ABSTRACT
Edible coatings are safe, legal, and sensory acceptable for food applications and they can be incorporated as natural additives due to their antimicrobial activity, thickening capacity, nutrient content, and bioactive agents for protecting seafood from physical, chemical, and microbiological damage that affects its shelf-life. This study aimed to evaluate the effect of the guar gum bioactive coating with thyme oil on the quality of tilapia fish fillets for 15 days of storage at 4 °C, as a means to extend shelf-life. pH, moisture, ash, fat, color, thiobarbituric acid reactive substances (TBARS), total volatile basic nitrogen (TVB-N), microbiological, and sensory examinations were investigated, and the results were analyzed by analysis of variance. The treatments were control (uncoated, UC), GGC (coated with guar gum, GGC), and guar gum combined with thyme oil (GGCTH). Tilapia fillets were stored at 4 °C, the safe temperature for refrigerated storage for 15 days. GGCTH had a slower increase of pH after 15 days of storage in comparison with GGC and UC (p < 0.05). GGC and GGCTH resulted in lower and lowest lightness (L*; p < 0.05) values, lower and lowest redness (a*; p < 0.01) values, and greater and greatest yellowness (b*; p < 0.05) values compared to UC, respectively. UC reduced shear force at 5 (0.37 kgf), 10 (0.32 kgf), and 15 (0.30 kgf) days post-storage in comparison with GGC (0.43, 0.43, and 0.43 kgf) and GGCTH (0.43, 0.44, and 0.44 kgf), respectively. There was less (p < 0.05) deterioration, as well as differences in textural and sensorial variables between uncoated and coated fish fillets. The microbiological analyses demonstrated that there was greater microbial growth in the uncoated fillets than in the coated ones. It was concluded that this bioactive coating with thyme oil retards microbial colonization of fish and reduces degradability of quality variables, therefore, it is a reliable and effective alternative to extend the shelf-life of tilapia fillets.
ABSTRACT
Fungal hydrolysis of ellagitannins produces hexahydroxydiphenic acid, which is considered an intermediate molecule in ellagic acid release. Ellagic acid has important and desirable beneficial health properties. The aim of this work was to identify the effect of different sources of ellagitannins on the efficiency of ellagic acid release by Aspergillus niger. Three strains of A. niger (GH1, PSH and HT4) were assessed for ellagic acid release from different polyphenol sources: cranberry, creosote bush, and pomegranate used as substrate. Polyurethane foam was used as support for solid-state culture in column reactors. Ellagitannase activity was measured for each of the treatments. Ellagic acid was quantified by high performance liquid chromatography. When pomegranate polyphenols were used, a maximum value of ellagic acid (350.21 mg/g) was reached with A. niger HT4 in solid-state culture. The highest amount of ellagitannase (5176.81 U/l) was obtained at 8 h of culture when cranberry polyphenols and strain A. niger PSH were used. Results demonstrated the effect of different polyphenol sources and A. niger strains on ellagic acid release. It was observed that the best source for releasing ellagic acid was pomegranate polyphenols and A. niger HT4 strain, which has the ability to degrade these compounds for obtaining a potent bioactive molecule such as ellagic acid.
La hidrólisis fúngica de los elagitaninos produce ácido hexahidroxidifénico, considerado como una molécula intermedia en la liberación de ácido elágico. El ácido elágico tiene importantes y deseables propiedades benéficas para la salud humana. El objetivo de este trabajo fue identificar el efecto de la fuente de elagitaninos sobre la eficiente liberación de ácido elágico por Aspergillus niger. La liberación de ácido elágico se realizó con tres cepas de A. niger (GH1, PSH y HT4) en presencia de diferentes fuentes de polifenoles (arándano, gobernadora y granada), usadas como sustrato. Se empleó espuma de poliuretano como soporte para el cultivo en estado sólido en reactores en columna. Se midió la actividad elagitanasa a cada uno de los tratamientos. El ácido elágico liberado se cuantificó por cromatografía líquida de alta resolución. Cuando se utilizaron los polifenoles de granada, se alcanzó un valor máximo de 350,21 mg/g de ácido elágico con A. niger HT4 en cultivo en estado sólido. La mayor actividad elagitanasa (5176.81 U/l) se obtuvo a 8 h de cultivo cuando se usaron los polifenoles de arándano como sustrato y A. niger PSH. Los resultados demostraron el efecto que tiene la fuente de polifenoles y la cepa de A. niger en la liberación de ácido elágico. Se observó que la mejor fuente para la liberación de ácido elágico fueron los polifenoles de granada y que la cepa A. niger HT4 posee la habilidad de degradar estos compuestos para la obtención de potentes moléculas bioactivas, como el ácido elágico.
Subject(s)
Aspergillus niger/isolation & purification , Ellagic Acid/analysis , Polyphenols/analysis , Aspergillus niger/physiology , Chromatography, High Pressure Liquid/methodsABSTRACT
Fungal hydrolysis of ellagitannins produces hexahydroxydiphenic acid, which is considered an intermediate molecule in ellagic acid release. Ellagic acid has important and desirable beneficial health properties. The aim of this work was to identify the effect of different sources of ellagitannins on the efficiency of ellagic acid release by Aspergillus niger. Three strains of A. niger (GH1, PSH and HT4) were assessed for ellagic acid release from different polyphenol sources: cranberry, creosote bush, and pomegranate used as substrate. Polyurethane foam was used as support for solid-state culture in column reactors. Ellagitannase activity was measured for each of the treatments. Ellagic acid was quantified by high performance liquid chromatography. When pomegranate polyphenols were used, a maximum value of ellagic acid (350.21 mg/g) was reached with A. niger HT4 in solid-state culture. The highest amount of ellagitannase (5176.81 U/l) was obtained at 8h of culture when cranberry polyphenols and strain A. niger PSH were used. Results demonstrated the effect of different polyphenol sources and A. niger strains on ellagic acid release. It was observed that the best source for releasing ellagic acid was pomegranate polyphenols and A. niger HT4 strain, which has the ability to degrade these compounds for obtaining a potent bioactive molecule such as ellagic acid.
