Salwa Bornaz

Filtration in hydrophobic media: 2. A triglyceride partition phenomenon as observed by tangential filtration of butter oil

Having demonstrated a partition of a hydrophobic medium (butter oil) under crossflow filtration and having tentatively explained the phenomenon on stereochemical and saturation basis, the molecular partition was studied by tangential filtration. Under specific hydrodynamic conditions, a filtration phenomenon was demonstrated. The solid fat content (SFC) at 20°C of the fractions obtained was investigated accordingly. When the molecular partition takes place, an SFC divergency between the permeate and the retentate is observed. The amplitude of the divergency depends on experimental conditions.

Heat treatment of cream: A model of the butter texture response in relation with triglyceride composition

The effects of thermal treatments on butter texture are known and have been used since 1935 on an industrial scale, but without fundamental knowledge. Butter composition influences firmness, as observed through seasonal and regional variations. Experiments were carried out at 15°C by using a cone penetrometer and an industrial testing machine. A significant correlation between heat treatment efficiency and some prevalent triglycerides and fatty acids on butter firmness was outlined. Three fatty acids (myristic, oleic, palmitic) and four major groups of triglycerides mainly affected the firmness, sometimes leading to an inversion of the thermal effect, according to individual sample composition. A crystallographic and thermodynamic model based on triglycerides properties was developed.

Effect of Plant Originated Coagulants and Chymosin on Ovine Milk Coagulation

The coagulation of ewes milk was studied by using plant source coagulants namely the artichoke, Cynara scolymus L. cv. Blanca, and latex from the fig tree (Ficus carica L.). A turbidimetric method was used to evaluate and compare the coagulation properties of the novel coagulants with chymosin treated samples. Syneresis capacity and sensory evaluation of resultant cheese samples were studied and it was found that both cynara and chymosin produced sigmoidal increase in turbidity to the milk with three distinct phases. The coagulation kinetics was affected substantially by both coagulants. Plant coagulant induced shorter gelation time compared to chymosin however required longer time for restructuration (end of coagulation). The coagulum obtained with the latex of Ficus carica had a higher yield, owing to its high water retention capacity. With the exception of color, the overall sensory attributes did not show significant differences among coagulants.

Effect of Milk Fat Substitution of Rennet Milk Induced Coagulation on Physico-Chemical Properties

The objective of this paper was to study the effect of milk fat substitution by (W1/O/W2) multiple emulsions based on olive oil in comparison with full and low-fat milks on milk behavior during rennet coagulation. Therefore, based on the turbidimetric and conductivimetric methods, a follow up of enzymatic coagulation is realized. Drainage of renneted gels was followed by syneresis study and cheese yield. The comparison between the coagulation aptitude of low fat milk and milk-olive oil emulsion showed that the hydrolysis phase extended up to 35 minutes for full fat milk and up to 38 minutes for milk-olive oil emulsion. The transition phase solid/gel was shorter in the case of the whole milk. The reticulation phase was shorter in the case of milk-olive oil emulsion. The milk conductivity depended on the milk richness in fat content. Milk-olive oil emulsion showed the lowest cheese-making yield compared to its full and low-fat counterpart.

The behaviour of Arabian donkey milk during acidification compared to bovine milk

To better understand the fermentation kinetic of Arabian donkey milk, its physicochemical properties, conductivity and viscosity were assessed during acidification, and compared to that of the bovine milk. Donkey milk showed a shorter latency phase and slightly lower acidification rate than bovine milk. Measurement of electric conductivity during acidification showed that maximum demineralisation of casein micelles occurred at around pHI 5.44 for donkey milk and pHI 5.16 for bovine milk. Donkey milk was also found to be less viscous. The technological characteristics of donkey milk were different from those of bovine milk due to intrinsic physicochemical properties of both milks.