Juice volatile composition differences between Valencia orange and its mutant Rohde Red Valencia are associated with carotenoid profile differences

Non-targeted metabolomic analysis reveals the mechanism of quality formation of citrus flower-green tea

BACKGROUND

Citrus flower-green tea (CT) is a scented tea processed from green tea (GT) and fresh citrus flower, which is favored by consumers due to its potential health benefits and unique citrus flavor. This study evaluated the quality of CT and revealed the mechanism of its quality formation.

RESULTS

The CT had a significant citrus flavor and a good antioxidant activity, and its sensory quality was superior to that of GT. Headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) analysis revealed that the scenting process resulted in a significant increase of alkenes such as β-pinene, trans-β-ocimene, α-farnesene, isoterpinolene, and γ-terpinene, as well as a significant decrease of alcohols such as α-terpineol, l-menthol, and linalool in CT in comparison with GT. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis revealed that the levels of flavonoids (such as neohesperidin, hesperidin, tangeritin, hesperetin 5-O-glucoside, and nobiletin) and alkaloids (such as trigonelline and theobromine) in CT increased significantly after scenting process, while the levels of amino acids (such as valine and l-phenylalanine) and organic acids (such as ascorbic acid) decreased significantly.

CONCLUSION

These observations showed that the scenting process promoted the absorption of aroma from citrus flowers by GT and the changes in its non-volatile metabolites, leading to the formation of citrus flavor quality in CT. © 2024 Society of Chemical Industry.

Non-volatile and volatile compound changes in blueberry juice inoculated with different lactic acid bacteria strains

BACKGROUND

Lactic acid bacteria (LABs) are widely present in foods and affect the flavour of fermented cultures. This study investigates the effects of fermentation with Lactobacillus acidophilus JYLA-16 (La), Lactobacillus plantarum JYLP-375 (Lp), and Lactobacillus rhamnosus JYLR-005 (Lr) on the flavour profile of blueberry juice.

RESULTS

This study showed that all LABs strains preferentially used glucose rather than fructose as the carbon source during fermentation. Lactic acid was the main fermentation product, reaching 7.76 g L-1 in La-fermented blueberry juice, 5.86 g L-1 in Lp-fermented blueberry juice, and 6.41 g L-1 in Lr-fermented blueberry juice. These strains extensively metabolized quinic acid, whereas oxalic acid metabolism was almost unaffected. Sixty-four volatile compounds were identified using gas chromatography-ion mobility spectrometry (GC-IMS). All fermented blueberry juices exhibited decreased aldehyde levels. Furthermore, fermentation with La was dominated by alcohols, Lp was dominated by esters, and Lr was dominated by ketones. Linear discriminant analysis of the electronic nose and principal component analysis of the GC-IMS data effectively differentiated between unfermented and fermented blueberry juices.

CONCLUSION

This study informs LABs selection for producing desirable flavours in fermented blueberry juice and provides a theoretical framework for flavour detection. © 2023 Society of Chemical Industry.

Release of glycosidically-bound volatiles in orange juice under natural conditions

Glycosidically-bound volatiles (GBV) can be released by exogenous acid and enzymatic hydrolysis. However, the liberation of GBV in natural juice is not reported. It was found that part of the GBV in orange juice (OJ) under natural conditions can be released and the types of volatiles were considerably fewer than the ones under exogenous acid, or enzymatic hydrolysis. Seven types of aroma substances were released under endogenous enzyme, among which ethyl 3-hydroxyhexanoate and eugenol are characteristic aroma substances of OJ. Six kinds of aroma substances can be released under natural acidic conditions, none are characteristic aroma substances of OJ. Ten kinds of substances were released under endogenous enzymes in combination with the acidic condition, among which benzyl alcohol, ethyl 3-hydroxyhexanoate, citral, and eugenol are characteristic aroma substances of OJ. The results indicated that GBV may play an important role in resisting the decrease of free aroma in OJ during storage.

Quantitative metabolomic analysis reveals the fractionation of active compounds during lemon fruit juicing

In this study, metabolomic analysis was employed to investigate the separation (fractionation) of active compounds into lemon juice (LJ) and lemon pomace (LP) during lemon juicing. A total of 968 metabolites were identified, and 438 differentially abundant metabolites (DAMs) were screened out between LJ and LP, suggesting significant metabolite fractionation during juicing. The "flavonoids", "phenolic acids", and "saccharides and alcohols" were mainly retained in the LP, while the fractionation of major "organic acids" was differentiated. Seven of the 12 potential bitter metabolites were more abundant in the LP and two were more abundant in the LJ, suggesting that LP would be more bitter. L-Ascorbic acid, thiamine, and acitretin were significantly lost during juicing, while riboflavin was newly dissolved during juicing. The antioxidant capacity of LP was significantly higher than that of LJ, which was closely related to the higher abundance of phenolic acid metabolites in LP. These findings suggtested that promoting the release of flavonoids and phenolic acids from LP is a potential strategy to improve the quality of LJ. Results also provides important information and reference for developing high-value products by using LP.

Factors affecting aroma compounds in orange juice and their sensory perception: A review

Orange juice is the most widely consumed fruit juice globally because of its pleasant aromas and high nutritional value. Aromas, contributed by free and bound aroma compounds, are an important attribute and determine the quality of orange juice and consumer choices. Aldehydes, alcohols, esters, and terpenoids have been shown to play important roles in the aroma quality of orange juice. Many factors affect the aroma compounds in orange juice, such as genetic makeup, maturity, processing, matrix compounds, packaging, and storage. This paper reviews identified aroma compounds in free and bound form, the biosynthetic pathways of aroma-active compounds, and factors affecting aroma from a molecular perspective. This review also outlines the effect of variations in aroma on the sensory profile of orange juice and discusses the sensory perception pathways in human systems. Sensory perception of aromas is affected by aroma variations but also converges with taste perception. This review could provide critical information for further research on the aromas of orange juice and their manipulation during the development of products.

Fruit quality and volatile constituents of a new very early-ripening pummelo (Citrus maxima) cultivar 'Liuyuezao'

'Liuyuezao' (LYZ) pummelo (Citrus maxima) originated from a spontaneous bud sport on a 'Guanxi' (GXB) pummelo tree and was released as a new very early-season cultivar. The objective of this study was to present the sensory and nutritional profiles of LYZ fruits, and compare it with other major commercialized pummelo cultivars including GXB, 'Sanhong' (SH) and 'Hongrou' (HR). LYZ had higher contents of organic acids (12.01 mg/g), phenols (669.01 mg/L), vitamin C (75.73 mg/100 mL) and stronger antioxidant capacity (77.65 mg/100 mL) but lower levels of soluble sugars (62.85 mg/g), carotenoids (0.25 mg/L) and flavonoids (46.3 mg/L) when compared to the other pummelos. Moreover, a smaller number (49) and much less content (7.63) of fruit volatiles were detected in LYZ than them in GXB, SH and HR. The relatively high levels of fructose (20.6 mg/g) and organic acids and low levels of volatile compounds in LYZ mainly contributed to its sweet and mildly sour taste and moderate aroma of pummelo note. LYZ is presented as an alternative pummelo cultivar with the potential for commercialization.

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.

Volatile composition changes in lemon during fruit maturation by HS-SPME-GC-MS

BACKGROUND

Volatiles are determinants of fruit aroma and flavor characteristics and also provide valuable information for lemon as ingredient for the food and drinks industry. Volatiles in 'Eureka' lemon and 'Xiangshui' lemon pulps from 130 to 186 days after flowering were enriched by headspace-solid-phase microextraction (HS-SPME), and analyzed by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Seventy-seven volatiles of two lemon cultivars at the different ripening stages were identified and divided into six categories. Varieties and ripening stages had significant effects on individual volatiles in each category. The proportion of monoterpenes was found to be higher in 'Eureka' lemon, while 'Xiangshui' lemon had a higher proportion of sesquiterpenes, aldehydes and alcohols. The proportion of monoterpene fluctuation decreased during fruit ripening, while fluctuation of sesquiterpenes, alcohols, aldehydes and esters increased. Among the hydrocarbons, monoterpenes decreased their relative abundance from 91.67% to 81.04% in 'Eureka' lemon, and from 83.01% to 60.04% in 'Xiangshui' lemon; conversely, sesquiterpenes increased from 0.73% to 2.89% in 'Eureka' lemon, and from 3.21% to 8.48% in 'Xiangshui' lemon. Among the oxygenated volatiles, the proportions of alcohols, aldehydes and esters were higher at 186 days after flowering in both two cultivars.

CONCLUSION

The volatile organic compounds during fruit ripening of lemon varieties with different resistance were elucidated. The proportion of oxygenated volatiles increased during fruit ripening, and disease-resistant varieties had a higher proportion. These results provided important theoretical support for the utilization of lemon fruits and the innovation of disease-resistant germplasm resources. © 2021 Society of Chemical Industry.

Effect of Six Lactic Acid Bacteria Strains on Physicochemical Characteristics, Antioxidant Activities and Sensory Properties of Fermented Orange Juices

Six lactic acid bacteria strains were used to study the effects on physicochemical characteristics, antioxidant activities and sensory properties of fermented orange juices. All strains exhibited good growth in orange juice. Of these fermentations, some bioactive compositions (e.g., vitamin C, shikimic acid) and aroma-active compounds (e.g., linalool, 3-carene, ethyl 3-hydroxyhexanoate, etc.) significantly increased in Lactiplantibacillus plantarum and Lactobacillus acidophilus samples. DPPH free radical scavenging rates in L. plantarum and Lacticaseibacillus paracasei samples increased to 80.25% and 77.83%, respectively. Forty-three volatile profiles were identified, including 28 aroma-active compounds. 7 key factors significantly influencing sensory flavors of the juices were revealed, including D-limonene, linalool, ethyl butyrate, ethanol, β-caryophyllene, organic acids and SSC/TA ratio. The orange juice fermented by L. paracasei, with more optimization aroma-active compounds such as D-limonene, β-caryophyllene, terpinolene and β-myrcene, exhibited more desirable aroma flavors such as orange-like, green, woody and lilac incense, and gained the highest sensory score. Generally, L. paracasei fermentation presented better aroma flavors and overall acceptability, meanwhile enhancing antioxidant activities.

Aroma characterization of regional Cascade and Chinook hops (Humulus lupulus L.)

Aroma compounds in Cascade and Chinook hops harvested from multiple Virginia locations were identified by gas chromatography-mass spectrometry-olfactometry (GC-MS-O) and aroma extract dilution analysis (AEDA). Selected aroma compounds were quantitated by combination of stable isotope dilution analysis (SIDA) and standard addition method (SAM). A total of 33 aroma-active compounds were detected in five samples with β-myrcene, methyl octanoate, geraniol and linalool being the predominant compounds based on their high flavor dilution (FD) factors and odor activity values (OAVs). L-Calamenene and germacrene B was the major characteristic component unique to Cascade and Chinook variety, respectively. Principal component analysis (PCA) showed distinctive aroma profiles for all samples except for Blacksburg and Petersburg Cascade. Hierarchical cluster analysis (HCA) reflected the higher contents of most aroma-active compounds in Meadowview Cascade and Chinook when compared to their counterparts. The significant variations suggested the potential influences of environmental factors and agronomic practices on hop aroma quality.

Synergistic effects of ultrasound and β-d-glucosidase in aroma of orange juice

The synergistic effects of ultrasound and β-d-glucosidase in aroma of orange juice were investigated. β-d-Glucosidase significantly increased the content of ester, aldehyde, alcohol, terpene, acid, and phenol, and insignificantly increased the ketone content in orange juice. Enzyme-treated orange juice, compared with fresh untreated orange juice, was found to contain 15 novel aroma compounds, whereas three aroma compounds disappeared. Ultrasound improved the enzymatic action and the retention of more active flavors in juice than treatment with enzyme alone. However, simultaneous ultrasound and enzyme treatment decreased aroma quality. Therefore, the choice of the mode of ultrasound treatment is highly important. The present investigation will provide a reference for aroma-enhancing application of ultrasound combined with β-D-glucosidase. PRACTICAL APPLICATION: The study supplies a reference method for the aromatization of fruit juice.

New Trends in the Use of Volatile Compounds in Food Packaging

In the last years, many of the research studies in the packaging industry have been focused on food active packaging in order to develop new materials capable of retaining the active agent in the polymeric matrix and controlling its release into food, which is not easy in many cases due to the high volatility of the chemical compounds, as well as their ease of diffusion within polymeric matrices. This review presents a complete revision of the studies that have been carried out on the incorporation of volatile compounds to food packaging applications. We provide an overview of the type of volatile compounds used in active food packaging and the most recent trends in the strategies used to incorporate them into different polymeric matrices. Moreover, a thorough discussion regarding the main factors affecting the retention capacity and controlled release of volatile compounds from active food packaging is presented.

Characteristic Volatile Fingerprints and Odor Activity Values in Different Citrus-Tea by HS-GC-IMS and HS-SPME-GC-MS

Citrus tea is an emerging tea drink produced from tea and the pericarp of citrus, which consumers have increasingly favored due to its potential health effects and unique flavor. This study aimed to simultaneously combine the characteristic volatile fingerprints with the odor activity values (OAVs) of different citrus teas for the first time by headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Results showed that the establishment of a citrus tea flavor fingerprint based on HS-GC-IMS data can provide an effective means for the rapid identification and traceability of different citrus varieties. Moreover, 68 volatile compounds (OAV > 1) were identified by HS-SPME-GC-MS, which reflected the contribution of aroma compounds to the characteristic flavor of samples. Amongst them, the contribution of linalool with sweet flower fragrance was the highest. Odorants such as decanal, β-lonone, β-ionone, β-myrcene and D-limonene also contributed significantly to all samples. According to principal component analysis, the samples from different citrus teas were significantly separated. Visualization analysis based on Pearson correlation coefficients suggested that the correlation between key compounds was clarified. A comprehensive evaluation of the aroma of citrus tea will guide citrus tea flavor quality control and mass production.

Effects of microwave heating on the chemical composition and bioactivity of orange juice-milk beverages

The effect of microwave heating (MH, 65 and 75 °C for 15, 30, and 60 s) on the bioactive compounds, fatty acid profile, and volatile compounds of orange juice-milk beverage (OJMB) was evaluated during 28 days of refrigerated (4 °C) storage. Conventionally pasteurized (75 °C/15 s) and untreated beverages were used as controls. MH-OJMB presented a lower browning index and higher levels of ascorbic acid, total phenolics, and carotenoids, higher antioxidant activity, and greater α-amylase, α-glucosidase, and ACE inhibitory activity than the pasteurized product, similar to the untreated beverage. No significant differences were observed in the volatile organic compounds and fatty acids levels. Lower temperatures (65 °C) and longer process times (60 s) resulted in higher retention of bioactive compounds. MH can be an alternative to conventional pasteurization for OJMB processing.

Aroma characteristics of cloudy kiwifruit juices treated with high hydrostatic pressure and representative thermal processes

The commercial kiwifruit juice is deficient in a theoretical basis for the control of aroma characteristics during sterilization. To investigate the different sterilization methods on the aroma of kiwifruit juice, three sterilized kiwifruit juice samples, including pasteurization (PS), high temperature short time (HTST) and high hydrostatic pressure (HHP) sterilization, were observed. Results showed that a total of 15 major aroma-active compounds were identified in fresh kiwifruit juice by combination of detection frequency (DF) analysis and odor activity value (OAV); while the changes of these aroma-active compounds during PS, HTST and HHP sterilization were further studied. Quantitative descriptive analysis (QDA) was applied to validate the sensory differences, showing fruity and grassy notes changed a lot after sterilization, and the HHP sample was similar to fresh sample (FS) in comparison of samples treated by other sterilization methods. Further partial least squares regression analysis (PLSR) coincided with the overall note. Among these aroma-active compounds, the decrease of C6 aldehydes and C6 alcohols such as hexanal, (E)-2-hexenal and 1-hexanol might result in the great change of grassy note while the change of fruity note might be well correlated with the decrease of esters such as methyl butyrate and ethyl butyrate during processing.

Storage effects on the quality quartet of orange juice submitted to moderate thermosonication: Predictive modeling and odor fingerprinting approach

The effects of moderate thermosonication (MTS) on the quality quartet: physico-chemical, microbial, nutritional and sensory qualities of orange juice (OJ) inoculated with Alicyclobacillus acidoterrestris (AAT) were studied during 24 days of storage at ambient and refrigerated temperatures. The bioactive compounds and antioxidant activity of OJ decreased with storage, while the pectin methyl esterase (PME) increased. Nonetheless, noticeable changes were observed from the 12th day of storage. There was no obvious (p > 0.05) variation in pH and total soluble solids. To determine the nutritional and microbial quality characteristics of OJ during storage, non-linear kinetic curves were successfully fitted with least square fitting polynomial and four-parameter log-logistic distribution models. The E-nose sensors succeeded in discriminating between the aroma of non-treated and treated OJ based on linear discriminant analysis (LDA). Furthermore, terpenes, alcohol and partially aromatic compounds were the main spoilage indicators of OJ during storage based on E-nose analysis and confirmed by HS-SPME-GC/MS analysis. Thus, MTS significantly extended the shelf life of the quality quartet of natural OJ at 4 °C. E-nose-GC/MS fusion offered odor fingerprints to AAT microorganisms that can be used as spoilage index without using traditional food analysis techniques. The proposed approach can be used as an alternative tool for rapid detection of spoilage microorganisms in OJ.

Tracing the production area of citrus fruits using aroma-active compounds and their quality evaluation models

BACKGROUND

Aroma is one of the most important aspects of fruit quality and can reflect the characteristics of different fruits. Aroma-active compounds can usefully be employed to trace the production areas of two citrus cultivars ('Eureka' lemon and 'Huapi' kumquat) and to evaluate their aroma quality.

RESULTS

'Huapi' kumquat peel displayed higher monoterpene and sesquiterpene compound content, whereas 'Eureka' lemon peel exhibited higher monoterpene and monoterpene aldehyde compound content. 'Eureka' lemon peel ('Wanzhou' cultivar) had higher nerol acetate and geraniol acetate compound content. Kumquat peel ('Suichuan' and 'Rongan' cultivars) had higher sesquiterpene content. In addition, 30 and 31 aroma-active compounds were observed in kumquat and lemon, respectively, based on their odor activity values. Principal component analysis (PCA) and hierarchical clustering analysis (HCA) results indicated that classification for production areas based on aroma-active compounds was useful. The selected aroma-active compounds have been checked as aroma quality parameters that could be used with multivariate analysis to establish a model of aroma quality evaluation. Higher aroma quality values from kumquat and lemon were collected from Rongan and Wanzhou cultivars, respectively.

CONCLUSION

Aroma-active compounds can be used to discriminate production areas using multivariate statistics. An objective method was established to evaluate the aroma quality of citrus fruits. 'Huapi' kumquat and 'Eureka' lemon, which had the highest aroma quality, was harvested from the Rongan and Wanzhou production areas. This was the first time that the aroma quality of citrus fruits was evaluated using multivariate analysis. © 2019 Society of Chemical Industry.