Fjölrit RALA - 22.03.1979, Page 17

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(AOAC 16.032, except beakers were used in place of platinum
crucibles.)
Ash: Measured in samples after determining dry matter.
Beakers placed in an incubator (550°C) overnight, cooled in
a desiccator and weighed.
(AOAC 16.035, except beakers were used in place of Pt crucibles.)
Minerals: Calcium and magnesium were measured by atomic
absorption spectrophotometry, sodium and potassium by flame
photometry and phosphorus by fluorometry.
Lactic Acid: The amount of acid present was measured
by titrating 25 ml of whey or concentrated whey with 0.1N
NaOH using phenolphthalein as an indicator.
(AOAC 16.023)
Protein: A Kjeldahl instrument was used to measure the
protein content. About 4 g of whey were weighed into appro-
priate flasks. Added were 10 ml of concentrated H^SO^, 6 ml
of 30% H^O^ and a pinch of SeO2(seleniumdioxide) catalyst.
This mixture is heated for 2-3 hours on the appropriate
heating block. Ten ml of 20N NaOH are then added to the
solution and the ammonia distilled over 2% boric acid (HBr)
and then titrated with 0.01N HCl.
5. Shelf-Life
• The effects of storage at refrigerator and room tempera-
tures on D^+and were studied. Skyr droplets and color
changes were inspected regularly. In addition, a flavor
evaluation test was carried out after a 3 week storage
period (experiment nr. 3 in the chapter on sensory eval-
uation).
• It was inspected daily whether there were any skyr
droplets in D^+, and whether there was any precipitation
in D^+, A^, Ag and A^ (in order to see this, the mixtures
were put into 50 ml graduated cylinders).
• A^, A2, D+ and were centrifuged for 15 seconds at
300 rpm. The supernatents were funneled off and put into
50 ml graduated cylinders. They were then heated in boil-
ing water for 2 minutes for pasteurization and then refrig-