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SCHEMATIC OF THE FIBER OPTIC TRANSMISSION EQUIPMENT
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ABSTRACTA fiber optic transmission technique using single fibers to deliver and receive light was investigated for measuring the milkfat content of homogenized skim milk. Light transmission through skim milk for wavelengths of 400 to 1000 nm was measured using a fiber optic spectrophotometer. Transmission was measured for distances of 0.5, 1, 2, 3,...
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... From the viewpoint of further improvement of the price-to-quality ratio, analyzers based on light scattering are most promising. Some approaches to measurements of the content of milk components, based on light scattering are described in [8][9][10][11][12]; however, there are no commercial implementations of such sensors. ...
... Основният принцип на който се основава турбидиметрията като оптичен метод е измерване на интензитета на преминалата през дисперсната среда светлина [88]. Интензитетът на падащия светлинен поток отслабва в резултат на разсейването от частиците съдържащи се в дисперсната система. ...
... 4. Водна баня с терморегулатор. Влакнесто-оптичното измервателно устройство (ВОИУ) се състои от измервателен блок, две микрометрични масички, осигуряващи точно изместване и съосяване на държачите на оптичните влакна (входно и изходно) по X, Y и Z, гониометрична масичка за завъртане на изходното влакно спрямо входното в диапазона от 0 до 90º, работна кювета и термостатна вана [40,88]. ...
In the current dissertation, a fiber-optic device was developed and presented for tracking the processes of structural changes of proteins during enzymatic coagulation, chemical and thermal denaturation. To carry out the experiments, natural combined full-fat cow's milk (NCFM) was used, procured from the Agroecological Center of the Agricultural University - Plovdiv, natural skimmed fresh milk (NSFM) procured from a milk processing plant with a constant composition and physico-chemical properties suitable for the purposes of the conducted experiments, dry reconstituted skimmed cow's milk (DRSM).
For the first time, a systematic study of the kinetics of aggregation of different types of milk with different concentrations of the milk protein contained in them was done. The developed optical-spectral method for component analysis of milk can be used to study polycomponent dispersed samples. The effect of independent variables such as temperature, pH, protein concentration, coagulant enzyme concentration and CaCl2 on the course of the enzymatic coagulation and denaturation process was investigated.
A methodology was developed for determining the size of protein particles in highly diluted protein solutions obeying the Rayleigh theory (r ≤ λ) on the example of natural fresh milk, used in processing the empirical results of fluorescence and atomic force microscopy.
It was found that with the help of the proposed predictive model, the most informative wavelengths of the scanning light source can be selected in the study of protein structural changes. It was established that during chemical denaturation of proteins, the optical properties change, which is related to the destruction of the α-helices. The degree of destruction of the α-helices is determined by the difference in the optical properties that the proteins exhibit before and after denaturation.
The correlation analysis proved the statement that any monochromatic light source with a wavelength between 650 nm and 850 nm with sufficiently high reliability of the results can be used to study the process of thermal denaturation of serum proteins in natural skimmed fresh milk. It was established that Raman spectroscopy is a suitable method for studying the structural changes of milk proteins during chemical and thermal denaturation. According to literature sources, the band near 935 cm-1 is determined in the polypeptide chain of serum proteins as an α-helical conformation.
Upon heating, this band shifts to 962 cm-1, reflecting a decrease in α-helical content in the protein. Changes in the spectral bands of Amid III and Amid I suggest the presence of significant β-sheet structures in the gel.
Upon thermal denaturation of NOPM in the temperature range from 20ºС to 80ºС, the Amid I spectral band changes from a broad line without sharp features to a line with a peak at 1630 cm-1. As the temperature of the solution increases to 80 ºС, a narrowing of the Amid I spectral band is observed, which is a sign of redistribution of the intensities and positions of the spectral lines during thermodenaturation.
It was found that the use of fluorescence spectroscopy and the method of isopotential excitation-emission matrices of the fluorescence spectrum is a suitable method for studying the structural changes of milk proteins. It was found that, regardless of the obvious clarity of the methods of fluorescence and atomic force microscopy when studying the structural changes of milk proteins, they have a certain drawback, namely the preparations that are prepared on a flat support (glass slide) create a prerequisite for significant deformation of the clusters.
Moreover, it is very difficult to assess the change of milk gel structure during the actual coagulation because the deformation of the structure is too great and for this reason it is necessary to use other methods, including optical methods.
For the first time, a complex analysis of the structural changes of the proteins of different types of milk with different concentration of the milk protein was made using different optical methods. All results presented in this dissertation were obtained independently or with the personal participation of the doctoral student.
The reliability of the obtained experimental results is based on:
the consistency of the obtained results when using different optical research methods;
the application of strict mathematical transformations in the used models;
the modern high-precision measuring scientific research equipment used;
the coincidence of the experimental results obtained during the measurement with results obtained by other methods;
the coincidence of the experimental results during the measurement with those obtained from control objects of research;
that the results obtained from the experiments do not contradict the known theories of physics, chemistry and biology and agree with the theoretical and experimental results of other researchers.
В настоящият дисертационен труд е разработено и представено влакнесто-оптично устройство за проследяване процесите на структурни изменения на белтъците по време на ензимна коагулация, химична и термо- денатурация. За извършване на експериментите е използвано натурално сборно пълномаслено краве мляко (НСПМ), набавено от Агроекологичен център на Аграрен Университет - Пловдив, натурално обезмаслено прясно мляко (НОПМ) набавено от завод за преработка мляко с постоянен състав и физико-химични свойства, подходящи за целите на проведените експерименти, сухо възстановено обезмаслено краве мляко (СВОМ).
За първи път е направено систематично изследване на кинетиката на агрегацията на различни видове млека с различна концентрация на съдържащият се в тях млечен белтък. Разработеният оптично-спектрален метод за компонентен анализ на млека може да бъде използван за изследване на поликомпонентни дисперсни образци. Изследван е ефектът на независимите променливи такива като, температура, рН, концентрация на белтък, концентрация на коагулиращ ензим и CaCl2 върху протичането на процеса на ензимна коагулация и денатурация. Разработена е методика за определяне размера на белтъчните частици в силно разредени протеинови разтвори, подчиняващи се на теорията на Релей (r ≤ λ) на примера на натурално прясно мляко, използвана при обработка на емпиричните резултати от флуоресцентната и атомно-силова микроскопия.
Установено е, че с помощта на предложения предсказващ модел могат да бъдат избрани най-информативните дължини на вълните на сканиращият светлинен източник при изследване на структурните изменения на белтъците. Установено е, че при химична денатурация на белтъци се променят оптичните свойства, което е свързано с разрушаването на α – спиралите. По разликата в оптичните свойства, които проявяват белтъците преди и след денатурация се определя степента на разрушаване на α – спиралите. Доказано е чрез направеният корелационен анализ твърдението, че всеки монохроматичен светлинен източник с дължина на вълната между 650 nm и 850 nm с достатъчно висока достоверност на резултатите може да се използва за изследване на процеса на термо денатурация на серумни белтъци при натурални обезмаслени пресни млека. Установено бе, че рамановата спектроскопия е подходящ метод за изследване на структурните изменения на млечни белтъци при химична и термо-денатурация. Съгласно литературните източници, лентата близо до 935 cm-1 се определя в полипептидната верига на серумните белтъци като α-спирална конформация. След загряване тази лента се измества до 962 cm-1, отразявайки намаляването на α-спиралното съдържание в белтъка. Промените в спектралните ивици на Amid III и Amid I предполагат наличието на значителни β-листови структури в гела.
При термична денатурация на НОПМ в температурен диапазон от 20ºС до 80ºС, спектралната полоса Amid I се превръща от широка линия без остри признаци, в линия с пик при 1630 cm-1. С увеличаване на температурата на разтвора до 80 ºС се наблюдава стесняване на спектралната полоса Amid I, което е признак за осъществяване на преразпределение на интензитетите и позициите на спектралните линии по време на термо- денатурация.
Установено бе, че използването на флуоресцентна спектроскопия и метода на изопотенциалните възбудно-емисионни матрици на спектъра на флуоресценция е подходящ метод за изследване на структурните изменения на млечни белтъци. Установено бе, че независимо от очевидната нагледност на методите на флуоресцентна и атомно-силова микроскопия при изследване на структурните изменения на млечни белтъци, те притежават определен недостатък, а именно препаратите които се подготвят върху плоска подложка (предметно стъкло) създават предпоставка за значителна деформация на клъстерите. Освен това, много трудно е да се оцени промяната на структурата на млечния гел по време на същинската коагулация т.к. деформацията на структурата е твърде голяма и поради тази причина за нейното изследване е необходимо използването на други, в т.ч. оптични методи.
За първи път е направен комплексен анализ на структурните изменения на белтъците на различни видове млека с различна концентрация на млечния белтък с различни оптични методи. Всички резултати представени в настоящият дисертационен труд са получени самостоятелно или с личното участие на докторанта.
Достоверността на получените експериментални резултати се базира на:
съгласуваността на получените резултати при използването на различните оптични методи на изследване;
прилагането на строги математически преобразувания в използваните модели;
използваната съвременна високо точна измервателна научно-изследователска апаратура;
съвпадението на експерименталните резултати получени по време на измерването с резултати получени чрез други методи;
съвпадението на експерименталните резултати при измерването с такива получени от контролни обекти на изследване;
това, че получените от експериментите резултати не противоречат на известните теории от физиката, химията и биологията и се съгласуват с теоретичните и експериментални резултати на други изследователи.
... Light-scattering analyzers appear capable of further improving price-performance ratio. Some approaches to measuring the content of milk components based on light-scattering effects have been reported in [13][14][15][16]. The spatial distribution of diffuse transmission from a layer of milk which is a few millimeters thick is measured with a digital camera using three LEDs emitting at different wave lengths, and then analyzed by a regression model to determine the content of fat and protein [13,14]. ...
... The spatial distribution of diffuse transmission from a layer of milk which is a few millimeters thick is measured with a digital camera using three LEDs emitting at different wave lengths, and then analyzed by a regression model to determine the content of fat and protein [13,14]. The optical transmission and internal reflectance of milk, which are sensitive to the fat level due to diffuse scatter, can be measured using fiber optic technologies [15][16][17]. Judging by the technologies on offer on the milking equipment market, despite the availability of the principles for sensing the milk composition in the cited works, there are no commercial implementations of such sensors. ...
A compact laser scatterometric device for determining the fat percentage of milk filling a cylindrical tube has been designed. The device operates by detecting the angular distribution of the scattered radiation of a semiconductor laser using an axial array of photodiodes. We have experimentally found that the light-scattering indicatrix in cow milk has a monotonous dependence on milk fat content. The intensity at side- or forward-scattering angles normalized to the backscattering intensity proves to be a reliable, informative parameter. A polynomial approximation for the calibration curve of fat percentage versus normalized scattering intensity is constructed to enable fat content measurements in the fairly wide range of ~0.01–10%. Furthermore, the intensity at forward scattering angles responds to the presence of large-scale particles in milk. The device was tested in a laminar flow regime at milk flow rates up to 100 mL/s.
... The absorbance response at 530 nm is considered for further experiments because of the availability of low cost green light sources. The increase in absorbance could be attributed to the significant variation of RI with increasing fat percentages which is in correlation with the reported literature [29,30]. Hence, it confirms the higher influence of fat on the RI sensitivity of the sensor probes in comparison to protein and other solid-not-fat (SNF) content. ...
Milk fat content is an important parameter for milk quality assessment in the dairy industry. This study reports the development of a hand-held, highly sensitive fiber optic milk fat sensor using U-bent plastic optical fiber (POF) probes based on the refractive index (RI) of milk, an inherent physicochemical property of milk, which is significantly influenced by the milk fat content. The U-bent POF sensor probes facilitate dip type sensing and offer non-destructive assessment of milk quality in real-time. The sensor works on the principle of intensity modulation technique by exploiting evanescent wave absorbance and refractive losses. The fiber optic probes sense a change in RI of the medium as a result of attenuated total reflection by virtue of the evanescent wave interactions of light at the fiber core/cladding interface with the surrounding medium. A relative change in the refractive index property of milk as a result of variation in fat content and addition of water is investigated using U-bent POF probes for milk quality assessment. The sensor shows an optical absorbance sensitivity of 0.15 ΔA/Δ% fat for the variation of fat content in the milk. Besides, the response of the sensor to water addition in wide concentration range was studied. Furthermore, a low cost portable optoelectronic device is reported for instantaneous milk quality monitoring in farm fields. This sensor could be of huge potential in dairy industries, milk collection centers as well as end-user applications for real-time milk quality monitoring.
... The VIS light region (360 -780 nm), where the scatter strongly dominates, is rarely used in quantitative milk analysis (Crofcheck et al., 2000). Cabassi et al. (2013) reported, that particularly in the region below 1 100 nm, the scatter strongly dominates over weak absorption. ...
Milk fat content is an important indicator of milk quality because of nutritional and technological aspects of dairying. In this sense the milk fat determination is important practice procedure. The work goal was to do an effective overview and comparison of reference and routine methods of fat determination during their development. Nowadays, there exist a number of methods for determining milk fat content. Reference methods require accurate analysis in compliance with the International Standard ISO, whereas routine methods perform analysis using routine instrumental techniques for faster and cheaper results with acceptable accuracy. Quality control measures have a significant role for result determination reliability and they include internal quality controls, external quality controls, precision of evaluation, and blank samples. In conclusion, due to continuous development and improvement, routine methods will be used more often.
... Moreover, this mechanism exhibits temperature dependence , where a greater increase in particle size should be seen at higher heat treatment temperatures, as more protein denaturation occurs and therefore increases the amount of free sulphide groups with the potential to form proteineprotein interactions (Anema, Lowe, & Lee, 2004; Vasbinder, Alting, & de Kruif, 2003a). Optical sensors for dairy food products have been developed to analyse milk coagulation and synaeresis (Castillo, Payne, Hicks, & Lopez, 2000; Fagan et al., 2007; Fagan, Castillo, O'Donnell, O'Callaghan, & Payne, 2008) and milk and whey fat (Castillo, Payne, L opez, Ferrandini, & Laencina, 2005; Crofcheck, Payne, Hicks, Mengüç, & Nokes, 2000 ) concentration for improved monitoring and quality control in industrial processes using only simple optical sensor techniques, whether it be light backscatter/sidescatter (180 /90 , respectively) or light transmission (0 ). These studies all utilised a simple, non-destructive technique using a relatively inexpensive measurement system. ...
... For this reason, visible wavelengths are usually ignored as containing no intense characteristic absorption bands of the milk components. There are only a few published works exploiting the Vis region for milk analysis (Crofcheck, Payne, Hicks, Menguc, & Nokes, 2000; Muñiz et al., 2009). The scatter is generally considered as a ''parasitic'' phenomenon , complicating the spectroscopic analysis of opaque media. ...
A new optical spectroscopic method for milk fat and total protein analysis has been developed. In contrast to the conventional approach that generally relies on the components’ absorption, the suggested method is based on the phenomenon of light scatter by fat and protein particles. This fundamental distinction enables shifting the measurement to the cost-effective visible and adjacent near infrared region (below 1000 nm), where the scatter strongly dominates.Partial Least-Squares regression modelling on a designed set of training and validation milk samples resulted in root mean-square prediction errors of 0.05% and 0.03% for fat and protein content, respectively, which is close to the accuracy of reference analysis. It has been shown that multivariate data analysis is capable of distinguishing individual scatter spectra of fat and protein. This conclusion has been supported by Mie-theory calculations.The method is suitable for routine laboratory analysis or in-line quality monitoring in the dairy production.
... According to this equation the light extinction coefficient is used to describe how the original beam of light from the emitting fiber decreases as it travels trough the sample according to absorption and scattering principles. As reported by Crofcheck, Payne, Hicks, Mengüç, and Nokes (2000), the propagation of the light beam can be treated as a planar wave in these optically thin solutions. In this case first-order scattering prevails, meaning that scattering only occurs once before reaching the detector. ...
... The 18 wavebands obtained were in the range 500-1010 nm. Following the prediction models established by Crofcheck et al. (2000) and Castillo, Payne, López, Ferrandini, and Laencina (2005) to predict milk fat content in skim milk and whey fat concentration in cheese making, respectively, we suggest the following two models to predict the normalized intensity (I N 0 ) of the optical signal leaving the light source during meat emulsification, considering that scattering light distribution is dominant: ...
... As can be observed, backscatter response intensity was inversely proportional to fat lean ratio, especially in the central spectral scan corresponding to the orange-red (610-640 nm) and red (670-700 nm) regions where I N showed a clear decrease as R FL increased from 0.075 to 0.33. Crofcheck et al. (2000) observed a similar behavior of the normalized intensity at 724 nm in milk samples with various fat levels. However, when the change of I N is studied as a function of R FL (Fig. 3) this behavior changes accordingly with the changes of the spectral scan and chopping time analyzed. ...
Normalized light backscatter intensity (I(N)) response as a function of fat/lean ratio (R(FL); 0.075, 0.25, and 0.33), chopping time (CT; 2, 5 and 8 min) and fiber separation distances (d; 2. 2.5 and 3 mm), were measured using a fiber optic spectrometer. Models based on the apparent light extinction coefficient (model I), fat/nonfat solid concentrations (model II), and the intensity ratio between optical distances (model III), were tested for I(N0) prediction (I(N) at d = 0). Model I was significantly (P < 0.0001) better than model II for prediction at 570 nm (lambda), 8 min (CT), and 0.075 of R(FL). Model III showed maximum geometry values and extinction coefficients for optical fiber separations of 2 and 2.5 mm, yielding the higher R(2) as R(FL) and wavelength increased. The results demonstrated a high correlation between functional properties of meat emulsion (i.e., R(FL)) and optical wavebands that may have potential for predicting I(N0) using an optic sensor technology.
... These results suggest the dependency of the loss of I N measured during meat emulsification with the optical radial distances. A similar optical intensity behavior was obtained by Crofcheck et al. (2000) in skim milk samples measured at different radial distances from the light source. Fig. 4 also shows a linear increase of the optical density (Fig. 4B) and loss of intensity (Fig. 4C) as radial distance increases from 2 to 3 mm. ...
One of the major concerns in the meat processing industry is the loss of emulsion stability resulting in cooking losses. An optical sensor technology to control the emulsification process would minimize this problem. The normalized light intensity (IN) as a function of fat/lean ratio (RFL; 0.075, 0.25, 0.33) and chopping time (CT; 2, 5, 8 min) were measured at three radial distances (2, 2.5, 3 mm) from the light source to calculate the optical density (OD) and the loss of intensity (ILoss), using a fiber optic spectrometer. ANOVA results were highly significant for IN, ILoss. Normalized intensity decreased with increased chopping time as a result of emulsion homogenization, and with increased distance. Chopping time had a positive correlation with fat losses during cooking, which in turn had a negative correlation with IN and ILoss. These results suggest that light extinction spectroscopy could provide information about emulsion stability.
... El reciente interés por los fenómenos de absorción, fluorescencia y dispersión de la radiación en la leche es más cuantitativo que cualitativo (Lochte Watson et al., 1998). Gruen y Tao, 1985;Casal et al., 1988;Payne et al., 1993a;Kamishikiryo-Yamashita et al., 1994;Kuaye, 1994;Lochte-Watson et al., 1998;Crofcheck et al., 2000). ( McQueen et al., 1995). ...
La industria quesera demanda el desarrollo de instrumentos de medida en línea, sencillos, sanitarios y no destructivos, que permitan la monitorización del proceso de coagulación de la leche y la predicción de parámetros de control tales como tiempo de coagulación y, en especial, tiempo de corte. La determinación objetiva del tiempo de corte mejora el rendimiento quesero y la homogeneidad del producto. El objetivo general del presente trabajo ha sido el estudio de un sensor de fibra óptica que determina dispersión de radiación en el infrarrojo próximo, como método de monitorización de la coagulación y selección objetiva del tiempo de corte. A tal fin, se realizan tres experiencias mediante el empleo de sendos diseños de bloque completamente aleatorios, con tres réplicas cada uno. En cada una de estas experiencias se seleccionan diferentes factores y niveles experimentales para estudiar su influencia sobre la coagulación y, especialmente, sobre los algoritmos de predicción del tiempo de corte
