Effect of CaCl2, Citric Acid and Storage Period on Physico-Chemical Characteristics of Cherry Candy

B. N. Dar1， H. Ahsan2， S. M. Wani3 and M. R. Dalal4

1. Department of Food Science and Technology， PAU， Ludhiana， India

2. Department of Post Harvest Technology， SKUAST-K Srinagar， India

3. Department of Food Science and Technology， University of Kashmir， India

4. Department of Pomology， SKUAST-K Srinagar， India

Received: March 16， 2011 / Published: July 20， 2011.

Abstract: Cherry cultivar Misri (Bigarreau Noir Grossa) was used for making candy. Pitting of fruit was done manually and KMS(0.2%) was added for bleaching. The fruit was pretreated using 4 levels of CaCl2 (C0 = 0%， C1 = 1%， C2 = 1.5%， C3 = 2%) and stored in jars for 4 weeks. Thereafter， application of colour was done using Erythrosine (0.05%) followed by dipping pitted fruits in sugar syrup for 24 hours. The samples were treated with 4 levels of citric acid (T0 = 0%， T1 = 1%， T2 = 1.5%， T3 = 2%) and then concentrated subsequently till desired TSS of 70° Brix was attained. The samples were dried in cabinet drier at 80 ± 20 °C till constant moisture was attained. The product was packed in polyethene pouches and stored under ambient storage conditions. Results revealed that there was gradual increase in reducing sugars (%)， total sugars (%) during storage while as moisture content (%) decreased. The product developed was found economically profitable and viable for commercial production.

Key words: Cherry， Misri， candy， reducing sugars.

1. Introduction

Fruits are among the most important foods of mankind as they are both nutritive and indispensable for maintenance of health. Being rich source of carbohydrates， minerals， vitamins and dietary fibres， these constitute an important part of our daily diet. Moreover， they add flavour and diversity to diet. Cherry (Prunus avium L.) belonging to family Rosaceae is one of the most important fruit crops of temperate region of the world. In India， Jammu and Kashmir is the main cherry growing state having 2，570 hectares under this crop with the annual production of about 8，296 metric tonnes [1]. Shelf life of cherry fruit is very less and large quantities get wasted. Also there is lack of efficient post-harvest management of cherries， which leads to the rapid quality deterioration and sudden glut in the market. This crop can be saved from wastage and at the same time， can be converted into more valuable and priced commodity by processing into various products [2]. Various products prepared from cherries are juice， frozen cherries， dehydrated cherries， canned products， cherry jam， cherry juice concentrate， cherry juice powder， cherry bars and cherry candies.

Candy is a sweet food prepared from fruits or vegetables by impregnating them with sugar syrup followed by draining of excessive syrup and then drying the product to a shelf stable state. Fruits and vegetables like apples， ginger， mangoes， guava， carrots and citrus peels have been used to prepare candies [3-6]. Caronda， ber and Aonla candies have also been developed [7]. Candied products available these days are descended from the simplest confections first made more than 4，000 years ago. Candy making is fairly simple process. In traditional candy production， a mixture of sugar， water， and possibly corn syrup are mixed together and boiled until sufficient water has been boiled out of the candy mass. Current candy preparation techniques are grouped as semi-solid or soft candy (e.g.， chocolate-based， fruit-based， including tamarind， apple， cherry etc.) with or without chili or other visible particulate ingredients (i.e.， Chaca-Chaca， Pelon-Pelon Rico)， hard candy with or without visible particulate ingredient (chili) either in the candy or on the surface of the candy， hard candy with supplemental but separate salt and chili and powdered sugar or flavored salt products with or without other particulate ingredients. With this view， the study was undertaken to develop consumer friendly candies from cherries， to standardise different levels of CaCl2 and citric acid for product development for cherry candy and to study effect of storage on quality and stability of the product.

2. Materials and Methods

2.1 Raw Material

Fresh fruit of cherry cv. Misri was procured from a local fruit grower in cardboard boxes of 2 kg capacity and carried to the Division of Post Harvest Technology. Fruit was washed and manually pitted to remove the stone portion followed by bleaching with KMS(Potassium metabisulfite). Bleached fruit was stored in glass jars at ambient temperature (Temperature of the surroundings i.e. room temperature 25-30 °C).

2.2 Fruit Yield

Net pitted fruit yield was calculated by subtracting weight of stones and stalks from the weight of fruit and was calculated as percentage of total fruit weight.

2.3 Fruit Weight

The representative sample of 30 fruits in 5 replicates(6 fruits/replicate) were taken and weighed on electronic balance to calculate average fruit weight in grams.

2.4 Product Development

Pitted fruit was weighed to determine fruit stone ratio and were analysed for various physico-chemical parameters viz. moisture content (%)， total solids (%)， total soluble solids (oBrix)， total sugars (%)， reducing sugars (%).

2.5 Preparation of Candy

The pitted fruits were bleached using KMS(Potassium metbisulphite) @ 0.2% for 3-4 weeks. The bleached fruit was pre-treated with 0， 1， 1.5 and 2 per cent CaCl2 levels and colour (erythrosine @ 0.05%) was applied. Syrup was prepared and fruit was dipped in it. Concentration of syrup was subsequently raised to 70 oBrix and fruit was kept in it for 24 hours. The fruit was treated with 4 levels of citric acid viz. 0， 1， 1.5 and 2 percent. Syrup was drained and the product was dehydrated in air convection dryers. Dehydrated product was packaged in polythene pouches and stored at ambient temperature (room temperature) for 6 months and evaluated at 90 days interval to monitor the physico-chemical characteristics. 2.6 Total Soluble Solids (°Brix)

The total soluble solids were determined by using hand refractometer (Atago N1 Japan) and the values were corrected at 20 °C using correction factor.

2.7Moisture Content (%)

Moisture content in the samples was determined by hot air oven method [8]. 5 g of sample in triplicate was weighed accurately and dried at 70 ± 2 °C for 12 hours. The loss in weight was determined to calculate the moisture content.

2.8 Sugars

Total and reducing sugars were estimated by Lane and Eynon method [9]. 5 g of sample was blended with 100 mL distilled water， boiled for 1 hour in 250 mL beaker. Loss of water during boiling was made up by addition of distilled water. The solution was cooked， transferred to a 250 mL volumetric flask and neutralized using 1N NaOH. To it 2 mL of 45 per cent lead acetate was added， shaken well and left undisturbed for 10 minutes. Then it was de-leaded with 2 mL of potassium oxalate and volume made up to 250 mL. The solution was filtered and marked as solution (I).

For estimating reducing sugars， solution (I) was used， but for the estimation of total sugars， 50 mL of solution(I) was inverted in 200 mL of flask by adding 5 grams of citric acid to it and then boiled for 15-20 minutes and cooled， neutralized with 1N NaOH till pink colour appeared using phenopthalein as indicator. Volume was made up to 250 mL and solution designated as solution (II). 5 mL of each Fehlings solution (A) and (B) were taken in a titration flask containing 25 mL of distilled water titrated against solution (I) for estimation of reducing sugar and solution (II) for estimation of total sugars， till red colour was observed. After this 2 drops of methylene blue (indicator) were added and titration was continued till brick red precipitate was observed. During the entire period， the flask was kept on burner to keep the contents hot. Percentage of reducing sugars and total sugars were calculated using the following equation:

2.9 Economic Studies

The product formulation involves two types of costs. One fixed cost and other variable costs. Fixed costs are those which are run over many years and only a part of the services of these assets are utilized in a single production period while as variable costs are those which get transformed into the ultimate production during a particular season. Thus in our situation fixed costs relate to the machinery and equipments while as the variable costs involve expenses on chemicals， raw material， bottles corks etc. The costs stream in respect of fixed and variable costs was drawn and the economics was studied with computing benefit-cost ratio.

2.10 Statistical Analysis

The data was statistically analysed through Minitab Software using Completely Randomised Design (CRD) in factorial experiment with three replications.

3. Results and Discussion

3.1 Moisture

Maximum moisture content (16.537%) was recorded in case of samples pre-treated with CaCl2 (2%) as compared to that of untreated samples (15.907%)(Table 1). There was a significant effect of citric acid on moisture content as product samples treated with 2 per cent citric acid had the highest mean moisture content (16.653%) and with no citric acid treatment had lowest moisture content (15.842%). The initial moisture content of cherry candy (18%) showed gradual decrease during 180 days of storage period upto the value of 14.426 per cent. Similar findings have been reported by Rani and Bhatia [10] who reported a decrease in moisture content during storage in pear candy. A gradual fall in moisture content during storage was also reported in aonla [11] candy and in lemon peel waste candy [12]. The decrease in moisture content may be attributed to natural dehydration of product during storage at room temperature.

3.2 Reducing Sugars

The reducing sugars of product samples were significantly influenced by pre-treatments， and maximum reducing sugars (27.470%) were observed in samples pre-treated with CaCl2 (2%) as compared to that of untreated samples (26.782%). Samples with no citric acid treatment had the lowest reducing sugars(26.253%) and those treated with citric acid (2%) recorded highest reducing sugars (27.977%). The value at initial evaluation (26.762%) increased to 27.483 per cent after 180 days of storage (Table 2). Similar observations of increase in reducing sugar content during storage have been reported [13-15]. Increase in reducing sugar content was attributed to the gradual inversion of non-reducing sugar [11]. The increase in reducing sugars may also be attributed to the hydrolysis of sucrose by citric and during storage [16]. The ratio of reducing to nonreducing sugars is considerably promoted by acids， and consequently the reducing sugar contents are higher. The opposite effect occurs with nonreducing sugars， whose concentration increase as sucrose hydrolysis slows down. 3.3 Total Sugars

The total sugars of product samples were significantly influenced by pre-treatments， maximum reducing sugars (47.749%) were recorded in samples pre-treated with CaCl2 (2%) as compared to that of untreated samples (47.264%) (Table 3).

Samples with no citric acid treatment had the lowest total sugars (47.137%) and those treated with citric acid (2%) recorded highest sugars (48.352%). The total sugar content progressively varied with storage period. The value at initial evaluation (47.185%) increased to 48.002 per cent after 180 days of storage. These findings were in consonance with the findings in dehydration studies of muskmelon， guava and mango pulp [13] and pine apple [14]. Increase in total sugars may be attributed to the breakdown of complex polysaccharides into simple sugars during storage. The effect of different acidity levels on total sugars was due to faster rate of hydrolysis at higher acidity level. The increase might also be attributed to loss of moisture during storage at room temperature [17， 18]. Significant increase in total sugars in candied apples was also reported [4]. Drying also causes significant increase in total sugar content due to concentration effect of losing moisture after drying. Sucrose hydrolysis is doubly important: there is an increase in the sugar content of candied fruits and it also confers good mouth-texture and a pleasant taste to the candied product.

3.4 Economic Studies

The economic analysis indicated that there are better chances of value addition in case of cherry if it is processed into a product like candy. The benefit-cost ratios indicated that the product can compete well with other fruit based products available in the market. All the treatment combinations are profitable， however， C3T2 (2% CaCl2， 1.5% citric acid) shows highest benefit-cost ratio of 2.55. The benefit-cost ratio of 2.55 means that a processor can obtain Rs. 2.55 per rupee invested (Table 4). Further the product can be more profitable if prepared on industrial scale.

4. Conclusion

It was concluded from the present investigation that cherry candy prepared by using CaCl2 (2%) and citric acid (1.5%) proved superior with respect to overall acceptability scores in terms of color， taste， texture and flavor during entire period of storage. The product developed was found economically profitable and viable for commercial production.

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