The effect of inulin addition (0–4%) upon texture and microstructure of set yoghurt with different levels of fat (0.2%–3.5%) was investigated. A two-factor experimental design with four treatments was used for data analysis. Skimmed milk with various inulin and cream concentrations was standardized to 4% protein content, homogenized, heated to 92°C and fermented at 42°C until a pH of 4.6 was reached. The chemical composition, pH, consistency and microstructure properties of the yoghurts were analysed after 6 days of storage at 5°C. The statistical analysis showed that inulin and fat significantly affected the rheological and sensory results. Higher yield stress, “firmness” and “creaminess” values were observed in yoghurt produced with higher inulin additions, whereas the pH value was not affected. A significant correlation was found between yield stress and sensory determined firmness (r=0.91). The microstructure examined by confocal laser scanning microscopy (CLSM) was only slightly affected by the concentrations of inulin in the range studied, possibly due to weak protein interactions between the inulin and the milk protein network.

Among consumers there is a growing demand for food products with a natural nutritional-physiological advantage over comparable conventional products. As part of an EU funded project, Agroscope Liebefeld-Posieux ALP examined the possible impact of processing on nutritionally valuable milk components. using the example of conjugated linoleic acids (CLA). Among the many benefits ascribed to CLA, it is believed to have an anticarcinogeneic effect. The extent to which processing influences the CLA content of the end product was determined by literature research and own investigations of organic and conventional butter. Furthermore, new methods to determine the oxidation stability of butter were evaluated by ALP, and the storage stability of CLA enriched and conventional butter was examined. As a third objective, a process for low-input CLA enrichment of milk fat has been developed.

Les consommateurs recherchent de plus en plus les denrees alimentaires naturelles possedant une valeur nutritionnelle plus elevee que les produits traditionnels comparables. Dans le cadre d'un projet de l'Union europeenne, la Station de recherche Agroscope Liebefeld-Posieux ALP a etudie l'influence de divers processus de transformation sur les composants du lait a valeur nutritionnelle ajoutee, a l'exemple des acides linoleiques conjugues (ALC), qui possedent de nombreuses proprietes, notamment anticancereuses. Les processus de transformation influencent-ils la teneur en ALC du produit fini? Les chercheurs d'ALP ont tente de repondre a cette question en premier lieu par une recherche de litterature et par des analyses effectuees sur des beurres produits de maniere biologique et conventionnelle. Par ailleurs, ALP a developpe des methodes pour determiner la stabilite du beurre vis-a-vis de l'oxydation, qui ont permis d'etudier la stabilite du beurre enrichi en ALC et du beurre conventionnel durant le stockage. Un procede a en outre ete mis au point pour enrichir avec menagement (low input) la graisse de lait en ALC.

In the larger Swiss abattoirs the fat score (FS) is determined by default as an indicator of fat quality. The FS refers to the iodine number and is related to the degree of unsaturation of the outer layer of backfat. In a feeding trial with Large White gilts, the FS was determined in 47 carcasses. Meat and fat tissues were prepared for the production of salami (SAL), raw-cured bacon (RCB), pork hamburger (PHB) and Vienna sausage (VIS). In the different meat products, the FS was closely related to the percentage of saturated (SFA: r=-0.49 to -0.79) and polyunsaturated fatty acids (PUFA, r=0.36 to 0.79) for RCB, SAL and PHB (p⩽0.05), but not for VIS. For RCB, significant correlations with FS were seen for the meat:fat-ratio (r=0.39), fat firmness (r=-0.31) and one fat oxidation marker (1-octen-3-ol: r=0.51). The texture (r=-0.60), a(w)-value (r=0.63) and one fat oxidation marker (1-octen-3-ol: r=0.46) were significantly correlated with FS in SAL. On the whole, only a few variables correlated significantly with FS for SAL and RCB and the corresponding relationships were always linear. No significant correlation between FS and any of the technological and sensorial parameters were found for VIS or PHB.

The influence of native whey protein isolate (WPI) addition on the consistency and microstructure of set yoghurt was studied. Native WPI with nutraceutical properties was added (3–12%) to the yoghurt milk immediately before fermentation. The consistency of the yoghurts was analysed and compared using two rheological methods: the penetration resistance of a cylinder and an oscillation method for which a vane was used. The effects of the WPI on the rheologically determined values were quantified whereby a remarkably good correlation between the two methods was achieved. With both methods the texture characteristics of the different set yoghurts could be well characterized and enabled good comparisons. The addition of WPI gave rise to a weaker texture of the set yoghurt. Microstructure was observed by confocal laser scanning microscopy. The addition of WPI led to a less-coherent microstructure, which was in agreement with the rheological observations.

Texture and rheological attributes are among others important properties of yoghurt products. The consistency determination of the weak yoghurt gel network by rheologi- cal methods is problematic because the structure to measure can partly be damaged al- ready in the act of sample preparation. No standardised rheological methodology (e.g. IDF, ISO) for set yoghurt is available, therefore a method with minimal destruction of the weak structure before measuring is required, e.g. the vane measuring system or the cylinder penetration test. For decades experts have been studying how whey proteins could be applied in food- systems. Undenaturated whey proteins are investigated as dietary aid (1) and offer sev- eral benefits as material to formulate yoghurt products. Patocka et al. (2) reported on textural effects of soluble whey protein isolate (WPI) added to stirred yoghurt. The WPI was added as a nutraceutical (nutritional and pharmaceutical) rather than a technologi- cal ingredient at different levels (2-10%) to a commercially available stirred yoghurt, containing pectin and carrageenan. In this study (2) the apparent viscosity of the stirred yoghurt decreased with WPI concentration of 2-8%. In contrast, additions of WPI of 8 to 10% led to an increase of the apparent viscosity. The objectives of this study were 1) to measure the rheological characteristics of different set yoghurts with a vane directly in the yoghurt cup "as it is" with a minimum of destruction of the weak structure before the measurement and to compare the results with those of the cylinder penetration method and 2) the study and the quantification of the effect of native whey protein to the struc- ture of set yoghurt. The native whey protein (3-12%) was added to the yoghurt- milk just before fermentation.