José A. Rufián-Henares

Antimicrobial activity of coffee melanoidins - a study of their metal-chelating properties.

Melanoidins comprise a substantial proportion of severely heat-treated foods such as baked cereals or roasted coffee and are widely consumed dietary components. The antimicrobial activity of coffee melanoidins against different pathogenic bacteria has been studied, finding that such activity is due to their metal-chelating properties. Three different mechanisms have been observed: at low concentrations melanoidins exerted a bacteriostatic activity mediated by iron chelation from the culture medium; in the case of bacterial strains that are able to produce siderophores for iron acquisition, melanoidins chelate the siderophore-Fe3+ complex, which could decrease the virulence of such pathogenic bacteria; and, finally, coffee melanoidins also exerted a bactericide activity at high concentrations by removing Mg2+ cations from the outer membrane, promoting the disruption of the cell membrane and allowing the release of intracellular molecules.

Assessment of hydroxymethylfurfural intake in the Spanish diet

Estimation of hydroxymethylfurfural (HMF) exposure of the Spanish population from heat-processed food was performed. HMF levels in Spanish foods were obtained from the data previously published in peer-reviewed papers; in addition, it was identified which food categories contributed significantly to HMF exposure. The potential HMF exposure was calculated for three different scenarios by using individual food intakes and the minimum (scenario 1), median (scenario 2) and maximum (scenario 3) values of analytical data on the HMF content in foods. A mean HMF intake of 10 mg day−1 (corresponding to scenario 2) was obtained, which is only ten-fold lower than the tolerable daily intake. Coffee and bread are the most important food items that contribute nearly 85% to the total HMF daily exposure, although biscuits, breakfast cereals, beer, UHT milk and tomato products are also important for HMF exposure.

Acrylamide content of selected Spanish foods: Survey of biscuits and bread derivatives

An overview of the acrylamide content in commercial biscuits and bread derivatives (bread sticks, bread crust, crackers) marketed in Spain is presented. Acrylamide was determined by stable isotope dilution LC–MS with an LOQ of 30u2009µgu2009kg−1. Acrylamide content ranged from <LOQ–2085, <LOQ–151, <LOQ–296 and <LOQ–323u2009µgu2009kg−1 for biscuits, crisp bread, crackers and bread sticks, respectively. Acrylamide was significantly higher in samples when ammonium hydrogen carbonate had been used as a rising agent and high fibre content (>5%) used in the formulation, but lower when functional ingredients, such as polyols, were used. An estimation of the acrylamide dietary exposure related to biscuits and bread derivatives was calculated as 0.082u2009µgu2009kg−1u2009day−1. Estimated dietary intake were 0.002 and 0.058u2009µgu2009kg−1u2009day−1 for crackers and biscuits, respectively.

Biscuit melanoidins of different molecular masses protect human HepG2 cells against oxidative stress.

Soluble melanoidins from biscuits were enzymatically solubilized and isolated by sequential ultrafiltration and separated by molecular mass in three different fractions, below 3 kDa, between 3 and 10 kDa, and over 10 kDa; the latter was subsequently digested by simulating gastric plus pancreatic digestive conditions. The four fractions were investigated for their protective effect against an oxidative challenge in HepG2 cells. Pretreatment of cells for 20 h with 0.5-10 microg/mL of any of the four fractions prevented the increased cell damage evoked by the challenge but, except for the intermediate size fraction, did not suppress the increased reactive oxygen species. Antioxidant defenses were rapidly restored after the challenge, and the increase of the oxidative stress biomarker malondialdehyde was prevented by the pretreatment with all but the undigested high molecular mass fraction. The results show that treatment of HepG2 cells with concentrations of biscuit melanoidins within the expected physiological range confers on the cells a significant protection against an oxidative challenge.

Contribution of melanoidins to the antioxidant capacity of the Spanish diet

Most foods included within the western diet are subjected to heat processing. During such treatment, the Maillard reaction takes place, generating brown polymers known as melanoidins. Melanoidins could have health beneficial properties such as chemopreventive, antimicrobial or antioxidant capacity. Here we have established the content of melanoidins in thermally processed foods consumed regularly in the Spanish diet (chocolate, sweet wine, balsamic vinegar, beer, bread, breakfast cereals and biscuits) and their antioxidant capacity by different in vitro methodologies (ABTS, FRAP, DPPH, ORAC, HOSC). The mean intake of melanoidins is 12.2g/person/day within the Spanish diet, bread, pilsner beer and biscuits being the foods that contributed most. The most antioxidant melanoidins were those from coffee, followed by balsamic vinegar and sweet wine. Finally, the average intake of antioxidant capacity coming from melanoidins was 717 μmol Trolox/day, melanoidins from coffee, biscuits, pilsner beer and chocolate being those which possessed more antioxidant capacity.

Maillard reaction in enteral formula processing: furosine, loss of o-phthaldialdehyde reactivity, and fluorescence

Abstract In order to evaluate heat effects induced during the manufacture of enteral formula, the following indicators were determined: furosine; loss of available amino groups, measured by decrease in o-phthaldialdehyde (loss of OPA reactivity); and fluorescence intensity (FI) associated with Maillard reaction (345 nm excitation, 415 nm emission). In addition, furosine and fluorescence were determined in model systems performed with the protein and carbohydrate ingredients of these products. The precision obtained for furosine, loss of OPA reactivity and fluorescence was 2.93, 1.89 and 1.72%, respectively. Furosine values decreased during the manufacturing process (UHT, standardization and sterilization). Heating at 120xa0°C produced a decrease in furosine content in model systems with whey proteins and an increase in systems with casein-carbohydrates. During the manufacturing, the loss of OPA reactivity reached 26.5 and 14% in the two types of formulas assayed. FI increased during heating in the formula processing and model systems

DETERMINATION OF FURFURAL COMPOUNDS IN ENTERAL FORMULA

HPLC methods are described for the determination of furanic compounds (hydroxymethylfurfural and furfural) in enteral formulas prepared with dextrinomaltose and milk proteins, and in model systems enclosing these ingredients. These compounds were extracted in aqueous solution, purified with organic solvents, and separated in a reversed-phase C18 column with water-acetonitrile (95:5 v/v). Average recovery rates of HMF and furfural were 99.2% and 71.1%, respectively. The variation coefficients for HMF and furfural were 2.41% and 1.23%, respectively. The detection limit was 0.01 mg/L for both compounds. HMF and furfural levels in enteral formulas ranged from 0.05 to 19.1 mg/L and from 0.14 to 0.72 mg/L, respectively.

Nutritional and physicochemical characteristic of commercial Spanish citrus juices

Citrus juices are perceived as healthy foods by consumers due to their richness in antioxidant compounds. Despite the large number of papers about the antioxidant activity of citrus juices, less is known about the relationship with physicochemical properties. This paper shows that the overall antioxidant activity of citrus juices is underestimated with the standard methodologies, being up to 10-times higher with the GAR method (including an in vitro gastrointestinal digestion). 70% of the antioxidant activity was found in the soluble fraction and citrus juices contributed up to 12% of the overall antioxidant intake within the Spanish diet. Physicochemical parameters, such as colour, fluorescence, 5-hydroxymethylfurfural and furfural contents, were correlated with nutritional parameters in some samples. The intake of HMF was negligible from commercial citrus juices and was absent in freshly squeezed ones. Finally, a mathematical model is developed to classify juices depending on their nature or storage conditions.

Melanoidins in Coffee

Abstract Coffee roasting influences the taste of the coffee brew by physically and chemically changing the coffee seed. Different compounds found in green coffee beans, such as proteins, polysaccharides, and phenolic compounds, are degraded/transformed to some extent, giving rise to a decrease of the amount of carbohydrates and chlorogenic acids and the appearance of melanoidins. Melanoidins are brown nitrogen-containing polymers produced during the last steps of the Maillard reaction. The amount of coffee melanoidins accounts for up to 25% of roasted coffee beans, and their presence increases with the severity of roasting. The different melanoidin fractions exert a large variety of biological activities according to their different chemical composition and/or structure. Therefore, the understanding of the structure and formation of coffee melanoidins is a relevant issue in the food chemistry field.

Biological Effects of Coffee Melanoidins

Coffee melanoidins are brownish high-molecular-weight compounds produced during coffee roasting. There are a plethora of fractions with different chemical composition–structure and probably different biological effects behind the term “coffee melanoidins.” Such biological activities include antioxidant, antimicrobial, antihypertensive, prebiotic, chelating, or even detoxifying activities. These biological properties could even increase the shelf life of foods by decreasing lipid oxidation or avoiding the overgrowth of pathogen microorganisms. Then, coffee melanoidins are pluripotent compounds that could be used in the near future for the formulation of new functional foods with improved organoleptic and/or technological properties.