Md Mizanur Rahman
Department of Horticulture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
Md Mokter Hossain*
Department of Horticulture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
Md Abdur Rahim
Department of Horticulture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
Md Humayun Kabir Rubel
Department of Horticulture, Bangladesh Agricultural University, Mymensingh-2202, Bangladesh
Md Zahurul Islam
Horticulture Center, Kallyanpur, Chapainawabgonj-6300, Bangladesh
Fruit bagging, Skin color, Nutritional quality, Guava (Psidium guajava L.)
Germplasm Centre (BAU–GPC), Bangladesh Agricultural University
Quality and Nutrition
The experiment was conducted at BAU Germplasm Centre, Bangladesh Agricultural University (BAU) during March to July 2016. The experimental area was under the subtropical climate characterized by heavy rainfall during the months of May to July 2016 and scanty rainfall during the rest period of the year.
2.1 Treatments and experimental design Fruit bagging materials was considered the treatments and no fruit bagging (open fruit) was treated as control. Therefore, the experimental consisted of five treatments, viz. control (open fruit, T0), brown paper bag (T1), white paper bag (T2), white polythene bag (T3), and black polythene bag (T4). Brown paper and polythene sheets were purchased from the local market and the bags were handmade. There were 15 fruits of two guava trees under one bagging treatment in one replication. So there were 6 trees for 3 replications under each treatment and 30 trees for 5 treatments. The experiment was conducted in Randomized Complete Block Design (RCBD) with three replications. After one month of fruit setting, the fruits were wrapped with respective bagging materials as per the treatments. A small portion of two corner of each bag was cut in order to prevent water deposition inside the bag. The bags were tied tightly with the help of rope so that water and insect could not enter into the bag. All trees were maintained under uniform cultural practices during the course of the investigation. Fruits were harvested at fully mature stages after three months of fruit setting. The maturity of guava fruits were confirmed by the visual symptoms, for example, the disappearance of the fruit ridges and changes of fruit colour from green to pale green.
2.2 Physical quality assessment Immediately after harvesting of mature guava fruits, weight of harvested fruits was taken by using an electrical balance. The length and breadth of fruits were measured manually by using a slide calipers. Skin colour was determined at fully mature stage by comparing with a reference colour chart and expressed in language as light green, yellow green. An approximately 10 g portion sample from each guava was taken from each freshly harvested guava in porcelain crucible oven dried at 70 0C until the constant weight was attained. Percent moisture and dry matter contents were calculated from the weight loss of initial sample weight (before drying).
2.3 Chemical quality assessment 2.3.1 Total, reducing and non-reducing sugars Extraction of sugar from guava pulp was done by using the following method of Loomis and Shull (1937). Two grams of guava pulp was cut into small pieces and immediately plunged into boiling ethyl alcohol and was allowed to boil for 5∼10 minutes (10∼20 ml of alcohol was used per g of pulp). The extract was filtered through two layers of cloths and the ground tissue was re-extracted for 3 minutes in hot 80% alcohol, using 2∼3 ml of alcohol per g of tissue. The second extraction was ensured complete removal of alcohol with suitable substances. The extract was cooled and passed through two layers of cloths. Both of the extracts were filtered through Whatman No.1 filter paper. The volume of the extract was evaporated to about 25% of the volume over a steam bath and cooled. This reduced volume of extract was transferred to a 100 ml volumetric flask and was made up to the mark with distilled water.
Total sugar content of guava fruit was determined calorimetrically by the anthrone method (Jayaraman, 1981). An aliquot of 1 ml of pulp extract was pipetted in test tubes and 4 ml of anthrone reagent was added to each of this solution and mixed well. Glass marbles were placed to top of each test tube to prevent loss of water through evaporation. Then the tubes were placed in a boiling water bath for 10 minutes and then it was recovered and cooled. A reagent blank was prepared by taking 1 ml of water and 4 ml of anthrone reagent in a tube and treated similarly. The absorbance of blue-green solution was measured at 620 nm in a colorimeter and total sugar concentration was estimated from a standard curve of a series of glucose solutions. Reducing sugar concentration of guava fruit extract was determined by dinitrosalicylic acid (DNS) method. For the determination of reducing sugar concentration, an aliquot of 1ml of the extract was pipetted into a test tube and 3 ml of DNS reagent was added to each of these solutions and mixed well. The test tube was heated for 5 minutes in a boiling water bath. After the development of color, 1 ml of 40% rochelle salt was added when the contents of the tubes were still warm. The test tubes were then cooled under a running tap water. A reagent blank was prepared by taking 3 ml of distilled water and 3 ml DNS reagent in a tube and treated similarly. The absorbance of the solution was measured at 575 nm in a colorimeter .
The amount of reducing sugar was calculated from the standard curve of glucose. The non-reducing sugar concentration of guava was calculated by using the following equation: %NRS = %TS − %RS (1) where, NRS = Non-reducing sugar, TS = total sugar, and RS = reducing sugar.
Fundamental and Applied Agriculture Vol. 3(1), pp. 363–371: 2018
Journal