This study investigated the potential of olive leaf extract (OLE), as a functional ingredient, to improve cheese properties, because it is rich in phenols. Milk and dairy products are poor in phenolic compounds. The main objective was to determine the most effective coagulation method and timing of OLE supplementation to maximize retention in the cheese matrix. Experimental cheeses were produced using the rennet and acid coagulation methods, with OLE added either directly to the cheese milk or to the curd phase. Three OLE effective concentrations corresponding to 25%, 50%, and 75% inhibition of DPPH reagent (EFC25, EFC50, and EFC75, respectively) were added, i.e., 11.5 mg GAE L⁻¹, 16.6 mg GAE L⁻¹, and 26.3 mg GAE L⁻¹, respectively. The results showed that OLE significantly increased the concentration of total phenols, total flavonoids, and antioxidant activity in all cheese samples and in the residual whey, especially at higher effective concentrations (EFC 50 and EFC 75). Rennet-coagulated cheese to which OLE was added prior to coagulation (EM 25, EM 50, EM 75) exhibited higher hardness, gumminess, and chewiness but lower elasticity, suggesting alterations in the paracasein matrix. OLE did not adversely affect acidity, water activity, or cheese yield. However, higher EFC resulted in significant colour changes (∆E* > 3.0). In conclusion, the enrichment of cheesemaking milk with OLE and the application of the rennet coagulation method are the most suitable to optimise the production of OLE-enriched cheese. This research shows the potential to improve the nutritional value of cheese while maintaining its desired characteristics.

The dairy industry produces large amounts of whey as a by- or co-product, which has led to considerable environmental problems due to its high organic matter content. Over the past decades, possibilities of more environmentally and economically efficient whey utilisation have been studied, primarily to convert unwanted end products into a valuable raw material. Sustainable whey management is mostly oriented to biotechnological and food applications for the development of value-added products such as whey powders, whey proteins, functional food and beverages, edible films and coatings, lactic acid and other biochemicals, bioplastic, biofuels and similar valuable bioproducts. This paper provides an overview of the sustainable utilisation of whey and its constituents, considering new refining approaches and integrated processes to covert whey, or lactose and whey proteins to high value-added whey-based products.

The food industry generates large quantities of biowaste, including olive (Olea europaea L.) leaves, which are rich in phenolic compounds with proven antioxidant and antimicrobial activity. In this study, a microwave-assisted olive leaf extract was produced and evaluated. Antioxidant potential (20.23 ± 0.31 µmol TE g⁻¹), antimicrobial activity against Staphylococcus aureus (MIC 17.62 mg GAE g⁻¹), and cytotoxic effects in breast (MDA-MB-231 (IC₅₀ = 38.9 ± 1.8 µg mL⁻¹), MCF-7 (IC₅₀ = 58.9 ± 5.4 µg mL⁻¹) and prostate cancer PC-3 (IC₅₀ = 69.2 ± 7.6 µg mL⁻¹) cell models were confirmed. Further, the extract was incorporated into a whey protein isolate (WPI) edible coating mixture and applied to semi-hard cheese over a 60-day ripening period. When applied to cheese, WPI-based coatings enriched with OLE contributed to an improved antioxidant potential (289.79 ± 16.16 µmol TE L⁻¹), elevated retention of total phenols and flavonoids, and slightly reduced microbial growth without compromising cheese safety. Compared to the uncoated control, coated samples showed higher total solids (up to 62.87 ± 0.13%, CWPIM) and fat contents (up to 26.59 ± 0.17%, CWPIM), moderated proteolysis (WSN in CWPIM: 3.15 ± 0.09% vs. 4.48 ± 0.02% in C0), maintained cohesiveness and resilience compared to the control, and exhibited less pronounced color deviation (ΔE) in some coated samples during ripening. These results highlight the potential of olive leaf extract as a bioactive, sustainable ingredient for functional edible coatings that improve the nutritional, technological, and microbiological quality of ripened cheese.

Oxidative stress and the associated inflammation play key roles in the development of many chronic diseases. As alternatives to synthetic antioxidants, plant-derived materials with potential anti-inflammatory and antioxidant properties, such as olive (Olea europaea) leaves, thyme (Thymus vulgaris) and green walnut (Juglans regia) husks, have attracted increasing scientific interest. These materials are rich in phenolic compounds, including oleuropein and hydroxytyrosol in olive leaves, thymol and rosmarinic acid in thyme, and ellagitannins and juglone in green walnut husks. Numerous studies have demonstrated the strong antioxidant activity of these extracts using analytical assays such as DPPH, FRAP and ABTS. However, such in vitro antioxidant capacity does not necessarily translate directly into biological efficacy in vivo, as polyphenol stability, release, metabolism and bioavailability may be strongly influenced by interactions with proteins, lipids and other components of dairy matrices. Their incorporation into dairy products has shown promising technological effects, including improved oxidative stability, reduced lipid oxidation, delayed microbial spoilage and potential shelf-life extension. Reported application contents vary substantially among studies and product types, including 0.4–5 % for olive leaf extract in yogurt systems, 0.4–0.8 % for thyme extract in yogurt, 0.1–1 mg/mL for thyme extract in milk systems, 0.5–3 % for olive leaf extract in cheeses, and 100–200 mg/kg for green walnut husk extract in cream-based products. However, these values should be interpreted cautiously because extract composition, matrix type and units of expression differ among studies. Nevertheless, evidence supporting direct health benefits in humans remains limited, and further in vivo and human intervention studies are needed to confirm their physiological relevance. This review summarises the polyphenolic profiles of the olive leaf, thyme and green walnut husk extracts, their technological and sensory effects in dairy matrices, and advances in sustainable extraction methods. Overall, the available findings support their potential as natural, clean-label ingredients for innovative dairy products, primarily from a technological and functional formulation perspective.