LD2668 .T4 1941 S63 / Master of Science

LD2668 .T4 1942 E3 / Master of Science

Call number: LD2668 .T4 1943 O3 / Master of Science

Call number: LD2668 .T4 1949 C49 / Master of Science

Call number: LD2668 .T4 1952 P9 / Master of Science

Call number: LD2668 .T4 1954 B7 / Master of Science

Call number: LD2668 .T4 1959 D72

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

<p>Halten näringsämnen i livsmedel varierar bland annat med tillagningsmetod, lagringstid och lagringsförhållanden, som exponering för ljus och syre. Oklarheter finns för mikrovågors inverkan på näringsämnen och framförallt på vitamin B₁₂. Eftersom många äldre drabbas av brist på vitamin B₁₂, är detta av intresse eftersom många hemmaboende äldre människor får hemleverans av färdiga matportioner som är avsedda att värmas, ofta i mikrovågsugn. Syftet med studien var att kunna ge en indikation på om uppvärmning genom mikrovågor påverkar halten vitamin B₁₂ i färdiga kylda måltider. Detta gjordes genom litteratursammanställning om vitamin B₁₂ och mikrovågar samt genom bioassay med <em>Lactobacillus delbrueckii</em>. Vitamin B₁₂ i ouppvärmd lax, lax värmd i mikrovågsugn samt lax värmd i konventionell ugn analyserades. Tillväxten av bakterier uppskattades genom mätning av turbiditet. Högst vitamin B₁₂-halt sågs i mikrovågsvärmd lax, därefter ouppvärmd lax och ugnsvärmd lax. Statistiskt signifikanta skillnader sågs för analyserade vitamin B₁₂-halter mellan ouppvärmt- och ugnsvärmt prov respektive mellan mikrovågsvärmt- och ugnsvärmt prov. De varierande vitaminhalterna kan bero på metodfel, otillräcklig vitaminextraktion eller att bakterierna inte konsumerat allt tillgängligt vitamin vid turbiditetsmätning. Slutsatsen av studien är att halten vitamin B₁₂ i livsmedel inte verkar påverkas negativt av mikrovågor, däremot finns tendenser att halten minskar beroende av temperatur och tillagningstid.</p>

The present study was designed to investigate the effects of exercise on vitamin B-6 metabolism. Four groups of subjects (intermittent, college, untrained, and high school) consisting of nineteen male and two female individuals, participated in the study. The subjects exercised either on a bicycle ergometer, by running three 1500 meter intervals, or both. Blood samples drawn prior to exercise (pre), after exercise (post), and 30 minutes after exercise (30 minute post), were analyzed for plasma pyridoxal 5'-phosphate (PLP), plasma B-6 (PB6), glucose, hemoglobin and hematocrit. A 24-hr urine collection the day before and the day of exercise was analyzed for urinary B-6 (UB6), 4-pyridoxic acid (4PA), creatinine, and urea nitrogen. The dietary intake of the four groups was greater than the RDA in vitamin B-6, riboflavin, thiamin, niacin, vitamins A and C, calcium and iron. The B-6/protein ratios of the college and untrained groups were adequate while the high school group's ratios were considered inadequate. The bicycle ergometer had a significant effect on the plasma PLP levels of the college and untrained groups (P< 0.005) and PB6 levels of the college group following exercise (P< 0.005). The 30 minute post plasma PLP levels were significantly lower for the college group (P< 0.005). During the run, the college group had significantly higher post exercise levels of plasma PLP (P< 0.005) and PBS (P< 0.005} as compared to the pre exercise sample. The high school group also had significantly higher levels of plasma PLP following, exercise for all three runs (P< 0.005, P< 0.025, and P< 0.01, respectively) as well as higher PB6 levels (P< 0.025, P< 0.01, and P< 0.025, respectively). The college athletes had a greater percent change in plasma PLP (P < 0.01) from the pre to post sample during the run as compared to the high school athletes. Urinary B-6 and 4PA were not significantly altered during either exercise suggesting a shift in PLP and the unphosphorylated forms of vitamin B-6 from one compartment to another. The significantly higher levels of plasma PLP and PB6 following exercise were attributed to an increased utilization of glycogen phosphorylase in the skeletal muscle with a subsequent release of PLP. / Graduation date: 1982