Eggshell is a solid waste, with production of several tons per day. Eggshell is mostly sent to the landfill with a high management cost. It is economical to transform the eggshell waste to create new values from these waste materials. The present article is an attempt to summarize the possible applications of eggshell. The eggshell waste can be used (a) at biodiesel production as a solid base catalyst used for biodiesel pollutants minimization, reducing the production costs of biodiesel and making the process of biodiesel production fully ecological and environment-friendly; (b) as an absorbent of heavy metals from wastewater as it is a serious environmental problem in the ecosystem; (c) as biomaterial in order to replace bone tissues due to the rise in the number of patients; (d) as a fertilizer and calcium supplement in nutrition for human, animals, plants, etc. Number of research articles have been included in this review to describe a methodical growth in this subject matter.

Bread is the main staple for most Iranians. Five main breads and their fermented and unfermented doughs were prepared and analyzed for protein, ash, ether extract, crude fiber (CF), neutral detergent fiber (NDF), acid detergent fiber (ADF) and amino acid profiles. Ether extract decreased and CF, NDF, and ADF increased as a result of all five baking procedures. In addition, baking decreased lysine for the five breads. Chemical scores of amino acid profiles indicated that in the bread made with lower extraction flours (barbari, lavash and taftoon), lysine, isoleucine and threonine were the first, second and third limiting amino acids respectively. With higher extraction flours (sangak and village) isoleucine was as often the first limiting amino acid as lysine.

The effect of flour extraction rate, type and length of fermentation and baking conditions on relative bioavailability of zinc of five distinctly different Iranian flat breads and their unfermented doughs, was determined using weanling rats fed low (5.5 ppm) levels of dietary zinc. When breads rather than unfermented doughs were used for preparation of diets, with one exception, bioavailability of Zn significantly (P < 0.05) improved. Rats on the barbari-breadbased diet showed the highest weight gain and femur zinc content. There was no significant difference in weight gain among rats on dough-based diets. High correlation of weight gain and femur zinc with feed intake and low or no correlation with fiber or Zn:phytate molar ratio of the diets was observed.

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The effect of soda (sodium bicarbonate) as a leavening agent on pH, phytic acid hydrolysis and physical quality of a fermentation model system and two popular Middle Eastern breads, Iranian taftoon and Pakistani naan (Arabic) were studied. Supplementing 0.2 and 0.4% soda invariably decreased phytic acid hydrolysis. In sour starter supplemented dough, phytic acid was reduced by 82% after 3 hr. However, when 0.4% soda and sour starter were added loss of phytic acid did not exceed 29%. Supplementing soda in taftoon and naan bread formula significantly lowered phytic acid hydrolysis during fermentation. Soda had no apparent improvement on physical quality of breads but increased the dough water absorption and lengthened the mixing time.