Title: QUALITY OF STRAWBERRIES AFTER STIMULATED AIR FREIGHT CONDITIONS
Abstract: The fastest way to transport highly perishable horticultural crops over long distances is air shipment. This rapid delivery is however constrained by the fact that the optimal conditions required for fresh fruits and vegetables are hardly ever maintained onboard the aircraft. The temperature during flight can sometimes exceed 20°C and the cargo holds are usually pressurized to 0.7 atm. The objective of this study was to evaluate the impact of the low pressure usually encountered during flight on the quality of fresh strawberries. The fruit, previously equilibrated to 1°C, were stored for 8 hours at 0.7 atm, in air or in 70% N2 + 30% O2 (= 0.21 atm O2) at 20°C and 98% relative humidity (RH). Strawberries stored for 8 hours at 1 atm in air at 20°C and 98% RH were used as the control. After 8 hours the fruit were transferred to 1°C for 7 days with normal pressure and 96% RH. Weight loss, visual quality, firmness, titratable acidity, and soluble solids content were evaluated after harvest, after air freight simulation, and after 3, 5, and 7 days of storage. There were no significant differences between treatments for weight loss, visual quality, firmness, titratable acidity, or soluble solids content of the fruit. No evidence of stress in strawberry fruit was observed in response to low pressure during a simulated 8-h flight. The results suggest that the low pressure usually encountered during flight does not have a negative impact on the quality of strawberries. However, the combined effects of low pressure, temperature fluctuations, and low RH still need to be investigated in order to have a better understanding of the physiological behavior of perishable horticultural crops during transport by air. INTRODUCTION The quality of fresh horticultural crops shipped by air may decline faster compared to other modes of transportation if product requirements for humidity and temperature are disregarded (Nunes et al., 2000). In fact, factors such as temperature, relative humidity, and pressure may interfere with the quality of fresh produce during loading, unloading and in-flight operations. Detrimental effects on perishables of temperature abuse, which often occurs during ground operations and/or in-flight, have been reported (Nunes et al., 2000; Laurin et al., 2003). Other authors have reported the negative impact of low relative humidity on the quality of perishables during storage or transport (Barth et al., 1990; Paull, R.E., 1999; Tu et al., 2000). However, no data have yet been reported in the literature regarding the impact of low pressure in the range found during commercial flights on the quality of fresh fruits and vegetables. Information on the response of fresh horticultural crops exposed to low pressure during a relatively short period of time is therefore necessary in order to have a global understanding of the behavior of air-transported produce. Such information will allow the adjustment of technologies already in use or the development of new procedures valuable to the air cargo industry. The objective of this work was to study the response of strawberry fruit to potential low-pressure stress occurring during air transportation. MATERIALS AND METHODS ‘Camarosa’ strawberries were harvested at the 3⁄4 to full ripe maturity stage from a commercial field in Floral City, Florida on March 28 and April 2, 2002. Fruits were Proc. Int. Conf. Quality in Chains Eds. Tijskens & Vollebregt Acta Hort. 604, ISHS 2003 660 forced-air cooled promptly after harvest and transported to University of Florida, Gainesville within 2 hours. Prior to the beginning of the experiments, fruits were equilibrated to 1°C for four hours. After conditioning, 3.1 kg of strawberries, free from defects and with uniform color and size, were selected and placed into 7.5 L glass desiccators (in order to simulate the fruit/volume ratio normally found in aircraft containers). Strawberries were then stored for 8 hours at 0.7 atm in air or in 70% N2 + 30% O2 (= 0.21 atm O2) at 20°C and 98% RH. Fruit stored for 8 hours at 1 atm in air at 20°C and 98% RH were used as the control. After 8 hours, the fruit were removed from the desiccators, placed in 0.47 L clamshells (10 fruit per clamshell, three clamshells per treatment per day) and transferred to a cold room at 1°C for 7 days with normal pressure and 96% RH. Weight loss, visual quality, firmness, soluble solids content, and titratable acidity were evaluated right after harvest, after flight simulation (8 hours at 20°C, which corresponds to day 2), and after 3, 5, and 7 days of storage. Temperature and Relative Humidity and Pressure Monitoring The temperature and the RH inside the low pressure containers as well as inside the storage room was monitored with Hobo H08-007-02 temperature and relative humidity loggers (-40°C to 120°C ± 0.7°C; 10 to 95% ± 5%) (Onset Computer Corp., Pocasset MA). Pressure was monitored with Hobo HPA-0015 pressure loggers (0.03 to 1.09 atm ± 1%). Weight Loss Three samples of 10 strawberries per treatment were weighed before being placed inside the desiccators, after the air flight simulation (8 hours at 20°C day 2), and after 3, 5, and 7 days of storage. Visual quality Superficial color, firmness, shriveling, and decay severity of three samples of 10 strawberries per treatment were evaluated using rating scales of 1 to 5 adapted from Nunes and Emond (2002). Results were expressed as the mean of the four factors combined. Firmness Measurement Firmness of three replicate samples of 10 strawberries per treatment was measured on the equatorial part of the strawberry fruit with an Instron Universal Testing Instrument (Model 4411, Canton, MA). A 5-kg load cell was used for firmness determination. Crosshead speed was 1 mm·sec. A 5 mm diameter convex tip probe was used. The force required to reach a deformation of 2 mm in the strawberry was recorded as kgf and converted to Newtons (N) using the following formula: N = kgf × 9.8 (Kader, 1982). In order to avoid differences in firmness due to temperature, strawberries were removed from cold storage and allowed to warm up to 20°C for 4 hours prior to firmness measurements. Soluble Solids Content (SSC) and Titratable Acidity (TA) Three replicated samples of 10 fruit per treatment were homogenized in a laboratory blender at high speed for 2 min. The homogenates were centrifuged at 20,000 gn for 20 min at 4°C, filtered through cheesecloth, and the % SSC of the resulting clear juice samples was determined with a temperature compensated digital refractometer. Aliquots (6.00 g) of juice were diluted with 50 ml distilled water and the TA determined by titration with 0.1N NaOH using an automatic titrimeter (Fisher Titrimeter Π, No. 9-313-10, Pittsburg, PA) to an end point of pH = 8.2. The results were calculated as percent citric acid (Nunes and Emond, 1999).
Publication Year: 2003
Publication Date: 2003-07-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 3
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