Impact of CO2 -enriched atmosphere on postharvest life and flavor quality of muscadine grape By: Shirin Shahkoomahally Department of Horticultural Science University of Florida

Introduction Grape has postharvest problems because of a reduction of firmness, shriveling, browning, decay and weight loss during storage. Controlled atmosphere with altering O2 and CO2 level can restrain grape postharvest decay during storage. Low levels of O2 and elevated levels of CO2 can decrease the rate of respiration, along with delaying senescence and browning, preserving color, decreasing metabolic processes, and thereby prolonging the postharvest life. Muscadine (Vitis rotundifolia Michx.) is a kind of grape with a distinctive flavor, thick skin and different shape, color, and dimensions. It can be stored for 2-3 months in 1 to 5 °C with 85% to 95% (RH). But, like other grapes, muscadines has postharvest problems concerning reduction of firmness, shriveling, browning, decay and weight loss during cold storage. Alternative methods such as MA, CA, and enriched CO2, with decrease the rate of respiration, and metabolic processes, can , and delay senescence and prolong muscadine postharvest life.

Objective The objective of the study is to evaluate the potential of elevated CO2 and CA to preserve the appearance and textural quality of muscadine grape. In the current work, we evaluated postharvest life based on appearance and changes in muscadine grape during storage. Our objective was to determine the potential of elevated CO2 and CA to preserve the appearance and textural quality of muscadine grape.

Materials & Methods Muscadine grape was purchased from Walmart Twenty-five berries were selected randomly, weighted, and set in a glass jar The jars were kept at 4 ± 1 °C and ventilated with a continuous flow of O2, N2, and CO2-enriched or air in approximately 95% relative humidity. Storage conditions was as follows: 1) air (control with the fumigation under normal air) 2) controlled atmosphere (6 % O2 + 11% CO2) 3) elevated-CO2-treated fruit (4% O2 + 29% CO2) Samples were being examined and analyzed at 11- day intervals throughout the 22 days of storage Firstly, fruit was purchased from the market. Afterward, berries were transported to the laboratory. Fruits were stored in the same boxes overnight at 4 °C for cooling. Then, berries were selected on the basis of uniform size, color, firmness, and lack of physical and pathological defects. Twenty-five berries were selected randomly, weighted, and set in a glass jar. The fruits were divided among two treatments (CA and elevated CO2 with different rate of CO2 and O2) and control (with air).

2 1 Here is some picture of sample preparation, weighting and putting in the jars (pic 1), then seal the jars (pic 2), and finally releasing the gas inside the containers from a gas cylinder (pic 3), after regulating the required amount of CO2, O2, and N2 for each treatment (pic 4). 3 4

Firmness Berry firmness was calculated with Firmtech on 10 berries. Color The color was measured at four positions around the equator of the fruit with a colorimeter. The results were given in hue and chroma (CIELAB) color space co-ordinates. The samples were examined and analyzed at 11-day intervals throughout the 22 days of storage. Several quality parameters such as firmness, color, TA, and TSS were monitored during the storage period.

Total soluble solids and Titratable acidity Ten berries were blended and centrifuged to extract the juice. TA was measured with an automatic titrator. TSS was measured with a refractometer.

Result

The color of the samples were measured recording chroma and hue angle The color of the samples were measured recording chroma and hue angle. The chroma value describes brightness while the hue angle represents a coordinate in a standardized color space. Muscadines were brighter (larger chroma value) in initial stage for all samples. However, they had dropped throughout the storage period, especially control was less bright (lower chroma value). Muscadine maintained more red (lower hue angle) with the enriched-CO2 and CA treatments than control (darker red and higher hue angle) during the storage period.

In comparison to TSS levels at initial stage (12°Bx), TSS increased in all sample. Throughout storage period, TSS was highest in control (Figure, 02). This increase in TSS could be related to the advance of the ripening process in control fruit. The total titratable acidity (TA) was calculated as tartaric acid, which is the dominant acid in grapes ( Figure 03). For all fruits, the initial TA value was highest around 1.2% then TA was decreased during the storage period. The acidity in CA was slightly unaltered throughout storage while a decrease could be detected in the enriched- CO2 treatment and control . Figure 02. TSS of muscadine grape stored at 4 ºC in air, CA (6 % O2 + 11% CO2), and enriched- CO2 (4% O2 + 29% CO2). Figure 03. TA of muscadine grape stored at 4 ºC in air, CA (6 % O2 + 11% CO2), and enriched- CO2 (4% O2 + 29% CO2).

Firmness of berry was strongly influenced by CA and elevated-CO2 treatment. Firmness of control berries sharply decreased during storage after 22 d of storage. Figure 04. Firmness of muscadine grape stored at 4 ºC in air, CA (6 % O2 + 11% CO2), and enriched-CO2 (4% O2 + 29% CO2).

Conclusion CO2 enriched and controlled atmosphere (CA) extended the storage period of muscadine grape without affecting their organoleptic characteristics The beneficial effect of enriched- CO2 and CA during storage was evident by the extension of the postharvest life in muscadine, by the increase in firmness and maintaining fruit quality in treated fruits, because of the slow advance of the ripening process as a consequence of the prolonged storage period. CA and CO2 enriched atmosphere slowed down the ripening process in muscadine.

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