Numphung Rujithamkul. Iodine fortification in Som-Fak and its characteristics during fermentation, storage and after cooking . Master's Degree(Nutrition). Mahidol University. : Mahidol University, 2003.
Iodine fortification in Som-Fak and its characteristics during fermentation, storage and after cooking
Abstract:
Som-fak is a low-salt fermented fish product in Thailand, prepared from 83% minced
fish, 3% salt, 8% garlic, 3% cooked rice and 3% water. In this study the physical properties,
pH, acidity, salt, iodine content, number of total bacterial count and lactic acid bacteria were
evaluated at 0 and 2 days fermentation (at 25-30oC) and at every week throughout 45 days
storage (at 5oC). The effect of different cooking methods on stability of iodine in 2-day
fermented Som-fak was also evaluated.
The resulted showed that smell, odour, colour and texture of iodine fortified Som-fak,
by visual inspection was similar to Som-fak prepared by regular salt. Total bacterial count and
lactic acid bacteria increased significantly from 5.3 x 107 and 3.6 x 106 CFU/g at day 0 to
5.9 x 108 and 6.1 x 108 CFU/g at day 2 (p<0.05) of fermentation, respectively. The pH
decreased rapidly from 6.06 to 4.81 after 2 days fermentation and decreased slightly to 4.5
after the first week (p<0.05) in a refrigerator and no change was observed thereafter. During
fermentation, the acidity (% lactic acid) increased rapidly from 0.34 to 1.12% and gradually
increased to 2.05% within 3 weeks (p<0.05) and then remained constant until the end of the
storage period. The level of iodine in iodine fortified Som-fak was significantly reduced (p
<0.05), ranging from 7% during 2-day fermentation to 23% after a storage period of 45 days
in a refrigerator. This is likely due to the allicin in garlic, which might reduce iodine by its
antioxidant effect. Different degrees of iodine loss were exhibited during different cooking
methods. Frying and steaming presented moderate loss of iodine, about 20%. Grilling
showed a minimum effect on the loss of iodine (7%). Since a serving of cooked Som-fak
contributes about 50-55% of Thai RDI of iodine, cooked Som-fak should be recommended to
consumers in order to prevent parasite infestation. The iodine-fortified Som-fak could be
beneficial in preventing and controlling iodine deficiency disorder among the groups at risk
from of iodine deficiency. Its production should be promoted among commercial and homemade
producers of Som-fak.