Thirty milk samples [high-temperature short-time (HTST) milk, extended shelf life (ESL) milk (directly heated, indirectly heated, microfiltered), ultra-high temperature milk] from 17 German dairies were analysed. Total viable counts of directly or indirectly heated ESL milk were significantly lower than those in microfiltered ESL and HTST milk. Evaluation of indigenous enzyme activity revealed sufficient heat treatments in all milk samples. The manufacturing processes were differentiated by estimating furosine and acid soluble whey proteins. Sensory examinations revealed a preference for HTST heated and microfiltered ESL milk. However, a significant discrimination of drinking milk types was not possible. Vitamin losses were not detected, and concentrations of vitamins in different types of milk were comparable.

Extended shelf life (ESL) milk was processed with integrated microfiltration (pore size 1.4 µm). The germ‐enriched retentate was not used for the final whole milk. Microfiltration led only to a negligible change in the content of the main components of the ESL product compared with the source milk. The total protein was only slightly decreased (0.02–0.03%) and the ratio of the protein fractions was unchanged within the measurement accuracy. The furosine content of the isolated fat globuline membrane fraction could be used as a diagnostic to prove cream had been subjected to high‐temperature treatment. The shelf life of the ESL milk was distinctly prolonged compared to HTST‐pasteurized milk.

Jusqu'a present, les analyses portant sur les effets de la reticulation de proteines lactiques avec la transglutaminase (EC 2.3.2.13) sur les proprietes des produits laitiers fermentes furent avant tout realisees dans des produits a consistance ferme. L'etude en question presente pour la premiere fois l'influence de la reticulation enzymatique des proteines lactiques sur les proprietes des produits laitiers brasses comme le yaourt et le lait caille. Les analyses ont demontre que les produits brasses (yaourt et lait caille) peuvent etre fabriques avec des proprietes rheologiques et sensorielles a peu pres analogues, independamment du fait que la reticulation enzymatique se deroule dans le lait de yaourt ou que des produits de proteines lactiques traites a la transglutaminase soient ajoutees au lait avant la fermentation. Independamment des conditions d'incubation et de brassage ainsi que des produits pulverises utilises, les produits brasses (yaourt et lait caille)fabriques de lait enzymatiquement modifie ont une viscosite superieure et une synerese inferieure a celle des produits provenant de lait non-traite. Si l'incubation avec la transglutaminase se deroule dans le lait de yaourt, les produits de yaourt brasse ont des agregats de proteines visibles, induits par les enzymes. Ces agregats ne sont pas detruits par le processus de brassage. Par contre, des gels de yaourt a apparence lisse peuvent etre produits en ajoutant des produits de lait ecreme traites a la transglutaminase ou des proteines lactiques au lait non-traite. Les valeurs de viscosite dependent du type de proteines lactiques ajoutees et augmentent dans l'ordre: addition de poudre de lait ecreme < addition de proteine lactique complete < addition de caseinate de sodium. Des differences dans les proprietes sensorielles de produits laitiers fermentes traites a la transglutaminase ou non-traites ne sont verifiables que si le traitement enzymatique est realise dans le lait. Ainsi des echantillons de lait traites enzymatiquement ont un gout moins aigre, ressemblent moins a un yaourt typique et l'intensite totale des attributs est moindre. Leur apparence est moins lisse et leur consistance plus ferme.

La microfiltration pour le traitement du lait est connue depuis les annees 80. Au debut, elle etait employee comme methode de separation mecanique pour reduire les microorganismes dans le lait ecreme. En general, la separation se faisait par des membranes ceramiques ayant une dimension moyenne des pores de 1,4 μm. Grâce a la forte reduction des teneurs bacteriennes, le traitement thermique ulterieur pouvait etre realise de maniere plus indulgente. Le traitement preliminaire est avant tout employe en Scandinavie pour le lait de fromagerie. En Allemagne, on emploie avant tout des centrifugeuses de degermage. Parallelement a l'emploi de la microfiltration dans la fabrication fromagere, des procedes de fabrication pour le lait de consommation a duree de conservation prolongee ont ete developpes et introduits dans quelques pays. La premiere partie de cette etude contient un resume des connaissances actuelles sur ces procedes decrites dans la litterature specialisee. Les configurations actuellement employees sont presentees ainsi que les resultats des examens obtenus pour le lait. La deuxieme partie de l'etude presente les resultats obtenus avec des propres configurations, pour lesquels le retentatobtenu n'est pas utilise dans la fabrication de laitde consommation. En meme temps, le lait cru, les produits intermediaires et le lait de consommation fabrique sont soumis a des analyses chimiques et microbiologiques. Dans ce contexte, bilan et composition proteiniques ainsi que differents indicateurs sont d'un interet particulier. Pendant la duree de conservation, le lait de consommation fabrique a egalement ete soumis a une analyse sensorielle. Tous les examens ont ete realises au site Kiel du BFEL (Centre federal de la recherche nutritionnelle et alimentaire) en vue d'une mise en pratique de cette configuration dans la fabrication de lait de consommation a duree de conservation prolongee. Le lait de consommation microfiltre, fabrique dans les deux variantes, ne s'est pratiquement pas distingue d'un lait entier a pasteurisation courte en ce qui concerne la teneur en ingredients principaux. La teneur en proteines n'etait que minimalement reduite par la microfiltration et restait invariable par rapport aux differentes fractions proteiniques. Du a une fraction microfiltree elevee (< 85 %), le lait de consommation avait une teneur reduite en cellules somatiques. La preuve pour la pasteurisation haute d'un flux partiel pendant le processus de fabrication ne pouvait etre faite que par une determination compliquee de la furosine dans la proteine de la membrane des globules gras. Lors de l'analyse de profile sensorielle des echantillons d'essai conserves a froid et de differents echantillons commerciaux, il n'y avait pas de differences substantielles par rapport a du lait a pasteurisation courte ou a pasteurisation haute tout au long de la duree de conservation. Le lait de consommation microfiltre avec une fraction a pasteurisation haute d'environ 23 % avait, par rapport aux deux autres types de lait, une duree de conservation nettement prolongee a une temperature de stockage d'environ 7 °C.

Le Centre Federal de Recherche de l'Industrie Laitiere, Kiel a participe a un projet europeen de recherche de deux ans (AIR3-CT94 2322, coordinateur scientifique: E.A. Hunter, Inst. Biomathematics & Statistics Scotland) pour l'elaboration d'une methodologie afin de comparer au-dela des frontieres nationales l'analyse sensorielle de fromage dur et a pâte demi-dure. La Grande-Bretagne, la Norvege, la Suisse, l'Italie et l'Allemagne ont participe aux travaux de recherche. Le but des analyses etait (i) de determiner les avantages et desavantages des differentes methodes pour caracteriser les fromages durs et demi-durs, (ii) de s'accorder sur une methodologie harmonisee pour l'analyse sensorielle et l'appreciation de fromage durs et demi-durs en Europe. Dans le cadre d'une premiere etude inter-laboratoires, 12 types de fromages europeens (fromages durs et a pâte demi-dure) ont ete apprecies selon la methode du pays pour la caracterisation des qualites sensorielles. Dans une deuxieme etude inter-laboratoires, les memes types de fromage ont ete caracterises selon une methode plus ou moins harmonisee avec des attributs organoleptiques convenus. Bien qu'il y ait eu des progres remarquables dans l'elaboration d'une methode de controle europeenne, les discussions entre les differents scientifiques ont montre qu'il existe en plus des differences methodologiques, des differences culturelles sur le role d'attributs sensoriels dans les pays partenaires. Non seulement des parametres de controle scientifico-techniques, mais aussi des vielles traditions dans la production des denrees et dans la culture culinaire jouent un role dans l'harmonisation au-dela des frontieres nationales des methodes sensorielles.

The Federal Dairy Research Centre Kiel was involved in a 2-year European research project concerned with the development of methodology for comparison of sensory assessment of hard and semi-hard cheese across international frontiers. Institutes in Denmark, France, Italy, Norway, Switzerland, UK and Germany have participated in this work. The main objectives of this project are: (i) Assess the strengths and weaknesses of different sensory methodologies for characterization of cheese, (ii) determine similarities between sensory vocabularies and (iii) devise a compromise strategy for sensory assessment of hard and semi-hard cheese. In addition, it is of interest to find sensory key attributes of hard and semi-hard cheese. In a first collaborative ring trial, 12 European hard and semi-hard cheeses were assessed according to the sensory methodology normally applied in the respective countries. In a second collaborative ring trial the same cheeses were characterized according to a harmonized protocol with a common sensory vocabulary. The results of the Kiel-panel are presented. The second collaborative ring trial has enabled considerable progress to be achieved in developing a European methodology. The resulting discussions, however, have shown that there exist not only technical, but also cultural differences in weighting sensory criteria of cheese samples in Europe. In harmonizing sensory methods across international frontiers, one has to take into account both: (i) scientific technical parameters as well as (ii) centuries-old traditions in Food production and eating habits.

Feeding value and acceptability of false flax expeller for ruminants were studied in experiments with four castrated wethers, six rumen fistulated and Is intact lactating cows. As to the acceptability false flax expeller can be fed to wether without any difficulties in a quantity up to 0.24kg per day and to dairy cows up to 2.4kg/d. Based on the results of the digestibility trial with wether the energetic feeding value was calculated to be 15,4 MJ ME/kg DM or 9,5 MJ NEL/kg DM.The intact and fistulated cows were fed concentrates containing 0%, 15% or 30% of false flax expeller and a grass/corn-silage as roughage. Due to the high content of polyunsaturated fatty acids in false flax expeller the ratio between acetic and propionic acid in the rumen fluid declined, decreasing from 3.1:1 to 3.0:1 to 2.7:1. The other parameters of rumen fermentation (pH-value, NH3-N content) were not affected significantly. In lactating cows yielding 22.7 kg FCM per day increasing amounts of false flax expeller led to a strong decrease of fat content from 3.73% to 3.28% to 2.46%, respectively. Milk protein content was affected as well decreasing from 3.20% to 3.18% or 3.05%, respectively. Feeding false flax expeller changed milk fat com position (i.e. quality of butter fat) remarkably. The percentage of saturated fatty acids up to Cia decreased from 75.3% to 62.7% and the percentage of monounsaturated fatty acids increased from 21.5% to 33.5% in contrast to the polyunsaturated fatty acids. The content of the latter was not affected, amounting on average 2.7%. An influence on the palatability of the milk was not detected.

The project was concerned with studies on the distinguishing features which allow heat treatment of milk to be evaluated. The aim of the project was to establish chemical, physical, processing and sensory parameters, which enable the reliable differentiation between heating ranges as normally applied in dairies such as thermisation, pasteurization, (short-time- and long-time heating, high temperature pasteurization), UHT treatment and sterilization and which provide, thus, the scientific grounds for establishing defined limits for each milk type. They allow, further, measures to be taken with which the thermal effect on milk can be reduced to a necessary minimum which is possible as regards the production process and is required from the hygienic viewpoint. They are, thus, a useful tool in improving the quality of fluid milk in the interest of the consumer. Raw milk from the experimental farm Schaedtbek of the Federal Dairy Research Centre was thermally treated using different temperature-time combinations in the range between 62-140 degrees C and holding times extended up to some minutes and the heat-induced changes of milk and their components analytically controlled. For thermal treatment of the milk samples a very broad temperature-time spectrum was, thus, selected. This was possible by use of a discontinuously operating autoclave and a continuous pilot heating plant with exchangeable holders at the Institute for Process Engineering of the Centre. In the range studied all legally admitted heating processes could be incorporated. As a basis for calculating the equivalent holding time the sterilization value F-0 was used. As chemical parameters furosine, N6-methyladenosine, lactulose, native (acid-soluble) alpha-lactalbumin and beta-lactoglobulin (genetic variants A+B) and immunoglobulins were analytically determined. Further, the contents of free amino acids, caseinophosphorus and free amino groups (OPA reaction) were determined and the thermally induced changes in the triglyceride/fatty acid pattern of milk examplarily investigated. Thermally induced protein changes were followed up analytically by measuring the degree with which enzymic proteolysis of milk protein was possible. As physical parameters the freezing point depression of milk, pH-and SH-values, as well as gelling- and browning behaviour were considered in evaluating the thermal effect on milk. As processing parameters for assessing the heat treatment process of milk all sterilization values (F0 values), on which the adjusted temperature-time combinations were based, were taken into consideration. As to sensory parameters a sensory profile analysis of the heat treated milk was performed, if possible, and included in the evaluation. The results from this study show that, without doubt, there exist, from the technological point of view, a number of suited chemical parameters which can also be analytically controlled. As heat indicators for establishing upper limits for the heating ranges of high temperature pasteurization, UHT treatment and sterilization they are, hence, suited to be used for limiting the heat load in these milk types to the minimum required for product safety in order to come, thus, up to the particular image of milk in terms of "Naturbelassenheit" and health promotion.

The results of sensory profile analysis and visual assessment of milks subjected to different heat treatments have shown that a taste panel trained in sensory assessment of milk awards milk subjected to thermisation- and pasteurization processes (short time and long-time heating) and obtained by applying the lower range of high temperature pasteurization a good to excellent quality as regards odour and flavour. The same taste panel has classified also milk obtained under conditions of UHT treatment to be perfect regarding odour and flavour and awarded a good quality, although with the temperature/ time combinations selected sterilization values up to 30 min were applied. In contrast to this milk obtained using the upper range of high temperature pasteurization at process temperatures of 105-125 degrees C and holding times corresponding to sterilization values of less than 0.3 min has been classified to be "faulty" from the sensory viewpoint. The reason for this might be a milk flavour which occurs particularly in the upper range of high temperature pasteurization but is not set free under conditions of UHT treatment, or is rather "casted out" from the milk matrix at the higher process temperatures of the UHT treatment range and is, thus, no longer effective from the sensory viewpoint. Additionally one should assume that the cooked flavour of UHT milk is today rejected neither by a trained taste panel from the viewpoint of flavour and odour.

L'objectif de l'etude etait d'etablir des parametres chimiques, physiques, de transformation et organoleptiques qui permettent de differencier les zones de chauffage habituellement appliquees en laiteries (thermisation, pasteurisation, traitement UHT et sterilisation). La definition de ces parametres permet, en outre, de reduire au minimum les alterations liees au chauffage du lait, en fonction du procede utilise et tout en assurant une bonne qualite hygienique. Du lait cru a ete traite thermiquement en appliquant differentes combinaisons temps/temperature entre 62 et 140°C et des durees de chambrage allant jusqu'a plusieurs minutes. Les changements induits ont ete analyses. Tous les procedes legalement admis utilisent des temperatures situees dans la zone etudiee. La valeur sterilisatrice F 0 a ete utilisee pour calculer la duree de chambrage equivalente. Les teneurs en furosine, N6-methyladenosine, lactulose, α-lactalbumine native et β-lactoglobuline (variants genetiques A+B) et des immunoglobulines ainsi que les teneurs en acides amines libres, caseine phosphorylee et groupes amines libres ont ete determinees et les changements du profil triglycerides/acides gras du lait etudies. Les modifications thermiques des proteines du lait sont mesurees par le degre de proteolyse enzymatique. Les principaux parametres physiques d'alteration thermique etudies ont ete l'abaissement du point de congelation, les valeurs de pH et de SH, ainsi que le pouvoir de gelification et de brunissement. Comme parametres de transformation, on a considere toutes les valeurs de sterilisation (valeurs F 0 ), resultant des combinaisonstemps/temperature. Une analyse organoleptique du profil du lait traite thermiquement a egalement ete effectuee. Les resultats obtenus montrent qu'il existe, du point de vue technologique, plusieurs parametres chimiques appropries pour le controle

UHT-milk samples were drawn in 2 enterprises respectively in Spain and the FRG and examined analytically and sensorially at the Institute for Process Engineering of the Federal Dairy Research Centre, Kiel, and only analytically at the Instituto del Frio, Madrid. During sampling the operation of the UHT-plants was controlled and the temperature-time relations measured. On the basis of the temperature-time curves determined the sterilization values (F(L) - for lactulose formation, F(m) - for destruction of B. steathermophilus and F(O)- for destruction of Cl. botulinum) were calculated and compared with the admmissible limit sterilization values. Except for the direct UHT plant, all others were found to be very close to the prescribed limit values. The analytical examinations of lactulose formation and proteolytic activity during storage at 20, 30 and 40-degrees-C showed an increase in lactulose concentration in all milks, a marked increase in enzyme activity, however, only as far as the Spanish samples were concerned. When determining the proteolytic enzyme activity a direct comparability of the results between the enzymatic and the HPLC method could not be established. The sensorial changes of the milks were examined according to profile analysis. Although the intensity of flavour and the kind of flavour were found to be rather varying from sample to sample, the Spanish milks were, on average, worse scored as regards quality.