Investigation on the Effect of Shapes on the Drying Kinetics and Sensory Evaluation Study of Dried Jackfruit

Jackfruits are seasonal and highly nutritional fruits indigenous to the Southwestern rainforests of India. However much of the produce are spoilt annually due to poor preservation techniques. Minimal studies have been conducted on the drying kinetics of jackfruit and the effect of shapes on the drying kinetics. In this research, drying curves of three different shaped jackfruit slices were obtained using a convective oven at 40oC, 50oC, 60oC and 70oC. Modified Midilli-Kucuk Model was found to be the best kinetic model for drying of jackfruits. At all temperatures, effective moisture diffusivity values and activation energy varied from 2.66 x 10-10 - 4.85 x 10-10 m2/s and 16.08 - 20.07 kJ/mol respectively. Drying was found to be most efficient at 50oC using the square shaped slices with a R2, RMSE and SSE value of 0.9984, 0.01127 and 0.002668 respectively. Sensory evaluation of untreated and additive-added dried jackfruit slices was conducted by 40 untrained sensory panelists. Jackfruit with ascorbic acid and sugar coating had highest aesthetics value due to better retention of colour by ascorbic acid. However sugar coated jackfruit had the most favorable taste and smell. Further optimization must be done to satisfy consumers collectively to enable a highly marketable product.


I. INTRODUCTION
Jackfruit is one of the many seasonal local fruits available in Malaysia and is indigenous to the South-western rain forests of India (Boning, 2006). Jackfruits are fruits rich in energy, dietary fibre, potassium, magnesium, iron, vitamin Bcomplex, vitamin C and many other nutrients. They are also free from saturated fats and cholesterol making it an excellent choice of fruit for consumers (Umesh, et al., 2010;Swami, et al., 2012). Many methods of preservation have been applied to preserve the multi-nutritional jackfruit for the consumers. However, nearly 75% of jackfruit in India still gets spoilt annually due to lack of proper preservation, an integrated supply chain and storage facilities during peak seasons of harvesting (GlobalVillageFruit, 2013).
Preservation of food has been a way of life since prehistoric times to maintain the availability of food for human consumption. Among many methods of food preservation, drying or dehydration is one of the oldest techniques to prevent damage and spoilage of the food by microorganisms; subsequently, presenting higher stability of food for easier storage and transport (Mulet, 2011). Currently, most jackfruit studies compare final values of antioxidant activity, total phenolic contents and phytochemical aspects of the fruit after undergoing different drying techniques (Shanmugapriya, Saravana, Payal, Mohammed, & Binnie, 2011;Baliga, Shivashankara, Haniadka, Dsouza, & Bhat, 2011). Minimal studies on the drying kinetics of the jackfruit have been studied because more researchers are concerned with the nutritional value of the jackfruit after drying. However, without a proper optimization of the drying process initially, conclusive values of nutritional values from different drying techniques should not be made.
In this experiment, the convection oven drying of jackfruit with three different shaped cuts was thoroughly studied for their drying kinetics to showcase the best fit of drying data in comparison to drying models from previous researches. The drying kinetics of jackfruit slices obtained can be used for better optimization of fruit dehydrators for jackfruits. Consecutively, the consumer acceptance of the dried jackfruit slices was analysed using sensory evaluation tests which target the three main senses namely sight, smell and taste. The preference typed sensory evaluation in this experiment allowed better understanding of the consumer demands and the perception of the general public on preserved dried jackfruit which was untreated compared to jackfruits which had food additives. The results of the sensory evaluation will provide a preliminary analysis for dried fruit manufacturers in Malaysia and especially India on whether to invest on the fabrication of a specific jackfruit oven dehydrator with drying technology using the proposed modelling obtained in this research.

Materials used in this research were: 1) Fruits
A whole jackfruit (Artocarpus heterophyllus Lam.) with no apparent damage was purchased at the local market in Bukit Jelutong, Shah Alam, Selangor. The seeds of the jackfruit was plucked out from every bulb and disposed as the drying experiment does not cover the drying of the jackfruit seeds. Only fruits from the same jackfruit are tested as a sample.

2) Chemicals and Equipment
Food grade ascorbic acid (Euro-chemo Pharma Sdn. Bhd.) and white sugar (CSR Brand) are the two chemical additives used in jackfruit drying for sensory evaluation. Convection oven (Memmert, loading model 100-800) was used for convective drying of the jackfruit. Precision mass balance (A&D Company Limited Model FX-3000i) was utilized as a mass balance for moisture loss calculations.

Sample Preparation
Each experiment at specified temperature utilizes the exact same batch of purchased fruit for every run to ensure consistency. Jackfruit bulbs were cut open and seeds were removed. Cuts of the jackfruit were made into three shapes, namely the triangle, rectangle and square. The weight of each sample was weighed to be approximately 10±0.5 g of pure jackfruit on the mass balance of 0.01 g accuracy. Sizes of all these samples must be fairly consistent and measured with sterilized measuring rulers (Tehranifar, Zarei, Nemati, Esfandiyar, & Vasifeshenas, 2010). Dimensions of the jackfruit samples in three different shapes are shown below in Fig. 1 with an accuracy of ±5 mm. Thicknesses of the slices varied on each slice but all were within the accuracy of 5mm ±1 mm.

Sample Drying
Total dry matter and determination of total moisture content was obtained by drying the jackfruit slices at 105 o C to a uniform mass (AOAC, 1995) overnight. The total moisture content (%water in 10±0.5g of fruit) is expressed as shown in Equation 1 below.
The average total moisture content for the triangle, rectangle and square jackfruits were 71.9%, 71.4% and 73.1% wet basis respectively. These values were the main assumptions in calculation of final moisture contents achieved in jackfruit slices after total drying. Convection oven drying of jackfruit was carried out at four temperatures; 40 o C, 50 o C, 60 o C and 70 o because drying at these temperatures retains most of the fruit's natural quality in terms of solid gain and water loss ratio (Alves, et al., 2005). Before experimental runs, the oven was ensured to be operating for at least one hour to stabilize the air temperature in the drying chamber (Chowdhury, et al., 2010). Triplicate samples of all three shapes were removed at 30 minute intervals for weighing on electronic mass balance of ±0.01g accuracy. Drying process was completed when three consistent readings of weight were achieved. This weight was assumed to be the equilibrium weight of the dried jackfruit at the particular drying temperature. Typically, equilibrium moisture content of unprocessed dried fruit should range from below 10% to 25% (Joslyn, 2012) with a general acceptability of 20% for most dried fruits (Reynolds, et al., 1993). Repeatability tests were done twice under the exact same conditions of experimental procedures, instruments and location to ensure the accuracy of the experimental results.

Mathematical Modelling
Non-linear regression analysis was performed using MATLAB R2012b. All fitting calculations were done in MATLAB with the nine semi-theoretical and empirical thin layer drying models namely the Newton Model, the Page Model, the Modified Page Model, the Henderson and Pabis Model, the Logarithmic Model, the Midilli-Kucuk Model, the Modified Midilli-Kucuk Model, the Diffusion Approach Model and the Wang and Singh Model to identify the constant parameters in each separate model. In thin layer drying models, the non-dimensional moisture ratio ( % ) is expressed as shown in Equation 2 below.
The indicator to evaluate the best fit among the nine thin layer drying models to the experimental data was the model with the highest R 2 and lowest RMSE and SSE values.

Sensory Evaluation
The sensory evaluation was a preference test using a set hedonic scale. The 40 untrained panellists were from an age group of 18-40. The evaluation space was conducted in a well-lighted area and timed from the mid-morning to early afternoon for the best judgment of taste (Rasco, 2006). Communication between all subjects was strictly prohibited to prevent side-tracked judgment. The sensory panellists were asked to sign a consent form as required by Monash University before given a set of instructions on paper to conduct the sensory test. Panellists were ensured to be free from taste perception disorders, odour perception disorders, colour blindness, denture defects, allergies, on medical treatment and prone to infections of the throat and nose.
Panellists were not informed about the differences between samples used in the sensory testing but were assured of its safety. They were instructed to evaluate each quality parameter -appearance, smell, and taste individually to prevent the Halo Effect which occ simultaneously evaluate different facto (Lawless and Heymann, 2010). All th presented in a random order on a white pl three digit number assigned to each sam Order Effect from occurring. The Order Ef samples are perceived differently due to their line-up. In smell evaluation, panellists coffee beans between samples. During fl panellists rinsed their palates with room t between samples. All the methodology fo conformed to standards of good practic sensory evaluation studies (Lawless and Evaluation sheets were collected after the analysis using the Nine Point Hedonic Acc

III. RESULT AND DISCUSS Drying Kinetics
Drying at 40 o C, 50 o C, 60 o C and 70 o C and 9 hours respectively. These values reduction of 2 drying hours when drying changed from 40 o C to 50 o C as compared to hour reduction when drying temperature w 50 o C to 60 0 C and 60 0 C to 70 o C respective jackfruit slices reached equilibrium moi 16.7%, 5.8%, 20.3% and 5.1% at 40 o C, 70 o C respectively which were all reas contents for dried fruits.
Generally, the highest R 2 values will lowest RMSE and SSE values. This w criterion to determine conclusively on the thin layer drying model. The Wang and S found to have the lowest R 2 values in dryin Assumptions of uniform initial moisture distribution, negligible external resistance and drying from the top of the sample was involved in these calculated values. From these assumptions, the equation is written in the following form: Effective moisture diffusivity values generally increased with increase in drying temperature. This is due to the dependence of C on temperature as shown in the Equation 4 below. When the temperature rises, the value of C will increase (Goyal, et al., 2007). Effective moisture diffusivity values were found to be in the general range of 10 -9 to 10 -11 m 2 /s for drying of food materials and comparable to values of by past experiments of jackfruit drying by Chowdhury (2010) and Giraldo-Zuniga (2006). Thus, it can be concluded that the results of the calculated C values are in good agreement with previous reported values. At drying temperatures of 40 o C and 50 o C, square shaped slices were found to have the highest values of C followed by triangles and lastly rectangles. However, at drying temperatures of 60 o C and 70 o C, rectangle shaped slices had the highest C values followed by squares and lastly triangles. Having low effective moisture diffusivity values is unfavourable to the drying process, thus it is safe to conclude that among the three shaped slices, square shaped slices are generally the most appropriate shape for drying of jackfruit slices for mass production. The diffusivity of jackfruit slices is often expressed by an Arrhenius equation as shown in Equation 4 below. Linearization of the equation will be able to determine the activation energy of diffusion by plotting a graph of lnDC E versus the reciprocal of absolute temperature,  From calculations above, the activation energy of diffusion was lowest for square slices followed by triangles and rectangle. The values ranged from 16.08 kJ/mol to 20.07 kJ/mol. Lower activation energies are preferable for drying processes as drying time and energy consumption can be lowered (Minaei, et al., 2011). Overall, due to the highest effective moisture diffusivity and lowest activation energy calculated in the experiment, square shaped jackfruit slices are justified to be the most appropriate model for drying of jackfruits.
Thus, by optimization of the Modified Midilli-Kucuk model, drying temperature of 50 o C and most effective squared shape slices, the most appropriate thin layer equation proposed was defined as: O = 1.027 exp(−0.003736 M.UK ) − 0.0427 (5)

Sensory Evaluation
Forty consumers evaluated jackfruit slices of three different attributes. The jackfruit slices dried for this sensory evaluation were square shaped and dried in convection oven at drying temperature of 50 o C. The three different attributes are namely a jackfruit slice with no additives (Code: C), a jackfruit slice coated with fine white sugar at the end of drying (Code: S) and a jackfruit slice pre-treated with an ascorbic acid and sugar solution for 2-3 minutes prior to drying (Code: AA). Results were analysed and summarized in Table 4 from evaluation of appearance, smell and taste of jackfruit samples on the set hedonic scale. The set hedonic scale used for this preference test had scores ranging from 1 to 9 which placed 5 as an average score. These values show that a combinatio can possibly be the most efficient way to product of dried jackfruit which will b consumers in all three main sensory aspect A very interesting discovery in the a was found in the analysis of AA sample scores around the mean score was larger co S samples for all three sensory evaluatio shows that pre-treatment of an ascorbic solution on jackfruit slices may result in preferability in consumers. Dried jackf ascorbic acid and sugar solution was est most preferred type of dried jackfruit b colour retention by ascorbic acid (food agent) and additional sweet taste. Th supported by AA jackfruits achieving t compared to C and S samples in the aesth However, the sour taste of the ascorbic treatment solution may have offset the natu jackfruit to a high extent, resulting in t having the lowest score in the taste test. T must be done on this pre-treatment meth capability of being an efficient pre-treat jackfruit drying.
In the sensory test, a question was as the overall acceptability of the three differ jackfruits. This question was to determine for mass production. The pie chart belo percentage breakdown of the overall acce by the Malaysian consumer market.  Fig. 3, more than half of the c chose jackfruit with sugar coating (S preferred dried jackfruit slice. This was outcome as Malaysian people are famous preference of sweet foods (Loh, 2009) percentage (8%) of consumers preferred due to its sour taste as commented by ma evaluation panellists. This further shows th the best aesthetic value, AA samples will by consumers at the purchase counter. Be be inferred that drastic change of the jackfruit into a sour tasting dried fruit was consumers. Furthermore, this low percent due to the fact that jackfruits are know somewhat an acquired taste. tion of all methods to innovate a final be able to satisfy ects. e analysis of scores ples. The spread of r compared to C and ations. This finding bic acid and sugar in higher or lower kfruit treated with estimated to be the t because of better od colour retention This finding was the highest score sthetics sensory test. ic acid in the preatural sweet taste of the AA jackfruits . Thus, optimization ethod to ensure its eatment method for asked to determine ferent types of dried ne the best jackfruit elow illustrates the cceptability as rated for most preferred sory tests e consumer sample (S) as their most as also an expected ous for having high 09). Only a small ed the AA samples many of the sensory s that despite having ill not be preferred Besides that, it can he naturally sweet as not preferred by entage may also be wn to be fruits of IV. CONL Based on the nine thin layer Midilli-Kucuk model was best f of the jackfruit drying process. was found to be the most optim drying. Amongst the three pr jackfruit slices, the square sh suitable drying shape configura moisture diffusivity (3.081 x 10 energy (16079.338 J/mol) value extra sugar coating was found t jackfruit in the sensory eva unfortunate discovery because e to our initial objective of m nutritional snack as an alterna Thus, further work should be do of jackfruit to ensure the procur at a more satisfactory level w These findings may be applicab oven dehydrators for jackfruits and wastage of the fruit due to months.
LUSIONS yer drying models, the modified st fitted to the experimental data ss. Drying temperature of 50 o C timum temperature for jackfruit proposed shapes for drying of shaped slices were the most uration due its highest effective 10 -10 m 2 /s) and lowest activation lues. Dried jackfruit slices with d to be the most preferred dried evaluation test. This was an e extra sugar will be detrimental making dried jackfruit into a rnative to unhealthy junk food. done to optimize drying kinetics curement of dried jackfruit chips without the addition of sugar. cable to design of fan-controlled its in India to prevent spoilage to overproduce during seasonal LEDGMENT ike to acknowledge Monash us for the financial support