, cecum, colon and rectum were mostly unchanged. Biochemical values such as hematocrit, cholesterol, triglyceride, GPT, and GOT were also unchanged. However, the quantity of leucocytes was increased and serum glucose was decreased by feeding rats with modified caseins. Significant decrease in weight gain of rats fed with modified casein was observed, and the rate of decrease depended on the degree of modification of casein by carbonyl compounds. From these results, we supported the suggestion that some inhibitory or antinutritional compounds might be formed during the modification of casein by carbonyl compounds.