Development and evaluation of physico-chemical quality markers of opuntia and pineapple squash

* S. ChennaKesava Reddy, K.V. Sucharitha, K. Jalarama Reddy and B.Syamala. Department of Home Science, S.V University, Tirupati-517502, AP, India. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

942 that due to the perishable nature of the fruits and vegetables they require immediate processing to avoid post-harvest losses (20-25%) The Opuntiaficusindica (L) Mill is a xerophyte popularly known as prickly pear plant in English. Prickly pear fruit has a similar nutritional value like other fruits, although it has much higher soluble solids content than many popular fruits such as apple, apricot, cherry, melon, peach and plum (Pimienta, 1990; Sepúlveda and Sáenz, 2000). This characteristic makes prickly pear fruit suitable for processing by concentration or dehydration, taking advantage of the reduced water activity and increased sugar content as a means of preservation.
The fruit and cladodes of prickly pear provide interesting sources of functional compounds, including fiber, hydrocolloids (mucilage), pigments (betalains and carotenoids), minerals, (calcium and potassium) and vitamins with antioxidant properties, such as vitamin C. These compounds are valued for their contribution to a healthy diet and also as ingredients for designing new foods (Sáenz, 2004). These compounds can be included in a new range of foods known as functional foods, which are as foods or beverages that provide physiological benefits. They enhance health, help to prevent or treat disease and/or improve physical or mental performance with the addition of one or more functional ingredients or using appropriate biotechnologies (Sloan, 2000).
The pineapple (Ananas comosus) is a tropical plant with edible multiple fruit consisting of coalesced berries, also called pineapples, and the most economically significant plant in the Bromeliaceous family. In a 100 gram serving, raw pineapple is an excellent source of manganese (44% Daily value (DV)) and vitamin C (58% DV), but otherwise contains no essential nutrients in significant content. It is an excellent source of antioxidant, vitamin C which is required for the collagen synthesis in the body. It contains micronutrients and it protects against cancer and this micro-nutrient break up blood clots is beneficial to the heart.
There are various methods of preservation of food including thermal processing, fermentation, pickling, dehydration, freezing etc. The technology for preservation also varies with type of products and targeted market. The processing of fruit as squash enhances the raw edible quality of fruit as well as its shelf life by the selection of appropriate fruit drink processing conditions. Squashes are sweetened juice of fruits containing minimum prescribed quantity of pulp. As per Indian Standards, squash should contain at least 25 per cent (by volume) of fruit juice. The squashes are consumed after dilution by drinking water in 1:3 ratio. These beverages contain added flavors and permitted class II preservatives. Since preservatives are added in adequate quantities, the shelf life of squashes is fairly longer at room temperature.
The present study was carried out for the development of fruit squash with prickly pear and pine apple fruits. The standardized and development of squash with different concentrations of pear and pine apple fruits and evaluation of the physico-chemical and sensory attributes.

Materials &Methods:-
Prickly pear juice:-Mature ripe fruits were collected from the experimental plot during April-May. Spines over the surface of the fruit were picked, pealed washed cut into slices and seeds were removed. The slices are crushed with an electric blender/mixer to get pulp. The pulp was heated up to 800 C and passed through a 1/32 inch nylon sieve to remove excess fiber and coarse pulp particles. Finally obtained juice was analyzed for TSS, PH, Titrable acidity, ascorbic acid and was used for preparation of blended fruit squash.
Pineapple juice:-Mature ripe fruits purchased from the local market were peeled, washed, cut into slices and crushed into pulp with electric blender/mixer. The crushed pulp was heated to 80 0 C and passed through a passed through a 1/32 inch nylon 943 sieve so as to remove excess fiber and coarse pulp particles finally obtained juice was analyzed for TSS, PH, Titrable acidity, ascorbic acid and was used for preparation of blended fruit squash.

Optimization and preparation of Squash:-
The clarified fruit juices of prickly pear and pineapple were mixed in different proportions and sample codes are represented in below Table 1. Collecting of mature ripe prickly pear and pineapple fruits.
Removing of hairy spines (Glochids) from the prickly pears.
Peeling of prickly pears and pineapple fruits.

TSS:
Total soluble solids (TSS) of different pulp, juice and products was measured with hand refractometer (ERMA, Japan) and expressed as 0 Brix at room temperature. Before taking the reading the refractometer was tested for error with distilled water (Ranganna, 1994).

Titrable acidity:
Titrable acidity was determined by diluting 5-10g of sample with distilled water then 10 ml of sample was taken in a 100ml volumetric flask and the volume was made up with distilled water. From this 10ml of aliquot was taken in a 100ml conical flask and titrated against 0.1N sodium Hydroxide (NaOH) solution using one (or) two drops of phenolphthalein indicator. Total titratable acidity was expressed as percent citric acid (g/100ml of sample) (AOAC 2005) Acidity % (As citric acid) = Titer value × Normally of NaOH × 64 × 100 Volume of Sample taken × 1000 Total sugars: The total sugar content was determined by the anthrone reagent method (Plummer, 2006). The fruit juice was prepared as described in 3.3.3.2 and transferred 1.0 ml of filtered juice to the 10 ml volumetric flask, and diluted to 10.0 ml with distilled water, having strength 100μl/ml, labelled as stock solution. Stock solution (0.1 ml) was transferred into 10 ml volumetric flask, and diluted to 10 ml with distilled water, having strength 10μl/ml. The anthrone reagent was prepared right before analysis by dissolving 0.2 g of anthrone (0.2%) in 100 ml of concentrated sulfuric acid, protected from light and used within 12 h. Anthrone reagent (4.0 ml) was added 945 cautiously to each tube containing 1.0 ml of standard solutions of glucose (10 -100 μg/ml) and test solution (10μl/ml).
Tubes were then placed 10 min at 5 0 C. Subsequently, tubes were boiled 5 min on constant boiling water bath. After heating, allowed to cool at room temperature for 15 min. The absorbance of the colored solution was measured at 620 nm against reagent blank. Readings were taken in triplicate. Spectrophotometric response was compared to a standard calibration curve of glucose, and total sugar content was expressed as g/100 ml of glucose. (AOAC 2005).

Reducing sugars:-
Weigh accurately an amount of sample such that after dilution the solution contains about 0.6% reducing sugars. Transfer the sample quantitatively to a 500 ml volumetric flask with the aid of hot water, cool to room temperature, dilute to volume and mix thoroughly. Pipette 25.0 ml of standardized mixed Fehling's Solution into a 200 ml Erlenmeyer flask and add a few glass beads. Add the sample solution by means of the burette to within 0.5 ml of the anticipated end point (determined by preliminary titration). Immediately place the flask on the wire gauze of the titration assembly, and adjust the burner so that the boiling point will be reached in about 2 min. Bring to boil and boil gently for 2 min. As boiling continues, add 2 drops of methylene blue indicator and complete the titration 10 g of each of the samples with the exception of fruits was accurately weighed and ground using mortar and pestle with an additional of 20 ml of metaphosphoric acid and acetic acid. The mixture was further ground and strained through muslin and the extract was made up to 100 ml with the metaphosphoric-acetic acid mixture. 5 ml of the metaphosphoric acid-acetic acid solution was pipetted into three of the 50 ml Erlenmeyer flask followed by 2 ml of the samples extract. The samples were titrated separately with the indophenol dye solution until a light rose pink persisted for 5s. The amount of dye used in the titration were determined and used in the calculation of vitamin C content.

Sulphur dioxide (So 2 ):
Sulphur dioxide content of the sample was distilled in the presence of acid in an inert atmosphere and absorbed by iodine which converts sulphurous acid to sulphuric acid and titrated against standard thiosulfate solution. The free and combined So 2 expressed in parts per million (PPM). (Askar 1981).

Sensory evaluation:
Sensory evaluation test carried out according to Nadir et al., (2005).Taste, color, texture, odor and overall acceptability of prickly pear fruit products of squash were assessed using ten panelists of Department of Home science, S.V University, Tirupati, India.

Statistical analysis:
Obtained data was subjected for statistical analysis by Duncan multiple range test (DMRT) for testing the significance, described by Dhamu and Ramamoorthy (2012).

Results & Discussion:-
The Opuntiaficusindica or prickly pears are spiny and pear shaped fruits. These fruits are emerging nutraceutical fruits with high therapeutic values. These xeropyte can be an alternative crop for drought prone areas.

Formulation and development of prickly pear fruit products:
The one of the main objective of the study was development of fruit products with prickly pear (PP). The quality of fruit products depends on the pulp quality. Prickly pear pulp contains less solids and more moisture. Hence the pulp is watery which will not suitable for the quality standards of the products like squash and bar. Blending of other 946 fruits will be desirable, for prickly pear squash preparation. A fruit with no colour and pleasant aroma is required, so that it will not interfere into the colour of prickly pear. Pineapple was selected to blend with prickly pear, because it has no colour and have pleasant aroma.
Fresh prickly pear fruits obtained from experimental plot and fresh fruits of pineapple obtained from local markets were utilized for preparation of blended fruit products squash. These fresh fruits pulp were analyzed for physicochemical parameters.   Table 2).

Physico-chemical quality characteristics of squash:-
The fruit squash is a non-alcoholic concentrated syrup used in beverage making. It is usually fruit-flavored, made from fruit juice, water, and sugar or a sugar substitute. To standardize the prickly pear and pineapple squash, five different variations of blending of prickly pear and pineapple treatments i.e T1 (25:0%), T2 (20:5%),T3 (15:10%), T4 (10:15%) and T5 (5:20%) in the ratios respectively, to standardize the best composition. The five samples were 947 analyzed for physico-chemical parameters and subjected to subjective evaluation to know the acceptance. The results are presented in Fig. 2 Potassium metabisulphate (stock solution 200g KMS dissolved in 1 ltr of distilled water = 1 ml of KMS stock solution will give 10 ppm of sulphur dioxide (So2) to 10 ltrs of juice solution) were added as preservative to increase the shelf life of the squash. The quality parameter So2 (Sulphur dioxide) can be maintained up to 500 ppm (as per FSSAI standards). In the present samples the So2 was analyzed, the T1, T2, T3, T4 and T5 contain 350, 348, 349, 350 and 348 ppm respectively, which is within the permitted levels of the FSSAI (Food Safety Standards Authority of India).
Results showed significant differences among the treatments for all the chemical components of the squash blends analyzed except for titrable acidity, TSS and So 2 which did not show significant differences between the treatments on 'Initial' days of storage. TSS in the range of 45 to 46 0 brix, P H 3.8 to 4.1, titrable acidity (% citric acid) 1.45 to 1.49, total sugars 35.3 to 37%, reducing sugars 15.2 to 16.8%, ascorbic acid 6.5 to 10.5 mg/100g and So2 348 to 350 ppm were observed in different juice blended squash treatments. The highest TSS (46 o Brix), Total sugars (37%), reducing sugars (16.8%) was observed in T3 prickly pear and pineapple juice blended ratio (15:10). The high acidity (1.48%) and ascorbic acid (10.9 mg/100g) were witnessed in T5 prickly pear : pineapple (5:20%) fruit juice blended squash; whereas high So2 content was seen in pure prickly pear squash (T1) and lowest P H (3.8) was seen with the squash blended prickly pear: pineapple (15:10%) fruit juices i.e T3. The ascorbic acid content was however found to be high in squash blends with increase in the proportion of pineapple juice from 5 to 20% in the present study. This may be due to high ascorbic acid content of pineapple juice (38 mg/100g) comparatively than prickly pear juice (26 mg/100g).

Sensory evaluation of prickly pear squash:
Sensory evaluation was carried out by a panel of 10 judges for appearance, taste, flavor, colour, consistency (mouth feel) and appearance on a 10 point scale where 1-2 poor, 3-4 fair, 5-6 good, 7-8 very good and 9-10 excellent (Askar 1981). The mean for each sensory attribute was computed for comparison and the overall acceptability scores were obtained by the summation individual sensory scores and means were computed for comparison.
The sensory characteristics taste, consistency (mouth feel) and appearance did not exhibit significant differences between the juice blends of the fresh squash tried, whereas the sensory parameters flavor, color and overall acceptability showed significant differences between the different juice blended fresh squash treatments (Table 3) Results of the sensory characteristics evaluation of fresh prickly pear squash and its blends with pineapple juice revealed that the squash blend T3-15:10% prickly pear and pineapple juice scored high sensory values for taste (8.6), flavor (8.8), consistency (mouth feel) (8.8) and appearance (8.5) and overall acceptability score (8.62) and followed by T2-20:5% prickly pear and pineapple juice blended squash and pure prickly pear squash T1-25% juice and T2-20:5% prickly pear and pineapple juice with overall acceptability scores of 8.36 and 8.42 respectively (table-23). The other squash blends T4-10:15% and T5-5:20% prickly pear and pineapple juice blends had comparatively low scores for all the sensory characteristics including the overall acceptability 8.28 and 8.11 respectively (Table 3).

Conclusion:-
Fruits and vegetables are important constituents of the diet and provide significant quantities of nutrients, especially vitamins, sugars, minerals and fiber.Results showed significant differences (p<0.05) among the treatments for all the chemical components of the squash blends analyzed. The highest TSS (46 o Brix), Total sugars (37%), reducing sugars (16.8%) was observed in T3 prickly pear and pineapple juice blended ratio (15:10). The high acidity (1.48%) and ascorbic acid (10.9 mg/100g) were witnessed in T5 prickly pear : pineapple (5:20%) fruit juice blended squash; whereas high So2 content was seen in pure prickly pear squash (T1) and lowest P H (3.8) was seen with the squash blended prickly pear: pineapple (15:10%) fruit juices i.e T3. The study concludes that, prickly pear and pineapple facilitates in the development of functional fruit squash with minor changes in physico-chemical markers and superior sensory attributes.