Hot topic: microstructure quantification by scanning electron microscopy and image analysis of goat cheese curd.

Five microstructural parameters of goat cheese curd (number of pores, their area and perimeter, strand thickness, and porosity) were studied by scanning electron microscopy and image analysis. Image analysis was used to characterize and quantify differences in all parameters and to provide a procedure for the measurement of strand thickness. The micrographs provided visual evidence of differences in the protein matrix and were quantified by image analysis at 3 production times: 34 ± 1 min (cutting), 154 ± 6 min (before molding), and 293 ± 35 min (after pressing). The data showed that this procedure is an adequate tool for quantifying differences in the parameters analyzed in industrial samples despite their natural heterogeneity. The procedure was reproducible and repetitive for the first 2 production times because no significant intragroup differences were observed. Significant differences were found when comparing the values of the microstructure parameters analyzed at 34 ± 1 min and those corresponding to 154 ± 6 min and 293 ± 35 min, but no significant differences between samples analyzed at 154 ± 6 min and 293 ± 35 min were found. All microstructure parameters analyzed were related at a significance level of at least 95%. This procedure enables the characterization of the microstructure of industrial goat cheese curd.

Modelos estructurales de la micela de caseína / Structural models for the casein micelle

La micela de caseína constituye un sistema coloidal muy estable en la leche. Este hecho tiene importantesimplicaciones prácticas relacionadas con la formación de los geles de caseína, así como con la estabilidad delos productos lácteos durante su tratamiento térmico, concentración y almacenamiento. Por este motivo, lamicroestructura de la micela de caseína ha sido intensamente estudiada durante las últimas cinco décadas. Apesar de ello, existen todavía muchas lagunas sobre su estructura y estabilidad, como se refleja en los resultadosderivados de recientes investigaciones basadas en el empleo de novedosas técnicas analíticas

Casein micelle constitutes a very stable milk colloidal system. This has significant practical implicationsespecially regarding to casein gel formation and stability of dairy products during heating, concentration andstorage. For that reason, the microstructure of the casein micelle has been intensively investigated during thelast five decades. However, specific questions about micelle structure and stability are still arising as new instrumentalmethodologies become available

Bienestar animal y calidad de la canal porcina según el sistema de aturdimiento / Animal welfare and pork carcass quality according to stunning system

En este trabajo se estudia la infl uencia de las técnicas tradicionales de aturdimiento por corriente eléctricay CO2 sobre el bienestar animal y la calidad de la canal, y se comparan con los obtenidos por otros autoresempleando sistemas de sujeción y aplicación instantánea de electronarcosis (Midas® y Piglift). Los resultadosmuestran que la aplicación de aturdido eléctrico convencional disminuye la calidad de la canal al aumentar laincidencia de fracturas óseas, petequias y hemorragias en piezas nobles, en comparación con el CO2. Medianteel aturdimiento en cámara de gases se obtiene una mejor calidad en la canal respecto a la electronarcosis,incluso cuando los animales experimentan reacciones convulsivas tras la misma como consecuencia de unaincorrecta aplicación de CO2 (elevada concentración y tiempo). En estos casos, se detecta un comportamientoanómalo en los cerdos —mayor estrés, defi ciente aturdimiento y desarrollo de convulsiones musculares— yen menor grado, los mismos problemas de calidad que los descritos en la electronarcosis. Por su parte, la proporciónde canales sin defectos de calidad supera el 94% en cerdos que no presentan reacción alguna tras elaturdimiento con CO2, muy por encima de cuando aparecen convulsiones (56,3%) o cuando se utiliza electronarcosis(14,4%). Con todo, la optimización de parámetros de anestesia con CO2 que eviten dichas reaccionespermitiría mejorar sustancialmente la calidad tecnológica de la canal

The aim of this paper was to study the infl uence of traditional stunning systems —electric and CO2 treatment—on animal welfare and carcass quality. Both systems were compared with them obtained by otherauthors using systems of immobilized and instantaneous application of electrical stunning (Midas® and Piglift). The results showed that the application of electrical stunning decreased carcass quality upon increasing theincidence of bone fractures, petechiaes and haemorrhages in noble pieces compared to CO2 stunning. CO2 stunningdetermined a better carcass quality, even when convulsive reactions after stunning were developed by pigslike consequence of an incorrect application of CO2 (high concentration and time). In these cases, an anomalousbehaviour in pigs —a greater stress, stunned faulty and stronger convulsions after stunning— and in small degree,the same problems of quality described in electric stunning, were detected. The proportion of carcasseswithout defects of quality was 94% in pigs that did not present reactions after CO2 stunning. When convulsionsappeared or electric stunning were used carcasses quality were 56,3% and 14,4%, respectively. Therefore, thecontrol of CO2 stunning parameters would avoid these reactions in pigs and improve the technological carcassquality outstandingly

Oxidación del colesterol en carne y derivados: Factores que determinan su formación / Cholesterol oxides in meat and meat products: formation determining factors

La oxidación del colesterol de la carne da lugar a una amplia gama de compuestos secundarios potencialmente tóxicos para el organismo, estando inversamente relacionada con la estabilidad oxidativa del resto de lípidos de la matriz cárnica. Tanto la especie animal como el aporte graso de la dieta condicionan el grado de insaturación de los lípidos y, en consecuencia, la síntesis de óxidos del colesterol en carne fresca. La mayor parte de técnicas de procesado, especialmente el cocinado y los tratamientos de irradiación, incrementan drásticamente la velocidad de formación de oxisteroles. Por otra parte, la síntesis de óxidos del colesterol puede verse reducida, tanto mediante técnicas de envasado en atmósferas protectoras y/o almacenamiento en congelación, como mediante la utilización de antioxidantes. En este último sentido, la suplementación de la dieta con vitamina E viene siendo considerada como uno de los métodos más eficaces para disminuir el grado de acumulación de este tipo de compuestos en carne fresca y productos cárnicos procesados (AU)

Cholesterol oxidative reactions in meats lead to a production of potentially toxic secondary compounds. Lipid and cholesterol oxidative stability are closely related. The amount and composition of cholesterol oxidation products in fresh meat varied significantly depending on animal species and dietary fat intake, since both factors determine the degree of unsaturation of meat fat. Most of processing methods, such as cooking or irradiation treatments, considerably increase the oxysterols formation rate. On the other hand, protective atmospheres packaging and/or frozen storage, and the incorporation of antioxidants minimize cholesterol oxidation. In this sense, vitamin E dietary supplementation is a powerful tool in order to prevent their synthesis in fresh and processed meat products (AU)

Isolation and characterisation of resistant-to-fermentation carbohydrate polymers from cultures of Rhizopus nigricans grown on agrofood waste materials.

Rhizopus nigricans was cultivated in a liquid medium using lemon, mandarin, orange, pear and melon peel or artichoke bracts as the carbon source. In all cultures, a carbohydrate polymer fraction remained resistant to fermentation. These fractions were isolated in gram amounts and characterised. The molecular weight distribution of the fractions and its sugar composition resembles those of the hairy-regions of the pectins. In the fractions, four main carbohydrates were found: 4-7 mol% Rha, 42-59 mol% Ara, 7-14 mol% Gal, 17-33 mol% GalA.

Determinación on-line del tiempo de coagulación en leche de cabra mediante dispersión de radiación nir / On-line determination of clotting time in goat's milk by backscatter of near infrared radiation

En el presente trabajo se estudia un sensor de fibra óptica que, instalado en línea, monitoriza la coagulación de la leche de cabra. El sensor determina el incremento de reflectancia difusa (880 nm) provocado por las modificaciones físico-químicas que causan la formación del gel de caseína. Los resultados obtenidos demuestran la fuerte correlación (R2 = 0,99) existente entre la variable de reflectancia difusa Tmax y el tiempo de coagulación de Berridge, parámetro de referencia para el estudio de la actividad de las enzimas coagulantes. Se observa que Tmax constituye un 89 por ciento del tiempo de coagulación de Berridge, lo que se atribuye a una mayor sensibilidad frente a la agregación del parámetro Tmax. Se estima que el porcentaje de hidrólisis de la K-caseína a tiempo Tmax es del 78 por ciento. Los resultados experimentales demuestran que Tmax no sólo responde a los cambios de concentración de enzima según la ecuación de Foltmann, sino que también refleja fielmente los efectos del resto de factores estudiados. Por su gran sensibilidad a la agregación y consistente capacidad de respuesta a los factores de la coagulación, Tmax representa una alternativa al método de Berridge y/o es útil como parámetro de predicción del tiempo de coagulación, lo que justifica el interés del sensor de dispersión como herramienta de control de proceso (AU)

Objective assessment of pork quality.

Several objective methods for estimating pork quality were studied: internal light scattering (FOP), electrical conductivity (EC), pH, colour, water holding capacity (WHC), soluble proteins (SP), pigment content, intramuscular fat (i.m. fat), and moisture. The measurements were made on the Semimembranosus and Longissimus thoracis at 45 min and 24 h post mortem in some cases and on the Semimembranosus in others. Most of the measurements are significantly different between normal, PSE and DFD quality categories. There is a good correlation between pH values in both muscles: pH(45)SM-pH(45)LT (r=0.74) and pH(24)SM-pH(24)LT (r=0.71). At 45 min the correlation of EC with FOP and pH was r=0.56 and r=0.48 respectively. Lower correlations were found in other parameters. The results from principal component analysis (PCA) showed that the three first components explained 60.3% of the total variation and the most important variables for the first PC were pH(45) and EC(45).

Objective meat quality measurements of ham: A practical classification method on the slaughterline.

Meat quality is one of the principal problems in Spanish dry cured ham productuon. At the experimental level, there are well developed objective instrumental measurements which can be made on the slaughterline and then, by applying the correct statistical treatment, these measurements can be used to classify hams with an acceptable degree of accuracy. These treatments, however, are not easy to apply in the industry. In this work, 312 pork carcasses were tested at three industrial abbatoirs. Ham meat quality was determined by internal light scattering (FOP), electrical conductivity (EC) and pH measurements in Semimembranosus (SM) muscle at 45 min and 24 h post mortem. The results obtained were: 21 (6.7%) DFD; 168 (53.9%) slightly DFD; 104 (33.3%) normal; 11 (3.5%) slightly PSE; and 8 (2.6%) PSE. A simplified method has been developed for classifying hams into quality categories, by deriving a theoretical quality value (Q) based on a simple statistical treatment of values for FOP, EC and pH. The multiple linear regression coefficient of Q was R(2) = 0.85 (P<0.001) with respect to the experimental variables.