Green technology approach for heavy metal adsorption by agricultural and food industry solid wastes as bio-adsorbents: a review

Heavy metal discharge from various metallurgical industries has been of particular concern in India over the last few decades. Similarly, management and disposal of wastes that are generated out of agricultural commodities processing is a huge task for processors. The researchers have been focusing on a new process for remediation of heavy metals, among which biosorption is an emerging technology. Adsorption using agricultural and food industry wastes (AFW) has shown a greater absorption rate than the conventional system due to the presence of the functional groups. In addition, these reported AFW exhibited better adsorption efficiency when modified with acid, alkaline, and other chemical solvents. In this context, utilization of agricultural and food waste as bio-sorbent could simultaneously benefit both water treatment and waste management. This review seeking to address the possibilities of using biosorption as green technological approach for removal of heavy metals and also focuses on various parameters that are required to use AFW as an efficient system for biosorption. However, commercialization and implementation of this process in industrial scale is necessary for successfully utilizing AFW as low-cost adsorbents.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05486-1.

Enzyme-assisted three-phase partitioning: An efficient alternative for oil extraction from Sesame (<em>Sesamum indicum</em> L.)

Three-phase partitioning (TPP) was explored for oil extraction from Sesamum indicum L. seeds. The process parameters, namely the salt concentration, slurry/t-butanol ratio and system pH were standardized. The optimum conditions for maximum oil recovery using TPP were an ammonium sulphate concentration of 40% (w/v), slurry/t-butanol ratio of 1:1 (v/v) and system pH of 5.0. The powdered seeds were subjected to enzyme-assisted three-phase partitioning (EATPP) which was pre-treated with pectinase, protease and a mixture of ɑ-amylase and amylo-glucosidase (1:1 ratio) followed by TPP (as standardized conditions) and its efficacy in recovering oil was compared with TPP and solvent extraction (SE). Out of all the enzymes studied, EATPP with pectinase resulted in the highest oil recovery (86.12%), which was higher than that of TPP (78.24%). The free fatty acids, saponification value and peroxide values were observed to be lower in the case of TPP and EATPP when compared to SE, indicating better oil quality.

Moisture sorption characteristics of ready-to-eat snack food enriched with purslane leaves

Green leafy vegetables are important part of our regular diet that provides us with essential nutrients necessary to support human life and health. Since these are produced in surplus and have limited shelf-life, preservation of vegetables can help to prevent wastage and increase nutrient availability in the diet during off-season. Purslane leaves, rich in micronutrients were dried using tray dryer at 60 ± 2 °C for 7 h. and incorporated at 20% level in khakhra. Organoleptic and physico-chemical properties of the product were evaluated. Further, the sorption properties of khakhra, were studied at 27 ± 2 °C over a range of water activity of 0.10-0.92. Several models were chosen to fit sorption behavior, but the Peleg model showed the best fit. The present study in fact provides a platform to understand the rationalities behind the physico-chemical changes in the product, which, in turn, helps in predicting the best suitable packaging material for storage in addition to the stability of the product.

Emerging technique for healthier frying for production of reduced-fat beetroot (Beta vulgaris) chips

In the present work, the processing variables were optimized to retain betalain compound and their effect on quality attributes (oil content, breaking force and color) of fried beetroot chips. The beetroot slices were fried in lab scale vacuum fryer. Experimental design with temperature (86-153 °C), absolute pressure (1.3-9.7 kPa) and frying time (2.6-9.4 min) as independent variables which produced 20 different combinations, were studied using response surface methodology to study the effect of these variables on product responses. Multiple regression equations were obtained to describe the effects of each variable on product responses. Results predicted that optimum frying conditions namely temperature ranging from 101 to 110 °C, pressure ranging from 2.9 to 4.4 kPa and time 6.0 min required for preparing beetroot chips with oil content (Y₁) ≤ 15.7, breaking force (Y₂) ≤ 11.53, L* value (Y₃) ≥ 27.94, a* value (Y₄) ≤ 17.87, b* value (Y₅) ≥ 6.46, betalain content (Y₆) ≥ 13.05 (mg/l) and overall acceptability (Y₇) ≥ 7.5. Further results showed that traditionally fried beetroot chips contain 2.6 mg/l betalain, 19.68 N breaking force, 21.1 L*, 15.18 a*, 2.38 b*, overall acceptability 6.0 and 38.41 % oil content.