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Browning Reaction (browning + reaction)
Selected AbstractsBrowning reactions during storage of low-moisture Australian sultanas: Further evidence for arginine-mediated Maillard reactions during storage, and some effects of vine-shading and harvest dateAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 3 2004DAMIAN FRANK Abstract Sultana grapevines (Vitis Vinifera L. cv. Sultana syn. Thompson Seedless) were subjected to four shading regimes: 50% shading (1), 25% shading (2), fully exposed-top of canopy (3) and beneath canopy (4) and harvested early (21 February) and late (13 March) in the 1996/1997 sultana season. Grapes from each of the eight field-treatment combinations represented a range of maturities (14.4 to 23.50oBrix). Grape samples from each of the treatments were dipped and dried to 18% moisture, with half of each of the sultana samples further reduced in moisture by sunfinishing on plastic sheets in direct sun. These field treatments resulted in sixteen unique dried sultana bulk samples with a range of initial chemico-physical properties; aw (0.481,0.691), skin-polyphenoloxidase (PPO) activity (4.40,9.05 ,mol O2/g.minute) free arginine in skin tissues (1.0,5.10 mg/g) and protein (16.40,27.18 mg/g). Sultanas were stored at 10oC and 30oC in either the presence or absence of oxygen for 10 months, and changes in CIE L*a*b* tristimulus values, hue-angle (hab*) and chroma (Cab*) were monitored. Significant changes in sultana colour occurred in samples stored at 30oC, especially in higher aw non-sunfinished sultanas. Although browning was more intense in the presence of oxygen, significant browning also occurred in the absence of oxygen. Lower concentrations of 5-hydroxy methylfurfural, a key marker of Maillard browning in samples stored at 30oC in the presence of oxygen, indicated that the non-enzymatic reactions were sensitive to oxygen. Changes in the concentration of trans -caftaric acid, the main substrate of grape PPO, were also measured during sultana drying. Storage browning (changes in L*, b*, hab*, Cab*)in dried sultanas could be predicted by regression models using pre-storage aw, free-skin arginine or Kjeldahl protein after 10 months' storage between 10oC and 30oC. Non-enzymatic and Maillard-type reactions (sensitive to both oxygen and aw), made an important contribution to sultana storage browning. We provide only weak evidence that either shaded (immature) or green fruit was more susceptible to storage browning. [source] PHYSICO-CHEMICAL ANALYSES, SENSORY EVALUATION AND POTENTIAL OF MINIMAL PROCESSING OF PEJIBAYE (BACTRIS GASIPAES) COMPARED TO MASCARENES PALMSJOURNAL OF FOOD QUALITY, Issue 2010J. JOAS ABSTRACT A palm species native of South America, pejibaye (Bactris gasipaes), was recently introduced in Reunion Island in an attempt to diversify its agriculture. Morphological analyses highlighted the agronomic advantages of pejibaye including a high weight-to-harvest-date ratio compared to three mascarenes palm species. Sensory analyses by a trained panel allowed the elaboration of sensory profiles of the four palms tested. Ranking test done by 120 consumers revealed that pejibaye was preferred to the Mascarenes palms at the 5% level of significance and triangle test showed that Acanthophoenix rubra (red palm), the most cultivated species for the local market, was significantly different from pejibaje at the 1% level. Phenolic profiles revealed that pejibaye differed from the other species by a peak absorbing at 272 nm and weak polyphenol oxidase activities. As no browning reaction was observed in fresh cut pejibaye, this palm could be used for minimal processing (local and export market). PRACTICAL APPLICATIONS Sensorial characteristics of fresh hearts of palm are different of those of canned heart of palm, and fresh heart palms are generally preferred by consumers. However, the marketing of fresh palm is limited by the high level of oxidation of most of palm species. The high stability of pejibaye after cutting and its slow rate of oxidation offer the possibility of minimal processing, without special additives. So the packaging in wrapped trays of this palm, cut and stored at low temperature opens up new perspectives, ensuring sensorial quality of a "fresh" product with a shelf life allowing a controlled management of market supply. [source] The role of peptides and proteins in melanoidin formation,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2009Anna Smaniotto Abstract High-molecular-weight (HMW) coloured compounds called melanoidins are widely distributed, particularly in foods. It has been proposed that they originate through the Maillard reaction, a non-enzymatic browning reaction, due to the interaction between protein or peptide amino groups and carbohydrates. The melanoidin structure is not definitively known, and they have been generally defined as HMW nitrogen-containing brown polymers. In order to gain information on the nature of melanoidins, a simple in vitro model was chosen to investigate the products of the reactions between sugars and peptide/proteins. This approach would elucidate whether melanoidin formation is due to the binding of different sugar units to a peptide/protein or vice versa. With this aim, the reactivity of two different peptides, EPK177 and physalaemin, and a low-molecular-weight (LMW) protein, lysozyme, was tested towards different saccharides (glucose, maltotriose (MT), maltopentaose and dextran 1000) in aqueous solutions at different temperatures. The incubation mixtures were analysed at different reaction times by MALDI/MS. Furthermore, in order to verify the possible role of sugar pyrolysis products in melanoidin formation, the products arising from the thermal treatment at 200 °C of MT were incubated with lysozyme, and the reaction products were analysed by the same MS approach. The obtained results allowed the establishment of some general views: melanoidins cannot simply originate by reactions of sugar moieties with proteins. In fact, the reaction easily occurs, but it does not lead to any coloured product, as melanoidins have been described to be; melanoidins cannot originate from the thermal degradation products of glycated proteins. In fact, the thermal treatment of glycated lysozyme leads to a severe degradation of the protein with the formation of LMW species, far from the view of melanoidins as HMW compounds; experimental evidence has been gained on the melanoidin formation through reaction of intact protein with the pyrolysis products of MT. This hypothesis has been supported either from MALDI measurements or from spectroscopic data that show an absorption band in the range 300,600 nm, typical of melanoidins. Copyright © 2009 John Wiley & Sons, Ltd. [source] Induction of Phenolic Compounds in Pea (Pisum sativum L.) Inoculated by Rhizobium leguminosarum and Infected with Orobanche crenataJOURNAL OF PHYTOPATHOLOGY, Issue 11-12 2007Y. Mabrouk Abstract Parasitic plants are among the most important problematic weeds, they are responsible of major losses of many crops. Early growth stages, such as seed germination stimulated by host root exudates and tubercle development, are key phases for these parasites development. Inhibition of these early phases could be a general strategic option for parasitic plants management. In our previous study, we have demonstrated that some Rhizobium leguminosarum strains decrease pea infection by Orobanche crenata and germinated seeds enhanced browning symptoms. These observations suggested the probability of toxic compounds accumulation such as gallic acid and naringenin used as a defence strategy by inoculated pea plants. In this study, we demonstrate that these two phenolic compounds cause severe physiological disorder of germination broomrape seeds. They inhibited germination of O. crenata seeds induced by strigol analogue GR24, and caused a browning reaction in germinated seeds. [source] Effect of Equivalent Thermal Treatments on the Color and the Antioxidant Activity of Tomato PureeJOURNAL OF FOOD SCIENCE, Issue 9 2002M. Anese ABSTRACT: The influence of different heat treatments on color and antioxidant properties of tomato purees was investigated. The treatments were designed to produce the same total thermal effect against spoilage microorganisms. Although the development of nonenzymatic browning reactions occurred by increasing process temperature, no changes in redness were observed in the heated samples, due to the "masking" effect of lycopene. Also, the heat treatments had equivalent effect on the chain-breaking activity of the aqueous and lycopene tomato fractions. However the redox potential values increased as the heating temperature increased. All data together showed that the thermal resistance constant z values for color and chain-breaking activity were close to 10°C, but lower than 10°C for reducing properties. [source] Dropping macadamia nuts-in-shell reduces kernel roasting qualityJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 13 2010David A Walton Abstract BACKGROUND: Macadamia nuts (,nuts-in-shell') are subjected to many impacts from dropping during postharvest handling, resulting in damage to the raw kernel. The effect of dropping on roasted kernel quality is unknown. Macadamia nuts-in-shell were dropped in various combinations of moisture content, number of drops and receiving surface in three experiments. After dropping, samples from each treatment and undropped controls were dry oven-roasted for 20 min at 130 °C, and kernels were assessed for colour, mottled colour and surface damage. RESULTS: Dropping nuts-in-shell onto a bed of nuts-in-shell at 3% moisture content or 20% moisture content increased the percentage of dark roasted kernels. Kernels from nuts dropped first at 20%, then 10% moisture content, onto a metal plate had increased mottled colour. Dropping nuts-in-shell at 3% moisture content onto nuts-in-shell significantly increased surface damage. Similarly, surface damage increased for kernels dropped onto a metal plate at 20%, then at 10% moisture content. CONCLUSION: Postharvest dropping of macadamia nuts-in-shell causes concealed cellular damage to kernels, the effects not evident until roasting. This damage provides the reagents needed for non-enzymatic browning reactions. Improvements in handling, such as reducing the number of drops and improving handling equipment, will reduce cellular damage and after-roast darkening. Copyright © 2010 Society of Chemical Industry [source] | ||||||||||