Physicochemical quality and metabolomics comparison of the green food apple and conventional apple in China

Volatile profile of postharvest hardy kiwifruits treated with chitosan-silica nanocomposite coatings

Chitosan (CTS) is a natural polysaccharide derived from the deacetylation of chitin. Chitosan-based coatings are widely used for the preservation of hardy kiwifruits. However, the effect of chitosan-based coating on fruit flavor during ripening is rarely reported. In this study, the postharvest qualities of hardy kiwifruits were investigated using chitosan coating and chitosan-silica nanoparticle coating (CTS-SiNPs) during storage at 25°C and 4°C. Physicochemical analyses showed that chitosan coating extended the shelf-life by delaying ripening and maintaining higher quality than uncoated fruits, and CTS-SiNPs treatment showed a superior preservation effect compared to CTS treatment. Untargeted metabolomics analysis based on HS-SPME-GC-MS was used to comprehensively evaluate the volatile profiles of hardy kiwifruits during postharvest storage. The metabolomics analysis showed that two chitosan coating treatments greatly delayed the accumulation of most volatiles while delaying the ripening process, and the differential volatiles were mostly involved in the terpenoids biosynthesis pathway. Notably, most green leaf volatiles (C6/C9 aldehydes, esters and alcohols) and methyl salicylate were up-regulated in the CTS-SiNPs coating groups. In addition, odor activity value (OAV) was used to characterize the key aroma-active compounds and odor profiles. A total of 32 compounds were identified as key aroma-active compounds (OAV ≥ 1) in hardy kiwifruits. The odor profile evaluation showed that the CTS-SiNPs coating treatment enhanced the intensity of the "herbal" odor, while reducing the intensity of "sweet" and "floral" odors in hardy kiwifruits at the eating-ripe stage.

Untargeted Metabolomics Comparison and Nutrition Evaluation of Geographical Indication Newhall Navel Oranges in China

The untargeted metabolomics of Newhall navel oranges from three areas in China-Ganzhou, Fengjie, and Zigui-with geographical indication (GI) was measured using LC-MS/MS. Orthogonal partial least squares discriminant analysis was performed for sample classification and important metabolite identification. This approach identified the best markers of the geographical origin able to discriminate Fengjie, Ganzhou, and Zigui orange samples. For peeled samples, 2-isopropylmalic acid, succinic acid, citric acid, L-aspartic acid, L-glutamic γ-semialdehyde, D-β-phenylalanine, hesperetin, hydrocinnamic acid, 4-hydroxycinnamic acid, and dehydroascorbate were the markers used to discriminate the geographical origin. All these markers were overexpressed in the peeled samples from the Zigui area, followed by the Ganzhou area. As for unpeeled samples, L-glutamic γ-semialdehyde, isovitexin 2'-O-β-D-glucoside, 2-isopropylmalic acid, isovitexin, diosmetin, trans-2-hydroxycinnamate and trans-cinnamate, L-aspartic acid, hydrocinnamic acid, and β-carotene were used to discriminate their origin. The first seven markers in Zigui-planted whole samples showed the highest levels, and the last three markers were richest in Ganzhou-planted samples. According to the variation in the markers for discriminating the origins of the peeled or unpeeled Newhall navel oranges with GI and the highest value of titratable acidity in those from Zigui, the samples planted in Ganzhou have the best balance between taste and nutrition. This work confirms that the approach of untargeted metabolomics combined with OPLS-DA is an effective way for origin tracing and overall quality evaluation.

Cultivar and origin authentication of 'Fuji' and 'gala' apples from two dominant origins of China based on quality attributes

Apple quality is closely related to its cultivar and origin. However, the apple quality characteristics of different cultivars and origins are unclear. The hypothesis that some quality indicators can effectively distinguish the cultivar and origin of apples. The result indicated that the discriminant accuracy of the models was above 90%, and the multilayer perceptron neural network (MLP-NN) model was superior to the linear discriminant analysis (LDA) model. The identification accuracy of cultivars was higher than origins. The main reason was that the single fruit weight, vitamin C, total soluble solid, soluble sugar, sweetness value, sorbitol, glucose, fructose, sucrose, malic acid, quinic acid and citric acid of 'Fuji' apples were significantly higher than 'Gala' apples. This study provides a foundation for the quality evaluation and further geographical traceability studies of apples. Further studies related to the regulatory mechanism of environmental conditions on apple quality characteristics should be explored for theoretical confirmation.

Metabolomics during the spontaneous fermentation in cocoa (Theobroma cacao L.): An exploraty review

Spontaneous fermentation is a process that depends on substrates' physical characteristics, crop variety, and postharvest practices; it induces variations in the metabolites that are responsible for the taste, aroma, and quality. Metabolomics makes it possible to detect key metabolites using chemometrics and makes it possible to establish patterns or identify biomarker behaviors under certain conditions at a given time. Therefore, sensitive and highly efficient analytical techniques allow for studying the metabolomic fingerprint changes during fermentation; which identify and quantify metabolites related to taste and aroma formation of an adequate processing time. This review shows that studying metabolomics in spontaneous fermentation permits the characterization of spontaneous fermentation in different stages. Also, it demonstrates the possibility of modulating the quality of cocoa by improving the spontaneous fermentation time (because of volatile aromatic compounds formation), thus standardizing the process to obtain attributes and quality that will later impact the chocolate quality.

Nano Coating of Aloe-Gel Incorporation Additives to Maintain the Quality of Freshly Cut Fruits

The edible coating is an environmentally friendly technology that is applied to fresh-cut fruit products. One of the natural ingredients that are potentially applicable is aloe-gel because it contains several functional components. The main advantage of aloe-coating is that additives can be incorporated into the polymer matrix to enhance its properties. Additives tend to improve the safety, nutritional, and sensory attributes of fresh fruits, but in some cases, aloe-coating does not work. Furthermore, particle size determines the effectiveness of the process on fresh-cut fruits. Aloe-gel nano-coating can be used to overcome the difficulty of adhesion on the surface of fresh-cut fruits. However, quality criteria for fresh cut fruit coated with aloe-gel nano-coating must be strictly defined. The fruit to be processed must be of minimal quality so that discoloration, loss of firmness, spoilage ratio, and fruit weight loss can be minimized. This study aims to discuss the use of nano-coating aloe-gel incorporated with additional ingredients to maintain the quality of fresh-cut fruits. It also examined the recent advances in preparation, extraction, stabilization, and application methods in fresh fruits.

Profiling Phenolic Composition in Pomegranate Peel From Nine Selected Cultivars Using UHPLC-QTOF-MS and UPLC-QQQ-MS

Pomegranate is widely cultivated across China, and the phenolics in its peel are principal components associated with health benefits. Ultra-high performance liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (UHPLC-QTOF-MS) and ultra-performance liquid chromatography coupled to a triple quadrupole mass spectrometer (UPLC-QQQ-MS) were used in this study, aiming at profiling the total phenolic composition in pomegranate peel from nine selected cultivars in 7 production areas. Sixty-four phenolic compounds were identified or annotated, and 23 of them were firstly reported in pomegranate peel. Principal component analysis (PCA) plots show differences and similarities of phenolics among nine cultivars. Furthermore, 15 phenolic compounds were quantified with the standards, and punicalagin, ellagic acid, gallocatechin, punicalin, catechin, and corilagin were found to be dominant. Punicalagin weighed the highest content (28.03–104.14 mg/g). This study can provide a deeper and more detailed insight into the phenolic composition in pomegranate peel and facilitate the health-promoting utilization of phenolics.