Sustainable extraction of proteins from lime peels using ultrasound, deep eutectic solvents, and pressurized liquids, as a source of bioactive peptides

The aim of this work was to develop, for the first time, sustainable strategies, based on the use of Ultrasound-Assisted Extraction, Natural Deep Eutectic Solvents, and Pressurized Liquid Extraction, to extract proteins from lime (Citrus x latifolia) peels and to evaluate their potential to release bioactive peptides. PLE showed the largest extraction of proteins (66-69%), which were hydrolysed using three different enzymes (Alcalase 2.4 L FG, Alcalase®PURE 2.4 L, and Thermolysin). The in vitro antioxidant and antihypertensive activities of released peptides were evaluated. Although all hydrolysates showed antioxidant and antihypertensive activity, the hydrolysate obtained with Thermolysin showed the most significant values. Since the Total Phenolic Content in all hydrolysates was low, peptides were likely the main contributors to these bioactivities. Hydrolysates were analyzed by UHPLC-QTOF-MS and a total of 98 different peptides were identified. Most of these peptides were rich in amino acids associated with antioxidant activity.

Sour orange (Citrus aurantium) seed, a rich source of protein isolate and hydrolysate - A thorough investigation

Sour orange (Citrus aurantium) seeds are typically discarded by juice processors as waste. This study aimed to extract protein isolates, produce hydrolysates from de-oiled sour orange seeds (SOS), and characterize their physicochemical properties. Previous studies have described methods to obtain protein isolates and hydrolysates from agricultural residues. However, there is limited data on the SOS. This research characterized protein isolates and hydrolysates from SOS, emphasizing yield, purity, and amino acid composition. Protein isolates were extracted using borate saline buffer, saline, and distilled water. Enzymatically hydrolysis was conducted using Protamex® (a commercial protease) at concentrations ranging from 0.2 to 5 g enzyme/100g protein isolate. Differential scanning calorimetry, electrophoresis, and FT-IR spectroscopy were utilized to characterize the isolates and hydrolysates. Data showed that using 5 % saline resulted in protein extraction with a yield and purity of 30 and 86 %, respectively. DSC analysis revealed that the denaturation temperature of the protein isolate was 68 °C, while the hydrolysates exhibited structural instability, as indicated by a decrease in enthalpy change compared to the isolate. The protein isolate had a 76° contact angle. The amino acid profile showed a significant presence of glutamic acid (130.530 mg/g) and arginine (70.210 mg/g). Electrophoresis analysis exhibited four major bands of the protein. The bands' intensity decreased, and new bands appeared after hydrolysis. The enzyme hydrolysis was confirmed using the O-phthaldialdehyde method and FTIR. Findings revealed that based on the free amine group quantity, the hydrolysate obtained using 5 g enzyme/100g protein isolate was 14.220 ± 0.299 μmol/mg protein. The study concluded that sour orange seeds are a good source of protein, with protein isolates and hydrolysates exhibiting desirable characteristics. More research needs to be conducted to acquire further information about their functional properties and potential applications.

Citrin: a novel food allergen in citrus seeds and citrus-derived pectin that shows cross-reactivity with cashew and pistachio

BACKGROUND

Patients exquisitely sensitive to cashew/pistachio are at risk for allergic reactions to citrus seeds and pectin.

OBJECTIVE

In this study, we sought to evaluate whether pectin is contaminated with citrus seeds, to identify a culprit antigen in citrus seeds, and to assess for cross-reactivity among allergens in citrus seeds, citrus pectin, and cashew or pistachio.

METHODS

Proteins from orange seed coats, orange seed endosperms, lemon seeds, grapefruit seeds, citrus pectin, apple pectin, and grapefruit pectin were extracted. Protein concentrations in all extracts were determined and visualized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique. Immunoglobulin E-binding capacity was determined with Western blot analyses and tandem mass spectrometry for the identification of the culprit allergen in citrus seeds and pectin.

RESULTS

In subjects with citrus seed, pectin, and cashew allergies, there was strong immunoglobulin E-reactivity to bands between 17 to 28 kDa and 28 to 38 kDa. The tandem mass spectrometry analysis of these bands indicated the presence of citrin as the culprit allergen. Citrin and Ana o 2 are both 11S globulins belonging to the cupin superfamily, and significant homology was found between these proteins.

CONCLUSION

Citrus pectin may be contaminated with citrus seeds. Citrin, a newly identified allergen in citrus seeds, seems to be the culprit antigen in citrus seeds and contaminated citrus pectin. Citrin is highly homologous with Ana o 2 in cashew and Pis v 2 in pistachio, suggesting potential for cross-reactivity and providing an explanation for co-allergenicity of cashew or pistachio, citrus seeds, and citrus pectin.

Oil and protein extraction from fruit seed and kernel by-products using a one pot enzymatic-assisted mild extraction

This research evaluated the application of a one-pot enzymatic extraction by using a protease for the concomitant and sustainable extraction of oils and proteins from fruit seeds/kernels of different species of stone, citrus and exotic fruits. The proteolysis improved the oil solvent-extractability of seeds/kernels of some fruit species compared to the use of acid and/or organic solvents and led to directly recover fat (10-33%) from mango, lemon and pumpkin seeds. Good protein extraction yields were obtained compared to conventional solvent extractions and with a good hydrolysis degree (almost 10%) in the case of lemon and pumpkin seed protein hydrolysates. The nutritional quality of all the protein hydrolysates was quite low, because of their limiting amino acids (histidine, methionine and lysine). On the contrary, the fruit seed/kernel oils resulted with high nutritional value, as they were mostly rich in unsaturated fatty acids, primarily oleic acid (>25%) and linoleic acid (till 40%).

Sequential ultrasound assisted deep eutectic solvent-based protein extraction from Sacha inchi meal biomass: towards circular bioeconomy

The need for high-quality dietary proteins has risen over the years with improvements in the quality of life. Deep eutectic solvents (DESs) have been regarded as potential green alternatives to conventional organic solvents for protein extraction from press cake biomass, meeting the needs of sustainable development goals. Sacha inchi seed meal (SIM) is generated as a by-product of the seed oil extraction industries containing high protein content. The current study presents a novel ultrasound assisted DES method for the extraction of SIM protein in a sequential manner. Four different DESs were screened, out of which choline chloride (ChCl)/glycerol (1:2) gave promising results in protein recovery and was further selected. The sequential ultrasound-ChCl/glycerol could effectively extract high total crude protein content (77.43%) from SIM biomass compared to alone ultrasound (29.21%) or ChCl/glycerol (58.32%) treatment strategies. The SIM protein extracted from ultrasound-ChCl/glycerol exhibited high solubility (94.39%) at alkaline pH and highest in vitro digestibility (71.16%) by digestive enzymes (pepsin and trypsin). The protein characterization by SDS-PAGE and FTIR elucidated the structural properties and presence of different functional groups of SIM protein. Overall, the sequential ultrasound-ChCl/glycerol revealed its significant potential for one-step biorefining of the waste Sacha inchi meal biomass for circular bioeconomy.

Valorization and extraction optimization of Citrus seeds for food and functional food applications

Valorization of food byproducts has attracted recently considerable attention. Citrus fruits provide considerable non-edible residues reach 80% in juice production. They are considered agri-wastes to comprise peel, pulp and seeds. Previous investigations have focused on peel and pulp to recover value-added products. The review presents for the first-time phytochemical composition of Citrus seeds' products, i.e., oil and extracts. Fatty acids, phytosterols and tocopherols amounted as the major bioactives in Citrus seeds, in addition to limonoids, dietary fibers and flavonoids. Besides their nutritional values, these chemicals have promising applications including production of biodiesel, food enhancers and antioxidants, especially from mandarin and grapefruit seeds. Optimum conditions of the different Citrus seeds' valorization are discussed to improve extraction yield and lessen environmental hazards of solvent extraction. This review presents the best utilization practices for one of the largest cultivated fruit seeds worldwide and its different applications.