One of the major challenges in sustainable waste management in the agri-food industry following the “zero waste” model is the application of the circular economy strategy, including the development of innovative waste utilization techniques. The conversion of agri-food waste into carriers for the immobilization of enzymes is one such technique. Replacing chemical catalysts with immobilized enzymes (i.e., immobilized/heterogeneous biocatalysts) could help reduce the energy efficiency and environmental sustainability problems of existing chemically catalysed processes. On the other hand, the economics of the process strongly depend on the price of the immobilized enzyme. The conversion of agricultural and food wastes into low-cost enzyme carriers could lead to the development of immobilized enzymes with desirable operating characteristics and subsequently lower the price of immobilized enzymes for use in biocatalytic production. In this context, this review provides insight into the possibilities of reusing food industry wastes, namely, eggshells, coffee grounds, and brown onion skins, as carriers for lipase immobilization.

Six medicinal plants Helichrysum italicum (Roth) G. Don, Angelica archangelica L., Lavandula officinalis L., Salvia officinalis L., Melilotus officinalis L., and Ruta graveolens L. were used. The aim of the study was to compare their extracts obtained by Soxhlet (hexane) extraction, maceration with ethanol (EtOH), and supercritical CO₂ extraction (SC-CO₂) targeted on coumarin content (by high performance liquid chromatography with ultraviolet detection, HPLC-UV), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging capacity, and total phenols (TPs) content (by Folin–Ciocalteu assay). The highest extraction yields were obtained by EtOH, followed by hexane and SC-CO₂. The highest coumarin content (316.37 mg/100 g) was found in M. officinalis EtOH extracts, but its SC-CO₂ extraction yield was very low for further investigation. Coumarin was also found in SC-CO₂ extracts of S. officinalis, R. graveolens, A. archangelica, and L. officinalis. EtOH extracts of all plants exhibited the highest DPPH scavenging capacity. SC-CO₂ extracts exhibited antiradical capacity similar to hexane extracts, while S. officinalis SC-CO₂ extracts were the most potent (95.7%). EtOH extracts contained the most TPs (up to 132.1 mg gallic acid equivalents (GAE)/g from H. italicum) in comparison to hexane or SC-CO₂ extracts. TPs content was highly correlated to the DPPH scavenging capacity of the extracts. The results indicate that for comprehensive screening of different medicinal plants, various extraction techniques should be used in order to get a better insight into their components content or antiradical capacity.

The present study investigated the possibility of spent coffee ground (SCG) transformation to a cellulose-based enzyme immobilization carrier using a multistep extraction procedure. In the first step, SCGs were extracted with n-hexane by Soxhlet extraction in order to obtain SCG oil, while the remaining solid residue was subjected to continuous solvent flow sequential subcritical extraction with 96% and 50% ethanol and water. Afterwards, the obtained solid residue was subjected to alkaline liquefaction with 8% NaOH in order to remove lignin and produce cellulose-enriched SCGs as a potential enzyme immobilization carrier. Multistep extraction transformation of SCGs was monitored by chemical analysis of extracts and obtained solid residues. Soxhlet extraction of 100 g of SCGs yielded 10.58 g of SCG oil rich in linoleic and palmitic acid, while continuous solvent flow sequential subcritical extraction of 100 g of defatted SCGs yielded a total of 1.63 g of proteins, 5.58 g of sugars, 204 mg of caffeine, 76 mg of chlorogenic acid, and 11.97 mg of 5-(hydroxymethyl)furfural. Alkaline liquefaction of 100 g of sequentially extracted defatted SCGs by 8% NaOH yielded 7.45 g of proteins, 8.63 g of total polyphenols, 50.73 g of sugars, and 20.83 g of cellulose-enriched SCGs. Based on the characteristics of cellulose-enriched SCGs including a volume-weighted mean particle size of 277 μm, relative narrow particle size distribution with a span value of 1.484, water holding capacity of 7.55 mL/g, and a lack of carrier leakage, it could be safely concluded that produced cellulose-enriched SCGs fulfills criteria to be used as potential enzyme immobilization carrier. Overall, it seems that the proposed multistep extraction transformation of SCGs has great potential to be used for the production of several high-value added products.

The positive effects of honey bee venom on human health and the high market price are the main reasons for beekeepers' increasing interest in its production. However, until today there is no standardized technology for honey bee venom collection. Today's methods are mainly based on collectors placed at the hive entrance. The main problems with this method are the application of the collector, and the contamination that collected venom may contain which consequently reduces its quality. The disadvantages of this technology can at least partially be eliminated by the use of collectors placed inside the hive. Therefore, this study aimed to evaluate the effect of the collection method on the honey bee venom quality and quantity. The results of the study showed that significantly higher amounts of venom could be collected with collectors within the hive, while at the same time the quality of the venom, considering the melittin content, remained equal. Having in mind that honey bee venom collection has not had a significant impact on strength of the colonies (in comparison to control colonies that were not subjected to venom collection), collection technology with collectors placed inside the hive is a better option.

The aim of this study was to evaluate the effect of processing (45 °C/48 h and 65 °C/6 h) and two years’ storage on sage (Salvia officinalis L.) honey and to determine the period in which the compliance to the regulations is fulfilled and degradation of nutritive components are minimal. The results showed that processing at higher temperature for shorter period had a greater impact on enzyme activity decrease and increase of color than heating at lower temperature for longer time. Processing had no significant effect on HMF increase, while during storage HMF content increased above maximum prescribed value. Although processing and storage increased phenolic content and antioxidant capacity, at the same time, quality was significantly degraded regarding enzyme activity and HMF content. Therefore, it is recommended to store sage honey for less than two years and if processing is necessary to heat it at as low temperature as possible.

Himalayan balsam (Impatiens glandulifera Royle) is an invasive garden ornamental plant species originating from Asia, which produces significant amounts of nectar. In Croatia, it is widely distributed along the banks of the Mura River. Although this plant species is widespread in Europe, there are still no available scientific data about this unifloral honey type. The results showed that Himalayan balsam honey is characterized by the high presence of pollen grains in the pollen spectrum (59–85%), natural higher diastase activity (39.1 ± 7.98 DN), negative specific rotation (−21.2° ± 6.89) and an extra light amber color (48.5 ± 12.69 mm Pfund). The carbohydrate profile is characterized by monosaccharides fructose (39.34 ± 0.65 g/100 g) and glucose (31.91 ± 1.42 g/100 g) with a ratio >1.23, while the most commonly represented disaccharide was maltose (3.04 ± 0.79 g/100 g). The average total phenolic content was 130.97 ± 11.17 mg gallic acid/kg honey, and the average antioxidant capacity value was 225.38 ± 29.58 µM Fe(II). The major mineral element was K, with an average of 533.92 ± 139.70 mg/kg. The sensory profile was characteristic with a light orange color and medium-intensity odor and aroma. The crystallization rate was moderate and characterized by the appearance of opalescence and gelatinous forms of crystals. The results of this study provide the first insight into the melissopalynological, physico-chemical and sensory profile of Himalayan balsam honey.