Peer-reviewed studies indicate that boiling vegetables affects their nutritional composition and leads to changes in vitamin C and other micronutrient levels.
The consumption of vegetables in Mexico includes a wide variety of plants that grow naturally as weeds in the fields. The intake of these vegetables is very important in the Mexican diet because these plants supply an important input of nutrients and compounds such as fiber, vitamins, minerals, and antioxidants. Thus, the plants may be universally promoted as healthy. However, there is little information about these vegetables of popular consumption, especially in terms of the nutritional changes caused by boiling. To determine the influence of boiling on five plants of popular consumption in Mexico, the nutritional composition (proximal analysis, dietary fiber, and oxalates), antioxidant compounds (ascorbic acid, phenolics), antioxidant activity (measured by ABTS and DPPH assays), and physicochemical characteristics (water retention capacity, viscosity, color, and SEM) were evaluated. The boiling affected the nutritional composition of plants, mainly soluble compounds as carbohydrates (sugars and soluble fiber), ash, ascorbic acid, and phenolic compounds and caused changes in food hydration and color. Therefore, it is recommended that these plants be consumed raw or with short boiling times and included the cooking water in other preparations to take advantage of the nutrients released in the food matrix. In the future, to complete studies, 3 to 5 min of cooking should be considered to minimize undesirable modifications in terms of the vegetables’ composition.
Vitamin C is important for the human body function. People usually fulfill their vitamin C needs with food intake. A supplement intake also exists when needed. Vegetables are rich in various phytochemicals, biologically active substances with beneficial health effects, and are daily sources of vitamins and minerals for the body. The vitamin C content of eight widely used vegetables was established with the use of two assays (NBS and DCPIP). Food processing i.e. boiling, steaming and microwaving was used to establish vitamin C retention in cauliflower, peppers (red and green), potatoes (yellow and red), carrots, cabbage, and eggplant. The results obtained suggest that the most suitable cooking technique in terms of vitamin C retention is steaming.
Aims: In relation to nutrient retention, cooking method is not a major factor considered when preparing vegetables at household level. The study evaluated the vitamin and mineral compositions of raw, boiled and steamed egg plant (Solanum macrocarpon) and ‘ukazi’ (Gnetum africanum) leaves. Methodology: Freshly purchased vegetables were washed and divided into three portions. The first was pulverised raw while the second and third were pulverised after boiling and steaming, respectively. Their micro nutrients profiles were chemically determined using standard procedures. Data obtained was statistically analysed using Statistical Product for Service Solution (SPSS) version 21.0 for descriptive statistics such as means and standard deviation. Significance was accepted at p ≤ 0.05. Results: Micro nutrients content of eggplant were significantly (p ≤ 0.05) higher in the raw than the steamed and boiled samples. However, no significant (p ≤ 0.05) difference was observed in the Original Research Article Davidson and Monulu; JSRR, 21(4): 1-8, 2018; Article no.JSRR.45255 2 vitamin B1 content of boiled (0.19 mg/100 g) and steamed (0.16 mg/100 g) samples. Except for vitamin B6, all the B-vitamins values of the raw and steamed ‘ukazi’ leaves were statistically similar. There was no significant difference in the beta carotene values of raw (587 mg/100 g), boiled (549 mg/100 g) and steamed (574 mg/100 g) samples. Mineral values of the three ‘ukazi’ samples were all significantly different (p=.05) and ranged from 0.28-181 mg/100 g in the raw, to 0.10-161 mg/100 g and 0.26-180 mg/100 g in the boiled and steamed samples, respectively. Conclusion: Steaming had better micro nutrient retention than boiling. Boiling and steaming the vegetables whole (without slicing) also enhanced their nutrient retention. To improve on the intake of micro nutrients, steaming whole vegetables rather than boiling them should be advocated.
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