There is growing public concern about the high proportion of saturated fatty acids in milk fat; however, feed intake, energy partitioning toward milk synthesis, and milk fat concentrations can decrease when cows are fed high concentrations of unsaturated lipids. The objective of this study was to identify the optimal rate for feeding OmegaBoostTM (a flaxseed supplement that was processed using a proprietary technique by Double Pass LLC, Tualatin, OR) to dairy cows. The central hypothesis was that supplementation with OmegaBoost will decrease the proportion of saturated fatty acids in milk fat in a dose dependent manner. Using a latin-square design, 10 Holstein cows in mid to late lactation were fed for two-week periods 0, 2, 4, or 6 lbs/d of OmegaBoost or 4lbs/d ground flax as top dressing to their total mixed ration. Feed intake, body weight, activity and resting time, milk production and milk composition were measured daily. At the end of each two-week period, milk and serum samples were taken and analyzed for fatty acid composition using gas chromatography. In addition, fresh Mozzarella cheese and butter was manufactured and tested to determine the fatty acid composition and the effects of flaxseed supplementation on texture. Feeding OmegaBoost at 2, 4, and 6 lbs/d linearly decreased the proportion of saturated fatty acids in milk by 6, 15, and 18%, respectively, and linearly increased the proportion of mono-unsaturated fatty acids (14, 32, and 35%), poly-unsaturated fatty acids (16, 49, and 82%), and α-linolenic acid (26, 52, and 70%). Similar changes in fatty acid composition were observed in butter and cheese samples, resulting in butter that was less hard and adhesive at refrigeration temperature in response to feeding cows increasing concentrations of OmegaBoost. Feed intake, body weight, serum metabolite concentrations, milk production and composition, and butter and cheese yield were not significantly affected by feeding processed flaxseed. Therefore, feeding 4 or 6 lbs/d of OmegaBoost to dairy cows is effective in improving the nutritional and textural profile of dairy products without negatively affecting feed intake, milk production, or weight gain. / Graduation date: 2012

Historically, consumer perceptions towards dairy products have been measured using a rational cognitive approach. However, recent consumer insights suggest that emotions play a dominant role in consumer decision making. The South African dairy industry therefore identified a need to determine emotive reactions to educational messages in addition to the reasons underpinning dairy consumption. Using a mixed method research approach, reactions from 81 South African dairy consumers were obtained, using three different, but interrelated measuring instruments. Descriptive statistics, hierarchical ladder maps and correlation analyses were used to examine emotive and cognitive consumer reaction to a number of generic dairy messages and products. The findings indicate that certain communication messages appear to have a stronger impact on consumers due to specific emotions that these messages elicit. Personal values underpinning dairy consumption decisions were also identified within the context of emotive reactions to the selected dairy products. / Business Management / M. Com. (Business Management)

Thesis (PhD (Food Science))--University of Stellenbosch, 2007. / Thermal pasteurisation failures in the dairy industry have often been found to cause end-products of poor quality and short shelf-life. Therefore, alternative methods to eliminate microbial contaminants in raw milk are being studied. Ultrasonication is one such non-thermal technology that could offer the dairy industry an alternative to traditional pasteurisation. The main objective of this dissertation was to evaluate the use of high-power lowfrequency ultrasound (20 kHz, 750 W, 124 μm) applied in batch mode to eliminate a selection of spoilage and potentially pathogenic microbes, commonly associated with milk. These included Gram-positive and negative microbes, comprising of rods and cocci, an endospore-former, and a yeast (Escherichia coli, Bacillus cereus, Chryseobacterium meningosepticum, Lactobacillus acidophilus, Lactococcus lactis, Listeria monocytogenes, Micrococcus luteus, Pseudomonas fluorescens and Saccharomyces cerevisiae). Three strains of E. coli (1 x 106 cfu.ml-1) tested, viz. ATCC 11775, a wild strain from raw milk, and an O157:H7 strain from milk were sensitive to ultrasonication. Complete elimination of viable cells occurred within 10 min. Viable counts of P. fluorescens were reduced by 100% within 6 min of ultrasonication and L. monocytogenes was reduced by 99.0% within 10 min. Lactococcus lactis was reduced by 97.0% and M. luteus, B. cereus and C. meningosepticum by 88.0%, 87.0% and 85.0% respectively. Lactobacillus acidophilus showed the most resistance to ultrasound with only 78.0% of viable cells being eliminated. Under similar conditions, S. cerevisiae was reduced by 99.7%. Microbial cell morphology, size and Gram status did not necessarily influence the efficacy of ultrasonication. Sterile saline solution and UHT milk were used as the suspension media, and the reputed protective effect of milk fat was not observed under the parameters used in this study. A higher wave amplitude (100%; 124 μm) was found to be more efficient in eliminating microbes than a lower wave amplitude (50%; 62 μm). Pulsed-ultrasonication did not enhance the efficiency of ultrasonication indicating that standing waves were absent. Limited success was achieved by ultrasonication itself, and the long batch treatment time (10 min or more) was found to be unrealistic for industrial implementation. Hence the simultaneous application of ultrasound and heat (thermoultrasonication) was examined. Thermo-ultrasonication proved to be more effective than either an ultrasonic or heat treatment with all viable M. luteus cells being eliminated within 4 min (100% amplitude at 72°C). Similarly, to eliminate E. coli and Lb. acidophilus from milk, only 2 min and 4 min thermo-ultrasonication was required, respectively. Bacillus cereus endospores remained resistant and after a 10 min thermo-ultrasonic treatment only 78.04% were eliminated. During this investigation both extensive surface (SEM) and internal (TEM) cell damage caused by ultrasonication were observed in E. coli, Lb. acidophilus and S. cerevisiae. Hence ultrasonication physically/mechanically damages these microbial cells causing cell death/injury. Microbial proteins and DNA released from cells into the environment after an ultrasonic treatment was measured and an increase in released microbial proteins and DNA was found to be indicative of a decrease in the number of viable cells, providing that the initial cell concentration was high enough. It was, however, not possible to correlate the concentration of released microbial proteins and DNA with the exact number of viable cells eliminated, rendering it an ineffective quality indicator for the industry. Ultrasonication had no statistically significant influence on the protein, fat and lactose content of both raw and pasteurised milk. The somatic cell count of raw and pasteurised milk was found to decrease after ultrasonication. Unlike with heating, activity of alkaline phosphatase and lactoperoxidase were not reduced by ultrasonication. Hence neither enzyme can be used to indicate a successful ultrasonic treatment of milk. This study has demonstrated that ultrasonication offers a viable alternative to pasteurisation as it is effective in eliminating microbes, and does not alter native milk components. However, to attain a more effective killing, thermo-ultrasonication is recommended for the treatment of milk to be used for the production of different dairy products.

At the last time, we can see increased interest of lactose-free dairy products. The aim of the thesis was to evaluate offer of such products at selected retail chains in the South Bohemian region, then to conclude a sensory assessment of selected products and to verify of public awareness about lactose intolerance with a questionnaire survey. The widest offer of lactose-free dairy products has been found in Globus and Tesco, in the opposite the lowest offer has been found in Billa. Location of these products within the store was most the transparent in Globus (compared other stores). Three samples of white lactose free yoghurts and two samples of milk (with lactose and lactose-free) were evaluated by a sensory assessment. The sample of yoghurt from the company Madeta, line Nature was rated the best. On the contrary sample of yoghurt from the company Tatranská mliekáreň, line Nature´s Promise was rated the worst. The preference between two milk samples among the evaluators was balanced, despite large to moderate differences of intensity were described between them. Most respondents (79 %) knew what the term lactose intolerance means, but substantial part (22 %) of respondents badly indicated this the issue as allergy to milk casein. Because of high number of lactose-intolerant people in population this issue is still very actual, and it needs to be addressed.

Os ácidos linoléicos conjugados (CLAs) consistem de um grupo de isômeros geométricos e posicionais do ácido linoléico aos quais tem sido atribuídos efeitos anticarcinogênico, antidiabético, antiaterogênico e modulador da composição corporal. As principais fontes naturais de CLA são o leite e a carne de ruminantes, uma vez que microorganismos ruminais são capazes de formar CLAs e seus precursores como intermediários da biohidrogenação. Para sua identificação e quantificação por cromatografia gasosa (CG) deve se tomar cuidado ao decidir um procedimento apropriado de metilação, a fim de evitar a isomerização dos CLAs. Dessa forma, o objetivo do presente trabalho foi de avaliar criticamente metodologias analíticas para caracterizar os isômeros conjugados c-9, t-11 e t-10, c-12 do ácido linoléico, identificando o melhor método para a esterificação e a melhor programação por cromatografia gasosa para a separação, identificação e quantificação dos CLAs através de sua análise em suplementos, cortes bovinos e laticínios. Para tanto, foram empregadas as técnicas de esterificação ácida com trifluoreto de boro metanólico, esterificação alcalina com metóxido de sódio metanólico e uma esterificação mista usando a combinação dos dois catalisadores na metilação de uma amostra comercial de suplemento de ácido linoléico conjugado na forma de triacilglicerol, o Tonalin® CLA TG 80, da Cognis. Os ésteres metílicos foram identificados sob três condições cromatográficas CLA01, CLA02 e CLA03. Também foram realizadas quantificações dos isômeros c-9, t-11 e t-10, c-12 CLA no Tonalin® CLA TG 80 e FFA 80 através de ressonância magnética nuclear do carbono 13 (13C-RMN). Os resultados obtidos permitiram decidir pelo emprego da técnica de esterificação alcalina, seguido da análise cromatográfica pelo método CLA03 para análise de cinco cortes bovinos fracionados em músculo e capa de gordura, creme de leite, iogurte integral e três tipos de queijo. O método de esterificação alcalina, seguido de separação por CG pelo método CLA03 mostrou-se o mais adequado para uma quantificação segura do perfil de ácidos graxos de alimentos que contenham os isômeros conjugados do ácido linoléico, uma vez que os resultados obtidos concordam com a literatura atual. / Conjugated linoleic acids (CLAs) are a group of geometric and positional isomers of linoleic acid which have been attributed to present anticarcinogenic, antidiabetic, antiaterogenic and body composition modulation effects. Major natural sources of CLA are ruminants milk and meat, since rumen microorganisms are able to produce CLAs and their precursors as intermediates of biohydrogenation. Before identification and quantification by gas chromatography (GC), the methylation procedure should be carefully decided to avoid isomerization of CLAs. Thus, the objective of this study was to critically evaluate analytical methods for characterizing conjugated linoleic acid isomers c-9, t-11 and t-10, c-12, by identifying the best method for esterification and the best gas chromatography programming for separation, identification and quantification of CLAs through quantification of CLAs in supplements, beef and dairy products. In order to accomplish this objetive, the techniques of acid esterification with boron trifluoride methanol, alkaline esterification with methanolic sodium methoxide and mixed esterification using a combination of the two catalysts were employed in the methylation of a commercial sample of conjugated linoleic acid supplement in triacylglycerol form, the CLA Tonalin® TG 80, from Cognis. The methyl esters were identified in 3 chromatographic conditions CLA01, CLA02 and CLA03. CLA isomers c-9, t-11 and t-10, c-12 were also quantified in CLA Tonalin® TG 80 and FFA 80 by carbon 13 nuclear magnetic resonance (13C-NMR). The results indicated the alkaline esterification technique followed by chromatographic analysis by CLA03 method as the best method for analyzing five cuts of beef fractionated in muscle and fat layer, cream, full yoghurt and three types of cheese. The alkaline esterification method followed by GC separation method CLA03 proved to be the most suitable for safe quantification of fatty acid profile in foods that contain conjugated linoleic acid isomers, once the results agreed with the data available in the current literature.

Le chrome (Cr) est un métal largement distribué sur la croûte terrestre. Les formes les plus couramment rencontrées sont le Cr (III), longtemps considéré comme un nutriment essentiel à la vie et le Cr(VI), cancérigène avéré pour l’homme. La source majeure d’exposition de la population au chrome total étant l’alimentation, des données en spéciation sont nécessaires afin d’évaluer le risque relatif à l’ingestion de chrome. La première partie de ce mémoire présente de façon générale la problématique du chrome. La deuxième partie a été consacrée à l’optimisation d’une méthode de séparation des espèces du chrome. La méthodologie des plans d’expériences a permis en un minimum d’essais d’évaluer l’influence des différentes facteurs et de leurs interactions afin de déterminer les conditions de séparation optimales. La troisième partie porte sur la mise au point d’une méthode d’extraction sélective du Cr(VI) dans les produits laitiers et céréaliers, par plan d’expériences également. Une étude de la correction des interférences et des inter conversions a également été réalisée démontrant de la justesse de la méthode. La méthode a ensuite été validée selon l’approche du profil d’exactitude et appliquée à l’analyse de 65 échantillons de produits laitiers et céréaliers ; aucune trace de Cr(VI) n’a été détectée. La quatrième partie présente le développement d’une méthode d’analyse sélective du Cr(III) dans les produits laitiers. Les performances de la méthode ont ensuite été évaluées avant son application à des échantillons réels. Les résultats confirment que le chrome total présent dans ces matrices serait bien sous forme de Cr(III). Il serait nécessaire de poursuivre ces travaux sur d’autres matrices afin de pouvoir estimer l’ensemble de l’exposition des consommateurs et de mieux évaluer les risques inhérents à la présence de chrome dans les aliments, selon sa forme présente / Chromium (Cr) is a metal widely distributed throughout the Earth’s crust. Most commonly forms found are Cr(III), which has long been considered as an essential nutrient for human health, and Cr(VI) which is carcinogenic to humans. The most important contribution to the overall exposure of total chromium in general population is through food. To improve risk assessment on the presence of chromium, there is a need to accurately determine the content of Cr(III) and Cr(VI) in food. The first part of this work focuses on the issue of chromium. The second part deals about the optimization of a separation method for chromium species. Experimental design allowed us to study effects of factors and their interactions in order to determine the best analytical conditions. Third part is the development and validation of selective alkaline extraction for Cr(VI) in dairy and cereal products, also using experimental design. A study of the correction of the interferences and of interconversions is also presented showing the accuracy of the method. Analytical performances were assessed by the accuracy profile method and the method was used to determine Cr(VI) in 65 samples of dairy and cereal products ; Cr(VI) was not detected in these samples. The last part is devoted to develop a selective determination method for Cr(III) in dairy products. Analytical performances of the method were assessed before its use to determine Cr(III) in dairy products samples. Results confirm that chromium in those matrices will be Cr(III). It would be interesting to continue this work in order to study other matrices to better assess consumer exposure and to improve risk assessment related to the presence of chromium in food, depending on its speciation

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-08-15T17:18:32Z No. of bitstreams: 1 2016 - Fernando Morais Rodrigues.pdf: 2322673 bytes, checksum: 8f5b741d438f97ba0f77ff0820d05b50 (MD5) / Made available in DSpace on 2017-08-15T17:18:32Z (GMT). No. of bitstreams: 1 2016 - Fernando Morais Rodrigues.pdf: 2322673 bytes, checksum: 8f5b741d438f97ba0f77ff0820d05b50 (MD5) Previous issue date: 2016-11-25 / The aim of this study was to evaluate the effect of high hydrostatic pressure on physical, chemical, microbiological and sensory characteristics of Minas Frescal cheese produced with reduced sodium content. Initially a literature review was presented on the main techniques used to reduce the sodium content. After identifying the optimal salt concentration of Minas Frescal cheese it was studied the effect of information regarding the excessive salt intake on health towards the consumer preference by means of survival analysis and by the acceptance in structured 9-point hedonic scales. Subsequently it was evaluated the effect of salt concentration and the salting method on production yield, physicochemical composition (moisture, ash, protein, fat), titrable acidity, pH, minerals (sodium and calcium content) and sensory characteristics (hedonic test and check-all-that-apply (CATA) of ?Minas Frescal? cheese. For both the experimental design involved the factorial combination of varying concentrations of sodium chloride (0.2, 1.6 and 3.0%) and salting method (salting and sant in the milk mass). Finally it was investigated the combined effect of pressurizing at different pressures (300, 400 and 500MPa / 5 min) and salt content (40, 70 and 100% NaCl) where 100% of NaCl is equivalent to 1.6% of NaCl content/volume of milk (this content set out in Chapter 3) on the physic-chemical, microbiological and sensorial characteristics (perception of salty taste) of Minas Frescal cheese, by using a complete factorial experimental design 2^2 with triplicate at the midpoint. From the data collected parametric models were obtained allowing the estimation of the optimum salt concentration: 3.2 +/- 0.4 (%NaCl). For the cheese with such salt concentration it was obtained 21.5% of consumer rejection, of which 8.3% for considering the Minas Frescal cheese of being "little salty" and 13.2% for considering it ?too salty?. Information on the health hazards due to excessive sodium intake was not significant (p>0.05) for the consumers. Either the effect of salt concentration and/or method of salting either individually or their interaction resulted in significant differences for the parameters moisture, ash, protein and minerals (p<0.05). The salt concentration showed the highest influence on the response variables evaluated in this study. The yield statistically varied among the treatments (p<0.05), and was influenced by the level of sodium, while calcium concentration and also the yield were affected by the salting method, salt concentration and interaction of the parameters (p<0.05). The yield values for different treatments were statistically different (p<0.05). With respect to the sensory analysis the salting methods influenced the acceptance only for the cheeses elaborated with 3.0% NaCl (p<0.05). Salt concentration (1.6%) for both salting methods achieved the highest average acceptance. Significant differences for the physical and chemical microbiological and sensory parameters (p < 0.05) were observed. The physical-chemical response variables more influenced by the treatments were: sodium content, calcium content, NaCl content, salt content, moisture, DPPH, proteolysis and antihypertensive activity. Higher levels of pressure and salt content resulted in further reduction in the microbial population. Bioactive properties (antihypertensive activity and antioxidant activity) of the Minas Frescal cheese was confirmed by the analyses. Regarding the sensory analysis no increase in the perception of salty taste occurred due to the high pressure treatments evaluated. / O objetivo do presente estudo foi avaliar o efeito da Alta Press?o Hidrost?tica sob as caracter?sticas f?sico-qu?micas, microbiol?gicas e sensoriais em queijo Minas Frescal produzido com teor reduzido de s?dio. Inicialmente apresentou-se uma revis?o de literatura sobre as principais t?cnicas utilizadas na redu??o do teor de s?dio. Ap?s, identificou-se a concentra??o ?tima de sal no queijo Minas Frescal e avaliou-se o efeito da informa??o sobre os malef?cios do consumo excessivo de sal ? sa?de na prefer?ncia do consumidor pelo produtos, por meio de an?lise de sobreviv?ncia e teste de aceita??o em escala hed?nica estruturada de nove pontos. Posteriormente, abordou-se o efeito da concentra??o de sal e o m?todo de salga sob o rendimento, composi??o centesimal (umidade, RMF, prote?na, gordura), acidez total, pH, minerais (s?dio e c?lcio) e caracter?sticas sensoriais com base em teste hed?nico de aceita??o e Check All That Apply (CATA) do queijo Minas Frescal. Para tanto, o delineamento experimental compreendeu a combina??o fatorial das vari?veis concentra??o de cloreto de s?dio (0,2; 1,6 e 3,0%) e m?todo de salga (salga no leite ou salga na massa. Por ?ltimo, investigou-se o efeito combinado da pressuriza??o (300, 400 e 500MPa / 5 min) e teores de sal (40, 70 e 100% NaCl) onde 100% de NaCl foi equivalente ao teor de 1,6% de NaCl /volume de leite (teor este definido no Cap?tulo 3) sob as caracter?sticas f?sicoqu?micas, microbiol?gica e sensorial (percep??o do gosto salgado) do queijos Minas Frescal, empregando-se delineamento experimental fatorial completo 2^2 com triplicata no ponto central. A partir dos dados processados, foram obtidos modelos param?tricos que permitiram estimar a concentra??o ?tima de sal para os queijos: 3,2 +/- 0,4 (%NaCl). Para esta concentra??o, houve 21,5% de rejei??o por parte dos consumidores, dos quais 8,3% por o queijo frescal estar ?pouco salgado?, e 13,2% de rejei??o por estar ?muito salgado?. A informa??o sobre os malef?cios ? sa?de do consumo excessivo de s?dio n?o foi significativo (p>0,05). J? para o efeito da concentra??o de sal e/ou m?todo de salga, foram observadas diferen?as significativas para os par?metros umidade, cinzas, prote?na e minerais (p<0,05). A concentra??o de cloreto de s?dio (%) apresentou maior influ?ncia sobre as vari?veis de resposta avaliadas. Os valores de rendimento para os diferentes tratamentos diferiram estatisticamente (p<0,05). O teor de s?dio, c?lcio e o rendimento foram afetados pelo m?todo de salga, concentra??o de sal e intera??o de ambos (p<0,05). Com rela??o ? an?lise sensorial, os m?todos de salga influenciaram a aceita??o apenas para os queijos elaborados com 3,0% de NaCl (p<0,05). Concentra??o intermedi?ria deste sal (1,6 %) para ambos os m?todos de salga alcan?aram as maiores m?dias de aceita??o. Para o efeito da Alta Press?o hidrost?tica,diferen?as significativas para os par?metros f?sico-qu?micos (p<0,05), microbiol?gicos e sensoriais foram observadas. As vari?veis de resposta f?sico-qu?micas mais influenciadas pelos tratamentos foram: s?dio, c?lcio, NaCl, %NaCl na umidade, atividade antioxidante, prote?lise e atividade antihipertensiva. Maiores n?veis de press?o e teor de sal resultaram em maior redu??o do n?mero de microrganismos analisados, conforme preconizado pela legisla??o. Propriedades bioativas (Atividade anti-hipertensiva e Atividade antioxidante) foram confirmadas atrav?s das an?lises realizadas. Com rela??o ? an?lise sensorial, n?o houve aumento da percep??o do gosto salgado para os tratamentos avaliados.

The objective of this thesis is to advance our understanding of how consumers use date labels and the implications of date-label use for household dairy product waste. It does this by investigating the effect of psychological, social, and contextual factors on date-label use and willingness to consume dairy products in relation to the expiry date. These effects are tested using structural equation models and survey data gathered from 548 Scottish consumers. The results of this study make two contributions to the literature on date-labelling and food waste. The first contribution is primarily theoretical. By improving our understanding of how consumers use date labels and the implications of date-label use for household dairy product waste, it supports the contention that food waste is best understood, not as a behaviour, but as the outcome of multiple behaviours. It argues that in order to understand why food waste is created, it is important to identify the factors that affect the individual behaviours that lead to it, such as date-label use, and how these behaviours relate to one another. These results also have implications for communications and campaigning around food waste reduction. The second contribution has policy relevance. It provides evidence of the likely limited effect of increasing the number of dairy products labelled with a best-before date rather than a use-by date on food waste. This is an approach recently proposed to reduce household food waste. It finds that better knowledge of the best-before date is associated with a higher willingness to consume products after the best-before date has passed. However, perceived risks about consuming products beyond their best-before date, including not just safety but quality, freshness, and social acceptability, appear to interact with date-label knowledge and dampen its influence. It argues that to be effective, any changes in date-labelling should be accompanied by communication that goes beyond improving date-label knowledge, and addresses the multifaceted nature of related risk perceptions and conceptions of date-label trust.

L’acide trans-palmitoléique (C16:1 n-7 trans, TPA) est considéré comme un marqueur de la consommation de produits laitiers. D’une part, la consommation de produits laitiers est associée à un moindre risque de syndrome métabolique. D’autre part, de forts taux circulants de TPA sont épidémiologiquement associés à un moindre risque de diabète de type 2. Les bénéfices de la consommation de produits laitiers peuvent-ils en partie être expliqués par le TPA ? À ce jour cependant, aucune étude de supplémentation en TPA n’existe pour confirmer ces associations, et les doutes sur l’origine formelle du TPA ne sont pas levés. Dans ce travail, nous montrons (1) que le TPA provient de la rétro-conversion endogène de l’acide trans vaccénique (C18:1 n-7 trans, TVA) alimentaire chez l’Homme, (2) que le TPA et le TVA sont apportés exclusivement par la matière grasse de ruminants (lait et viande de ruminants) en France, (3) la possibilité d’obtenir du TPA pur en quantités suffisantes pour mener des études nutritionnelles et (4) que la supplémentation en TPA pur chez la souris dans un contexte de mise en place de syndrome métabolique empêche la mise en place de certaines dysfonctions métaboliques. Dans l’ensemble, ces résultats montrent que le TPA, acide gras spécifique de la matière grasse laitière, peut expliquer en partie l’association épidémiologique entre consommation élevée de produits laitiers et moindre risque de syndrome métabolique. / Trans-palmitoleic acid (trans-C16:1 n-7, TPA) is usually considered as a biomarker of dairy fat consumption. On the one hand, dairy product consumption is associated with lower risk of metabolic syndrome. On the other hand, high circulating levels of TPA in humans are epidemiologically associated with lower risk of type 2 diabetes. Could benefits of dairy products consumption rely in part on TPA? So far, there is no nutritional study involving TPA to confirm such observational associations, and doubts remain as regards to the formal origin of TPA. In this work, we demonstrate (1) that TPA arises from the endogenous retro-conversion of dietary trans-vaccenic acid (trans-C18:1 n-7, TVA) in humans, (2) that both TPA and TVA intakes are exclusively ensured by ruminant products (milk and meat) consumption, (3) the ability to get pure TPA in enough amounts to carry out reliable nutritional studies and (4) that pure TPA supplementation on mice fed an obesogenic diet prevents from several metabolic dysfunctions. Taken together, our results demonstrate that the dairy fatty acid TPA may explain part of the epidemiological association between high consumption of dairy products and lower risk of metabolic syndrome.

The food industry could potentially benefit from using pervaporation, a membrane process, to concentrate flavours. This research aimed to investigate its application for concentrating flavours in dairy process streams. Pervaporation experiments were carried out at a range of operating conditions, using hydrophobic membranes. The feed mixtures were either aqueous model solutions of dairy flavour compounds (acids, esters and ketones), complex model mixtures containing flavour compounds plus non-volatile dairy components, or real dairy products. Flavour compound enrichment factors ranged from below one to above 30, with esters and ketones being concentrated more effectively than acids. Thus, the flavours could be partially fractionated based on their chemical structure. The permeation of acids was reduced by approximately 50% when the feed pH was increased to near their p Ka values. For flavour compounds with lower molecular weights than approximately 1 20 g mol- I , permeation was controlled mainly by sorption i n the membrane; for larger compounds it was controlled mainly by diffusion through the membrane. The mass transfer of each flavour compound increased with temperature, following an Arrhenius-like relationship. The activation energy was a function of each compound's heat of sorption, its molecular weight, and the elastic modulus of the membrane. The activation energy was also related to the Arrhenius preexponential factor. Thus, fluxes could be estimated through empirical correlations. The non-volatile feed composition was an important factor influencing the pervaporation performance. Milk protein isolate (4% w/v) or lactose (6% or 1 2% w/v) bound with the flavour compounds in the feed, thus lowering the enrichment of sorption-controlled compounds. Milk fat (up to 38% w/v, in the form of cream ) reduced the enrichment of all the flavour compounds tested. Esters and ketones became unavailable for pervaporation as they partitioned into the fat phase; acids remained mainly in the aqueous phase, but their permeation was reduced because the added cream increased the feed pH. Experiments with real dairy products showed that pervaporation could be used to concentrate diacetylin starter distillate, and to selectively recover short-chain esters from ester cream. Of these two products, starter distillate is the more promising for use as a pervaporation feed stream.