Change in taste-altering non-volatile components of blood and common orange fruit during cold storage

Qualitative Traits and Antioxidant Properties of Blood Oranges Are Affected by the Genotype and the Climatic Conditions

Blood oranges are increasingly cultivated worldwide as consumers become more aware of the health benefits of their nutraceutical properties and natural antioxidants, specifically polyphenols and anthocyanins. The amounts of these compounds in the fruit mostly depend on the cultivar, rootstock, maturity stage, and environmental conditions. This work focused on the study of the qualitative features of numerous blood orange cultivars grown in three different environments in Spain and Italy. The aim of the work was to investigate the accumulation of primary and secondary metabolites, including bioactive compounds, and to characterize fruit qualitative traits at the time of harvest. Simple sugars were identified and quantified by liquid chromatography and organic acids, polyphenols, and flavonoids by spectrophotometric analysis. The antioxidant potential of the juice was assessed by ABTS, DPPH, and FRAP assays. Cultivation area affected juice color, with Moro and T. Ippolito being the varieties with the highest pigmentation. The cultivation area also determined the pattern of primary and secondary metabolite accumulation in the Tarocco lines. Furthermore, the antioxidant potential was influenced by the diverse environments. Principal Component Analysis highlighted three clusters, two overlapping clusters for the varieties grown in the two Spanish plots and a third clearly separated cluster for the genotypes grown in Italy. This study provides novel knowledge on primary and secondary metabolite accumulation in blood oranges, elucidating the role of genotype and environmental conditions on fruit quality.

Identification of key sensory and chemical factors determining flavor quality of Xinyu mandarin during ripening and storage

Xinyu mandarin is popular for its good flavor, but its flavor deteriorates during postharvest storage. To better understand the underlying basis of this change, the dynamics of the sensory profiles were investigated throughout fruit ripening and storage. Sweetness and sourness, determined especially by sucrose and citric acid content, were identified as the key sensory factors in flavor establishment during ripening, but not in flavor deterioration during storage. Postharvest flavor deterioration is mainly attributed to the reduction of retronasal aroma and the development of off-flavor. Furthermore, sugars, acids and volatile compounds were analyzed. Among the 101 detected volatile compounds, 10 changed significantly during the ripening process. The concentrations of 15 volatile components decreased during late postharvest storage, among which α-pinene and d-limonene were likely to play key roles in the reduction of aroma. Three volatile compounds were found to increase during storage, associated with off-flavor development.

Metabolomic and transcriptomic analyses reveal the effects of grafting on blood orange quality

Introduction

Blood orange (Citrus sinensis L.) is a valuable source of nutrition because it is enriched in anthocyanins and has high organoleptic properties. Grafting is commonly used in citriculture and has crucial effects on various phenotypes of the blood orange, including its coloration, phenology, and biotic and abiotic resistance. Still, the underlying genetics and regulatory mechanisms are largely unexplored.

Methods

In this study, we investigated the phenotypic, metabolomic, and transcriptomic profiles at eight developmental stages of the lido blood orange cultivar (Citrus sinensis L. Osbeck cv. Lido) grafted onto two rootstocks.

Results and discussion

The Trifoliate orange rootstock provided the best fruit quality and flesh color for Lido blood orange. Comparative metabolomics suggested significant differences in accumulation patterns of metabolites and we identified 295 differentially accumulated metabolites. The major contributors were flavonoids, phenolic acids, lignans and coumarins, and terpenoids. Moreover, transcriptome profiling resulted in the identification of 4179 differentially expressed genes (DEGs), and 54 DEGs were associated with flavonoids and anthocyanins. Weighted gene co-expression network analysis identified major genes associated to 16 anthocyanins. Furthermore, seven transcription factors (C2H2, GANT, MYB-related, AP2/ERF, NAC, bZIP, and MYB) and five genes associated with anthocyanin synthesis pathway (CHS, F3H, UFGT, and ANS) were identified as key modulators of the anthocyanin content in lido blood orange. Overall, our results revealed the impact of rootstock on the global transcriptome and metabolome in relation to fruit quality in lido blood orange. The identified key genes and metabolites can be further utilized for the quality improvement of blood orange varieties.

The potential of different ripeness of blood oranges (Citrus sinensis L. Osbeck) for sale in advance after low-temperature storage: Anthocyanin enhancements, volatile compounds, and taste attributes

To explore the optimal early harvest time similar to the ripe fruit qualities, the effects of storage temperatures on maturity indexes, weight losses, colour parameters, anthocyanin profiles, volatile and taste components of blood oranges at six different maturity levels were investigated. Total anthocyanin contents of cold-treated fruits increased to or exceed that of ripe fruits (0.24 ± 0.12 mg/100 g), and fruits harvested from 260 d and 280 d after anthesis shared similar individual anthocyanin profiles to ripe fruits during storage at 8 °C for 30 d and 20 d (III-30 d and IV-20 d groups), respectively. Moreover, comparative analyses of e-nose and e-tongue demonstrated the distances of volatile components and scores of taste attributes including sourness, saltiness, bitterness, sweetness, and umami in III-30 d and IV-20 d groups were close to that of ripe fruits, indicating that the fruits could be sold about 20 to 30 d ahead of the season.

An up-to-date review: differential biosynthesis mechanisms and enrichment methods for health-promoting anthocyanins of citrus fruits during processing and storage

Anthocyanins, naturally found in citrus, play key roles in improving the qualities of citrus fruits and products. Dietary consumption of fruit-derived anthocyanins is concerned increasingly owing to health-promoting properties. However, anthocyanins are vulnerable to many physical and chemical factors during processing and storage, affecting fruit qualities and consumer acceptance. Thus, the aim of this review is to focus on main advances in chemical structures, differential biosynthesis mechanisms, enrichment methods, and bioactivities of anthocyanins in pigmented and unpigmented citrus fruits. In this review, anthocyanin species and concentrations display tissue specificity in citrus, and the chemical structures and contents of main anthocyanins are summarized. For differential biosynthesis mechanisms, the reasons why most citrus fruits lose the ability of anthocyanin biosynthesis compared with pigmented fruits, and the molecular differences of biosynthesis mechanisms in pigmented citrus fruits are both discussed in detail. Furthermore, anthocyanins' enrichment methods (low-temperature stimulus, light irradiation, xenobiotics inductions, and ripeness influence) during processing and storage have been summarized, which achieve quality improvement by promoting structural gene expression, reducing anthocyanin-degrading enzyme activities, or altering DNA methylation status. Meantime, the health benefits of extract from pigmented citrus and their waste are mentioned, which provides a new approach for citrus waste recycling. HIGHLIGHTSChemical structures of individual anthocyanins in citrus are reviewed.Differential anthocyanin biosynthesis in citrus depends on mutations of Ruby genes.Anthocyanins are enriched in response to exogenous stimulus during storage.Health benefits of extract in blood oranges and their waste are summarized.

Beneficial Effects of Sodium Nitroprusside on the Aroma, Flavors, and Anthocyanin Accumulation in Blood Orange Fruits

The quality of Tarocco blood orange (Citrus sinensis (L.) Osbeck), which has been cultivated for many years, has degraded substantially. Decreased sugar content, decreased blood color, and increased sour flavor have developed as a result. To improve fruit quality, we studied the effects of bagging and sodium nitroprusside, as a nitric oxide (NO) donor, on the fruit quality of Tarocco blood orange two months before picking. The results showed that NO treatment effectively improved the content of total soluble solids and limonene in the fruit, as well as the color and hardness of the fruit, but reduced the tannin content. It also increased the contents of soluble sugar, fructose, sucrose, vitamin C, amino acids, and mineral elements. NO treatment inhibited the activities of polygalacturonase and pectin esterase, delayed the degradation of protopectin, and promoted the accumulation of anthocyanins, total flavonoids, and flavonoids synthesis. Thus, NO treatment improved the aroma, flavors, and physical properties of blood orange fruit.

Review of phytochemical and nutritional characteristics and food applications of Citrus L. fruits

Since the dietary regimen rich in fruits is being widely recognized and encouraged, Citrus L. fruits have been growing in popularity worldwide due to their high amounts of health-promoting phytonutrients and bioactive compounds, such as flavonoids, phenolic acids, vitamins, carotenoids, pectins, and fatty acids. The diverse physicochemical properties and multiple utilization of citrus fruits in food industry are associated with their unique chemical compositions. Throughout the world, citrus has been used for producing various value-added and nutritionally enhanced products, including juices, wines, jams, canned citrus, and dried citrus. However, the current studies regarding the phytochemical and nutritional characteristics and food applications of citrus are scattered. This review systematically summarizes the existing bibliography on the chemical characteristics, functional and nutraceutical benefits, processing, and potential applications of citrus. A thorough understanding of this information may provide scientific guidance for better utilizing citrus as a functional fruit and benefit the extension of citrus value chain.

Estimating the sensory qualities of tomatoes using visible and near-infrared spectroscopy and interpretation based on gas chromatography-mass spectrometry metabolomics

The ability to estimate the sensory quality of intact tomatoes rapidly and non-destructively using visible and near-infrared spectroscopy (Vis-NIRS) is important for the tomato industry. In this study, a combination of partial least squares regression (PLSR) analysis and the stepwise selectivity ratio (SWSR) method was used to study the ability of Vis-NIRS to predict 19 sensory attributes in intact tomatoes. The PLSR models constructed based on the informative wavelengths selected by the SWSR method predicted 8 sensory attributes well, particularly the sweetness attribute (correlation coefficient of validation of 0.92). Moreover, based on the tomato metabolites determined by GC-MS analysis, high intercorrelations between sensory attributes, metabolites, and the selected informative wavelengths were found through principal component analysis, as well as the high correlation coefficients between them. The results confirm the feasibility and reliability of Vis-NIRS and the informative wavelengths selected by SWSR to predict the sensory quality of whole tomatoes.

Changes in Bioactive Compounds, Antioxidant Activity, and Nutritional Quality of Blood Orange Cultivars at Different Storage Temperatures

Information about the postharvest physiological behavior of blood orange cultivars can provide comprehensive insight into the best period of storage to maintain the highest fruit quality during prolonged cold storage. In this paper, changes in nutritional quality, bioactive compounds, and antioxidant enzymes in the juice of four blood orange cultivars ("Moro", "Tarocco", "Sanguinello", and "Sanguine") stored at 2 and 5 °C were studied. Parameters were measured after 0, 30, 60, 90, 120, 150, and 180 days, plus 2 days at 20 °C for shelf life. Sucrose was the sugar found in higher concentrations and decreased during storage in all cultivars, as did glucose and fructose. Organic acids decreased at both temperatures, with the highest content found in "Sanguinello", especially major (citric acid) and ascorbic acid. Total phenolics content (TPC), total anthocyanins (TAC), and individual cyanidin 3-glucoside and cyanidin 3-(6″-malonylglucoside) increased for all cultivars, with "Sanguinello" having higher concentrations. The antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) were also higher in "Sanguinello" and increased during storage. Overall, these results together with the sensory analysis suggested that "Sanguinello" would be the best cultivar for prolonged storage. The results of this study could be useful to select the best storage duration and temperature for each cultivar and provide the presence of such a high-value commodity for fresh consumption or juice processing long after the harvest season.

Rootstock effect on fruit quality, anthocyanins, sugars, hydroxycinnamic acids and flavanones content during the harvest of blood oranges 'Moro' and 'Tarocco Rosso' grown in Spain

The physico-chemical quality parameters (external and internal color, firmness, acidity, total soluble solids, anthocyanins, sugars, hydroxycinnamic acids and flavanones) of 'Moro' and 'Tarocco Rosso' blood oranges grafted onto eight different rootstocks at three harvest time were studied. The rootstocks were 'Carrizo', 'C-35', 'Cleopatra' mandarin, 'Citrus volkameriana', 'Citrus macrophylla', 'Swingle' citrumelo, 'Forner-Alcaide 5' and 'Forner-Alcaide 13'. All studied parameters were highly rootstock/scion-dependent and showed changes throughout harvest. The content of the main anthocyanins revealed their relation with internal fruit color in both cultivars. The rootstocks that led to fruit with the lowest anthocyanins displayed the least sucrose content. The differences detected in the amount of hydroxycinnamic acids (chlorogenic, ferulic and sinapic) and flavanones (hesperidin, narirutin and didymin) related to anthocyanins content, explained phenylpropanoid pathway.