Effects of Different Cooking Methods on the Vitamin D Content of Commonly Consumed Fish in Thailand

Abstract

This study determined vitamin D content in commonly consumed fish in Thailand and the effects of different cooking methods on vitamin D retention. Five species of freshwater fish and four species of marine fish were purchased from three representative markets. All of the fish were individually prepared according to common household practices. Vitamin D2 and D3 were determined using the HPLC standard method (AOAC method 995.05). The results indicated that vitamin D3 was the only detectable form of vitamin D in the fish. Vitamin D content of raw freshwater fish ranged from 2.42 to 48.5 µg per 100 g edible portion (EP), which was higher than that of raw marine fish (2.94 to 4.69 µg per 100 g EP). Common silver barb, Red Nile tilapia, and Nile tilapia (freshwater fish living in the limnetic zone) contained high levels of vitamin D (48.5 ± 26.5, 31.0 ± 7.7, and 19.8 ± 3.5 µg per 100 g EP, respectively). Boiled fish (except for Common silver barb), fried fish (except for Striped snakehead, Walking catfish, and Common silver barb), and grilled fish (except for Common silver barb, Giant sea perch, and Short-bodied mackerel) retained high levels of vitamin D, which were not significantly different (p > 0.05) from raw fish. Common silver barb, Red Nile tilapia, and Nile tilapia—cooked by boiling, frying, and grilling—are recommended for consumption as excellent sources of vitamin D.

Effect of Different Cooking Methods on Selenium Content of Fish Commonly Consumed in Thailand

“…Fried fish showed significantly highest Se levels compared to fresh and boiled fish. This finding was not similar to a previous study that investigated the effect of different cooking methods on vitamin D in Thai fish that suggested no effect of cooking methods on vitamin D content [ 19 ]. The different chemical forms of Se that are contained in fish may be one of the main factors that affect the loss of Se during cooking.…”

“…The 3–4 vendors from each market were randomly selected as representative of total stores. All fish species were prepared, cooked (boiling and frying), homogenized (with skin), freeze-dried, and assessed for moisture content according to procedures described elsewhere [ 18 , 19 ]. Briefly, all fish were weighed before and after removing inedible parts.…”

In Vitro Bioaccessibility of Selenium from Commonly Consumed Fish in Thailand

“…The percentage of relative standard deviation (%RSD) was assessed to determine the method precision. In this study, %RSD of CRMs was 4.00% for NMIJ7402-a and 6.59% for SRM1566b [ 21 ], which indicated good precision. Consequently, the method for Se analysis provided accurate and precise results.…”

“…Table 1 presents the common names of the fish sampled in this study, as well scientific names and other information. All fish samples were stored in cooling bags to retain freshness after purchase and until being sent to the Institute of Nutrition, Mahidol University, to be prepared as boiled and fried fish and then homogenized (with skin), after which the moisture content was evaluated according to procedures described elsewhere [ 20 , 21 ]. Briefly, the weights of all fish before and after eliminating inedible parts were recorded.…”

“…These CRMs were used to evaluate the accuracy and reliability of Se determination measurements. The experimental Se concentration for NMIJ7402-a in this study was 1.93 0.07 mg/kg (certified value at 1.80 0.20 mg/kg) and for SRM1566b was 2.08 0.13 mg/kg (certified value at 2.06 0.15 mg/kg) [ 21 ]. There were no significant differences between analyzed values and certified values of the CRM ( p > 0.05).…”