[Amount of nitrate and nitrite in daily menus containing more than 350 g of vegetables].

The contents of nitrate and nitrite in menus containing more than 350 g of vegetables per day were investigated. The amounts of vegetables in menu A developed by female students and menu B taken from a recipe book were 350+/-2 g and 457+/-77 g, respectively. The average content of the nitrate was 321.0+/-139.3 mg (104.2-636.9 mg) in menu A, and 245.7+/-90.7 mg (140.1-507.3 mg) in menu B. Sixteen and thirteen samples exceeded the ADI in menus A and B, respectively. This may be because menu A contained more raw vegetables than menu B (menu A; 120+/-58 g, menu B; 72+/-71 g). The contents of nitrite in menu A and B were 1.2+/-0.3 mg (0.7-1.8 mg) and 2.8+/-0.9 mg (1.3-4.6 mg), respectively, and 6 samples in menu B exceeded the ADI. Intake of 350 g of vegetables or more in a day may require careful consideration of selection, frequency of use and cooking method, especially for vegetables with high nitrate content. A questionnaire to female students showed that 80% or more of students recognized that vegetables containing high contents of nitrate, such as spinach and komatsuna, should be boiled before eating them.

Cholesterol intake is associated with lecithin intake in Japanese people.

Many dietary recommendations for the prevention of heart disease and hyperlipidemia include restriction of cholesterol intake. However, limiting cholesterol intake might also affect the intake of other nutrients. The daily intakes of cholesterol, lecithin, total fatty acids, and SFAs by 388 Japanese subjects (ages 6-59 y) were analyzed directly using the duplicate portion sampling technique. Intakes were 266.1 +/- 146.5 mg/d, 1.6 +/- 0.9 g/d, 39.3 +/- 16.8 g/d, and 12.8 +/- 6.9 g/d, respectively. There was a strong positive correlation between cholesterol and lecithin intakes (r = 0.864, P < 0.001), and when food intake was adjusted to 1 kg/d, the correlation remained high (r = 0.881, P < 0.001). In contrast, the correlation between total fatty acid and lecithin intakes was lower (r = 0.423, P < 0.001), and when food intake was adjusted to 1 kg/d, the correlation coefficient remained stable (r = 0.448, P < 0.001). These results strongly indicate that limiting cholesterol intake decreases lecithin intake. Lecithin intake can be estimated from the following regression equation: lecithin intake (g/d) = 0.005 x cholesterol intake (mg/d) + 0.16 (R2= 0.747, P < 0.001). Furthermore, the intake of choline derived from lecithin can be estimated by the following equation: choline (mg/d) = 0.724 x cholesterol (mg/d) + 21.5.

Effect of kiwifruit juice on beef collagen.

The objective of this study is to clarify the difference in susceptibility to protease digestion by kiwifruit juice between collagen domains under different conditions. In addition, the effect of pre-treatment with kiwifruit juice on collagen in meat during cooking processes was examined. Kiwifruit juice can degrade denatured collagen, but it can not cleave the triple helical domain of collagen. Thus, kiwifruit juice does not have collagenase activity. On the other hand, the cross-linked subunits of acid-soluble collagen were converted to monomeric subunits by kiwifruit juice treatment at acidic pH, suggesting that the globular domains, in which cross-links preferentially occur, can be degraded by kiwifruit juice. The pre-treatment with kiwifruit juice significantly decreased the shear force of connective tissue in comparison with other pre-treatments without protease activity, but inversely increased the liberation of collagen-related peptides in the outer solution by heating processes at 50 and 70 degrees C or by a shorter heating time at 100 degrees C. This can be explained by the protease-mediated degradation of globular domains. However, this effect was not observed with a prolonged heating period at 100 degrees C, and the liberation of collagen-related peptides by pre-treatment with kiwifruit juice at 100 degrees C was less than that at 70 degrees C for all heating periods. Thus, it can be suggested that the pre-treatment with kiwifruit juice might be useful in meat softening under vacuum-cooking and grilling, but not under stewing.