Key volatile compounds of ‘Fuji Kiku’ apples as affected by the storage conditions and shelf life: Correlation between volatile emission by intact fruit and juice extracted from the fruit

Superficial scald development in 'Granny Smith' and 'Nicoter' apples: The role of key volatile compounds when fruit are stored under dynamic controlled atmosphere

A positive correlation of α-farnesene and its oxidation metabolites with superficial scald is commonly reported in apples stored in air or controlled atmosphere (CA) systems, where O2 levels are above the lower oxygen limit (LOL) tolerated by the fruit. Nevertheless, the LOL can be monitored by the dynamic controlled atmosphere (DCA) techniques and to provide different physiological responses. Therefore, this study aimed to evaluate key volatile metabolites from 'Granny Smith' and 'Nicoter' ('Kanzi®') apples stored under dynamic controlled atmosphere (DCA) monitored by respiratory quotient (RQ), i. e. at extremely low oxygen partial pressures (ELO) and correlate their emissions with the incidence of superficial scald (SS). The volatile compounds (VCs) were isolated by solid phase microextraction (HS-SPME) and analyzed by gas chromatography. For the first time, higher concentrations of α-farnesene and its oxidation metabolites (6-methyl-5-hepten-2-one, and 6-methyl-5-hepten-2-ol) were negatively correlated with SS in DCA-RQ. This is likely due to the higher levels of ethanol in fruit stored under this condition having an inhibitory effect on SS incidence even when α-farnesene, 6-methyl-5-hepten-2-one, and 6-methyl-5-hepten-2-ol accumulate. Additionally, SS is more correlated to internal ethylene concentration (IEC) than α-farnesene accumulation and their metabolites, even when fruit were stored under ELO, where ethylene action is reduced.

Monitoring Volatile Organic Compounds in Different Pear Cultivars during Storage Using HS-SPME with GC-MS

Aroma, which plays an essential role in food perception and acceptability, depends on various mixture of volatile organic compounds (VOCs). Meanwhile, as a field of metabolomics, VOC analysis is highly important for aroma improvement and discrimination purposes. In this work, VOCs in pear fruits were determined via headspace solid-phase micro-extraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) to study variations among different cultivars and storage stages. In 12 cultivars of pear fruits, a total of 121 VOCs were quantified, including 40 esters, 32 alcohols, 16 aldehydes, 13 alkenes, 11 ketones, 4 acids, and 5 other compounds. The types and amounts of VOCs in different cultivars varied dramatically, which were in the range of 13-71 and 3.63-55.65 mg/kg FW (fresh weight), respectively. The Dr. Guyot cultivar showed the highest level of VOCs, both in type and amount. After 21 days storage at 4 °C, total concentration of VOCs increased from initial levels of 50.76 to 101.33 mg/kg FW. Storage at 20 °C made a larger contribution to production for VOCs than that at 4 °C, resulting in the maximum content of VOCs (117.96 mg/kg FW) in fruit after 14 days storage at 4 °C plus 7 days at 20 °C. During storage, the content of esters showed a gradual increase, while the content of alcohols and aldehydes decreased. Based on the results presented, related alcohols were recognized as the intermediates of conversion from aldehydes to esters.

Comparison of phenolic composition, vitamin C, antioxidant activity, and aromatic components in apricots from Xinjiang

As a famous table fruit in Xinjiang, apricot has gained an increasing number of consumers because of its rich nutritional value and seductive flavor. The aim of this study was to assess the sensory qualities, the nutritional value, antioxidant properties, and flavor of Xinjiang apricots, which were investigated using high-performance liquid chromatography (HPLC) and headspace-solid phase micro-extraction with gas chromatography-mass spectrometry (HS-SPME/GC-MS). The results revealed that while there were similarities in the components contributing to nutrition and flavor, the Xinjiang apricots had distinct features. The "Luopuhongdaike" cultivar was superior in taste based on the comprehensive evaluation of the sugar, and acid contents and the sugar-acid ratio. The "Suogejianali" and "Luopuhongdaike" cultivars were the best in terms of nutrients and antioxidant activity. All Xinjiang apricots possessed similar volatile compounds, including linalool, nonanal, decanal, (E)-2-nonenal, and octanal, which provided fatty, green, lemon, floral, and orange aromatic notes. In conclusion, Xinjiang apricots have high nutritional and aromatic value. These results will provide a complete chemical characterization of the taste, nutritional ingredients, and aroma of Xinjiang apricots, and help breeders better develop polyphenol-rich varieties with superior antioxidant activity. PRACTICAL APPLICATION: This study investigated the sensory characteristics, nutritional value, antioxidant activity, and flavor of fresh apricots in Xinjiang. The research results will provide a theoretical basis for the development of the sensory characteristics, aroma, nutritional value, and medicinal value of fresh apricots in Xinjiang.

Fungal growth, patulin accumulation and volatile profile in 'Fuji Mishima' apples under controlled atmosphere and dynamic controlled atmosphere

The objective of this study was to evaluate fungal and patulin contamination, together with its correlation with the volatile compounds (VCs), in 'Fuji Mishima' apples (up to 25% decayed) under controlled atmosphere (CA) and dynamic controlled atmosphere with respiratory quotient (DCA-RQ) of 1.3 combined with different partial pressures of carbon dioxide (0.8, 1.2, 1.6 and 2.0 pCO₂). Fruits were stored under the above conditions for 8 months at 0.5 °C plus 7 days shelf life at 20 °C. Toxigenic fungi and patulin accumulation were found in apples from all treatments. Penicillium expansum was the most prevalent species. For all storage conditions, patulin concentrations were above the maximum level allowed in Brazil (50  μg  kg^-1) with an exception of DCA-RQ1.3 + 0.8 kPa CO₂. This condition, with lower pCO₂, showed the lowest patulin accumulation, below the legal limit. The CA provided the highest patulin concentration (166 μg  kg^-1). It was observed that fungal growth could also contribute to changes in the volatile composition. Styrene and 3-methyl-1-butanol are considered P. expansum markers in some apple cultivars and were detected in the samples. However, it was not possible to identify volatile organic compounds (VOCs) that are biomarkers from P. expansum, because there were other fungi species present in all samples. In this study, styrene, n-decanoic acid, toluene, phenol and alpha-farnesene were the compounds that showed the most positive correlation with patulin accumulation. On the other hand, a negative correlation of patulin with acids has been shown, indicating that in treatments with a higher patulin concentration there were less acidic compounds.

Evolution of typical aromas and phenolic compounds of a red-fleshed apple throughout different fruit developmental periods in Xinjiang, China

Red-fleshed apple is attracting more and more attentions from both consumers and researchers thanks to its pleasant appearance and flavor. Accumulation and development of aromas of apple fruit are important factors to understand the fruit quality of a new cultivated variety. However, knowledge on the key aroma components development and accumulation of red-fleshed apple (Malus sieversii f. neidzwetzkyana(Dieck) Langenf) in Xinjiang through the fruit developmental periods is insufficient. In this paper, free and bound form aromas of a red-fleshed apple since young fruit period through expansion period and conversion period to ripen period were comparatively studied. We classified aroma substances according to the compound category (esters, aldehydes, alcohols, terpenes, and aromatics), and to the odor types. The concentration of bound form aroma compounds were higher than that of free form throughout the 4 periods and showed different evolution trends. Among the 4 periods, the bound aroma was the most in the expansion period; and terpenoids showed the greatest potential to release free form aromas. Total aromas were found the lowest concentration in expansion period and the highest concentration in ripen period. The observations in this study will provide theoretical support for the research of typical aroma formation regularity of red-fleshed apple, and guide for the aroma enhancement regulation.

The isolated or combined effects of dynamic controlled atmosphere (DCA) and 1-MCP on the chemical composition of cuticular wax and metabolism of 'Maxi Gala' apples after long-term storage

Apples have a continuous hydrophobic layer that covers the surface of the fruit, which is called the cuticle. The effects of 1-methylcyclopropene (1-MCP) on the cuticular wax layer of apples were reported after cold storage, although the interaction between 1-MCP and dynamic controlled atmosphere (DCA) is not yet known. Therefore, this study aimed to analyze the effects of 1-MCP on the wax composition and metabolism of 'Maxi Gala' apples after storage in a controlled atmosphere (CA) and dynamic controlled atmosphere based on chlorophyll fluorescence (DCA-CF) and respiratory quotient (DCA-RQ; RQ = 1.3 and 1.5). The 1-MCP treatment effectively decreased ethylene production for CA and DCA-CF treatments, while in DCA-RQ treatments produced no effect. The average extracted cuticular wax content of 'Maxi Gala' apples was 16.65 g m^-2 and no differences in storage conditions or 1-MCP application were observed. Alkanes, alcohols, fatty acids, aldehydes, and terpenoids were identified in the chemical composition of the cuticular waxes, being alkanes and fatty acids the predominant ones. Moreover, 1-MCP decreased fatty acid and 10-nonacosanol concentrations in the fruit. Fruit with the 1-MCP application and stored in DCA had lower α-farnesene concentrations. The wax compositions of the DCA-stored apples with and without 1-MCP were similar. However, 1-MCP treatment resulted in a greater mass loss in fruit stored in DCA.