Berry fruit by-products are a source of polyphenol compounds and highly nutritious oils and can be reused to fulfill the requirements of the circular economy model. One of the methods of obtaining polyphenol-rich extracts or oils is extraction. Applying conventional solvent extraction techniques may be insufficient to reach high polyphenol or lipid fraction yields and selectivity of specific compounds. Alternative extraction methods, mainly ultrasound-assisted extraction, pulsed electric field-assisted extraction, microwave-assisted extraction and supercritical fluid extraction, are ways to improve the efficiency of the isolation of bioactive compounds or oils from berry fruit by-products. Additionally, non-conventional techniques are considered as green extraction methods, as they consume less energy, solvent volume and time. The aim of this review is to summarize the studies on alternative extraction methods and their relationship to the composition of extracts or oils obtained from berry waste products.

The seeds of berry fruits are a component of fruit waste occurring in the production process. Circular economy rules focus on decreasing the amount of waste produced and reusing by-products when it is possible. To determine the possible applications of the studied fruit industry wastes, the thermal properties of berry seeds and of oil extracted from the tested material were examined. Differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC), and thermogravimetry (TG) of blackberry, chokeberry, and raspberry seeds were carried out. The properties of oil extracted in the Soxhlet apparatus were studied by pressure differential scanning calorimetry (PDSC), TG, and gas chromatography (GC) measurements. The results show that berry seeds lipids are from different melting fraction groups with a dominance of low-melting fraction, which consists of mono- and polyunsaturated fatty acids. There are also occurring residues of carbohydrates and inorganic, thermostable substances in the studied seeds. A GC analysis of oil confirms that the polyunsaturated fatty acids (PUFA) are most abundant and amount to 78.72 ± 0.06% in blackberry seed oil, 73.79 ± 0.14% in chokeberry seed oil, and 82.74 ± 0.03% in raspberry seed oil. The PDSC study showed that the most oxidative stable oil is blackberry seed oil, followed by raspberry and chokeberry seed oils. According to the obtained results, berry seeds can be used as a source of oil in food or other production chains. However, more detailed characteristics of berry seed oils are needed to determine their applicability.

Proper management of waste is one of the major challenges for the food industry. Fruit seeds are an example of by-products that are rich in bioactive substances and generated in significant amounts during fruit processing. Oils, including those obtained from seeds, should meet certain requirements to be allowed for human consumption. The aim of this study was to determine the quality of oils from black currant, strawberry and cranberry seeds by determining the following parameters: fatty acid composition by gas chromatography, distribution of fatty acids between sn-2 and sn-1,3 positions of triacylglycerols by partial enzymatic hydrolysis, oxidative stability by pressure differential scanning calorimetry and melting characteristics by differential scanning calorimetry. Additionally, health indices of atherogenicity (IA), thrombogenicity (IT) and hypocholesterolemic/hypercholesterolemic (HH) ratio were calculated. It was found that the oils studied were a rich source of unsaturated fatty acids. Linoleic acid was found to occupy the internal position of triacylglycerols in the highest proportion. Black currant and strawberry seed oils were of lower oxidative stability and, in the case of cranberry seed oil, high oxidative stability was determined. The shape of melting curves for black currant and strawberry seed oils indicated the presence of low-melting fractions of triacylglycerols containing polyunsaturated fatty acids. It can be concluded that cranberry seed oil, with low values of IA and IT, high values of HH index and the highest oxidative stability, can be considered the most favorable from a nutritional point of view concerning human health.

The present research focused on the extraction optimization of bioactive compounds from coffee silverskin (CS), a by-product generated in large amounts worldwide during the coffee roasting process. The effect of the different extraction conditions has been investigated by the exploitation of the response surface methodology (RSM). The antioxidant activity assays, such as ABTS and FRAP, total phenolics content (TPC), browning index (BI), and chromatographic analysis of caffeine and chlorogenic acids contents have been performed to evaluate the CS extracts characteristics. The most favorable extraction conditions on the maximum recovery of antioxidant bioactive compounds were found to be as follows: 50% aqueous solution of ethanol (v/v) in solvent solid ratio of 45 mL/g CS, during 30 min at 60 °C. The CS extract prepared in this extraction variant reached the values for ABTS, FRAP, TPC, and BI approximately 101.6 µmol Trolox/g d.m. CS, 132.3 µmol Fe (II)/g d.m. CS, 52.3 µmol GAE (gallic acid equivalent) per g d.m. CS, and 0.3, respectively. Additionally, this extract is rich in caffeine (6 mg/g d.m. CS) and chlorogenic acids (0.22 mg/g d.m. CS). In conclusion, this research demonstrates that CS could be considered as a valuable by-product of bioactive compounds with potential applications in the food industry.

The main goal of this research was to model and optimize the extraction process of bioactive compounds from spent coffee grounds (SCG). This study utilized response surface methodology (RSM) to determine the significance of the effects of independently tested extraction process conditions and their interactions. The quality of the SCG extracts was evaluated by performing the following determinations: total polyphenols content (TPC), ABTS and FRAP assays, browning index (BI), and caffeine and chlorogenic acids contents by high-performance liquid chromatography. The resultant optimal extraction conditions, which maximized recovery of antioxidant bioactive compounds, were 65% hydroethanolic solution (v/v) in a solvent–matrix ratio of 51 mL/g CS, followed by ultrasound-assisted extraction carried out for 30 min at 60 °C. The SCG extract obtained by this extraction variant had values for TPC, ABTS, FRAP and BI of approximately 38 mg GAE (gallic acid equivalent) per g d.m. SCG, 73 mg Trolox/g d.m. SCG, 81 µmol Fe (II)/g d.m. SCG, and 0.22, respectively. The sample was also characterized by a high content of caffeine (5 mg/g d.m. SCG) and chlorogenic acids (8 mg/g d.m. SCG). Based on the obtained results, SCG may be recognized as a coffee by-product that has abundant components with antioxidant activity and broad possible applications in agri-food processing fields.