Enhancing pectin extraction from orange peel through citric acid-assisted optimization based on a dual response.

Pectin is widely used in several products in the industry. Conventionally, strong and harmful acids are used for its extraction. This study optimized the extraction of orange peel's pectin using citric acid, considering yield and degree of esterification (DE) as response variables. Proximal analyses were performed, and the samples were subjected to a Box-Behnken design on three central points, considering as variables the temperature, time, and pH. The results of proximate analyses of the orange peels revealed 11.76 % moisture content, 87.26 % volatiles, 0.09 % ash, 50.45 % soluble carbohydrates, 70.60 % total carbohydrates, 0.89 % fixed carbon, 5.35 % lipids, and 36.75 mg GAE/g of phenolic compounds. The resulting second-order polynomial model described the relation of the input and output variables related to each other. The best performance to obtain a higher yield (18.18 %) of high methoxyl pectin (DE 50 %) was set at 100 °C/30 min/pH 2.48. Pectin showed antioxidant properties by ABTS and DPPH assays and similar thermal properties to the commercial polymer. Its equivalent weight was 1219.51 mol/g, and the methoxyl and anhydrouronic acid were 2.23 and 67.10 %, respectively. Hence, pectin extraction with citric acid results in a high-quality polymer and could be used as a gelling agent, stabilizer, or texturizer in food products.

Chemical and genetic basis of orange flavor.

Sweet orange (Citrus sinensis) exhibits limited genetic diversity and high susceptibility to Huanglongbing (HLB). Breeding HLB-tolerant orange-like hybrids is in dire need. However, our understanding of the key compounds responsible for orange flavor and their genetic regulation remains elusive. Evaluating 179 juice samples, including oranges, mandarins, Poncirus trifoliata, and hybrids, distinct volatile compositions were found. A random forest model predicted untrained samples with 78% accuracy and identified 26 compounds crucial for orange flavor. Notably, seven esters differentiated orange from mandarin flavor. Cluster analysis showed six esters with shared genetic control. Differential gene expression analysis identified C. sinensis alcohol acyltransferase 1 (CsAAT1) responsible for ester production in orange. Its activity was validated through overexpression assays. Phylogeny revealed the functional allele was inherited from pummelo. A SNP-based DNA marker in the coding region accurately predicted phenotypes. This study enhances our understanding of orange flavor compounds and their biosynthetic pathways and expands breeding options for orange-like cultivars.

Carnauba wax-based edible coatings retain quality enhancement of orange (Citrus sinensis cv. Moro) fruits during storage.

Fruit coatings serve a dual purpose in preserving the quality of fruits. Not only do they act as a barrier against water evaporation and fungal infiltration, but they also enhance the fruit's visual appeal in the market. Yet, their influence on the fruit's quality components, which play a crucial role in determining its nutritional value, taste, and overall flavor, has remained relatively unexplored. This study aimed to evaluate the effects of carnauba wax coating on the quality of Moro oranges during storage. The selected fruits were meticulously chosen for uniformity in size. The experiment involved applying carnauba wax, a commonly used type among local producers, at four different concentrations: 0%, 0.5%, 1%, and 1.5%. These treatments were applied during various storage periods, including immediately after fruits were harvested and after 40 and 80 days. Following the application of these treatments, the oranges were stored in a controlled environment (morgue) at a temperature of 4 ± 1 °C. Subsequently, several physicochemical parameters of both the fruit flesh and skin were examined. The results unveiled a decline in the overall ascorbic acid content of the fruits. In terms of phenol content, a general decreasing trend was observed after harvesting. At each sampling interval during storage, the phenol content in uncoated fruits consistently exceeded that of their waxed counterparts. Significant reduction in fruit weight was observed throughout the storage period. Both vitamin C and total acidity levels in the fruit exhibited decreases during the storage period. As time passed, fruit firmness gradually declined, while fruit decay increased during the 40- and 80-day storage periods for untreated Moro oranges. The anthocyanin content showed an increasing trend. The study also unveiled a decline in the antioxidant capacity of citrus fruits during storage. Strong significant positive correlations were observed between total phenol content and key parameters, such as antioxidant activity (0.941**), MDA (0.364*), vitamin C content, and total carbohydrate content (0.475**). Skin radiance showed a perfect correlation with chroma and hue (1.000**). Principal component analysis revealed that the first principal component accounted for 34.27% of the total variance, out of a total of five principal components that explained 77.14% of the variance. Through cluster analysis, the variables were categorized into three distinct groups; one associated with weight loss and another with ion leakage. Considering these findings, carnauba wax-based coating emerges as a promising solution for preserving Moro oranges. It effectively mitigates fruit weight loss and helps maintain fruit firmness during storage, making it a valuable tool for fruit preservation.

Comparison of green solvents for the revalorization of orange by-products: Carotenoid extraction and in vitro antioxidant activity.

Orange peels contain a considerable number of bioactive compounds such as carotenoids, that can be used as ingredients in high-value products. The aim of this study was to compare orange peel extracts obtained with different green solvents (vegetable oils, fatty acids, and deep eutectic solvents (DES)). In addition, the chemical characterization of a new hydrophobic DES formed by octanoic acid and l-proline (C8:Pro) was performed. The extracts were compared in terms of carotenoid extraction, antioxidant activity by three methods, color, and environmental impact. The results confirmed that the mixture of C8:Pro is a DES and showed the highest carotenoid extraction (46.01 µg/g) compared to hexane (39.28 µg/g). The antioxidant activity was also the highest in C8:Pro (2438.8 µM TE/mL). Finally, two assessment models were used to evaluate the greenness and sustainability of the proposed extractions. These results demonstrated the potential use of orange peels in the circular economy and industry.

Plasma proteome profiling reveals molecular mechanisms underlying the effects of daily consumption of 'Bahia' and 'Cara Cara' orange juices.

Orange juice is an important food source of bioactive compounds, mainly the flavanones hesperidin and narirutin. This study aimed to investigate the underlying molecular mechanisms of action of orange juice's health properties by analyzing changes in the plasma proteome of healthy Brazilian volunteers after consuming juices made from 'Bahia' (BOJ-source of flavanones) and 'Cara Cara' (CCOJ-source of flavanones and carotenoids) oranges cultivated in Brazil. We used an untargeted proteomic approach, with a particular emphasis on the juices' effects on blood coagulant activity. We identified 247 differentially expressed proteins, of which 170 significantly increased or decreased after BOJ consumption and 145 after CCOJ. These proteins are involved in 105 processes that can significantly regulate cell adhesion, cell signaling, cell metabolism, inflammation, or others. Bioinformatic analysis evidenced proteins with major cellular regulatory capacity (e.g., FN1 and GAPDH) and predicted transcription factors (TFs) (e.g., SP1 and CEBPA) and miRNAs (e.g., miR-1-3p and miR-615-3p) that could be involved in the regulation of differentially expressed proteins. In-silico docking analyses between flavanone metabolites and TFs evidenced the higher binding capacity of narirutin phase II metabolites with akt1 and p38, interactions that suggest how the expression of genes of differentially expressed proteins were activated or inhibited. Moreover, the study shed light on proteins of coagulation cascade that presented expression modulated by both juices, proposing the modulation of blood coagulant activity as a potential benefit of OJ (mainly CCOJ) consumption. Taken together, this study revealed that BOJ and CCOJ consumption affected plasma proteome in healthy individuals, suggesting potential molecular targets and mechanisms of OJ bioactive compounds in humans.

The effect of adding pomace on the bioactive composition and flavor volatiles in fermented orange juice with Lactobacillus.

BACKGROUND: The consumption of oranges generates huge amounts of pomaces, which are the potential raw materials to increase the nutritional value of the products. RESULTS: In this study, the bioactive composition and flavor volatiles in Lactobacillus fermented orange juice with added pomaces were researched. Results showed that the orange juices blended with pomaces were favorable substrates for Lactobacillus growth and the colony counts reached above 9.0 log CFU mL-1 , total phenolics, total flavonoids, and the antioxidant activity in orange juices were increased significantly after adding pomaces. Some amino acids, such as threonine (P < 0.0001), isoleucine (P < 0.01), and glycine (P < 0.01) were markedly higher in fermented orange juices with pomaces. The flavonoid diversity was more abundant by adding pomace fermentation and most flavonoids showed higher levels in fermented juices with the pomace, Lactobacillus fermentum 252 may transform some flavonoids through deglycosylation and reduction reaction. Furthermore, orange pomace mainly improved the flavor volatiles by increasing terpenoids and alcohol, such as d-limonene and benzyl alcohol, and decreasing volatile acids. CONCLUSION: This study presented a novelty in elevating the nutritional value of juice by the utilization of pomaces, its findings can provide a new way to mine the bioactive ingredient from Citrus by Lactobacillus, and can be used as a guide for the development of new Citrus processing technologies and functional foods. © 2023 Society of Chemical Industry.

Analysis of aroma components changes in Gannan navel orange at different growth stages by HS-SPME-GC-MS, OAV, and multivariate analysis.

The ripe Gannan navel oranges have an appealing aroma, but few studies have reported the changes of these aromatic substances during the growth of navel oranges. In this study, changes of aroma components in Gannan navel orange from 119 to 245 days after flowering were systematically studied using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) coupled with multivariate analysis, including principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). A total of 43 and 54 aroma components were identified in pulp and peel of navel orange, respectively. The odor active value (OAV) results indicated that 14 substances were the key aroma components during the growth of navel orange. Among them, the contribution of linalool, ß-myrcene and limonene were the highest. The multivariate statistical analysis further confirmed that 14 and 18 compounds could be used as key markers to distinguish the pulp and peel at different growth stages, respectively. Results from this study contributed to a better understanding of the dynamic variation and retention of aroma compounds during navel orange growth, and have great potential for industrial application.

Effects of irradiation on the aging and sensory quality of navel orange distilled spirits.

BACKGROUND: 60 Co-γ irradiation can simulate the effects of aging and enhance the flavor of distilled spirits. The present study aimed to investigate the effects of 0, 2, 4, 6, 8 and 10 kGy 60 Co-γ irradiation doses on the key aroma components in newly produced navel orange distilled spirits and thus determine the mechanism of their aging distilled spirits. RESULTS: The identification of aroma compounds demonstrated that ethyl hexanoate, d-limonene, ethyl octanoate, 3-methyl-1-butanol and linalool are the key aroma compounds in navel orange distilled spirits, which were increased except for linalool with irradiation doses of 2-6 kGy. Irradiation treatment simulated the effects of the aging of navel orange distilled spirits by promoting the content of total acids, total esters and aldehydes. Irradiation doses of 2-6 kGy increased the aroma intensity of navel orange distilled spirits, reaching an optimum at 6 kGy. However, irradiation doses as high as 8 and 10 kGy decreased the content of esters in navel orange distilled spirits, which led to a deterioration of the spirit flavor. CONCLUSION: Low doses of 60 Co-γ irradiation can simulate the effects of the aging by increasing the content of key aromatic compounds in navel orange distilled spirits. © 2023 Society of Chemical Industry.

Peracetic acid residues in orange juice can lead to a 5-vinylguaiacol-induced clove-like off-flavor via Baeyer-Villiger oxidation of hesperidin.

A balanced flavor is a major quality attribute of orange juice. Formation of 4-vinylguaiacol during storage can lead to an undesirable clove-like off-flavor. However, clove-like off-flavors were occasionally reported despite low 4-vinylguaiacol concentrations, suggesting an alternative molecular background. Application of gas chromatography-olfactometry and aroma extract dilution analysis to an orange juice with a pronounced clove-like off-flavor resulted in the identification of 5-vinylguaiacol. The compound showed the same odor as 4-vinylguaiacol, but was previously unknown in orange juice. In five of six commercial orange juices with clove-like off-flavors, 5-vinylguaiacol was even more odor-active than 4-vinylguaiacol. Spiking and model studies suggested that 5-vinylguaiacol is formed during pasteurization from the natural orange juice component hesperidin and residual peracetic acid used as cleaning agent by a Baeyer-Villiger oxidation. An activity-guided screening approach confirmed the role of hesperidin as 5-vinylguaiacol precursor. In conclusion, peracetic acid should no longer be used in orange juice processing plants.

Effect of hydrocolloid concentration in low-calorie orange jellies on preservation of bioactive compounds and antioxidant capacity.

The purpose of this paper was to avaliate of the concentration of hydrocolloids (low methoxyl pectin [LMP], guar gum [GG], and carrageenan gum [CG]) in low-calorie orange jellies in order to maximize the amount of bioactive compounds and antioxidant capacity, and to study the influence on degradation these compounds. A mixture design with seven tests was used to analyze the total phenolic compounds, ascorbic acid (vitamin C) and antioxidant capacity (ABTS, DPPH and ß-carotene/linoleic acid methods). The results were analyzed by response surface methodology and the Scott-Knott mean test at a significance level of 5% (p ≤ 0.05). In general, the regions containing 0.5% GG and 0.5% GC had higher levels of the variables under study, and this combination preserved the bioactive compounds and antioxidant activity of jellies in relation to that of orange juice.

Ultrasound Treatment Improves Fruit Quality of Postharvest Blood Oranges (Citrus sinensis L. Osbeck): Anthocyanin Enrichment and Its Biosynthesis.

This study was to investigate the effects of different nonthermal treatments on quality attributes, anthocyanin profiles, and gene expressions related to anthocyanin biosynthesis during low-temperature storage, including pulsed light (PL), magnetic energy (ME), and ultrasound (US). Among these treatments, 1 min US treatment was the most effective method for improving fruit quality and increasing total anthocyanin contents (by 29.89 ± 3.32%) as well as individual anthocyanins during low-temperature storage of 28 days. This treatment resulted in high color intensity, intact cellular architectures, and positive sensory evaluation. In contrast, PL and ME treatments displayed negative effects on quality improvement, leading to the destruction of cell architectures and inhibiting anthocyanin levels. Furthermore, qPCR analysis revealed that the structural genes (C4H, CHS1, CHS2, CHI, F3H, ANS, and GST) related to anthocyanin biosynthesis and transport were the target genes and upregulated in response to the cavitation effect of US treatment.

Evaluation of chemical characterization and antihyperlipidemic potential of orange peel powder (Citrus sinensis) in male human subjects.

Citrus sinensis is an important member of the genus Citrus which contains phenolic compounds and bioflavonoids which have antihyperlipidemic and antiatherogenic effects. It also has the potential to reduce oxidative stress. To investigate the antihyperlipidemic effect of orange peel powder was encapsulated and analyzed in hyperlipidemic patients. Results showed that it contains moisture (12.2%), ash content (7.9%), crude fat (0.78%), crude protein (12.37%) and crude fiber (13.2%). Total phenolic content and total flavonoid content were observed as 163.17 mg and 17.23mg in quercetin equivalent per gram a dry weight basis. Furthermore, the Orange peel powder was given in the form of medicinal capsules to hyperlipidemia male subjects. The experimental groups (G1 and G2) were given orange peel powder in capsules 400mg/d to the G1 group and 800mg/d to the G2 group for the time of 45 days. The serum lipid profile of patients was measured before and after the experimental trial. The result showed that G1 and G2 showed a decrease in plasma lipid parameters and increased high-density lipoprotein content in blood substantially as compared to G0. Thus, it was concluded from the results that orange peel powder depicts a significant impact on treating hyperlipidemia.

Comparing the antioxidant properties and volatile compounds of carrot-orange juice blend processed through varied chemical, pasteurization and ultrasound conditions.

Ultrasound technique is one of the green technologies that is being utilized widely for varying food processes. Our aim in this study was to carry out ultrasonication, pasteurization and chemical preservation (Potassium metabisulfite) techniques on a carrot-orange juice blend. Additionally, the effect of these treatments on the storage period of about 21 days was also determined. The study displayed an array of results under the effect of different treatments. Throughout the storage period of 21 days' significant results were presented by the carrot juice blend subjected to the ultrasound technique (25 min) giving the highest values for total phenolic content (25.56 ± 1.29 mg GAE/100 mL), total antioxidant activity (573.48 ± 2.29 mg Trolox /100 mL), DPPH (32.32 ± 1.83 %) and reducing power (45.45 ± 1.92 mg AAE/100 mL) with least deterioration, followed by the blends treated with potassium metabisulfite (KMS) and pasteurization. The physicochemical analysis showed a non-significant effect of treatments on pH and total soluble solids (oBrix) of carrot-orange juice blends whereas, the changes in color parameters L*, a* and b* were noted to show changes in treated blends. Similarly, the results for the GC-MS quantification of volatile compounds displayed the highest concentrations in the ultrasonicated blends as compared to other techniques. The peak quantity was obtained for the hexanal (9903.43 ± 7.61 µg.kg-1) followed by 3-Methylbutanal (2638.7 ± 5.44 µg.kg-1), terpinolene (2337.16 ± 5.28 µg.kg-1), elemicin (2198.28 ± 5.28 µg.kg-1), myristicin (1936.62 ± 6.72 µg.kg-1). The use of sonication can effectively enhance the nutritional qualities of juice, as perceived by consumers.

Dietary fiber extraction from citrus peel pomace: Yield optimization and evaluation of its functionality, rheological behavior, and microstructure properties.

Citrus fruits were widely used in processing and production, generating a large amount of peel pomace and a low utilization rate, resulting in substantial economic losses and environmental risks. It was important to extract compounds from citrus peel pomaces and find suitable preparation methods to improve their yield and physicochemical properties. Grapefruit peel pomace (GP) and navel orange peel pomace (OP) were used as raw materials in this study to prepare green and edible soluble dietary fiber (SDF) and insoluble dietary fiber (IDF). Analysis was done on the effects of solid-liquid ratio, cellulase hydrolysis time, cellulase dosage, and ultrasonic time on dietary fiber (DF) yield. To obtain the best DF preparation conditions, we used range analysis, variance analysis, and orthogonal experimental design. We also analyzed the structural, physicochemical, and rheological characteristics of SDF and IDF. According to the study's findings, SDF and IDF showed a loose and expansive structure with reduced particle size, higher specific surface area, and noticeably better physical and chemical properties after treating GP and OP with ultrasound-assisted composite enzyme method. Both SDF solution and IDF suspension were discovered through rheological analysis to be non-Newtonian pseudoplastic fluids, which was advantageous for expanding their applications in the field of food packaging. In conclusion, DF prepared using the ultrasound-assisted composite enzyme method was an excellent source of edible packaging materials, offering a benchmark for the recycling of other citrus peel wastes and ultimately paving the way for new methods of recycling citrus waste.

Electrohydrodynamic drying of citrus (Citrus sinensis L.) peel: Comparative evaluation on the physiochemical quality and volatile profiles.

Based on the concept of circular economy, citrus peel was considered a valuable source of bioactive compounds for high-value foods. Electrohydrodynamic (EHD) drying is a novel technology appropriated for the dehydration of heat-sensitive products such as citrus peel. In current work, EHD drying of citrus peel was performed based on alternating current (AC) or direct current (DC) sources at various voltage levels (9, 18, 27, 36, and 45 kV). The effect of EHD on drying characteristics, water retention capacity, enzyme inactivation, phytochemical contents (phenolic compounds and carotenoids), and volatile compounds of citrus peel were evaluated and compared. Results showed that the drying time in the AC electric field was shorter compared to DC electric field at the same applied voltages due to the polarization layer formed by unipolar charges. The applied voltage determined electric field strength as well as the degree of tissue collapse and cell membrane rupture. EHD elucidated the transformation and degradation of phytochemicals including phenolic compounds, carotenoids, and volatile composition in proportion to the applied voltage. The findings indicate that EHD drying with AC improves drying behaviors, inactivates enzymes, and retains the phytochemical properties of citrus peel.

Comparison of different drying technologies for brocade orange (Citrus sinensis) peels: Changes in color, phytochemical profile, volatile, and biological availability and activity of bioactive compounds.

This study evaluated the effects of freeze drying (FD), heat pump drying (HPD), microwave drying (MD), and far-infrared drying (FID) on the quality of brocade orange peels (BOPs). Although the most attractive appearance, maximum levels of ascorbic acid (0.46 mg/g dry weight (DW)), carotenoids (total 16.34 µg/g DW), synephrine (15.58 mg/g DW), limonoids (total 4.60 mg/g DW), phenols (total 9142.80 µg/g DW), and antioxidant activity were observed in FD-BOPs, many aroma components in FD-BOPs were in the minimum levels. HPD-, and MD-BOPs depicted similar trends to FD-BOPs, but they contained the highest concentrations of limonene and ß-myrcene. Phenols and ascorbic acid in MD-BOPs generally featured the highest levels of bioavailability, being to 15.99% and 63.94%, respectively. In comparison, FID was not beneficial for the preservation of bioactive compounds and volatile. Therefore, considering time and energy costs, HPD and particularly MD are more appropriate for the commercial production of dried BOPs.

Fingerprinting Chemical Markers in the Mediterranean Orange Blossom Honey: UHPLC-HRMS Metabolomics Study Integrating Melissopalynological Analysis, GC-MS and HPLC-PDA-ESI/MS.

(1) Background: Citrus honey constitutes a unique monofloral honey characterized by a distinctive aroma and unique taste. The non-targeted chemical analysis can provide pivotal information on chemical markers that differentiate honey based on its geographical and botanical origin. (2) Methods: Within the PRIMA project "PLANT-B", a metabolomics workflow was established to unveil potential chemical markers of orange blossom honey produced in case study areas of Egypt, Italy, and Greece. In some of these areas, aromatic medicinal plants were cultivated to enhance biodiversity and attract pollinators. The non-targeted chemical analysis and metabolomics were conducted using ultra-high-performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS). (3) Results: Forty compounds were disclosed as potential chemical markers, enabling the differentiation of the three orange blossom honeys according to geographical origin. Italian honey showed a preponderance of flavonoids, while in Greek honey, terpenoids and iridoids were more abundant than flavonoids, except for hesperidin. In Egyptian honey, suberic acid and a fatty acid ester derivative emerged as chemical markers. New, for honey, furan derivatives were identified using GC-MS in Greek samples. (4) Conclusions: The application of UHPLC-HRMS metabolomics combined with an elaborate melissopalynological analysis managed to unveil several potential markers of Mediterranean citrus honey potentially associated with citrus crop varieties and the local indigenous flora.

The Phytochemical and Pharmacological Properties of Citrus sinensis 'Maltese Half-blood' Essential Oil Peels Extracted and Optimized by Response-surface Methodology.

BACKGROUND: Citrus fruits have been a valuable economic crop for thousands of years. Furthermore, citrus essential oils are significant in the perfume, food, and beverage sectors, as well as aromatherapy and medical medicines. AIMS: The present study aims to evaluate the phytochemical and pharmacological potentials of the optimized Citrus sinensis 'Maltese half-blood' essential oils peels (CsEO) extraction yields using Response-Surface Methodology (RSM). OBJECTIVE: There have been few investigations on Citrus sinensis 'Maltese half-blood' essential oil. METHODS: Citrus sinensis 'Maltese half-blood' essential oil peels (CsEO) extraction yields were performed by hydro-distillation and optimized by using Response-Surface Methodology (RSM). The oils were analysed by GC-MS. Different chemical tests were used to evaluate antioxidant activities. The healing potential was evaluated using models' wounds on Wistar rats. RESULTS: The RSM optimization demonstrated the highest yield of CsEO of 6.89 g/100 g d.b. All three tested factors significantly influenced the CsEO extraction yield: washing saline solution concentration, washings number, and drying percentage of peels. Significant antioxidant activities were noted in CsEO: the DPPH assay reported an IC50 of 0.225 ± 0.014 mL/mg, the FRAP assay showed an IC50 of 0.235 ± 0.001, and the NO assay was an IC50 in order of 0.259 ± 0.019. CsEO was not genotoxic and considerably decreased the levels of DNA lesions induced by oxidants. Also, applying a cream with CsEO on wounds promotes significantly rapid wound healing. CONCLUSION: CsEO could be considered a rich natural source of antioxidants and bio-compounds to accelerate wound healing. It can be used in pharmaceutical sectors as an alternative to synthetic chemicals.

Sensory quality of Citrus scion hybrids with Poncirus trifoliata in their pedigrees.

Hybrids of Poncirus trifoliata L. Raf. with Citrus have shown degrees of tolerance to the deadly citrus greening disease, hence prompting interest as potential commercial varieties. Although P. trifoliata is known to produce fruit that is inedible, fruit from many advanced hybrid trees have not been evaluated for their quality potential. The sensory quality of selected Citrus hybrids with varying degrees of P. trifoliata in their pedigrees is reported herein. Four Citrus × P. trifoliata hybrids developed through the USDA Citrus scion breeding program-1-76-100, 1-77-105, 5-18-24, and 5-18-31-had acceptable eating quality and sweet and sour taste, with mandarin, orange, fruity-noncitrus, and floral flavors. On the other hand, hybrids with higher proportion of P. trifoliata in their pedigrees, US 119 and 6-23-20, produced a juice characterized by green, cooked, bitter, and Poncirus-like flavor and aftertaste. Partial least square regressions revealed that the Poncirus-like off-flavor is likely due to a combination of higher than typical amounts of sesquiterpene hydrocarbons (woody/green odor), monoterpenes (citrus/pine), and terpene esters (floral) and a lack of aldehydes with typical citrus odor (octanal, nonanal, and decanal). Sweetness and sourness were mostly explained by high sugars and acids, respectively. Further, carvones and linalool contributed to sweetness in the samples from early and late seasons, respectively. In addition to highlighting chemical contributors to sensory descriptors in Citrus × P. trifoliata hybrids, this study provides useful information on sensory quality for future citrus breeding efforts. PRACTICAL APPLICATION: The relationships between the sensory quality and secondary metabolites of Citrus × P. trifoliata hybrids described in this study help identify disease-resistant Citrus scion hybrids with acceptable flavor and help mobilize this resistance in future breeding efforts. It also shows potential of such hybrids to be commercialized.

Valorization of orange peels exploiting fungal solid-state and lacto-fermentation.

BACKGROUND: Orange peels can serve as a cost-effective raw material for the production of lactic acid. Indeed, given their high concentration of carbohydrates and low content of lignin, they represent an important source of fermentable sugars, recoverable after a hydrolytic step. RESULTS: In the present article, the fermented solid, obtained after 5 days of Aspergillus awamori growth, was used as the only source of enzymes, mainly composed of xylanase (40.6 IU g-1 of dried washed orange peels) and exo-polygalacturonase (16.3 IU g-1 of dried washed orange peels) activities. After the hydrolysis, the highest concentration of reducing sugars (24.4 g L-1 ) was achieved with 20% fermented and 80% non-fermented orange peels. The hydrolysate was fermented with three lactic acid bacteria strains (Lacticaseibacillus casei 2246 and 2240 and Lacticaseibacillus rhamnosus 1019) which demonstrated good growth ability. The yeast extract supplementation increased the lactic acid production rate and yield. Overall, L. casei 2246 produced the highest concentration of lactic acid in mono-culture. CONCLUSION: To the best of our knowledge this is the first study exploiting orange peels as low-cost raw material for the production of lactic acid avoiding the employment of commercial enzymes. The enzymes necessary for the hydrolyses were directly produced during A. awamori fermentation and the reducing sugars obtained were fermented for lactic acid production. Despite this preliminary work carried out to study the feasibility of this approach, the concentrations of reducing sugars and lactic acid produced were encouraging, leaving open the possibility of other studies for the optimization of the strategy proposed here. © 2023 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.