Browsing by Subject "Electromyography"

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Making milking easier
reducing physical strain of parlor workers during milking cluster attachment
(2017) Cockburn, Marianne; Schick, Matthias
Milking personnel have been affected by musculoskeletal disorders for many years. In parlor workers the shoulders, wrists and lower back are most affected. As the procedure of milking cluster attachment has been reported to be the most strenuous during milking, we took a three- step approach to reduce the physical strain of this task. In the first step, we used the computer-assisted recording and long-term analysis system (CUELA) to record flexion angles of multiple joints during milking. The posture of 30 milkers was evaluated on 15 farms. Milking parlor types evaluated included the Herringbone 30°, the Herringbone 50°, and the Parallel as well as the Rotary parlor. The 5th, 50th and 95th percentiles of the data recordings were classified against ISO Norms and it was found that joint flexion angles were concerning. The statistical analysis revealed a significant interaction between milking parlor type and a working height coefficient, which reflected the ratio between the subject’s height and the effective udder height (udder height + depth of pit). By using model predictions, we calculated working height coefficients that could improve joint flexion angles. These working height coefficients were calculated for each parlor type and used within the newly developed “milking health formula” to calculate the ideal depth of pit, under the consideration of the milker’s height, milking parlor type and udder height. As the working heights recommended within the milking health formula were relatively low for all parlor types, and the recommendations made for the Herringbone 30° were broad, we aimed to further validate our findings by using surface electromyography to monitor muscle contraction intensities of 16 milkers (nine females, seven males). The second step of this thesis was performed in a laboratory setting where the milking cluster was attached to an artificial udder. It was important to ensure that the milking health formula enabled a consistent setting of working heights for milkers of different body heights, as well as ensuring that lower working heights reduced muscle contraction intensities of the upper limb and shoulder muscles. The results showed that lower working heights decreased muscle contraction intensities of the shoulder muscles, but not of the lower and upper arms. Further, since the subjects body height had no effect on muscle contraction intensities, it can be concluded that the formula offers an effective way to set comparable working heights for milkers of different body heights. Posture of milkers is not only affected by working heights, but also by the horizontal reaching distance between the milker and the cows’ udder. It has recently been assumed that milking stall dimensions are currently too small for dairy cows and that they should be increased to ensure their welfare. This could however increase the reaching distance between the udder and the cow and thus negatively affect ergonomics. In the third step of the thesis, we therefore used surface electromyography, in both a Herringbone 30° and a Side by Side milking parlor, to investigate the effect of increased milking stall dimensions on muscle contraction intensities of the upper limb and shoulder muscles during milking. Nine male subjects milked 30 cows twice per parlor type, where the milking stall dimensions were large on one side of the milking parlor and standard sized on the other. Milking stall dimensions had no effect on muscular contraction intensities in the Side by Side parlor and a controversial effect in the Herringbone 30° parlor. The contraction intensities in the right lower and upper arm were higher when cows were milked in standard sized milking stalls, but were higher in the left upper arm when cows were milked in large milking stalls. The effect of milking stall dimensions on the work environment should therefore be further investigated. In conclusion, the current project has developed a method to calculate beneficial working heights for a variety of milking parlor types. These derived recommendations have been further validated and it was shown that lower working heights reduced muscular load of the shoulder muscles.
Oral processing of anisotropic food structures: A modelling approach to dynamic mastication data
(2024) Oppen, Dominic; Weiss, Jochen
Materials that have been generated through a directionally oriented growth process often exhibit anisotropic properties. Plant materials such as tubers and roots or animal matter used to produce products such as steaks or pasta filata are characterized by an alignment of molecules, aggregates or cells in certain dimensions leading to differing properties depending on direction. Such an anisotropic property behavior is important for a wide range of quality attributes such as texture, appearance, stability and even aroma and taste. Especially the former is of critical importance to consumer liking and acceptance of foods. Structure-texture relationships have already been established for certain foods. For anisotropic foods though, a determination of such relationships is difficult, since the comminution of foods during chewing causes complex changes to the underlying anisotropic structure elements that are not easily measurable using conventional mechanical texture analysis tests such as cutting, shearing or compression. On the other hand, sensory tests using panels are very time consuming and often do not reveal structural causes for texture like or dislike by consumers. The lack of availability of suitable analytical techniques that allow for a description of texture properties relevant to mastication hampers especially the development of meat substitutes that are currently trending. The aim of this work was therefore to characterize changes to anisotropic structures induced by chewing (henceforth referred to as "oral processing") using a novel measurement approach that records kinematic and electromyographic properties of the chewing process. The kinematics of jaw movement were recorded using a 3D motion tracking system. Muscle activity was recorded using an electromyograph. From the measured data, characteristics for individual chews were calculated, which were represented in a linear mixed model as a function of the food structure. Section I provides the scientific basis for this work through a preface and a literature review. Grown and manufactured anisotropic foods are identified and described. A general overview of the production, phase phenomena and characterization methods for anisotropic food materials is given. Section II contains the oral processing experiments. In Chapter III, the focus was put on the impact of fiber length of grown structures on mastication behavior. Meat model systems with different microstructures but the same composition were produced. The model systems with anisotropic and isotropic microstructures were comminuted to different sizes, and the fiber length was inferred from the length of the particles, taking into account the particle size effect of chewing. The results indicate that longer fibers cause greater jaw movement and muscle activity. For instance, estimate peak muscle activity of anisotropic samples is 58.2857 µV higher (p=0.0156) compared to isotropic samples. Chapter IV describes minced meat products in which certain phase volumes were replaced by a finely comminuted meat mass. The aim of the study was to find detection limits beyond which an increase or decrease in muscle fiber cells does not lead to a further adjustment of the mastication properties. In the study, a transition point was identified at around 50 % of batter-like substances. Food models with more than 50 % of batter-like substance showed a smaller change in mastication parameters. The effect was more pronounced with higher proportions of fibrous material. Chapter V dealt with the topic of meat substitutes. A simple model of meat substitutes was used to test whether the effects found in anisotropic animal-based products can also be found in plant-based products. Hydrocolloid gels with different phase volumes of wet textured plant protein were produced. Similar effects for the animal-based products were observed, although the correlation was not as strong. It was hypothesized that a large part of the effect was due to the weak binding ability of hydrocolloid gels. Thus, the anisotropic particles could not be held together with a low proportion of the outer hydrocolloid gel and required less muscle activity despite a higher content of structured phase. Section III assessed alternative data evaluation strategies to the linear mixed model. The aim of the study in Chapter VI was to anticipate the model products from Chapter III using a classification approach. Algorithms of three categories were trained with the data set of the chewing processes. Two approaches were used to evaluate whether the algorithms could either resolve each individual food model with variations in microstructure (anisotropy) and macrostructure (particle size) or in microstructure only. For both approaches, the algorithms performed significantly better compared to a random guessing. The best classification results were achieved by the boosted ensemble learner "XGBoost", which assigned 96.617 % of all bites to the corresponding food microstructure. Furthermore, it was demonstrated that standardized and normalized oral processing data are almost not subject-dependent. In addition, feature importance analysis confirmed that lateral jaw movement is a good indicator of the presence of anisotropic food material and, with a weight of 0.39205, is the most important feature for classifying samples according to their structure. In summary, this work was able to show that the dynamic characteristics of mastication change depending on anisotropic properties. In general, modeling of mastication characteristics has never been conducted before and represents a promising advance over mean-based evaluation. The machine learning approach is also new in the field of oral processing and proved to be promising. For future research, it is proposed to correlate the dynamic features with sensory texture data to obtain direct correlations between chewing characteristics and texture attributes.
Oral processing, rheology, and mechanical response: Relations in a two‐phase food model with anisotropic compounds
(2023) Oppen, Dominic; Weiss, Jochen
Food‐material poses a challenging matrix for objective material scientific description that matches the consumers' perception. With eyes on the emerging structured food materials from alternative protein sources, objectively describing perceived texture characteristics became a topic of interest to the food industry. This work made use of the well‐known methodologies of jaw tracking and electromyography from the field of “food oral processing" and compared outcomes with mechanical responses to the deformation of model food systems to meat alternatives. To enable transferability to meat alternative products, an anisotropic structuring ingredient for alternative products, high‐moisture texturized vegetable protein (HM‐TVP), was embedded in an isotropic hydrocolloid gel. Data of the jaw movement and muscle activities exerted during mastication were modeled in a linear mixed model and set in relation to characteristic values obtained from small‐ and large‐strain deformation. For improvement of the model fit, this work makes use of two new data‐processing strategies in the field of oral processing: (i) Muscle activity data were set in relation to true forces and (ii) measured data were standardized and subjected to dimensional reduction. Based on that, model terms showed decreased p‐values on various oral processing features. As a key outcome, it could be shown that an anisotropic structured phase induces more lateral jaw movement than isotropic samples, as was shown in meat model systems.