The effects of microwave heating on the retention of selected nutritional components in animal muscle was studied. We determined the degree of retention of the thermolabile vitamin B6 and thiamine after thermal treatment of pork and chicken meat in a conventional oven (Tatramat) and in a microwave oven (model GUM 2S [A] and Toshiba ER-5300D ).
In conventionally roasted samples 48–96% of thiamine was retained, whereas microwave-treated samples showed retention as high as 85.6–94.2% (oven A) and 88–96% (oven B).
After conventional roasting, meat samples retained only 21.6–48.5% of vitamin B6. Microwave treatment, on the other hand, retained 59.9–80.9% (oven A) and 64.2–86.8% (oven B) of vitamin B6.
[b]The measured values of vitamin retention demonstrate clearly that heating of muscle tissue with microwaves is less destructive to heat-sensitive vitamins than is conventional roasting and that, therefore, microwave cooking and roasting can be recommended for food preparation in the food industry, households, restaurants and hospitals.
The proximate composition, fatty acid and tocopherol levels of egg yolk were determined in raw eggs and after different cooking processes: boiling for 3 and 10 min, heating in a microwave oven, and frying. Of the protein, lipid, ash and moisture contents, only the last decreased with microwave cooking. The predominant fatty acid was oleic (18:1) (36.10–42.6%), followed in decreasing amounts by palmitic (16:0), linoleic (18:2), linolenic (18:3) = arachidonic(20:4) = docosanoic (22:0), docosahexanoic (22:6) and myristic acid (14:0). Of the polyunsaturated fatty acids, 18:2, 18:3, 20:4 and 22:6 decreased in the samples subjected to microwaves. α-Tocopherol (6.1–2.9 mg per 100g) was the predominant isomer in all the samples followed by (β + γ)-tocopherol and δ-tocopherol, while α-tocotrienol was detected in trace amounts. All these tocopherols were reduced during cooking by up to 50% in omelettes and microwave treatments.
The effects of microwave cooking and other traditional cooking methods such as boiling and autoclaving on the nutritional composition and anti-nutritional factors of chickpeas (Cicer arietinum L.) were studied. Cooking treatments caused significant (P<0.05) decreases in fat, total ash, carbohydrate fractions (reducing sugars, sucrose, raffinose and stachyose, while verbascose was completely eliminated after cooking treatments), antinutritional factors (trypsin inhibitor, haemagglutinin activity, tannins, saponins and phytic acid), minerals and B-vitamins. Cooking treatments decreased the concentrations of lysine, tryptophan, total aromatic and sulfur-containing amino acids. However, cooked chickpeas were still higher in lysine, isoleucine and total aromatic amino acid contents than the FAO/WHO reference. The losses in B-vitamins and minerals in chickpeas cooked by microwaving were smaller than those cooked by boiling and autoclaving. In-vitro protein digestibility, protein efficiency ratio and essential amino acid index were improved by all cooking treatments. The chemical score and limiting amino acid of chickpeas subjected to the various cooking treatments varied considerably, depending on the type of treatment. Based on these results, microwave cooking is recommended for chickpea preparation, not only for improving nutritional quality (by reducing the level of antinutritional and flatulence factors as well as increasing in-vitro protein digestibility and retention rates of both B-vitamins and minerals), but also for reducing cooking time.
Marissa Little wrote:
I have found several papers that talk about various things changing in foods but not what that means or if they change more or less than conventional cooking. In short, I have yet to find a scientific paper showing MORE damage across the board for microwave cooking than for boiling/roasting.
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