Background: Legumes are a good source of protein, and are also abundant in carbohydrates, B-group vita-mins, dietary fibre and mineral compounds.
Material and methods: This work evaluates the retention of ash, eleven minerals and two heavy metals in products obtained from two common bean cultivars harvested before reaching full maturity, with a dry matter content of about 40%. Analyses were conducted on raw, blanched and cooked seeds and three products prepared for consumption after 12-month storage: two frozen and one canned (sterilized). The former comprised two types of frozen product: one traditionally produced (blanching-freezing-frozen storage-cooking), the other a convenience, "ready-to-eat" product obtained using a modified method (cooking-freezing-frozen storage-defrosting-heating to consumption temperature in a microwave oven).
Results: In cooked bean seeds of both cultivars, levels of potassium, calcium, magnesium and copper were significantly lower, the only exception being the content of ash and sodium (due to added salt), than in blanched seeds; the changes in the remaining components were not so clear-cut and depended on the cultivar. Seeds frozen using the modified technology generally showed higher levels of the elements investigated than frozen products produced traditionally, with the exception of chromium, nickel and lead. Sterilized seeds had lower levels of ash, phosphorus, calcium, magnesium, iron, zinc, manganese, copper and chromium compared with both types of frozen product; retention levels of individual components depended on the cultivar examined. Conclusions. Compared with the traditionally produced frozen product, prepared for consumption, seeds after modified method of freezing (convenience food) contained significantly higher levels of ash and all macroelements, regardless of the cultivar. Seeds preserved by sterilization, compared with frozen seeds (either method of production) prepared for consumption, had lower content of most of the analyzed components.