Antioxidant and emulsifying properties of alcalase-hydrolyzed potato proteins in meat emulsions with different fat concentrations.

The effect of hydrolyzed potato protein (HPP), a natural antioxidant, on emulsion quality was investigated using a factorial design with two Fat (15%, 30%) and two HPP (0%, 2.5%) levels, with three replications. The colour of the raw emulsions as well as cooking losses, textural properties and TBARS of cooked frankfurters were measured. Increasing the Fat proportion significantly (P<0.05) increased L(∗), H(ab)(0) and decreased a(∗), b(∗), C(ab)(∗) and hardness. Meat emulsions with added HPP were darker (lower L(∗)) than those made without HPP and also had lower values of a(∗) and b(∗). The addition of HPP (2.5%) significantly (P<0.05) decreased cooking losses and fracture force, and had a significant (P<0.05) inhibitory effect on lipid oxidation in cooked frankfurters. These results suggest that HPP has both antioxidant and emulsifying properties which may be of potential use in meat emulsion manufacturing.

Novel online sensor technology for continuous monitoring of milk coagulation and whey separation in cheesemaking.

The cheese industry has continually sought a robust method to monitor milk coagulation. Measurement of whey separation is also critical to control cheese moisture content, which affects quality. The objective of this study was to demonstrate that an online optical sensor detecting light backscatter in a vat could be applied to monitor both coagulation and syneresis during cheesemaking. A prototype sensor having a large field of view (LFV) relative to curd particle size was constructed. Temperature, cutting time, and calcium chloride addition were varied to evaluate the response of the sensor over a wide range of coagulation and syneresis rates. The LFV sensor response was related to casein micelle aggregation and curd firming during coagulation and to changes in curd moisture and whey fat contents during syneresis. The LFV sensor has potential as an online, continuous sensor technology for monitoring both coagulation and syneresis during cheesemaking.

Modelling casein aggregation and curd firming in goats' milk from backscatter of infrared light.

A kinetic model was proposed for describing the curd assembly of skimmed goats' milk during enzymic coagulation. The enzymic coagulation of milk was monitored using an optical sensor that measured diffuse reflectance (light backscatter) at 880 nm. The appearance of a shoulder, at low temperatures and protein concentrations, in the diffuse reflectance ratio profile after the inflection point of the curve (Tmax) appeared to separate the aggregation and curd firming steps. The diffuse reflectance ratio profile after Tmax was attributed to the overlapping of casein micelles aggregation and curd firming reactions. The developed kinetic model combined a second order reaction model to describe aggregation reactions and a first order reaction model to describe firming processes reactions. A completely randomised block design with three replications was used to determine the effect of protein concentration and temperature on kinetic constants. Milk was adjusted to three levels of protein (30, 50 and 70 g/kg), and coagulated at five temperatures (20, 25, 30, 35 and 40 degrees C) to test a wide range of processing conditions. Data points from each profile after Tmax were fitted to the proposed model using non-linear regression. The average R2 and standard error of prediction (SEP) for 45 tests conducted were in the range of 0.9975 +/- 0.0027 and 0.0081 +/- 0.0037, respectively. A significant increase in characteristic times for aggregation (tau2) and curd firming processes (tau1) were found when temperature decreased or protein increased. Theoretical asymptotic value of reflectance ratio, R(infinity), increased with increasing level of protein and temperature (P < 0.05). The parameter beta1, which represented the fraction of diffuse reflectance ratio attributed to aggregation, decreased with increasing temperature and decreasing protein.

Effect of protein and temperature on cutting time prediction in goats' milk using an optical reflectance sensor.

An objective method for determining the coagulum cutting time is needed to improve consistency and processing efficiency of goats' cheese. A fibre optic sensor was used to measure the backscatter of near-infrared radiation at 880 nm during the coagulation of skimmed goats' milk for the purpose of predicting coagulum cutting time. A randomised block design, replicated three times, was used to test the effect of three protein concentrations (3, 5 and 7% (w/w)) on diffuse reflectance parameters for cutting time prediction of milk coagulated at five different temperatures (20, 25, 30, 35 and 40 degrees C) to assure a wide range of coagulation rates. The inclusion of a protein term in the existing algorithms was essential to reduce the standard error of prediction to under 6.2 min. An algorithm including a time-based parameter and a protein term, Tcut=beta0 T2min (1 + gamma% Protein) was found to predict cutting time with a SEP of 2.42 min and an R2 of 0.98. Gamma was considered constant (gamma=-0.0674, goats' milk) representing the protein effect on beta0. Algorithms using response-based parameters (such as change in reflectance ratio) and the composition parameter protein required additional regression parameters such as temperature and an intercept term to predict the cutting time with the same precision as algorithms using only time-based parameters. Time-based parameters were found to decrease proportionally with increasing temperature and decreasing protein concentration. Response-based and mixed-based parameters were found to decrease with decreasing temperature. Reflectance ratio at cutting time did not significantly change with protein concentration for skimmed goats' milk. The activation energy of kappa-casein hydrolysis was calculated based on changes in reflectance profile parameters and was found to be in the range 63-72 kJ mol(-1).

Convective-diffusion-based fluorescence correlation spectroscopy for detection of a trace amount of E. coli in water.

Fluorescence correlation spectroscopy (FCS) is adapted for a new procedure to detect trace amounts of Escherichia coli in water. The present concept is based on convective diffusion rather than Brownian diffusion and employs confocal microscopy as in traditional FCS. With this system it is possible to detect concentrations as small as 1.5 x 10(5) E. coli per milliliter (2.5 x 10(-16) M). This concentration corresponds to an approximately 1.0-nM level of Rhodamine 6G dyes. A detailed analysis of the optical system is presented, and further improvements for the procedure are discussed.

Characterization of milk properties with a radiative transfer model.

To characterize milk through light-scattering measurements, a semianalytical radiative transfer model was used to simulate the backscatter of light in milk having homogenized fat levels from 0.05 to 3.2 wt. %. The input parameters to the model include the incident wavelength, refractive index of particles and medium, and particle number densities. By varying the wavelength, we can obtain a reasonable fit between experimental data and the model for lower fat milks. Results indicate that the model is most sensitive to the particle diameter and size distribution and less sensitive to the number and index of refraction of the particles.