RESUMEN
This review discusses the basic chemical reactions that affect food flavor quality. Although there are many reactions that can lead to the deterioration of quality in foods, this review focuses on lipid oxidation and how it adversely affects flavor principals. It also presents technological advances for studying the basic mechanism of lipid oxidation, for measuring its intensity, and for retaining food quality. The food commodities that provide the subject matter for this review include vegetable oils, legumes, cereal grains, eggs, beef, lamb, poultry, seafoods, and catfish. The methodologies for assessing food quality form a multidisciplinary approach that includes primarily instrumental analysis by direct gas chromatography, chemical analysis by the TBA test, and sensory analysis by quantitative descriptive determinations. The author hopes that the information presented in this review is applicable to food commodities not discussed.
Asunto(s)
Alimentos , Peroxidación de Lípido , Antioxidantes , Cromatografía de Gases , Alimentos/normas , Control de Calidad , Gusto , TiobarbitúricosRESUMEN
Several effects of peroxides on protein have been described in the literature. Some of the effects have been ascribed to alterations in protein conformation but this has never been examined directly. This paper described responses of peanut storage globulin (arachin) to rancid oil and hydrogen peroxide as measured by electrophoretic mobility, antigenicity and circular dichroism of the globulin. Rancid oil and 3% hydrogen peroxide had little effect on these properties but 30% hydrogen peroxide increased the mobility, abolished the antigenicity and reduced the ordered structural modes of the protein. The results indicated that changes in protein conformation do not occur after contact with organoleptically rancid oil or dilute peroxides but do occur with concentrated peroxides.
Asunto(s)
Peróxidos , Proteínas de Plantas , Arachis , Dicroismo Circular , Epítopos/análisis , Inmunodifusión , Proteínas de Plantas/aislamiento & purificación , Conformación ProteicaRESUMEN
Lipoxygenase, prepared from Virginia-type peanuts, was used to catalyze the oxidation of linoleic acid and methyl linoleate to form the C-9 and C-13 hydroperoxides. These reactions were monitored by rapid unconventional direct gas chromatography-mass spectroscopy. An aliquot of the enzymatic reaction mixture, without prior extraction or chemical modification, was secured directly into the heated (40-70 C) or nonheated (room temperature) injection system. When the reaction mixture was analyzed at room temperature, only hexanal was found. At elevated temperatures, five major and several minor components were identified. The predominant compounds identified were pentane, hexanal, 2-pentylfuran, trans-2,cis-4-decadienal, and trans-2,trans-4-decadienal. These products originate from decomposition of either the C-9 or C-13 hydroperoxides generated by peanut lipoxygenase.
Asunto(s)
Ácidos Linoleicos/metabolismo , Lipooxigenasa/metabolismo , Arachis , Cromatografía de Gases , Ácidos Linoleicos/análisis , Peróxidos Lipídicos/análisisRESUMEN
Shelled brown rice (100 g/bag) was packed in regular plastic bags in air, in laminated film (nylon-EVA) bags in air, and in laminated bags plus CO2. Samples of each were stored in the dark at 4 C and at 24 C, and samples were removed after 1, 3, 5 and 7 months for analysis of odor changes, free fatty acids, total microbial counts, total lipolytic fungi and bacteria, lipid peroxides and gas chromatographic volatiles profiles. Brown rice in laminated bags plus CO2 was more stable under refrigerated conditions than at ambient temperatures. However, at 24-C storage there was no consistent significant decrease in free fatty acids, lipid peroxides and volatile compounds in these bags compared to the other types of packing. Laminated bags seem to have had an adverse effect on total microbial populations at both 4 and 24 C. Selection of either type of package for brown rice would be governed by end use, storage time and conditions.
RESUMEN
Acidic and alkaline lipoxygenase isozymes were separated and assayed for activity while incubated in the presence of various concentrations of cyanide. Inhibition due to cyanide per se was not found. Instead, cyanide caused an increase in pH, which decreased the activity of the acidic isozyme to a rate corresponding to the same pH on the activity curve for the cyanide-free reaction.
Asunto(s)
Cianuros/farmacología , Lipooxigenasa/metabolismo , Semillas/enzimología , Arachis , Concentración de Iones de Hidrógeno , CinéticaRESUMEN
Lipoxygenase activity in three cultivars (purple, green, and white) of eggplant, Solanum melongena, were compared. Activity was greatest in the purple and lowest in the white variety. In contrast to reports that NaCN did not inhibit eggplant lipoxygenase, in these studies cyanide completely inhibited the enzyme in all three varieties.