Numerous health benefits have been attributed in the last decades to the regular consumption of fruits, vegetables, herbs and spices, along with honey, in a balanced diet. In this context, the aim of the present review was to provide the literature with the most relevant studies focusing on the determination protocols of these polyphenols and other reducing agents in selected fruits (orange, lemon, grapefruit, prunus, apricot, peach, plum, sweet cherry), spices (oregano, cinnamon, clove, saffron, turmeric) and honey of different botanical origin (nectar or honeydew). In addition, the content and the extraction methods of these compounds, along with their metabolic pathway, have been critically evaluated and discussed. Results showed that all fruits, spices and honey exhibit a considerably high antioxidant activity, which is mainly owed to their phytochemical content. Therefore, a balanced diet consisting of the combination of the foods studied herein may comprise a shield against chronic and other pathophysiological disorders and may be achieved through consecutive educational programs for consumers at an international level.

The present study aimed to investigate whether different citrus peel powders (orange, mandarin, and lemon) could be incorporated into polylactic acid (PLA), for the preparation and characterization of biodegradable films made of this fruit waste. In particular, films were prepared by the solvent casting method and tested in terms of physicochemical and biochemical parameters, along with mechanical properties. Furthermore, the citrus peel powders were tested for their physicochemical and biochemical properties after ethanolic extraction. The results showed that the addition of citrus powders into PLA proved to be efficient compared to the control films (PLA). The citrus peel-based films showed high antioxidant capacity (38.37%–32.54%), a considerable total phenolic content (17.2–12.58 mg GAE/L), good lightness (L*: 42.83–41.93), elastic Young’s modulus (257.95–175.38 MPa), oxygen transmission rate (976.5 mL m⁻² day⁻¹–1218 mL m⁻² day⁻¹), elongation at break (183.06%–135.95%), and tensile strength (6.15–4.56 MPa), which were affected significantly (p < 0.05) by the botanical origin of citrus peel. Concerning the citrus peel extracts, the highest values in antioxidant capacity (52.56%), total phenolic content (724.8 mg GAE/L), and titratable acidity (714.67 mg of citric acid/L) were recorded in the extract of lemon peel powders. The corresponding values for orange peel powder extracts were 39.43%, 563.8 mg GAE/L, and 576 mg of citric acid/L, while those for mandarin were 33.01%, 558.46 mg GAE/L, and 54.67 mg of citric acid/L. The application of multivariate analysis of variance and linear discriminant analysis on the mechanical properties, physicochemical, and biochemical data resulted in the differentiation of pure PLA and PLA-based films fabricated with citrus peel powder. From the above findings, it is concluded that citrus peel powders are sources of phytochemicals and can be used for the preparation of PLA-based films for potential applications in food preservation.