Magnetic Resonance Imaging, texture analysis and regression techniques to non-destructively predict the quality characteristics of meat pieces

The quality of meat products is traditionally assessed by chemical or sensorial analysis, which are time consuming, need specialized technicians and destroy the products. The development of new technologies to monitor meat pieces using non-destructive methods in order to establish their quality is earning importance in the last years. An increasing number of studies have been carried out on meat pieces combining Magnetic Resonance Imaging (MRI), texture descriptors and regression techniques to predict several physico-chemical or sensorial attributes of the meat, mainly different types of pig ham and loins. In spite of the importance of the problem, the conclusions of these works are still preliminary because they only use the most classical texture descriptors and regressors instead of stronger methods, and because the methodology used to measure the performance is optimistic. In this work, we test a wide range of texture analysis techniques and regression methods using a realistic methodology to predict several physico-chemical and sensorial attributes of different meat pieces of Iberian pigs. The texture descriptors include statistical techniques, like Haralick descriptors, local binary patterns, fractal features and frequential descriptors, like Gabor or wavelet features. The regression techniques include linear regressors, neural networks, deep learning, support vector machines, regression trees, ensembles, boosting machines and random forests, among others. We developed experiments using 15 texture feature vectors, 28 regressors over 4 datasets of Iberian pig meat pieces to predict 39 physico-chemical and sensorial attributes, summarizing16,380 experiments. There is not any combination of texture vector and regressor which provides the best result for all attributes tested. Nevertheless, all these experiments provided the following conclusions: (1) the regressor performance, measured using the squared correlation (R2), is from good to excellent (above 0.5625) for 29 out of 39 attributes tested; (2) the WAPE (Weighted Absolute Percent Error) is lower than 2% for 32 out of 37 attributes; (3) the dispersion in computer predictions around the true attributes is lower or similar than the dispersion in the labeling expert’s for the majority of attributes (85%); and (4) differences between predicted and true values are not statistically significant for 29 out of 37 attributes using the Wilcoxon ranksum statistical test. We can conclude that these results provide a high reliability for an automatic system to predict the quality of meat pieces, which may operate on-line in the meat industries in the futureThe authors wish to acknowledge the funding received from the FEDER-MICCIN Infrastructure Research Project (UNEX-10-1E-402), Junta de Extremadura economic support for research group (GRU15173 and GRU15113), from the Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2016–2019) and from the European Union (European Regional Development Fund — ERDF)S

Feature extraction algorithms from MRI to evaluate quality parameters on meat products by using data mining

This thesis proposes a new methodology to determine the quality characteristics of meat products (Iberian loin and ham) in a non-destructive way. For that, new algorithms have been developed to analyze Magnetic Resonance Imaging (MRI), and data mining techniques have been applied on data obtained from the images.The general procedure consists of obtaining MRI of meat products, and applying different computer vision algorithms (texture and fractal approaches, mainly), which allow the extraction of sets of computational features. Figure 1 shows the design of the proposed procedure.To achieve this, different research have been done, based on:high-field and low-field MRI scannersdifferent acquisition sequences: Spin Echo (SE), Gradient Echo (GE) and Turbo 3D (T3D)different texture approaches: Gray Level Co-occurrence Matrix (GLCM), Gray Level Run Length Matrix (GLRLM) and Neighboring Gray Level Dependence Matrix (NGLDM)fractals algorithms: Classical Fractal Algorithm (CFA), Fractal Texture Algorithm (FTA) and One Point Fractal Texture Algorithm (OPFTA)FTA [1] and OPFTA [2] have been developed in this thesis. They allow analyzing MRI images, properly, noting OPFTA for its simplicity and lower computational cost. At the same time, the meat products, Iberian hams and loins, were also analyzed by means of physico-chemical and sensory techniques. Databases were constructed with all these data. Different data mining techniques have been applied on them: deductive (Multiple Linear Regression (MLR)) [3], classification (Decision Trees (DT) and Rules-based Systems (RBS)) [4], and prediction techniques [5-7]. Figure 2 shows the MRI images of fresh and dry-cured Iberian loins (Figure 2A and 2B) and fresh and dry-cured hams (Figure 2C and 2D).The accuracy of the analysis of the quality parameters of Iberian ham and loin is affected by the MRI acquisition sequence, the algorithm used to analyze them and the data mining technique applied. Considering the data mining techniques, MLR and DT are appropriate, respectively, to deduce physico-chemical parameters of hams, and to classify as a function of salt content in hams. Regarding to the predictive technique, MLR could be indicate it allows obtaining equations to determine the physico-chemical characteristics and sensory attributes of Iberian loins and hams with a high degree of reliability, and analyzing the quality of these meat products in a non-destructive, efficient, effective and accurate way

Feature extraction algorithms from MRI to evaluate quality parameters on meat products by using data mining

This thesis proposes a new methodology to determine the quality characteristics of meat products (Iberian loin and ham) in a non-destructive way. For that, new algorithms have been developed to analyze Magnetic Resonance Imaging (MRI), and data mining techniques have been applied on data obtained from the images.The general procedure consists of obtaining MRI of meat products, and applying different computer vision algorithms (texture and fractal approaches, mainly), which allow the extraction of sets of computational features. Figure 1 shows the design of the proposed procedure.To achieve this, different research have been done, based on:high-field and low-field MRI scannersdifferent acquisition sequences: Spin Echo (SE), Gradient Echo (GE) and Turbo 3D (T3D)different texture approaches: Gray Level Co-occurrence Matrix (GLCM), Gray Level Run Length Matrix (GLRLM) and Neighboring Gray Level Dependence Matrix (NGLDM)fractals algorithms: Classical Fractal Algorithm (CFA), Fractal Texture Algorithm (FTA) and One Point Fractal Texture Algorithm (OPFTA)FTA [1] and OPFTA [2] have been developed in this thesis. They allow analyzing MRI images, properly, noting OPFTA for its simplicity and lower computational cost. At the same time, the meat products, Iberian hams and loins, were also analyzed by means of physico-chemical and sensory techniques. Databases were constructed with all these data. Different data mining techniques have been applied on them: deductive (Multiple Linear Regression (MLR)) [3], classification (Decision Trees (DT) and Rules-based Systems (RBS)) [4], and prediction techniques [5-7]. Figure 2 shows the MRI images of fresh and dry-cured Iberian loins (Figure 2A and 2B) and fresh and dry-cured hams (Figure 2C and 2D).The accuracy of the analysis of the quality parameters of Iberian ham and loin is affected by the MRI acquisition sequence, the algorithm used to analyze them and the data mining technique applied. Considering the data mining techniques, MLR and DT are appropriate, respectively, to deduce physico-chemical parameters of hams, and to classify as a function of salt content in hams. Regarding to the predictive technique, MLR could be indicate it allows obtaining equations to determine the physico-chemical characteristics and sensory attributes of Iberian loins and hams with a high degree of reliability, and analyzing the quality of these meat products in a non-destructive, efficient, effective and accurate way

Optimization of the image acquisition procedure in low-field MRI for non-destructive analysis of loin using predictive models

The use of low-field magnetic resonance imaging (LF-MRI) scanners has increased in recent years. The low economic cost in comparison to high-field (HF-MRI) scanners and the ease of maintenance make this type of scanner the best choice for nonmedical purposes. However, LF-MRI scanners produce low-quality images, which encourages the identification of optimization procedures to generate the best possible images. In this paper, optimization of the image acquisition procedure for an LF-MRI scanner is presented, and predictive models are developed. The MRI acquisition procedure was optimized to determine the physicochemical characteristics of pork loin in a nondestructive way using MRI, feature extraction algorithms and data processing methods. The most critical parameters (relaxation times, repetition time, and echo time) of the LF-MRI scanner were optimized, presenting a procedure that could be easily reproduced in other environments or for other purposes. In addition, two feature extraction algorithms (gray level co-occurrence matrix (GLCM) and one point fractal texture algorithm (OPFTA)) were evaluated. The optimization procedure was validated by using several evaluation metrics, achieving reliable and accurate results (r > 0.85; weighted absolute percentage error (WAPE) lower than 0.1%; root mean square error of prediction (RMSEP) lower than 0.1%; true standard deviation (TSTD) lower than 2; and mean absolute error (MAE) lower than 2). These results support the high degree of feasibility and accuracy of the optimized procedure of LF-MRI acquisition. No other papers present a procedure to optimize the image acquisition process in LF-MRI. Eventually, the optimization procedure could be applied to other LF-MRI systems

Automatic marbling prediction of sliced dry-cured ham using image segmentation, texture analysis and regression

Dry-cured ham is a traditional Mediterranean meat product consumed throughout the world. This product is very variable in terms of composition and quality. Consumer’s acceptability of this product is influenced by different factors, in particular, visual intramuscular fat and its distribution across the slice, also known as marbling. On-line marbling assessment is of great interest for the industry for classification purposes. However, until now this assessment has been traditionally carried out by panels of experts and this methodology cannot be implement in industry. We propose a complete automatic system to predict marbling degree of dry-cured ham slices, which combines: (1) the color texture features of regions of interest (ROIs) extracted automatically for each muscle; and (2) machine learning models to predict the marbling. For the ROIs extraction algorithm more than the 90% of pixels of the ROI fall into the true muscle. The proposed system achieves a correlation of 0.92 using the support vector regression and a set of color texture features including statistics of each channel of RGB color image and Haralick’s coefficients of its gray-level version. The mean absolute error was 0.46, which is lower than the standard desviation (0.5) of the marbling scores evaluated by experts. This high accuracy in the marbling prediction for sliced dry-cured ham would allow to deploy its application in the dry-cured ham industryThis work has received financial support from the Xunta de Galicia (Centro singular de investigación de Galicia, accreditation 2020– 2023) and the European Union (European Regional Development Fund–ERDF), Project ED431G-2019/04. IRTA’s contribution was also funded by the CCLabel project (RTI-2018- 096883-R-C41) and the CERCA programme from Generalitat de CatalunyaS

Use of ultrasound for the characterization and correction of textural defects in dry-cured ham

Tesis por compendio[EN] Dry-cured ham is a product highly appreciated by consumers, nevertheless, there are a large number of manufacturing process-related parameters, as well as ham intrinsic factors, that compromise its final quality. One of the main problems in the quality of dry-cured ham is the appearance of textural defects, in particular, the development of pastiness. This defect is characterized by an excessive softness and loss of elastic behavior of the ham and when tasted, it provokes a feeling similar to the mouth-coating sensation produced by a flour-water paste during the mastication process. Pastiness also makes slicing difficult and promotes the adhesiveness between slices. Currently, the methods available to measure ham pastiness are time-consuming and destructive. For this reason, the seek of faster and non-destructive technologies capable of detecting pastiness is of great importance. In this sense, different technologies such as near infrared spectroscopy, X-rays or ultrasound, that have been previously tested for the nondestructive characterization of different meat products, could be of interest for the detection of ham pastiness. Different approaches, such as the use of high hydrostatic pressure (HHP) or the application of low-temperature long-time thermal treatments (LTLT) at the end of the ham manufacturing, have been previously addressed for the correction of pastiness in dry-cured ham. Notwithstanding, the high cost and the long time required for the HHP and LTLT treatments, respectively, highlights the need for moderate cost and faster alternatives. In this context, the main goals of this thesis were to determine the feasibility of using low intensity ultrasound to non-destructively detect the appearance of pastiness during ham manufacturing and to characterize the level of pastiness in the final product, as well as to explore the feasibility of mild ultrasonic assisted thermal treatments to correct this textural defect. To meet the goal of ham pastiness characterization and correction, a customized drycured ham manufacturing was designed and carried out in order to obtain hams with different levels of pastiness with no remarkable differences on the salt content. During ham manufacturing, the feasibility of using contact ultrasound to monitor the appearance of pastiness was addressed. The ultrasonic velocity was measured in the raw ham, at the end of the salting and post-salting stages, 3 times during the drying-maturation and once the manufacturing was finished. At the end of the manufacturing, the pastiness level (high, medium and no pasty) was also sensory evaluated by an expert panel. As the manufacturing progressed, a progressive increase in the ultrasonic velocity, from 1536 m/s in the raw ham to 1713 m/s in the final dry-cured ham, was found. Notwithstanding, the increase in the ultrasonic velocity was not related with the pastiness defect, probably because the ham texture changes linked to pastiness were masked by the great influence of the compositional changes (salt gain and moisture loss) on the ultrasonic velocity. Therefore, the ultrasonic velocity was not an effective parameter to detect the appearance of pastiness in hams during manufacturing, neither to classify them according to its pastiness level at the end of the manufacturing. Contact ultrasound was also used to monitor the compositional and textural changes taking place along the ham post-salting stage. For this purpose, another batch of hams was salted and post-salting times from 7 to 56 days were tested. During post-salting, the hams were weighted and the ultrasonic velocity was measured every 2 days. Each 7 post-salting days, the composition and the textural properties of a different ham were destructively analyzed. The ham weight loss during the post-salting stage was satisfactorily (r=0.95) described by the increase in the ultrasonic velocity. Moreover, the salt distribution and the moisture loss in the internal parts of the ham were satisfactorily related (r=0.93 and r=0.86, respectively) with the increase in the ultrasonic velocity. The variation in the ham hardness during post-salting was negligible and hence, the velocity increase was mainly attributed to the compositional changes, being barely affected by the changes in texture. The hams obtained after the customized manufacturing were sliced and the ultrasonic velocity and attenuation were measured on the Biceps femoris muscle with the aim of nondestructively finding out its pastiness level. Furthermore, in order to better analyze this textural defect, the composition, protein degradation, instrumental texture and microstructure of the hams were analyzed. Pasty samples presented the highest proteolysis index (38.7% compared to 33.1% for non-pasty hams), exhibited the more relevant structural degradation (merged myofibril structures and appearance of large gaps) and consequently, were the softest (5.4 N of hardness compared to 16.7 N for non-pasty hams) and presented the most intense viscous behavior (0.434 compared to 0.372 for non-pasty hams), although a high degree of experimental variability was found. The non-destructive assessment performed with ultrasound revealed that ultrasonic attenuation could be successfully applied for the grading of dry-cured ham slices according to its pastiness level. Thus, the greater the pastiness, the higher the ultrasonic attenuation, being the average attenuation coefficient for high, medium and no-pasty samples 48.2, 45.4 and 43.1 Np/m, respectively. Notwithstanding, the ultrasonic velocity was similar in all the ham samples, regardless its pastiness level. As observed in whole hams, the ultrasonic velocity was not a satisfactory parameter to detect pastiness in sliced ham, since the large influence of the composition on the ultrasonic velocity added to a similar salt and moisture content of the samples, regardless its pastiness level, led to a similar velocity for the different pastiness levels. Air-coupled ultrasonic techniques in both through-transmission and pulse-echo modes were developed for the characterization of dry-cured ham texture. The non-invasive nature of aircoupled ultrasound allows a contactless measurement, which makes easier its industrial implementation compared to conventional ultrasound techniques for high speed applications without material surface alteration and cross-contamination between food items. As for corrective actions of the texture defects in dry-cured ham, mild thermal treatments in two different heating media (water and air) were evaluated. Furthermore, the feasibility of intensifying these mild thermal treatments with the assistance of power ultrasound was considered. For that purpose, commercial vacuum-packed dry-cured ham slices were heated in a liquid medium, with and without ultrasonic assistance, at different temperatures (40, 45 and 50 ºC), measuring the temperature in the Biceps femoris and in the Semimembranosus muscles. Regarding the treatments in air, commercial vacuum-packed dry-cured ham cylinders were used. In the first set of experiments, ham was heated at a constant air velocity (2 m/s) until different temperatures (40, 45 and 50 ºC) were reached. While in the second set of experiments, ham was treated at constant air temperature (50 ºC) at different air velocities (1, 2, 3, 4 and 6 m/s). In both sets, the treatments were performed with and without power ultrasound application, measuring the temperature in the center of the cylinder. Thermal treatments were extended until a target temperature of 5 ºC lower than the medium (water-air) heating temperature was reached, thus, holding temperature stage did not exist and the treatments only considered the heating one. The heating kinetics of the ham treated in both water and air heating media were mathematically described by means of a heat conduction model. Once the heating finalized, the textural changes of ham (hardness and elastic behavior) were evaluated. The experiments showed that power ultrasound application sped up the heat transfer, significantly (p<0.05) shortening the heating time and increasing the apparent thermal diffusivity up to 51 and 37% for water and air heat treatments, respectively. For the thermal treatments using water, the increase in temperature during the heating brought about a lower ultrasonic intensification (the apparent thermal diffusivity was increased by 51% at 40 ºC compared to the 21% at 50 ºC). On the contrary, in experiments with air, the higher the temperature, the greater the ultrasonic enhancement (the apparent thermal diffusivity was increased by 5% at 40 ºC compared to the 38% at 50 ºC). The effect of the ultrasound application decreased as the air velocity increased, being minimal when the air velocity was the highest (the apparent thermal diffusivity was increased by 21% at 1 m/s compared to the 5% at 6 m/s). As regards the changes in the textural properties of ham after the mild thermal treatments at short times, an increase in hardness and elastic behavior was observed. Finally, the texture correction in dry-cured ham with different levels of pastiness was tackled. For this purpose, vacuum-packed dry-cured ham slices with high, medium and no pastiness were heated in a liquid medium at 40 and 50 ºC for a longer time (5 h, including heating and holding stages) than heating experiments, with and without the assistance of power ultrasound during the heating phase. The texture (hardness, elastic behavior and adhesiveness) and the microstructure of the ham was evaluated in both treated and control samples. After the mild thermal treatments, the texture of ham was improved since the hardness was increased (102%) and the viscous behavior diminished (11%). On average, the increase of hardness at 50 ºC was 159% higher than at 40 ºC, while the decrease of the viscous behavior was 13.5% larger at 50 ºC compared to 40 ºC. The ham adhesiveness was also enhanced independently of the treatment temperature, with a 55% reduction being observed. The application of power ultrasound during the heating phase did not involve any additional textural change. Likewise, after the thermal treatments, the microstructure of hams with pastiness notably changed, experiencing a severe shrinkage of the myofibrils, which contributed to explain the reported textural changes. In conclusion, pastiness is a relevant and highly complex textural defect in dry-cured ham. The use of contact ultrasound and the measurement of the ultrasonic attenuation could be considered a potential technology to non-destructively detect and characterize pastiness in sliced dry-cured ham. Future work should focus on extending this approach to identify pasty whole hams, considering for this purpose the use of air-coupled ultrasound. Moreover, the use of mild thermal treatments in liquid or gas media could be a feasible method to correct the defective texture of dry-cured hams and the application of power ultrasound during the heating phase could be a relevant means of speeding up the thermal treatments.[ES] El jamón curado es un producto muy apreciado por los consumidores, sin embargo, existen numerosos parámetros relacionados con el procesado, así como factores intrínsecos del jamón, que comprometen su calidad final. Uno de los principales problemas de calidad del jamón curado es la aparición de defectos de textura, concretamente, el desarrollo de pastosidad. Este defecto se caracteriza por una textura excesivamente blanda y un comportamiento menos elástico del jamón. A nivel sensorial, provoca una sensación de recubrimiento en boca similar a la masticación de una pasta de harina y agua. La pastosidad también dificulta el loncheado y promueve la adhesividad entre lonchas. Actualmente, los métodos disponibles para caracterizar la pastosidad requieren mucho tiempo y son destructivos. Por esta razón, la búsqueda de tecnologías más rápidas y no destructivas capaces de detectar la pastosidad es de gran importancia. En este sentido, distintas tecnologías como espectroscopía de infrarrojo cercano, rayos-X o ultrasonidos, que han sido ensayadas previamente para la caracterización no destructiva de diferentes productos cárnicos, podrían ser de interés para la detección de pastosidad en jamón. Diferentes alternativas, como el uso de altas presiones hidrostáticas (HHP) o la aplicación de tratamientos térmicos de larga duración a baja temperatura (LTLT) al final del proceso de elaboración del jamón, han sido abordadas previamente para la corrección de pastosidad en jamón curado. Sin embargo, el elevado coste y el largo tiempo requerido para los tratamientos HHP y LTLT, respectivamente, pone de manifiesto la necesidad de encontrar alternativas con un coste moderado y más rápidas. En este contexto, los principales objetivos de esta tesis fueron determinar la viabilidad de la utilización de ultrasonidos de baja intensidad para detectar de manera no destructiva la aparición de pastosidad durante el proceso de elaboración de jamón curado y caracterizar el nivel de pastosidad en el producto final, así como explorar la viabilidad de tratamientos térmicos moderados asistidos por ultrasonidos de alta intensidad para corregir dicho defecto de textura. Para cumplir el objetivo de caracterizar y corregir el defecto de pastosidad en jamón, se diseñó y se llevó a cabo un proceso de elaboración para obtener jamones con distintos niveles de pastosidad sin diferencias considerables del contenido en sal. Durante el procesado, se abordó la viabilidad de utilizar ultrasonidos por contacto para monitorizar la aparición de la pastosidad. Así, la velocidad ultrasónica se midió en el jamón fresco, al final de las etapas de salado y postsalado, 3 veces durante el secado-maduración y una vez terminado el proceso de elaboración. Al final del procesado, también se evaluó el nivel de pastosidad (alto, medio y sin pastosidad) en el jamón loncheado por un panel experto. A medida que avanzó el proceso de elaboración, se observó un aumento progresivo de la velocidad ultrasónica, de 1536 m/s en jamón fresco hasta 1713 m/s en jamón curado. Sin embargo, el aumento en la velocidad ultrasónica no se relacionó con el defecto de pastosidad, probablemente porque los cambios de textura del jamón vinculados con la pastosidad fueron enmascarados por la gran influencia de los cambios composicionales (ganancia de sal y pérdida de humedad) en la velocidad ultrasónica. Así, la velocidad ultrasónica no fue un parámetro útil para detectar la aparición de pastosidad en jamón durante su procesado ni para clasificar los jamones según su nivel de pastosidad al final del procesado. Los ultrasonidos por contacto también se utilizaron para monitorizar los cambios composicionales y texturales que tienen lugar a lo largo de la etapa de postsalado del jamón. Para ello, se saló otro lote de jamones y se evaluaron distintos tiempos de postsalado, desde 7 hasta 56 días. Durante el postsalado, los jamones se pesaron y se midió su velocidad ultrasónica cada 2 días. Cada 7 días de postsalado, se analizó destructivamente la composición y las propiedades texturales de un jamón. La pérdida de peso de los jamones durante la etapa de postsalado fue descrita satisfactoriamente (r=0.95) por el aumento de la velocidad ultrasónica. Además, la distribución de sal y la pérdida de humedad en el interior del jamón se relacionaron de forma satisfactoria (r=0.93 y r=0.86, respectivamente) con el aumento de la velocidad ultrasónica. La variación en la dureza del jamón durante el postsalado fue no significativa y, por ello, el aumento de la velocidad ultrasónica se atribuyó principalmente a los cambios de composición, siendo apenas afectada por los cambios de textura. Los jamones obtenidos con distintos niveles de pastosidad después del proceso de elaboración, se cortaron y se midió la velocidad y la atenuación ultrasónica del músculo Biceps femoris con el objetivo de averiguar de forma no destructiva su nivel de pastosidad. Además, con el fin de analizar mejor este defecto de textura, se analizaron el índice de proteólisis, la microestructura, la textura instrumental y la composición de los jamones. Las muestras pastosas presentaron el índice de proteólisis más alto (38.7% comparado con el 33.1% de los jamones no pastosos), mostraron la degradación estructural más relevante (estructuras miofibrilares fusionadas y aparición de grandes huecos) y, en consecuencia, fueron las más blandas (5.4 N de dureza en comparación con los 16.7 N de los jamones no pastosos) y presentaron el comportamiento viscoso más intenso (0.434 comparado con el 0.372 de los jamones no pastosos), aunque se encontró una gran variabilidad experimental. La evaluación no destructiva llevada a cabo mediante ultrasonidos reveló que la atenuación ultrasónica se podría aplicar con éxito para la clasificación de las lonchas de jamón curado según su nivel de pastosidad. Así, cuanto mayor fue la pastosidad, mayor fue la atenuación ultrasónica, siendo el coeficiente de atenuación promedio de las muestras con alta, media y sin pastosidad de 48.2, 45.4 y 43.1 Np/m, respectivamente. Sin embargo, la velocidad ultrasónica fue muy similar en todas las muestras de jamón, independientemente de su nivel de pastosidad. Como se observó en los jamones enteros, la velocidad ultrasónica no fue un parámetro útil para cuantificar el defecto de pastosidad en jamón loncheado, ya que la gran influencia de la composición en la velocidad ultrasónica sumada al contenido similar de sal y humedad de las muestras, independientemente de su nivel de pastosidad, dio lugar a una velocidad similar en todos los niveles de pastosidad. Se desarrollaron dos técnicas de ultrasonidos acoplados por aire, tanto en modo transmisión-recepción como en pulso-eco, para caracterizar la textura de jamón curado. El carácter no invasivo de los ultrasonidos acoplados por aire permite llevar a cabo medidas sin contacto, facilitando su aplicación a nivel industrial en comparación con las técnicas ultrasónicas convencionales, ya que pueden realizarse medidas a mayor velocidad, sin alterar la superficie del material y evitando la contaminación cruzada entre alimentos. En cuanto a las medidas de corrección de defectos texturales en jamón curado, se evaluaron tratamientos térmicos moderados en dos medios de calentamiento diferentes (agua y aire). Además, se consideró la viabilidad de intensificar dichos tratamientos mediante la aplicación de ultrasonidos de alta intensidad (o de potencia). Para ello, se calentaron lonchas de jamón curado comercial envasadas al vacío en medio líquido, con y sin la aplicación de ultrasonidos, a diferentes temperaturas (40, 45 y 50 ºC), midiendo la temperatura en los músculos Biceps femoris y Semimembranosus. Respecto a los tratamientos en aire, se utilizaron cilindros de jamón curado comercial envasado al vacío. En el primer set de experimentos, el jamón se calentó a velocidad de aire constante (2 m/s) a diferentes temperaturas (40, 45 y 50 ºC); mientras que, en el segundo experimento, el jamón se calentó a temperatura de aire constante (50 ºC) a distintas velocidades (1, 2, 3, 4 y 6 m/s). En los dos sets, los tratamientos se llevaron a cabo con y sin la aplicación de ultrasonidos de potencia, midiendo la temperatura en el centro del cilindro. Los tratamientos térmicos se prolongaron hasta alcanzar la temperatura objetivo, definida como 5 ºC por debajo de la temperatura del medio de calentamiento (agua o aire). Así, no se llevó a cabo una fase de mantenimiento de la temperatura y sólo se consideró la fase de calentamiento de los tratamientos térmicos. Las cinéticas de calentamiento del jamón tratado tanto en agua como en aire se describieron matemáticamente considerando que la transferencia de calor estuvo únicamente controlada por conducción. Una vez finalizado el calentamiento, se evaluaron los cambios texturales del jamón (dureza y comportamiento elástico). Los experimentos mostraron que la aplicación de ultrasonidos de potencia aceleró la transferencia de calor, reduciendo significativamente (p<0.05) el tiempo de calentamiento y aumentando la difusividad térmica aparente hasta un 51 y 37% en los tratamientos térmicos en agua y aire, respectivamente. En el caso de los tratamientos térmicos en agua, el aumento de la temperatura durante el calentamiento provocó una intensificación ultrasónica menor (la difusividad térmica aparente aumentó un 51% a 40 ºC comparado con el 21% a 50 ºC). Por el contrario, en las experiencias en aire, cuanto mayor fue la temperatura, más efectiva fue la aplicación de los ultrasonidos (la difusividad térmica aparente incrementó un 5% a 40 ºC comparado con el 38% a 50 ºC). El efecto de la aplicación de los ultrasonidos disminuyó con el aumento de la velocidad del aire, siendo mínimo con la velocidad de aire más alta ensayada (la difusividad térmica aparente aumentó un 21% a 1 m/s comparado con el 5% a 6 m/s). En cuanto a los cambios de las propiedades texturales del jamón después de los tratamientos térmicos moderados limitados a la fase de calentamiento, se observó un aumento en su dureza y en su comportamiento elástico. Por último, se abordó la corrección de textura en jamón curado con distintos niveles de pastosidad. Para ello, se calentaron lonchas de jamón con alta, media y sin pastosidad envasadas al vacío en medio líquido a 40 y 50 ºC durante tiempos más largos (5 h, incluyendo las fases de calentamiento y mantenimiento) que en las experiencias sólo de calentamiento, con y sin la aplicación de ultrasonidos de potencia únicamente durante la

Development and evaluation of tools to improve the texture and quality of dry-cured ham

El jamón curado es considerado un producto típico de la región mediterránea elaborado con las patas traseras del cerdo, las cuales se salan y curan durante un período largo. Sin embargo, existen otros productos curados como el jamón curado de cordero, el Fenalår, típico de Noruega, que se sala, se ahúma y se cura durante un período más corto de tiempo. La textura de los productos curados es un criterio de calidad importante para los consumidores. Sin embargo, el desarrollo de la textura, así como también de los defectos de textura de los productos curados tanto de cerdo como de cordero son un tema complejo puesto que hay muchos factores involucrados. Por este motivo, hay un interés creciente de la industria alimentaria en encontrar soluciones para reducir la incidencia de productos con texturas blandas y/o defectuosas.El principal objetivo de esta Tesis es desarrollar y evaluar herramientas para mejorar el proceso de elaboración y la calidad de dos productos curados: el jamón curado y el Fenalår. Para ello, se han llevado a cabo diferentes estudios los cuales se presentan en esta Tesis en diferentes artículos científicos. El artículo I aborda los principales factores que afectan al desarrollo de la textura y a la modelización de la textura. El segundo artículo muestra los resultados de la microbiología predictiva utilizada para estudiar la seguridad alimentaria en relación con el proceso de elaboración y la reducción del contenido de sal, así como también la omisión de nitrificantes (artículo II). En el artículo III se investigó un método para evaluar de manera no destructiva el punto final del proceso en función de las medidas obtenidas en la superficie del jamón. En el artículo IV,se presentan los resultados obtenidos de un primer intento para el desarrollo de un método para evaluar la pastosidad con el reómetro y evitar así los tediosos análisis sensoriales. Finalmente, el uso de un tratamiento de altas presiones como acción correctora para productos con texturas defectuosas se presenta en el artículo V.Con la finalidad de estudiar de forma más detallada el desarrollo de la textura, se desarrolló un modelo matemático (artículo 1), que relaciona las condiciones de procesado y las características de la materia prima con la textura del producto. Este modelo no sólo permite evaluar el efecto de estos factores, sino que también podría permitir una optimización del proceso de elaboración a nivel industrial. Los resultados mostraron que el contenido de sal, el pH, las características de la materia prima y las condiciones de procesado (temperatura de secado y merma final) son factores importantes que afectan al desarrollo de la textura, tal y como se presenta en el artículo I, y a la vez comprometen la seguridad del producto. En el artículo II, la reducción del contenido de sal no sólo dio como resultado texturas más blandas, sino que también produjo un incremento de los riesgos microbiológicos, especialmente cuando se omitieron los nitrificantes, tal y como muestran los resultados obtenidos mediante los modelos de microbiología predictiva. Además, los defectos de textura en ambosproductos curados representan un importante desafío para la industria.A pesar de los esfuerzos realizados para mejorar el proceso de elaboración, es posible que algunos productos sigan siendo defectuosos, evidenciando así la necesidad de nuevas herramientas y/o tecnologías con potencial para su aplicación a nivel industrial. En esta Tesis, se estudió una metodología para evaluar si el producto tenía o no la textura adecuada para su comercialización (artículo III), así como también un análisis para evaluar instrumentalmente el defecto de pastosidad en jamón curado loncheado (papel IV). Los resultados presentados en el artículo III muestran que el método ITAS permitió evaluar de manera no destructiva el punto final del proceso; esta metodología consiste ensimular la valoración táctil en la superficie del jamón realizada actualmente por los expertos. La máxima precisión de clasificación fue del 82,1%, obtenida al combinar las mediciones junto con el espesor de la grasa subcutánea. La implantación de esta tecnología a nivel industrial no sólo mejoraría la calidad del producto, sino que también supondría un ahorro económico, energético y de espacio, ya que permitiría un mejor ajuste del tiempo de secado necesario para cada jamón.En el artículo IV se presentan los resultados obtenidos en un primer estudio para el desarrollo de un método para evaluar la pastosidad utilizando un reómetro. Los resultados obtenidos mostraron un aumento de la viscosidad de los extractos a medida que aumentaba la intensidad del defecto de pastosidad, mostrando así la posibilidad de detectar instrumentalmente este defecto utilizando el reómetro. Sin embargo, hay otros factores a parte de la viscosidad que pueden afectar/alterar los resultados y el reómetro sólo permite discriminar las muestras con una pastosidad intensa de aquellas que tienen un defecto medio o que no son pastosas.También se han llevado a cabo acciones correctoras en lonchas de jamón curado utilizando tratamientos mediante altas presiones a diferentes temperaturas (artículo V).Los resultados obtenidos muestran que, si bien las temperaturas de 7 ºC y 20 ºC son útiles para corregir el defecto en las lonchas con pastosidad media, se necesita una temperatura superior (35 ºC) para las de pastosidad intensa. Por lo tanto, conocer las características iniciales de textura del producto es clave para definir las condiciones óptimas para su procesado mediante altas presiones cuando se busca mejorar la textura sin deteriorar el color ni el aroma.Las metodologías desarrolladas y evaluadas en esta Tesis pueden utilizarse para mejorar el proceso de elaboración y la calidad del jamón curado. Además, representan un primer paso en el desarrollo de nuevas herramientas para uso industrial.Dry-cured ham is considered a typical product of the Mediterranean area made of pig¿s hind leg which is dry-salted and has a long maturation period. However, there are other typical dry-cured products such as the dry-cured lamb ham, Fenalår, from Norway, which is dry-salted and smoked followed by a short maturation period. The texture of dry-cured products is an important quality criterion for the consumers. However, texture development and also texture defects of dry cured products from both pork and lamb are a complex issue since many factors are involved. For this reason, there is an increasing interest of the industry in finding solutions to reduce the incidence of products with soft and/or defective textures. The main objective of this PhD Thesis dissertation was to develop and evaluate tools to improve the manufacturing process and the quality of two examples of dry-cured products; dry-cured ham and Fenalår. For this reason, different studies were conducted and herein presented as different papers. First one addresses the main factors affecting texture development and texture prediction modelling (presented in paper I). The second paper presents the results of predictive microbiology used to study food safety in relation to manufacturing process with reduced salt and nitrites addition (in paper II). Next study investigated a method to non-destructively evaluate the end of process based on the measurements taken at the surface of the ham (in paper III). The results of an attempt to develop a method to evaluate pastiness with a rheometer to avoid the tedious sensory analysis are presented in paper IV. Finally, the use of high pressure treatments as a corrective action for products with defective textures is presented in paper V. In order to study texture development in more detail, mathematical models were developed (paper I), that relate processing conditions and raw material characteristics to the texture of the product. These models not only allow the effect of these factors to be evaluated but could also enable further optimisation of the process in the industry. The results showed that salt content, pH, raw material characteristics and processing conditions (drying temperature and final weight loss) are important factors affecting texture development, as shown in paper I, while affecting product safety. In paper II, reduced salt content not only resulted in softer textures but also in an increase of microbiological hazards especially when no nitrite was used as evaluated by predictive microbiology models. Furthermore, texture defects in both dry-cured products represent an important challenge for the industry. Despite the efforts to improve the manufacturing process, some products may still be defective and the need for new tools and/or technologies with potential for industrial application is emerging. In this Thesis, a methodology to evaluate whether the product had the appropriate texture to be sent to the market or not (paper III) and an analysis to instrumentally evaluate pastiness defect in sliced dry-cured ham (paper IV) were studied. Results presented in paper III show that ITAS method allowed to non-destructively assess processing end point; this methodology consist of simulating the tactile assessment of ham surface as currently made by the experts. The maximum classification accuracy was 82.1% obtained when combining measurements with subcutaneous fat thickness. The implementation of this technology in industry would not only improve the quality of the product but also economic, energy and space savings, as it would enable better adjustment of required drying time for each ham. Results of the study in paper IV represent a first attempt for the development of a method to evaluate pastiness using a rheometer to avoid the tedious sensory analysis. An increase in viscosity of water extracts with an increase in pastiness intensity, show the ability to instrumentally detect this defect using the rheometer. However, there are factors other than viscosity that can affect/alter the results and this method allows discriminating only samples with high pastiness intensity from those with medium or non-pastiness defect. Corrective actions for dry-cured ham slices using HPP treatments at different temperatures were also analysed (paper V). The obtained results show that while temperatures of 7 ºC and 20 ºC are useful to correct ham slices with medium pastiness, higher temperature (35 ºC) is needed in the case of high pastiness. Therefore, knowing textural properties of the product is key information to define optimal HP processing conditions when aiming to improve texture without deteriorating colour and aroma. The methodologies developed and evaluated in the present work can be used to improve the manufacturing process and quality of dry-cured ham. They represent a first step in development of new tools for industrial use. <br /

Digital Image Filtering Optimization Supporting Iberian Ham Quality Prediction

Digital images of food for later analysis tend to be heterogeneous in terms of color and luminosity. Improving these images by using filters is necessary and crucial before further processing. This paper compares the non-use of filters and the use of high-pass filters in the images of hand-cut Iberian ham that will be used in a multifractal analysis for the study of fat and its infiltration. The yielded results show that with the use of a high-pass filter, more accurate fractal dimensions were obtained, which can be featured in predictive techniques of Iberian ham quality

Aplicación de técnicas de resonancia magnética nuclear al estudio de miosistemas

Las técnicas basadas en el principio de la Resonancia Magnética Nuclear (RMN) son herramientas de análisis no destructivo que aportan valiosa información sobre las matrices cárnicas, tanto a nivel estructural como a nivel bioquímico. Por un lado, se ha estudiado el potencial la Imagen de Resonancia Magnética (IRM) para estudiar la macroestructura de piezas musculares. Por otro lado, se ha evaluado la aptitud de la relaxometría de RMN para el estudio y caracterización de la microestructura de miosistemas cárnicos y, finalmente, se ha comprobado el potencial de la espectroscopía de alta resolución de RMN para el estudio del perfil metabólico de muestras de músculo íntegras y muestras de exudado. Estas metodologías permiten el análisis de matrices complejas de forma rápida, sin apenas preparación de la muestra y su carácter no invasivo y no destructivo aumenta su ámbito de aplicación. PLANTEAMIENTOSe ha empleado la RMN para el estudio de distintos miosistemas cárnicos. Por un lado, se ha analizado un derivado cárnico elaborado a partir de una pieza entera, el jamón curado. Por otro lado, se elaboraron distintos productos a partir de carne picada:modelos cárnicos y embutidos crudos curados, tipo chorizo y tipo salchichón. Se planteó un estudio longitudinal para monitorizar el proceso de maduración de estos productos,realizando un seguimiento de los cambios estructurales (mediante IRM y relaxometría de RMN) y bioquímicos (mediante espectroscopía de RMN) experimentados por la matriz cárnica durante del tiempo de curado. Además, se empleó la espectroscopía de RMN para el análisis de matrices líquidas procedentes de miosistemas cárnicos (exudados) y evaluar su potencial como matriz para monitorizar el proceso de conservación de la carne de cerdo..