DENATUREPROBE

DEVELOPMENT OF AN OPTICAL BACKSCATTER SENSOR FOR DETERMINING THERMAL DENATURATION OF WHEY PROTEINS DURING MILK PROCESSING

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 Obiettivo del progetto (Objective)

'The heat denaturation of whey proteins impacts the functional properties of milk. After denaturing, β-lactoglobulin (β-LG) associates with κ-casein (κ-CN), a protein located in the surface of the casein micelle. This association significantly impairs milk coagulation by creating a steric obstacle for κ-CN hydrolysis −a critical phenomenon initiating coagulation− and by increasing the gel moisture retention. Correlations of the degree of β-LG denaturation to gelation time, gel firmness, and gel moisture content have been widely documented. The resulting high moisture and soft gels are undesirable for cheese manufacture but advisable in yogurt processing, as it aids in preventing one of its most frequent defects, wheying-off. Early prediction of the potential gelling strength of milk will allow milk batches to be used for their most suitable purposes. The economical impact this would have on the dairy industry, in addition to the non-existence of a simple method of protein denaturation measurement, motivates this research. The goal of this project is the development of an optical sensor technology for inline determination of β-LG denaturation and subsequent association with κ-CN during milk heat treatment. Given the scattering properties of the micelles, light backscatter was chosen for optical measurement. Preliminary experiments indicate that light backscatter response is proportional to heat treatment intensity, which suggests that light scatter could be used to determine the whey protein denaturation degree. The development of the proposed sensor technology will require: a) finding the adequate wavelength/s, b) developing a robust prediction algorithm, and c) obtaining chemical data supporting the observed optical responses. Successful development of this optic sensor technology will aid in the decision-making process of dairy plants for the efficient use of raw milk and the assurance of a high quality product.'

Introduzione (Teaser)

Milk contains whey proteins that become denatured on heat treatment, thereby altering its functional properties, moisture content and texture. If functional properties are detected, this could optimise decision making as well as product quality with regard to selecting cheese or yoghurt for manufacture from milk.

Descrizione progetto (Article)

The EU-funded project DENATUREPROBE will develop an inline optical sensor technology that will detect light backscatter from casein micelles present in milk. This will help assess the degree of denaturation in milk proteins as high intensity heat treatment will increase backscattering from micelles. This is due to the increased attachment of free sulphide groups of the denatured whey proteins with the k-casein on the casein micelle surface.

Researchers successfully set up a laboratory for performing optical measurements on thermally denatured milk proteins. Light backscattering properties were investigated in response to varying temperature levels, micelle particle size and pH using different waveband ratios.

Results demonstrated a decrease in light backscatter intensity from micelles with an increase in pH. An association was found between heat intensity treatments at different pH levels on light backscattering. A mathematical model was successfully developed to correlate changes in casein micelle size with temperature and pH from light backscattering data. Predictive methods were used to determine particle size from light backscatter data measurements that were temperature-dependent. A patent disclosure application is in progress for developing an inline optical sensor to measure casein particle size cheaply and non-invasively.

Successful project outcomes will lead to the development of a novel inline sensor for non-invasive whey-denaturation measurement in milk. This will address the critical gap in the dairy industry for determining optimal temperature settings for milk pasteurisation treatment. The optimal pH and degree of gelation differ significantly for cheese and yoghurt. Hence, predicting the degree of gelation from heating will help optimise decision making for the consistent and high-quality production of these dairy products.