Inactivation of polyphenoloxidase by pulsed light.

The effect of pulsed light on the inactivation of polyphenoloxidase (PPO) in model solutions was investigated focusing on the effect of enzyme concentration and total energy dose of the treatment. PPO inactivation increased with the dose of the treatment. Complete enzyme inactivation was achieved by pulsed light doses higher than 8.75 J cm(-2) . At low PPO concentrations (4 to 10 U), the enzyme resulted highly inactivated by pulsed light treatment. Further increase in enzyme units determined a progressive decrease in PPO inactivation. The latter was attributed to protein structural modifications including cleavage and unfolding/aggregation phenomena. PPO amounts higher than 10 U probably favoured enzyme conformations that were less prone to intermolecular rearrangements leading to inactivation.

Optimization of process for reduction of antinutritional factors in edible cereal brans.

Reduction of various antinutritional factors in cereal brans by different treatments (microwave heating, dry heating and wet heating) were studied. There was significant difference (p ≤ 0.05) in reduction of antinutritional factors of treated cereal brans except for dry heating at low temperature. Microwave heating at 2450 MHz for 2.5 min resulted in 53.85%, 57.21%, 65.00% and 100% reduction in phytic acid, polyphenols, oxalates and saponins, respectively. Wet heating resulted in maximum reduction in trypsin inhibitor activity (83.07%) at 110 °C for 25 min. Processing treatment resulted in increase in bulk density and slight darkening of the brans. The most effective method of detoxifying most of the toxicants was microwave heating for 2.5 min, and therefore it could be exploited for making treated brans an ideal source for potential food application.

Determinación de carboximetillisina en alimentos tostados y horneados / Determination of carboximetillysine in toasted and baked foods

La carboximetillisina (CML) es un indicador de etapas avanzadas de la reacción de Maillard. Su formación en los alimentos dependerá directamente de la composición de los mismos, pero también dela temperatura y tiempo de calentamiento al que se ven sometidos durante el procesado. Concretamente, se ve favorecida cuando el tratamiento térmico es más severo, de ahí que esté presente en alimentos tostados u horneados como los productos de panadería o bollería. En el presente trabajo se analizó el contenido de CML en 9 tipos de alimentos: pan integral, pan de molde tostado a diferentes tiempos, colines, torta de inés rosales, palmera, caracola, suizo y medianoche y galleta integral más o menos horneadas. La determinación de CML se realizó mediante cromatografía de gases acoplada a espectrometría de masas, previa reducción, hidrólisis y derivatización. Los valores de CML determinados en las muestras del estudio oscilaron entre 1,38 mg/100 g muestra (palitos no integrales) y 10,4 mg/100 g de muestra (galleta más tostada). El pan de molde mostró un incremento en el contenido de CML paralelo al tiempo de tostado, pasando de 6,31 mg/100 g sin tostar, a 6,44mg/100g con 1 minuto de tostado y a 8,95 mg/100 g con 6 minutos de tostado. En conclusión, es importante conocer la cantidad de CML que contiene un alimento, para controlar su ingesta, especialmente en los sometidos a tostado u horneado, ya que, como se ha comprobado en este estudio, el contenido de CML incrementa paralelamente al tratamiento térmico(AU)

Carboximetillysine (CML) is an indicator of advanced stages of Maillard reaction. Its formation in foods depends on their composition but, moreover, on temperature and time of thermal treatment whom they are submitted during processed. Particularly, it is favored when thermal treatment is more severe, with the result that it is present in toasted or baked foods such as bakery products. In the present study, CML content in 9 different foods was analyzed: integral bread, sliced bread which was toasted at different times, breadsticks, “inés rosales” cake, heart-shaped pastry, flaky pastry, bun with sugar and bun and integral biscuit more or less baked. Determination of CML was carried out by GCMS, after reduction, hydrolysis and derivatization. CML values in studied samples ranged from 1.38mg/100 g of sample (no integral breadsticks) to 10.4 mg/100 g of sample (more toasted biscuit). In sliced bread a relationship between CML content and time of toasting was observed, increasing from6.31 mg/100 g without toasting to 6.44 mg/100 g with 1 min and to 8.95 mg/100 g with 6 min of toasting. In conclusion, it is important to know CML content in foods in order to control its intake, especially in toasted or baked foods since, as it has been tested in this study, CML content is related to the thermal treatment(AU)

Determinación de acrilamida y furosina en harinas y papillas infantiles / Determination of acrylamide and furosine in flour and infant formulas

Una de las modificaciones más importantes inducidas en el alimento durante el calentamiento es la reacción de Maillard, donde participan aminoácidos y azúcares reductores, pudiendo producirse mejora de las características organolépticas del alimento pero también pérdida del valor nutritivo y aparición de compuestos tóxicos. Los cereales infantiles son hidrolizados durante el procesado, aumentando los niveles de azúcares reductores, por lo que en el tostado o desecado de estas muestras puede favorecerse el desarrollo de la reacción de Maillard. Los niños son especialmente susceptibles ala disminución del valor nutritivo y al consumo de compuestos potencialmente tóxicos, de ahí la importancia de conocer el grado de desarrollo de esta reacción en dichos productos. En este estudio se determinó el contenido de acrilamida y furosina en harinas crudas y tostadas y en papillas infantiles, con el fin de evaluar la extensión de la reacción de Maillard. El contenido de furosina osciló entre11,5-34,6 mg/100 g de proteínas en las muestras de harinas y entre 122-1193 mg/100 g de proteínas en las muestras de papillas. No se detectó acrilamida en las muestras de harinas y osciló entre 0,22 y 9,6Cg/kg en las papillas. Las pérdidas de lisina pueden considerarse altas en algunas muestras, pero no suponen riesgo de déficit nutricional al consumirse estos productos con leche. La acrilamida sólo se encontró en niveles cuantificables en cuatro muestras y en concentraciones muy bajas; éstas se encuentran lejos de la dosis máxima permitida y por lo tanto no deberían representar problemas adversos tras su consumo(AU)

One of the most important modifications originated in foods during thermal treatment is Maillard reaction, in which amino acids and reducing sugars are participants. This reaction can improve the organoleptic characteristics of foods but, moreover, can lead to nutritional value losses and apparition of toxicological compounds. Infant cereals are hydrolyzed during processing, increasing reducing sugar levels thereby Maillard reaction can be favored in toasted or dried samples. Infants are especially susceptible to the decreased nutritional value and to the toxicological compounds consumption. Thus it is important to know the development rate of this reaction in these products. In this study acrylamide and furosine content in raw and toasted flour and in infant formulas were determined, in order to evaluate Maillard reaction evolution. Furosine content ranged from 11.5 to34.6 mg/100 g of proteins in toasted flour samples and from 122 to 1193 mg/100 g of proteins in formula samples. Acrylamide was not detected in flour samples ranging from 0.22 and 9.6 Cg/kg in formula samples. Lysine losses can be considered to be high in several samples, but it does not suppose a nutritional deficiency risk because these products are consumed together with milk. Acrylamide only was found in quantified levels in four samples and in very low concentrations. These values are lower than the maximum dose allowed and, therefore, they should not represent adverse problems after their consumption(AU)

Microwave-assisted Maillard reactions for the preparation of advanced glycation end products (AGEs).

The application of microwaves as an efficient form of volumetric heating to promote organic reactions was recognized in the mid-1980 s. It has a much longer history in the food research and industry where microwave irradiation was studied in depth to optimize food browning and the development of desirable flavours from Maillard reactions. The microwave-promoted Maillard reaction is a challenging synthetic method to generate molecular diversity in a straightforward way. In this paper we present a new rapid and efficient one-pot procedure for the preparation of pentosidine and other AGEs under microwave irradiation.

Evolution of quality characteristics of minimally processed asparagus during storage in different lighting conditions.

The effect of different types of lighting (white, green, red, and blue light) on minimally processed asparagus during storage at 4 degrees C was studied. The gas concentrations in the packages, pH, mesophilic counts, and weight loss were also determined. Lighting caused an increase in physiological activity. Asparagus stored under lighting achieved atmospheres with higher CO(2) and lower O(2) content than samples kept in the dark. This activity increase explains the greater deterioration experienced by samples stored under lighting, which clearly affected texture and especially color, accelerating the appearance of greenish hues in the tips and reddish-brown hues in the spears. Exposure to light had a negative effect on the quality parameters of the asparagus and it caused a significant reduction in shelf life. Hence, the 11 d shelf life of samples kept in the dark was reduced to only 3 d in samples kept under red and green light, and to 7 d in those kept under white and blue light. However, quality indicators such as the color of the tips and texture showed significantly better behavior under blue light than with white light, which allows us to state that it is better to use this type of light or blue-tinted packaging film for the display of minimally processed asparagus to consumers.

On the time behaviour of the concentration of pyrazinium radical cations in the early stage of the Maillard reaction.

During the early stage of the Maillard reaction pyrazinium radical cations were detected by ESR within the reaction system d-glucose/glycine. The spectra were characterized by completely resolved hyperfine structure. The partial pressure of oxygen and the radical concentrations were measured directly in the reaction mixture by ESR using solutions of the spin probe TEMPOL and of DPPH, respectively. There are quantitative and qualitative relations of the actual concentration of the radical ions to the partial pressure of oxygen, the temperature-time regime and the mechanical mixing of the reaction system. These macroscopic parameters significantly affect both the induction period and the velocity of the time-dependent formation of free radicals. From in situ variations of p(O2) and p(Ar) including the connected mixing effects caused by the passing the gases through the reaction mixture, steric and chemical effects of the stabilization of the radical ions were established. The determination of suitable and relevant conditions for stabilization and subsequent radical reactions contributes to the elucidation of the macroscopically known antioxidant activity of Maillard products.