Influence of processing steps and fruit maturity on volatile concentrations in juices from clementine, mandarin, and their hybrids

Comparison of Some Fruit Quality Parameters of Selected 12 Mandarin Genotypes from Black Sea Region in Turkey

Mandarins are mostly preferred specie of Citrus genus, and there has been a continuous rise in consumption and global marketing due to having easy-to-peel, attractive flavor, and fresh consumption advantages. However, most of the existing knowledge on quality traits of citrus fruit comes from research conducted on oranges, which are the main products for the citrus juice manufacturing industry. In recent years, mandarin production in Turkey surpassed orange production and took the first place in citrus production. Mandarins are mostly grown in the Mediterranean and Aegean Regions of Turkey. Due to suitable climatic conditions, they are also grown in the microclimatic condition in Rize province located in the Eastern Black Sea region. In this study, we reported the total phenolic content, total antioxidant capacity, and volatiles of 12 Satsuma mandarin genotypes selected from Rize province of Turkey. Considerable differences in the total phenolic content, total antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl assay), and fruit volatile constituent were found among the 12 selected Satsuma mandarin genotypes. The total phenolic content ranged from 3.50 to 22.53 mg of gallic acid equivalent per 100 g of the fruit sample in the selected mandarin genotypes. The total antioxidant capacity was the highest in genotype HA2 as 60.40%, and followed by IB (59.15%) and TEK3 (58.36%), respectively. A total of 30 aroma volatiles were detected from the juice samples of 12 mandarin genotypes by GC/MS, which comprised six alcohols, three aldehydes (including one monoterpene), three esters, one ketone, and one other volatiles. The main volatile compounds were identified in fruits of all Satsuma mandarin genotypes as α-terpineol (0.6-1.88%), linalool (1.1-3.21%), γ-terpinene (4.41-5.5%), β-myrcene (0.9-1.6%), dl-limonene (79.71-85.12%), α-farnesene (1.1-2.44), and d-germacrene (0.66-1.37%). Limonene accounts for most of the aroma compounds (79.71-85.12%) in fruits of all Satsuma genotypes. The genotypes MP and TEK8 had the highest total phenolic content, and HA2, IB, and TEK 3 had the highest antioxidant capacity. The YU2 genotype was found to contain more aroma compounds than the other genotypes. The genotypes selected on the basis of their high bioactive content could be used to develop new Satsuma mandarin cultivars with high human health promoting contents.

Citrus juice off-flavor during different processing and storage: Review of odorants, formation pathways, and analytical techniques

As the most widespread juice produced and consumed globally, citrus juice (mandarin juice, orange juice, and grapefruit juice) is appreciated for its attractive and distinct aroma. While the decrease of characteristic aroma-active compounds and the formation of off-flavor compounds are easy to occur in processing and storage conditions. This review provides a comprehensive literature of recent research and discovery on citrus juice off-flavor, primarily focusing on off-flavor compounds induced during processing and storage (i.e., thermal, storage, light, oxygen, package, fruit maturity, diseases, centrifugal pretreatment, and debittering process), formation pathways (i.e., terpene acid-catalyzed hydration, caramelization reaction, Maillard reaction, Strecker degradation, and other oxidative degradation) of the off-flavor compounds, effective inhibitor pathway to off-flavor (i.e., electrical treatments, high pressure processing, microwave processing, ultrasound processing, and chemical treatment), as well as odor assessment techniques based on molecular sensory science. The possible precursors (terpenes, sulfur-containing amino acids, carbohydrates, carotenoids, vitamins, and phenolic acids) of citrus juice off-flavor are listed and are also proposed. This review intends to unravel the regularities of aroma variations and even off-flavor formation of citrus juice during processing and storage. Future aroma analysis techniques will evolve toward a colorimetric sensor array for odor visualization to obtain a "marker" of off-flavor in citrus juice.

Determination of Bioactive Components in Mandarin Fruits: A Review

During the last decade, there has been a continuous rise in the consumption of fresh easy-to-peel mandarins. However, the majority of the knowledge comes from other citrus fruit, like orange, while there are relatively few studies about mandarins and no comprehensive research on literature data about them. One of the most important steps in the analytical process is sample preparation. Its value is evident in analyzing the samples with complex matrices, such as in mandarin fruit. In addition, mandarin contains hundreds to thousands of various compounds and metabolites, some of them present in extremely low concentrations, that interfere with the detection of one another. Hence, mandarin samples are commonly pretreated by extraction to facilitate analysis of bioactive compounds, improve accuracy and quantification levels. There is an abundance of extraction techniques available, depending on the group of compounds of interest. Finally, modern analytical techniques, have been applied to cope with numerous bioactive compounds in mandarins. Considering all the above, this review aims to (i) list the most valuable procedures of sample preparation, (ii) highlight the most important techniques for extraction of bioactive compounds from mandarin fruit, and (iii) summarize current trends in the identification and determination of bioactive compounds in mandarin.

Biogenic volatile organic compound emissions from leaves and fruits of apple and peach trees during fruit development

Biogenic volatile organic compounds (BVOCs) are widely involved in a variety of atmospheric chemical processes due to their high reactivity and species diversity. To date, however, research on BVOCs in agroecosystems, particularly fruit trees, remains scarce despite their large cultivation area and economic interest. BVOC emissions from different organs (leaf or fruit) of apple and peach trees were investigated throughout the stages of fruit development (FS, fruit swelling; FC, fruit coloration; FM, fruit maturity; and FP, fruit postharvest) using a proton-transfer-reaction mass spectrometer. Results indicated that methanol was the most abundant compound emitted by the leaf (apple tree leaf 492.5 ± 47.9 ng/(g·hr), peach tree leaf 938.8 ±  154.5 ng/(g·hr)), followed by acetic acid and green leaf volatiles. Beside the above three compounds, acetaldehyde had an important contribution to the emissions from the fruit. Overall, the total BVOCs (sum of eight compounds studied in this paper) emitted by both leaf and fruit gradually decreased along the fruit development, although the effect was significant only for the leaf. The leaf (2020.8 ±  258.8 ng/(g·hr)) was a stronger BVOC emitter than the fruit (146.0 ± 45.7 ng/(g·hr)) (P = 0.006), and there were no significant differences in total BVOC emission rates between apple and peach trees. These findings contribute to our understanding on BVOC emissions from different plant organs and provide important insights into the variation of BVOC emissions across different fruit developmental stages.

Investigation of changes in non-traditional indices of maturation in Navel orange peel and juice using GC-MS and LC-QTOF/MS

Changes in non-traditional indices of maturity, such as flavonoids and volatile compounds, during maturation were studied in Navel orange. Navel oranges were obtained at four stages of maturation, and non-volatile and volatile compounds in the peel and juice were analysed using liquid chromatography coupled with a quadrupole time-of-flight detector (LC-QTOF/MS) and gas chromatography with mass spectrometry and a flame ionisation detector (GC-MS/FID), respectively. Twenty-eight non-volatile and 62 volatile compounds in the peel as well as 22 non-volatile and 11 volatile compounds in the juice were found to have significant changes (p < 0.05) in abundances during maturation. Notably, most flavonoids (e.g. narirutin) and limonoids (e.g. nomilin) showed decreasing abundances during maturation. For volatile compounds, majority of detected alcohols peaked in abundances during middle maturation stages, while almost all detected aldehydes peaked at full maturity. Most terpenes peaked at earlier maturation stages in juice extracts compared to peel oil extracts. This comprehensive study could facilitate selection of Navel oranges for the extraction of valuable bioactive or flavour contributing compounds that are of interest to fragrance, flavour and nutraceutical industries.

Effect of fruit maturity on volatiles and sensory descriptors of four mandarin hybrids

Mandarins (or tangerines) are mainly consumed as fresh fruits due to the ease of peeling and desirable flavor. Sweetness, acidity, and flavor of mandarin are the most important criteria for consumer preference. The objective of this study was to evaluate the effects of harvest date on sensory and chemical components of four mandarin cultivars (Murcott, 411, Temple, and 'LB8-9' Sugar Belle®). Volatiles were extracted from the headspace of juice samples with solid phase microextraction (SPME) and analyzed using gas chromatography-mass spectrometry (GC-MS). The optimum harvest window for eating quality of 411 was late January to mid-February (soluble solids content [SSC]/titratable acidity [TA]: 11.3 to 14.0), Sugar Belle® fruits were best tasted when harvested from mid- to end of January (SSC/TA: 14.1 to 16.1), and February was the best month for harvesting Murcott (SSC/TA: 13.10 to 18.0) and Temple (SSC/TA:10.3 to 12.50). Sensory perception of sweetness, ripeness, and juiciness increased as SSC/TA increased while sourness and bitterness decreased. Pumpkin flavor, an indicator of overripe fruit, was mainly noticed late in the season. Tangerine flavor tended to decrease, whereas fruity-noncitrus flavor tended to increase with fruit maturity. Monoterpenes were the most abundant volatiles and tended to decrease with fruit maturity, whereas alcohols, esters, and aldehydes increase. Aldehydes, esters, and alcohols were positively correlated with sweetness, ripeness, juiciness, and fruity characteristics, and negatively with sourness and bitterness. On the other hand, monoterpenes were positively correlated with bitterness and tangerine flavor, and negatively correlated with sweetness and fruity-noncitrus flavor. The highest number of esters was found in Temple, whereas Murcott and 411 were high in aldehydes.

Determination of the Volatile Profile of Lemon Peel Oils as Affected by Rootstock

Citrus limon (L.) Burm is an important crop that grows between latitudes 30° North and 30° South, the main producers being China, the USA, Mexico, India, Brazil, and Spain. In Spain, lemon grows mainly in Mediterranean areas such as Murcia, Valencia, and Andalucía. The most cultivated varieties are “Fino” and “Verna”. In this study, five varieties of lemon, “Verna”, “Bétera”, “Eureka”, “Fino 49”, and “Fino 95” were evaluated on different rootstocks: three new Forner-Alcaide (“FA13”, “FA5”, “FA517”), Citrus macrophylla, Wester, and Citrus aurantium L. Hydrodistillation was used to obtain essential oil from fresh peels and then the volatile profile was studied by gas chromatography-mass spectrometry (GC-MS). A total of 26 volatile compounds were identified, limonene being the main one followed by β-pinene, γ-terpinene, sabinene, and α-pinene. The results revealed that Forner-Alcaide rootstocks (“FA5” > “FA517” > “FA13”) proved to be the best rootstocks for the aroma quality as they led to high volatile contents, followed by C. aurantium and C. macrophylla. Among the other varieties, the most aromatic one was “Eureka”. The whole trend was as follows (in decreasing order): “Eureka” > “Bétera” > “Fino 95” > “Verna” > “Fino 49”.

Diversity among mandarin varieties and natural sub-groups in aroma volatiles compositions

BACKGROUND

Mandarins constitute a large, diverse and important group within the Citrus family. Here, we analysed the aroma volatiles compositions of 13 mandarin varieties belonging to seven genetically different natural sub-groups that included common mandarin (C. reticulata Blanco), clementine (C. clementina Hort. ex. Tan), satsuma (C. unshiu Marcovitch), Mediterranean mandarin (C. deliciosa Tenore), King mandarin (C. nobilis Loureiro), and mandarin hybrids, such as tangor (C. reticulata × C. sinensis) and tangelo (C. reticulata × C. paradisi).

RESULTS

We found that mandarin varieties among tangors ('Temple', 'Ortanique'), tangelos ('Orlando', 'Minneola') and King ('King') had more volatiles, at higher levels, and were richer in sesquiterpene and ester volatiles, than other varieties belonging to the sub-groups common mandarin ('Ora', 'Ponkan'), clementine ('Oroval', 'Caffin'), satsuma ('Okitsu', 'Owari') and Mediterranean mandarin ('Avana', 'Yusuf Efendi'). Hierarchical clustering and principal component analysis accurately differentiated between mandarin varieties and natural sub-groups according to their aroma-volatile profiles.

CONCLUSIONS

Although we found wide differences in aroma-volatiles compositions among varieties belonging to different natural sub-groups, we detected only minor differences among varieties within any natural sub-group. These findings suggest that selecting appropriate parents would enable manipulation of aroma-volatile compositions in future mandarin breeding programmes.

Fruit volatile profiles of two citrus hybrids are dramatically different from those of their parents

Volatile compounds released from the fruit of two hybrid Citrus genotypes (FxCh90 and FxCh77) were compared to those from their parental varieties, Fortune mandarin and Chandler pummelo. A series of 113 compounds were identified, including 31 esters, 23 aldehydes, 20 alcohols, 17 monoterpenoids, and other compounds. The differences in the volatile profile among these four genotypes were essentially quantitative. The most striking result was that the volatile profile of the hybrids was not intermediate between their parents and completely differed from that of Chandler, but came closer to Fortune. This was because 56 of the 113 volatile compounds in the hybrids showed significantly higher or lower levels than in any of the parents. Such transgressive behavior in these hybrids was not observed for other fruit quality traits, such as acidity or soluble solid content. The combination of volatile profiling and chemometrics can be used to select new Citrus genotypes with a distinct volatile profile.

Recent developments in minimal processing: a tool to retain nutritional quality of food

The modernization during the last century resulted in urbanization coupled with modifications in lifestyles and dietary habits. In the same era, industrial developments made it easier to meet the requirements for processed foods. However, consumers are now interested in minimally processed foods owing to increase in their awareness to have fruits and vegetables with superior quality, and natural integrity with fewer additives. The food products deteriorate as a consequence of physiological aging, biochemical changes, high respiration rat,e and high ethylene production. These factors contribute substantially to discoloration, loss of firmness, development of off-flavors, acidification, and microbial spoilage. Simultaneously, food processors are using emerging approaches to process perishable commodities, along with enhanced nutritional and sensorial quality. The present review article is an effort to utilize the modern approaches to minimize the processing and deterioration. The techniques discussed in this paper include chlorination, ozonation, irradiation, photosensitization, edible coating, natural preservative use, high-pressure processing, microwave heating, ohmic heating, and hurdle technology. The consequences of these techniques on shelf-life stability, microbial safety, preservation of organoleptic and nutritional quality, and residue avoidance are the limelight of the paper. Moreover, the discussion has been made on the feasibility and operability of these techniques in modern-day processing.

Characterization and Comparison of Volatile Constituents of Juice and Peel from Clementine, Mandarin and their Hybrids

The volatile compositions of juice and peel of clementine ( Citrus reticulata x Citrus sinensis var. Commune), mandarin ( Citrus reticulata Blanco var. Willow Leaf) and their hybrids were analyzed by headspace solid-phase extraction (HS-SPME) coupled with gas chromatography and either a flame ionization detector (FID) or a mass spectrometer (MS). The major compounds of the volatile fractions of clementine and mandarin were limonene and limonene/γ-terpinene, respectively. The volatile compositions of juice and peel of the same fruit showed qualitative and quantitative differences. The data analysis established the existence of three main groups based on volatile compounds that correlated with sample genotypes (clementine and mandarin) and fruit samples (peel and juice).