Stability of fatty acid composition after thermal, high pressure, and microwave processing of cow milk as affected by polyunsaturated fatty acid concentration

Abstract

Interest has been increasing to enhance the contents of healthy polyunsaturated fatty acid (PUFA) in milk. However, trans fatty acids and conjugated linoleic acid (CLA) can be altered after thermal processing and high pressures disrupt the milk fat globule membrane, exposing the lipid core and helping its oxidation. The objective of the present research was to study whether processing can alter the fatty acid composition of milk and if these changes are affected by PUFA concentration as previous studies suggest. Two cow milk batches (500 L each), one naturally enriched in PUFA, were processed to obtain pasteurized; high temperature, short time; UHT; high pressure; and microwave pasteurized samples. The detailed fatty acid composition was analyzed with special attention to trans fatty acids and CLA isomers. Results showed that after high temperature, short time processing, total CLA content increased in both milk batches, whereas sterilization resulted in a sigmatropic rearrangement of C18:2 cis-9,trans-11 to C18:2 trans-9,trans-11. The extent of these effects was greater in milks naturally enriched in PUFA.

Microwave Processing: Current Background and Effects on the Physicochemical and Microbiological Aspects of Dairy Products

“…However, Rodríguez-Alcalá et al (2014) affirmed that MW heating at 650 W for 1.30 s did not change the concentration of total SFAs, monounsaturated FAs (MUFAs), polyunsaturated FAs (PUFAs), and CLA; and as FA composition was detailed, a better stability was achieved for most compounds in all samples. Iuliana et al (2015) and Dumuta et al (2011) observed a reduction in the total solids content after the application of MW heating to cow milk and concluded that it resulted in a quantitative decrease in protein, lactose, and fat contents and also possible decrease in some vitamins, for example, A, B9, C, and E. The total solids content was reported to be an indicator of the nutritional value of milk and to have a direct effect on the use of raw milk for concentrated milk products.…”

“…However, Rodríguez‐Alcalá et al. () affirmed that MW heating at 650 W for 1.30 s did not change the concentration of total SFAs, monounsaturated FAs (MUFAs), polyunsaturated FAs (PUFAs), and CLA; and as FA composition was detailed, a better stability was achieved for most compounds in all samples.…”

“…The authors have assembled a glass tube fitted across a waveguide in which raw milk was passed through and exposed to MW energy during gravity falling. Since then, several other studies on MW heating of milk have been performed, the majority of them focused on the assessment of the potential enhancement of the milk shelf‐life, the application of MW energy to inactivate milk pathogens and enzymes, the influence of MW treatment on nutritional and sensory aspects of milk, and the nonuniform temperature distribution during the MW treatment, in which many of these studies include a comparison with conventionally thermal treated milk samples (Chiu, Tateishi, Kosikowski, & Armbruster, ; Choi, Marth, & Vasavada, , ; Clare et al., ; Dehghan, Jamalian, Farahnaky, Mesbah, & Moosavi‐Nasab, ; Dumuta, Giurgiulescu, Mihaly‐Cozmuta, & Vosgan, ; Géczi et al., ; Iuliana, Rodica, Sorina, & Oana, ; Jaynes, ; Kudra, de Voort, Raghavan, & Ramaswamy, ; Lin & Ramaswamy, ; Manjunatha, Prabha, Ramachandra, Krishna, & Shanka, ; Rasooly, Hernlem, He, & Friedman, ; Rodríguez‐Alcalá, Alonso, & Fontecha, ; Sieber, Eberhard, & Gallmann, ; Tremont et al., ; Villamiel et al., ; Wang & Guohua, ).…”

“…The most important structural and chemical changes that occur during MW heating are protein denaturation and aggregation, Maillard reactions, and lactose isomerization, which are mostly related to thermal effects of MW heating (Iuliana et al, 2015). Hence, indicators traditionally employed in conventional thermal treatments can also be used to determine the severity of MW heating, such as appearance of lactulose, furosine, 5-hydroxymethylfurfural (HMF), fluorescence of advanced Maillard products, and soluble tryptophan (FAST) index, N ε -1carboxymethyl-L -lysine (CML), glycoxidation products, denaturation, and aggregation of proteins (β-lactoglobulin), free fatty acids (FA), and so on (Dehghan et al, 2012;Laguerre et al, 2011;Rodríguez-Alcalá et al, 2014). Dumuta et al (2011) observed a reduction of protein bioavailability with the application of MW heating.…”

Isolation and Analysis of Phospholipids in Dairy Foods

“…Independently of the abovementioned advantages supporting dairy products as an interesting source of polar lipids for the elaboration of new products it must not be forgotten that processing can affect the composition of dairy lipids [29, 30]. Moreover, some recent studies have found that pasteurization of bovine milk resulted in lower concentrations of myristic acid (C14:0), palmitic acid (C16:0), oleic acid (C18:1 c9), and EPA (C20:5 n3) [31].…”