Short communication: Variation in the composition and properties of Swedish raw milk for ultra-high-temperature processing

Abstract

The composition and properties of raw milk are of great importance for the quality and shelf life of the final dairy product, especially in products with a long shelf life [e.g., ultra-high-temperature (UHT)-treated milk]. The objective of this study was to investigate the compositional variation in raw milk samples before processing at the dairy plant. Moreover, we wanted to investigate the effect of the UHT process on this variation (i.e., if the same variation could be observed in the corresponding UHT milk). The quality traits analyzed included detailed milk composition, counts of total and psychrotrophic bacteria, proteolytic activity, and color, as well as predictive measures of stability (i.e., ethanol stability and heat coagulating time). Samples of raw milk and the corresponding produced UHT milk were collected and analyzed on a monthly basis during 1 yr. Principal component analysis was used to identify months showing similarities and differences with respect to total variation. In contrast to previous studies, we observed only small variations between months and no clear effect of season for the raw milk. For the UHT milk, July and the winter months (December, January, and February) tended to separate from the other months. Quality traits showing significant variation were only to some extent identical in raw milk and UHT-processed milk. A better understanding of the natural variation in raw milk quality will provide opportunities to improve the shelf life of UHT-treated milk products.

Changes in stability and shelf-life of ultra-high temperature treated milk during long term storage at different temperatures

“…From the dairy plant, in total eleven batches of UHT milk were collected on a monthly basis during one year, with the exception of August, whereas from the pilot plant, two batches were produced; one in November and another one in February. An earlier published study, describing the properties of the commercial raw milk and the corresponding freshly produced UHT milk provides detailed information on the milk composition, including total bacterial count, somatic cell count and enzymatic activity (Karlsson et al., 2017). In the unprocessed commercial raw milk collected during the indoor period, we observed on average total bacterial counts of 29′000 cfu/mL, somatic cell count of 182′000 cells/mL and total proteolysis of 40.58 mM leucine equivalents.…”

Composition and properties of bovine milk: A study from dairy farms in northern Sweden; Part II. Effect of monthly variation

“…The characteristics of cheese are known to depend on the composition and properties of raw milk (Skeie, 2007;Guinee and O'Brien, 2010), which has been shown to vary with the season in regions with a seasonal calving pattern (Li et al, 2019). Seasonal variation in the composition and properties of raw milk has been investigated for different dairy farming systems in regions with predominantly seasonal calving [e.g., New Zealand (Auldist et al, 1998) and Ireland (Lin et al, 2017)] and in regions with year-round calving [e.g., the Netherlands (Heck et al, 2009) and Sweden (Larsen et al, 2010;Karlsson et al, 2017)]. Various factors may contribute to observed seasonal differences in milk characteristics, depending on regional climate conditions and differences associated with lactation stage, cow nutrition, and cow health (Williams, 2002;Heck et al, 2009;O'Brien and Guinee, 2016).…”

“…Larsen et al (2010) compared milk produced in central and southern Sweden and showed that milk quality attributes were influenced by differences in climate, feeding regimen, and breeds between the 2 regions of Sweden. Karlsson et al (2017), who investigated dairy silo milk intended for the production of UHT processed milk in northern Sweden, reported monthly variation in the milk quality characteristics investigated, but variation was not associated with the season. The present case study, which focused on dairy production in a cheeseproducing region (Västerbotten) in northern Sweden, aimed to investigate the influence of monthly variation on the composition and properties of raw farm milk intended for long-ripening hard cheese.…”

Accurate and precise determination of 90Sr at femtogram level in IAEA proficiency test using Thermal Ionization Mass Spectrometry

“…In the water samples, the 90 Sr concentrations were in the same range, 23.7 Bq kg −1 (4.6 fg g −1 ) and 11.2 Bq kg −1 (2.2 fg g −1 ) respectively. In the milk powder it was higher, 99.9 Bq kg −1 (19.5 fg g −1 ), although it corresponds to 13 Bq kg −1 (2.5 fg g −1 ) in the original milk sample since the average dry matter content of a raw cow milk is around 13% 14 . Thus, stable Sr and 90 Sr concentrations were different in samples, 90 Sr/ 88 Sr isotope ratio also differed and varied in the range from 1.37 × 10 −7 to 9.04 × 10 −9 .…”