With the steadily growing world population, effective methods are needed to alleviate food shortages. One possible strategy could be to utilize agro-waste materials that accumulate in large quantities at every stage of the economic chain during harvesting, food production, and consumption. Peel-based agro-waste consists of promising materials that can be utilized to potentially substitute commonly used raw materials in products traditionally made from wheat, tapioca, and rice flours. In this systematic review, we aim at establishing prospective proximate components as basic nutrients and their valorization potential as substitutes in traditional flour products (bread, biscuits, etc.). Generally, the peel contains high levels of fiber and relatively low digestible carbohydrates, providing a healthier food ingredient. In terms of protein, it should be pointed out that seeds such as wheat utilize insoluble gluten as their major storage protein, while proteins in peel were found in quite high percentage although they were not yet well characterized. However, the general effect of using peel to substitute wheat in food products are the reduction of dough elasticity, increased hardness of the end-products, faster water absorption rate of the products, and in some cases, bitter taste and darker colors. The latter two could have been contributed by the secondary metabolites such as phenolic compounds. On the other hand, substitution of peel into food products can have valuable health benefits, e.g., retention of antioxidant activity due to the phenolic compounds or simply adding fiber. In this review, literature on the composition of promising agro-waste raw materials is being discussed in the relationship with physical properties and appearance of potential end-products. Antinutritional compounds and pretreatment processes are also being considered. It is hoped that a critical discussion will lead to a better understanding and higher acceptance of the incorporation of peel into food products.

Tomato (Lycopersiconesculentum Mill. cv. Rampai) is rich in lycopene, a carotenoid group compound with many biological activities, one of which is as an antioxidant. Conventional tomato cultivation is not optimal due to the susceptibility of tomato plants to pests and diseases, even though the need for lycopene continues to increase. Plant tissue culture method can be one solution for lycopene production. Callus tomato cv. Rampai was initiated from cotyledons on MS medium (Murashige& Skoog) with the addition of 1 ppm BA (benzyladenine) and 1.5 ppm IAA (indole-3-acetic acid). Callus aged one week to four weeks were harvested and lycopene was extracted by maceration method using hexane:acetone (9:1) as solvent. The presence of lycopene in callus was confirmed by TLC (thin-layer chromatography) (retention factor value/Rf = 0.56) and UV-Vis spectrophotometry (wavelength that gives maximum absorbance = 472 nm). Lycopene content in tomato callus increased with increasing callus age and was directly proportional to the callus growth index. The highest lycopene level was found in callus aged 4 weeks, which was 0.3094 mg/100 g dry weight callus.