There is an ever growing interest in the development of biochar from a large variety of agrowastes. Herein, the main objective is the conversion of pomegranate peel powder biochar and its post-functionalization by phosphoric acid treatment, followed by arylation organic reaction. The latter was conducted using in situ-generated diazonium salts of 4-aminobenzoic acid ( H2N-C6H4-COOH), sulfanilic acid ( H2N-C6H4-SO3H) and Azure A dye. The effect of diazonium nature and concentration on the arylation process was monitored using thermal gravimetric analysis (TGA) and Raman spectroscopy, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). SEM pictures showed micrometer-sized biochar particles with tubular structure having about 10–20 μm-wide channels. SEM studies have shown that arylation did not affect the morphology upon arylation. The porous structure did not collapse and withstood the arylation organic reaction in acid medium did not collapse upon arylation. TGA and Raman indicated gradual changes in the arylation of biochar at initial concentrations 10– 5, 10– 4 and 10– 3 mol L− 1 of 4-aminobenzoic acid. The detailed Raman spectra peak fittings indicate that the D/G peak intensity ratio leveled off at 3.35 for 4-aminobenzoic acid initial concentration of 10– 4 mol L− 1, and no more change was observed, even at higher aryl group mass loading. This is in line with formation of oligoaryl grafts rather than the grafting of new aryl groups directly to the biochar surface. Interestingly, Azure A diazonium salt induced much lower extent of surface modification, likely due to steric hindrance. To the very best of our knowledge, this is the first report on diazonium modification of agrowaste-derived biochar and opens new avenues for arylated biochar and its applications.

An agricultural waste, pomegranate (Punica granatum L.) peel is known to be rich in total phenolics, which are flavonoids having strong antioxidant effects. In this study, pomegranate peel sponge cakes were prepared with varying ratios of freeze dried pomegranate peel powder (0, 1, 3, 5, 7% (w/w)) to examine their effect on quality characteristics, retrogradation and antioxidant activities. The specific gravity and moisture contents of 3, 5, and 7% pomegranate peel powder showed higher values than the control and 1% group. Addition of pomegranate peel powder increased the batter yield, while there was a significant decrease in baking loss. Increasing pomegranate peel powder content significantly decreased the lightness (L) (from 75.03 to 57.04) and pH values, whereas redness (a), yellowness (b) and ΔE were increased. Increasing concentration of the peel powder also increased the hardness and chewiness, while the springiness and cohesiveness decreased. Considering the Avrami equation, Avrami exponene (n) decreased from 1.8055 (control) to 0.9199 (7% pomegranate peel powder). Time constant (1/k) was lowest in control (at 17.64) and highest in the 7% group (39.84). Total polyphenol, flavonoid content, DPPH and ABTS radical scavenging activities significantly increased with increments in the content of pomegranate peel powder. A sensory evaluation by the 7-point scaling method showed that the sponge cake containing 7% pomegranate peel powder had the highest scores in color, flavor, sweetness, chewiness and overall acceptability. Hence, it is considered that sponge cake supplemented with 7% pomegranate peel powder is the most appropriate for quality characteristics, retrogradation and antioxidant activities.

Functional foods are of great significance since our society is accelerating into aging. An aging society has many physiological metabolic diseases such as hypertension, diabetes, heart disease, cancer, dementia and geriatric diseases. Fundamental treatments for the elderly are almost impossible and the social burden is heavy. If these diseases can be prevented or alleviated by improving dietary habits using functional foods, the significance would be very large. Pomegranate has been found to have 124 different kinds of phytochemicals. Polyphenols have a wide range of protective effects including various physiological metabolic diseases and cancers. It is necessary to develop functional foods such as preservatives and food extenders which can contribute to food safety, required in the food industry, by using such bioactive substances. Pomegranates have been reported to decrease the impact of many serious illnesses. There is a considerable amount of bioactive substances in the peel of a pomegranate, which has potent anticancer, antioxidant, antimicrobial and anti-apoptotic properties. Unfortunately, the peel is typically discarded after processing. Despite knowledge regarding the bioactive substances in the pomegranate peel and peel extracts, including their functionality and diversity, the knowledge is not well known by consumers in general. The aim of this study was to review up to date research trends for processing and developing new functional foods by utilizing nutritional functional substances, favourite food materials, and materials for processing food contained in pomegranate peels and pomegranate peel extracts. This study will summarize the data found in pomegranate peel and pomegranate peel extract literature mainly recently published in Science Direct. There are polyphenolic compounds (ellagitannins, punicalagin, proanthocyanidin, flavonoids, polysaccharides, etc.) in the fruit peel, making up about 50% of the pomegranate’s weight. The polyphenol content of a pomegranate fruit peel is 149.91 mg/g, which is about 100 times higher than the juice. Paying attention to the fact that the ellagitannin content (14.22 mg/g) in the fruit peel is also twice as high as that of the fruit juice and seeds, that confirms the possibility of utilizing the peel as a food ingredient capable of developing new, functional bioactive foods.