Stability of Apple Polyphenols as a Function of Temperature and pH

Stability of Propolis Phenolics during Ultrasound-Assisted Extraction Procedures

Propolis has gained popularity in recent years as a potential preventive and therapeutic agent due to its numerous health benefits, which include immune system boosting, blood pressure lowering, allergy treatment, and skin disease treatment. The pharmacological activity of propolis is primarily attributed to phenolics and their interactions with other compounds. Given that phenols account for most of propolis's biological activity, various extraction methods are being developed. The resin-wax composition of the propolis matrix necessitates the development of an extraction procedure capable of breaking matrix-phenol bonds while maintaining phenol stability. Therefore, the aim of this study was to assess the stability of two major groups of phenolic compounds, flavonoids and phenolic acids, in propolis methanol/water 50/50 (v/v) extracts obtained after ultrasound-assisted extraction (USE) under different extraction parameters (extraction time and pH) and heat reflux extraction (HRE). The methodology involved varying the USE parameters, including extraction time (5, 10, and 15 min) and pH (2 and 7), followed by analysis using liquid chromatography-tandem mass spectrometry (LC-MS/MS) to quantify phenolic recoveries. Results revealed that benzoic acid and chlorogenic acid derivatives demonstrated excellent stability across all ultrasound extraction procedures. The recoveries of flavonoids were highly diverse, with luteolin, quercitrin, and hesperetin being the most stable. Overall, neutral pH improved flavonoid recovery, whereas phenolic acids remained more stable at pH = 2. The most important optimization parameter was USE time, and it was discovered that 15 min of ultrasound resulted in the best recoveries for most of the phenols tested, implying that phenols bind strongly to the propolis matrix and require ultrasound to break the bond. However, the high variability in phenol extraction and recovery after spiking the propolis sample shows that no single extraction method can produce the highest yield of all phenols tested. As a result, when working with a complex matrix like propolis, the extraction techniques and procedures for each phenol need to be optimized.

Unveiling Apple Diversity: The Quality of Juice Produced from Old vs. Commercial Apple Cultivars

This research is focused on comparing the compositions of juice produced from old and commercially grown apple cultivars. We examined factors such as pH, total acids, soluble dry matter, polyphenol profile, and antioxidant activity, which impact the attributes, safety, shelf life, and nutritional value of the juice. Our analysis revealed differences between these two groups of cultivars. For instance, pH values ranged from 3.04 (in 'Bobovec') to 3.69 (in 'Fuji'). The proportions of acids varied from 0.07 g/100 mL (in 'Fuji') to 0.19 g/100 mL (in 'Wagener'). Soluble dry matter content ranged from 14.10% (in 'Fuji') to 18.50% (in 'Kraljevčica'). We also observed variations in sugar content and composition among cultivars; for example, sucrose levels varied from 16.11 g/L ('Fuji') to 39.36 g/L ('Golden Delicious). Glucose levels ranged from 4.95 g/L ('Jonagold') to 19.18 g/L ('Fuji'), while fructose levels spanned from 50.78 g/L ('Austrougarka') to 427.97 g/L ('Ilzer Rosenapfel'). Furthermore, old apple cultivars exhibited higher concentrations of phenols and flavonoids compared to commercial ones; we also noted significant variations in flavonol levels among different cultivars. The 'Wagener' and 'Božićnica' apple varieties had levels of myricetin measuring 0.53 and 0.52 µg/mL, respectively. On the other hand, 'Bobovec' stood out for its content of procyanidin B2 with a concentration of 422.61 µg/mL. When examining non-flavonoid compounds, it was found that old apple cultivars had higher concentrations of gallic acid, trans-ferulic acid, and chlorogenic acid. However, commercial cultivars showed dominance in caffeic and p-coumaric. Comparisons of antioxidant capacity using DPPH and ABTS assays clearly demonstrated the superiority of old apple cultivars. Overall, this study highlights the importance of utilizing apple cultivars for juice production. Their distinct compositions and higher antioxidant capacities contribute to potential health benefits. Preserving these cultivars for enhanced juice quality and nutritional value is encouraged. Further research could explore cultivation practices' impact on composition and health benefits.

Health Benefits of Apple Juice Consumption: A Review of Interventional Trials on Humans

Although numerous studies have reported the benefits of apple consumption on cardiometabolic health parameters and chronic disease prevention, few have focused on the effects of apple juice specifically. Juice consumption may be a convenient way to take advantage of the health effects of the bioactive components present in apples. The present review aims to summarize the current literature on health benefits of apple juice as reported in clinical trials in humans. Of the 67 studies retained, 20 interventional studies on humans were reviewed. Overall, cloudy apple juice consumption was found to be associated with several markers of cardiovascular health that may ultimately be relevant for cancer and neurodegenerative diseases. Most of the documentation was found regarding oxidative stress, as well as observations with other parameters such as markers of inflammation, lipid profile, and diabetes. This review suggests that, in 20 studies, apple juice consumed in moderation exerts positive effects on markers of cardiovascular disease risk (particularly on oxidative stress).

Alternative Methods of Bioactive Compounds and Oils Extraction from Berry Fruit By-Products—A Review

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.

Hydrothermal carbonization as a sustainable strategy for integral valorisation of apple waste

Hydrothermal carbonization makes feasible the integral and profitable recovery of industrial apple waste within a zero-residue bio-economy. 82-96% of the energy and 80-93% of the C in the apple bagasse are retained in the solids generated by hydrothermal treatment at 180 and 230 °C for 2 and 4 h. Such processes stabilize the apple waste and lead to CO₂ neutral solid fuels with calorific value close to 30 MJ/kg. The agrochemical properties of the solid by-products suggest their potential to improve soil quality. Aqueous streams containing valuable phenolic compounds and saturated fatty acids are generated simultaneously, which provide additional cost-effectiveness. The by-products characteristics can be suited to the final application by selecting the reaction temperature, whereas the process duration has less impact. Optical microscopy and reflectance measurements are presented, for the first time, as powerful tools for assessing the biomass transformation when subjected to hydrothermal treatment under different conditions.

Antimicrobial polyphenol-rich extracts: Applications and limitations in the food industry

One of the common ways to prevent food spoilage throughout product's shelf life is by using artificial/synthetic preservatives. However, the growing negative perception of consumers over synthetic preservatives has encouraged the food industry to consider their natural alternatives. Plant extracts, increasingly recognized as consumer-friendly, represent a valuable source of active compounds, mostly polyphenols, with potent antimicrobial and antibiofilm activities. Hence, this article focuses mainly on the antimicrobial activity of plant-based polyphenol-rich extracts as well as on their potential use and limitations in the food industry. Some new trends such as antimicrobial food packaging combined with plant extracts and photodynamic inactivation (PDI) combined with a natural photosensitiser, curcumin, are discussed as well.

Effects of convective drying and freeze-drying on the release of bioactive compounds from beetroot during in vitro gastric digestion

Drying may alter the microstructure of vegetables and influence the release of bioactive compounds during digestion.

Hydrothermal stability of phenolic extracts of brown rice

The phenolics were extracted and purified from brown rice and twenty-seven compounds were identified, including six phenolic acids, four phenolic acid glycosides, and eight flavonoid glycosides. Afterwards, the hydrothermal stability of phenolic extracts of brown rice was investigated after treatment at 60, 80, or 100 °C for 120 min. After hydrothermal treatment, ferulic acid, p-coumaric acid and free glucose were increased, while the phenolic glycosides were decreased. In addition, the total phenolic and total flavonoid content were decreased by 5.7%-9.2% and 3.5%-5.8% after initial 30 min, and then they were slightly recovered after treatment for 120 min. Consequently, there was a slight reduction (<10%) in the total antioxidant activity of the phenolic extracts after hydrothermal treatment. These results suggest that hydrothermal treatment of phenolic extracts of brown rice made some phenolic glycosides deglycosylated, but does not lead to a large reduction in their overall antioxidant activity.

Effect of the pH on the lipid oxidation and polyphenols of soybean oil-in-water emulsion with added peppermint (Mentha piperita) extract in the presence and absence of iron

This study evaluated the pH effect on the lipid oxidation and polyphenols of the emulsions consisting of soybean oil, citric acid buffer (pH 2.6, 4.0, or 6.0), and peppermint (Mentha piperita) extract (400 mg/kg), with/without FeSO₄. The emulsions in tightly-sealed bottles were placed at 25 °C in the dark, and lipid oxidation and polyphenol contents and composition were determined. The lipid oxidation was high in the emulsions at pH 4.0 in the absence of iron, however, iron addition made them more stable than the emulsions at pH 2.6 or 6.0. Total polyphenols were remained at the lowest content during oxidation in the emulsions at pH 4.0, and iron reduced and decelerated polyphenol degradation. The results strongly suggest that polyphenols contributed to decreased lipid oxidation of the emulsion via radical scavenging and iron-chelation, and rosmarinic acid along with catechin, caffeic acid, and luteolin were key polyphenols as radical scavengers in the extract.