Physicochemical Attributes, Volatile Profile and Sensory Quality of Organic Crimson Crisp Apples during On-Tree Maturation

Abstract

When new apple cultivars are planted, knowledge of their maturation and ripening behavior and, as a consequence, the best time for their harvest is of utmost importance for providing fruits of the highest quality to consumers. In this study, we followed the on-tree maturation and ripening behavior of organic Crimson Crisp apples over a period of almost 3 months. With the weekly analyses of basic fruit quality attributes (weight, fruit firmness, total soluble solids, titratable acids, starch degradation) in combination with the fruit volatilome (primary and secondary volatiles) and sensory analysis, we obtained a holistic picture of the maturation and ripening properties of this new variety. We could show that at the recommended harvest window, which is based on the degree of starch degradation alone, the fruit development is not finished. Synthesis of aroma volatiles—which is strongly related to the expression of pronounced fruity, apple-like flavor—requires two additional weeks of on-tree ripening. Results indicate an upregulation of 13-LOX at very early maturation stages, while upregulation of 9-LOX and enzyme systems involved in the β-oxidation pathway requires a prolonged on-tree maturation period. The results of this study demonstrate that the analysis of basic fruit quality attributes is not sufficient for understanding the properties of apples. However, we demonstrate that the analysis of the fruit volatilome is a valuable and necessary tool for optimizing the quality of new apple varieties.

Assessment of the Quality of ‘Red Jonaprince’ Apples during Storage after Delayed Harvesting and 1-Methylcyclopropene (1-MCP) Preharvest and Postharvest Treatment

“…Determining the optimum harvest window, meaning the optimal time to harvest a specific apple cultivar, often requires extensive experience and knowledge acquired over several years of work with a particular cultivar [17]. In spite of the fact that later harvesting time promotes better taste [18], delayed harvesting is not recommended, as other quality features begin to decrease, especially texture of fruits [6].…”

Physicochemical Attributes, Aroma Profile, and Sensory Quality of Organic Crimson Crisp Apples after Storage

“…Potentiometric titration of the total acids quantities was performed using a commercially available auto-titration system (785 DMP Titrino, Metrohm, Herisau, Switzerland). A total of 20 mL of the freshly produced apple juice (see Section 2.3.2) was titrated against 0.1 M NaOH (Convol NORMADOSE, VWR Chemicals, Vienna, Austria) until pH = 10 was reached [33]. The pH value was established at the beginning of each measurement with the integrated pH electrode and the equivalent point of the titration was calculated directly by the titration unit in terms of titration volume (mL).…”

“…2-Octanol (purity > 99%, Sigma Aldrich, Darmstadt, Germany) was used as internal standard (30 ng absolute in 10 µL methanol corresponding to 120 µg/kg purée, purity > 99%, Fisher Scientific, Schwerte, Germany). For the analysis of secondary aroma compounds, 100 µL of apple fruit juice was used with the addition of 100 mg NaCl and 2-octanol (30 ng absolute in 10 µL methanol corresponding to 300 µg/L juice, purity > 99%, Fisher Scientific, Schwerte, Germany) in 20 mL headspace vials [33]. All samples were analyzed in duplicate in randomized order.…”

“…For the sensory analysis of the stored Crimson Crisp fruits, a trained panel was asked to describe the aroma, texture and overall flavor of the three samples RA, CA and MCP by using 'open-ended questioning' (OEQ) as the sensory technique [41]. The application of this descriptive technique makes it possible to assess data about the stored apples beyond the scope of the predefined CATA analysis for fresh apples that we applied to follow the fruit development during on-tree ripening [33]. OEQ results were visualized as a biplot as a result via correspondence analysis (Figure 3).…”

“…Our recent investigations performed on the scab-resistant apple variety Crimson Crisp demonstrated, that this variety is best harvested after a prolonged on-tree ripening period [33]. We showed that the overall quality of the fruit increases significantly when on-tree maturation is prolonged until close to an overripe stage, arguably high starch value (9.7) compared to other cultivars [33]. However, as the suitability for storage is related to the ripeness of apple fruits, there is a need to investigate the storage behavior of late-harvested fruits.…”