Introduction: Plantain Plantains are one of the most important fruits in Puerto Rico’s agricultural economy (Cortés-Perez, Leticia-Gayol. 2004). Is easy to propagate and cultivate. It has important nutritional properties, such as high level of potassium and carbohydrates. It is low fat and a good source of fiber vitamins C, B6 and A. (FAO 2009). It occupies the fourth place in consumption after rice, wheat and corn (Comisión Veracruzana de Comercialización Agropecuaria, 2005)
Actual Situation In 2004, the presence of a fungus known Mycosphaerella fijiensis was detected on the western side of Puerto Rico (Añasco) (Alvarado-Ortiz 2005). Mycosphaerella fijiensis causes a disease called Black Sigatoka that affects the plant leaves is an aggressive and destructive pathogen, leading to yield loss, thus impacting Puerto Rico’s agricultural economy
Impact For fiscal year 2006-2007, the production of plantains in Puerto Rico represented 27% of the total of the agricultural income; ranking first in economic importance among produced crops. Plantain production for that year generated an income of ninety million dollars ($90 million) (Colón Ruiz, 2008).
Solution Production of hybrids resistant to this devastating disease that enable the secured supply of fruit to the market. The USDA’s Tropical Agricultural Research Station (TARS) initiated a study to evaluate the agronomic characteristics of Black Sigatoka resistant hybrids. Complete assessment of the hybrids’ potential requires an evaluation of the fruit’s characteristics for fresh and processing markets.
Objective Determine the potential use of the Black Sigatoka resistant hybrids by evaluating their fresh market and processing characteristics. Secondary objectives include the following: To evaluate the chemical properties of hybrids including pH, water activity and soluble solids content. To characterize the physiological maturation process during storage, including enzyme activity, water loss, color changes and respiration rate. To estimate glycemic index. To evaluate processing properties, specifically fat and moisture absorption and starch content. To determine consumer preference of selected varieties through sensory analysis.
Materials Maturity Index Figure 1: Hedonic commercial maturity scale
Maturity Index Scale Three samples were randomly taken from the sample pool and compared to the hedonic commercial maturity scale (Figure 1). Tests were performed on days 0, 5, 9, 14, 19, 23, 28 and 33. The average of the three samples was reported as the maturity index for the sample day. With this scale it is possible to compare varieties, and determine the degree of ripeness and estimate the changes of the fruit during storage.
Materials Peel and Pulp Color Hunter lab Miniscan Colorimeter http://www.ferret.com.au/odin/images/216401/MiniScan-EZ-portable- spectrophotometer-available-from-Novasys-Group.jpg
Peel and Pulp Color The peel and pulp color test were performed on days 0, 5, 9, 14, 19, 23 and 33. Three measurements of peel color were taken from the middle of the fruit. The colorimeter was configured to register L*, a* & b* parameters for a 10° observed and D65 illuminant.
Peel and Pulp Color For pulp color, a ½” ring of fruit was cut from the lower ¼ of each sample, peeled and used for color determination. The peeled ring was saved for the pH and soluble solids (°Brix) tests.
pH pH was measured in duplicate with a previously calibrated potentiometer (Accumet Basic AB15). The pH meter was previously standardized using 4.0, 7.0 and 10.0 standard solutions. The remaining macerated sample was kept for the °Brix measurement.
Materials Total soluble solids (°Brix) Digital Refractometer Pa202 http://www.professionalequipment.com/product_images/misco_product.jpg
Total soluble solids (TSS) - °Brix For °Brix determination, the fruit ring used for pulp color measurement was macerated and collected in a beaker. The reading was taken on storage days 0, 5, 9, 14, 19, 23, 28 and 33. A sample was placed in a Digital Refractometer Pa202 to determine ºBrix. Duplicate measurements were taken.
Mechanical damage – Cut strength The skin of collected samples was removed and the pulp was exposed for the test. The reading was taken on days 0, 5, 9, 14, 19, 23, 28 and 33. It is configured to measure force in compression (versus 1 cm distance) at a test speed of 1 cm/sec. Take the long segment of the cut fruit and remove the peel to expose the pulp. Measurements are taken in duplicate.
Mechanical damage – Impact A Texture Analyzer is used to inflict mechanical damage to fruits in sampling days. (Figure Damage readings were performed on 2, 9, 16, 23 and 30 days, to different samples of same variety, starting from their second day of harvest. The equipment was configured for different heights (velocities). Plantain was hit at different speeds on three locations along the fruit (labeled A, B & C).
Mechanical damage – Impact Each test speed represents a given drop height. The compressive force was set constant at 1.48 N. The first hit was labeled with the letter A, and represented a drop height of 5 feet (velocity of 5.47 m/s). Letter B corresponds to a height of 10 feet (velocity of 7.73 m/s). Letter C to 15 feet (velocity of 9.47 m/s). Pictures were taken to determine the mechanical damage in hybrids on 10, 20 and 30 days after impact damage.
Mechanical damage - Stack The test simulate damage caused by stacking fruit in a pile of various heights, the higher of the stack and the greater the force. Readings were taken 2, 9, 16, 23 and 30 days after harvest. The Texture Analyzer was set to measure distance in compression and configured with test speed of 1mm/sec and force holding time of 5 seconds. The applied force for each test condition appears in Table 3.
Mechanical damage - Stack The applied force for each test condition appears in Table. Stack Height (fruits) 10 20 30 Force (kilograms) 1.5 kg 3.0 kg 4.5 kg
Mechanical damage - Peelability The Texture Analyzer was configured to measure force in tension (versus 1 cm distance) at test speed of 1 cm/sec. The samples were made on 0, 7, 14, 21, 28 and 35 days after harvest. A portion of the peel was removed, and before testing, the peel was cut longwise in three sections.
Mechanical damage - Peelability The slope of the curve determines the peelability of the fruit. For each sample two readings were taken to determine their peelability.
Materials Respiration Rates Servomex Gas Analyzer
Respiration Rates Respiration rates are evaluated for each variety using three samples on 0, 2, 5, 7, 9, 12, 14, 16, 19, 21, 23, 26, 28, 30, 33 and 35 days. Three samples are placed in each of three jars (Figure ) and closed. After one hour in the jar, a sample of the gas (10 ml) inside the jar is collected with a syringe (Figure 9a) and injected in Servomex Gas Analyzer to obtain the CO 2 and O 2 % (Figure ).
Respiration Rates Plantain samples are removed from the jar and stored until the next sampling day. The test is performed three times for each variety. The equipment is calibrated with a gas standard at 30 and 99.9 % of CO 2 and gaseous nitrogen for the zero calibration (00.0)
Respiration Rates Where (Deza, 2006): Conversion factor = 1.84 at 20°C (Kader, 2002) Respiration rate is calculated with the following equation (Kader, 2002).
Pulp yield The whole plantain sample is weighted on a scale (Mettler PC 16). The peel is removed and the pulp weighted again. The following formula is used to calculate the yield of the pulp.
Moisture absorption The treated sample is boiled in water for 10 minutes, removed from the water, drained and cooled. Weights of the boiled and control pieces are collected and registered before drying both pieces in an oven at 100ºC for 24 hrs. Dried samples are cooled in a dissecator before weighting. Calculate moisture absorption with the following equations. (Table )
Moisture absorption Calculate moisture absorption with the following equations. (Table ) Metric Moisture content of fresh fruit Moisture content of boiled fruit Moisture absorption Formula
Fat absorption Place the treated sample in heated oil at 375ºF for 5 minutes, drain and cool. Reweight the treated sample. Determine fat content of both samples using method Soxhlet 16.285 of the AOAC (1984). Weight the control and treated samples and record data.
Fat absorption Calculate fat content and fat absorption using the following equations: Metric Fat content of fresh fruit Fat content of fried fruit Fat absorption Formulas
Materials Starch Content Hydrolysis Buffer Development Buffer Oxi Red Probe DMSO (anhydrous) Hydrolysis Enzyme Mix Development Enzyme Mix Starch Standard (2.0 mg/ml)