RUHUNA JOURNAL OF SCIENCE Vol 13 (2): 167-180, December 2022 eISSN: 2536-8400 Faculty of Science http://doi.org/10.4038/rjs.v13i2.123 University of Ruhuna Faculty of Science, University of Ruhuna Sri Lanka 167 Process optimization for the development of easy-to-cook jackfruit bulbs Chalani Akmeemana*, Indira Wickramasinghe, Piyumi Chathurangi Wanniarachchi and Thisum Vithanage Department of Food Science and Technology, Faculty of Applied Sciences, University of Sri Jayewardenepura, Nugegoda, Sri Lanka *Correspondence: chathurangichalani@sci.sjp.ac.lk, ORCID: https://orcid.org/0000-0002-1832-085X Received: 9th July 2022, Revised: 15th November 2022, Accepted: 29th December 2022 Abstract Overproduction of jackfruit (Artocarpus heterophyllus) in harvesting seasons and its short post-harvest shelf life make it an underutilized fruit species. The present study was conducted to analyze the feasibility of preparing processed jackfruit products to enhance utilization and reduce wastage. Jackfruit bulbs were cut into 4.5 cm ± 0.5 cm in length and 0.5 cm ± 0.3 cm in width pieces. The two- factor factorial technique was used as the experimental design when developing the products. As factors, the freezing operation and dipping treatment were considered. Hot water extracts of A. heterophyllus leaves and Trachyspermum ammi leaves were used as two dipping treatments and sensory evaluation tests were carried out to determine which dipping treatment is better. T. ammi dipping treatment had better sensory acceptance, and hence continued as the selected dipping method. The effect of freezing (-18 °C for 12 h), pre-cooking time, and rehydration on cooking time was also investigated. Frozen and non-dipped jackfruit bulb pieces had the highest sensory acceptance, hence its proximate composition, DPPH, total phenolic acid, and colourimetric values were determined. Moisture, ash, fat, crude protein and carbohydrate content of the frozen non-dipped jackfruit bulbs were 8.08 ± 0.28 %, 0.88 ± 0.01 %, 0.31 ± 0.03 %, 3.93 ± 0.06 %, 81.09 ± 0.54 % respectively. The colourimetric values (L*, a*, and b*) of the frozen non-dipped jackfruit bulbs were 79.40 ± 0.61, 1.87 ± 0.35, 25.43 ± 1.33, 25.50 ± 1.35 respectively. The results revealed that the freezing operation significantly (P<0.05) reduce the cooking time of jackfruit bulbs. Based on the sensory evaluation results, jackfruit bulbs that were frozen without dipping the T. ammi leaf extract were identified as having the best sensory acceptability. The final processed product possesses a good nutritional profile concerning the ash, fat, crude protein, carbohydrate, mineral content, DPPH and total phenolic acid content. Keywords: Easy to cook food, jackfruit bulb, Proximate composition. https://rjs.ruh.ac.lk/index.php/rjs/index http://doi.org/10.4038/rjs.v13i2.120 https://creativecommons.org/licenses/by-nc/4.0/ https://orcid.org/0000-0002-1832-085X http://orcid.org/0000-0003-1805-4923 htpp://orcid.org/0000-0003-3364-6433 https://orcid.org/0000-0002-5495-6724 https://orcid.org/0000-0002-1832-085X https://orcid.org/0000-0002-1832-085X C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 168 1 Introduction Jackfruit, Artocarpus heterophyllus belongs to the family Moraceae and is mainly grown in tropical and sub-tropical regions (Vazhacharickal et al. 2015). A mature jackfruit tree often yields between 10 - 200 fruits every year. Normally it takes around three to seven months for the development of fruit for edible purposes. A cross-section of jackfruit when studied from outside to inside, it consists of an outer peel, rags, latex, bulb, core, seeds and arils. Jackfruit bulbs as well as seeds are the edible portions of the fruit (Akmeemana et al. 2022), accounting for 25% to 30% of the total weight (Baliga et al. 2011). There are two main types of jackfruit: one is firm, less sweet, and crispy, while the other is extremely soft, sweet-tasting, small, and fibrous (Swami et al. 2012). Jackfruit is a healthier source of calories because it does not contain any cholesterol or saturated fats (Goswami and Chacrabati 2016). Every part of the jackfruit tree can be utilized in a wide range of ways because of that there is no waste generated (Ranasinghe et al. 2019). Every year, a huge post-harvest loss of jackfruit is reported due to a lack of knowledge on post-harvest technology, improperly organized marketing structures, having a smaller number of processing plants, poor demand in the local market, difficulty in initial processing steps, and rapid quality degradation of edible portion after removing from jackfruit peel (Vazhacharickal et al. 2015). Global acceptance of convenient instant food is increasing due to changing lifestyles, the need for convenience, an increase in the number of working professionals, and a growing inclination toward western culture. Low-caloric and highly nutritious instant food mixes are among the most preferred by consumers globally (Ajisha et al. 2018). The present study aimed to investigate the feasibility of using jackfruit bulbs to create an easy-to-cook novel food product, thereby effectively utilizing jackfruit bulbs thus reducing post-harvest losses. Furthermore, the objectives of the present study were (i) to examine the impact of A. heterophyllus and Trachyspermum ammi dipping treatments on sensory quality (ii) to determine the impact of pre-cook time, rehydration, and freezing on cooking time, and (iii) to analyze the proximate composition and antioxidant activity for the frozen-non-dipped jackfruit bulb treatment, which has the highest level of sensory acceptability. 2 Material and Methods 2.1 Raw materials and chemical ingredients Jackfruit bulbs, Artocarpus heterophyllus and Trachyspermum ammi leaves were harvested from the Piliyandala area (6°48′31.8"N 79°57′10.1"E) in Sri Lanka. Chemical reagents chloroform, methanol, concentrated sulfuric acid, boric acid, C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 169 hydrochloric acid, Kjeldahl catalyst tablets, Kjeldahl indicator, Sodium Hydroxide, Phenol, Standard D Glucose, Phenolphthalein indicator were of the analytical grade. 2.2 Collecting of raw materials and initial processing Jackfruit A. heterophyllus and T. ammi leaves harvested from the Piliyandala area in Sri Lanka were washed well using clean, running water. Jackfruit was cut and jackfruit bulbs were separated. Bulbs were stored in an airtight container and taken to the Food Science and Technology laboratory at the University of Sri Jayewardenepura, Sri Lanka. Jackfruit bulbs were cut into pieces (4.5 cm ± 0.5 cm length, 0.5 cm ± 0.3 cm width in size) and were stored at 4 °C temperature for further use. 2.3 Experimental design A two-factor factorial design was used to develop four sample formulations statically (Table 1). The variables freezing (-18 °C for 12 h) and dipping (T. ammi hot water extract) were used as factors. Table 1. Formulation of jackfruit bulbs for the two-factor factorial design. Sample No. Description 01 Non-frozen, non-dipped sample (Control sample) 02 Frozen, non-dipped sample 03 Non-frozen dipped sample 04 Frozen, dipped sample 2.4 Selection of the best dipping treatment Preparation of hot water extracts Hot water extracts of T. ammi leaves and A. heterophyllus leaves were prepared according to Fernando et al. 1991. In a shaking water bath, 200 g of each leaf material was placed in a beaker with 1000 ml of distilled and shaken for 3 hours at 100 °C until the final volume was reduced to 200 ml. Dipping treatment of jackfruit pieces To formulate three solutions with different concentrations, A. heterophyllus hot water extracts were diluted with distilled water by dilution factors of 1/10, 2/10, and 4/10. Similar series of solutions were prepared for T. ammi leaves extract using the same dilution factors mentioned above. C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 170 In each of the solutions prepared, 100 g of jackfruit bulb pieces were dipped for about 30 mins and were drained well. Then the drained jackfruit bulb pieces were dried in a dehydrator at 60 °C for 12 h. Optimization of dipping treatment Three sensory evaluation tests with 30 semi-trained panellists were used to select the best dipping treatment and concentration. The first sensory test was performed to determine which of the three concentrations of A. heterophyllus leaves solution-dipped jackfruit pieces provided the best sensory experience. The second sensory test was performed to determine the best sensory treatment among the three concentrations of T. ammi leaves solution-dipped jackfruit pieces. The selected concentration of A. heterophyllus leaves and T. ammi leaves dipped jackfruit bulb samples was used for the third sensory test to finalize the dipping treatment for the subsequent product development process. 2.5 Analysis of the effect of pre-cooking time, frozen operation, and rehydration for the cooking time To check whether the freezing, rehydration, and precooking processes affect the cooking time of the dehydrated jackfruit pieces, 15 ± 3 g samples were precooked at one-minute intervals for up to 15 minutes. Pre-cooked samples were dried in a dehydrator for 12 h at 60 °C. To demonstrate the effect of the freezing operation on the cooking time of jackfruit bulbs, another 15 samples of 15 g ± 3 g of jackfruit pieces were pre-cooked from 1 min to 15 min separately at the one-minute interval and were frozen at -18 °C for 12 h. Frozen samples were thawed for 15 mins and dried in a dehydrator for 12 h at 60 °C. Each dehydrated sample was divided into two sets. The first group was boiled in 250 ml of distilled water (100 °C) until the desired softness was obtained. The second group was prepared after soaking the jackfruit pieces in distilled water for 10 min and boiling (100 °C) them in 250ml of distilled water until they reached the desired softness. The samples were tested for softness by pressing them between the fingers and thumb (Sethi et al. 2014). 2.6 Final sensory evaluation Using a five-point hedonic scale rating with 30 semi-trained panelists, the final sensory evaluation test was conducted for four samples created using a two-factor factorial design. Before serving the samples for sensory analysis, they were rehydrated for 10 minutes in distilled water and boiled for 2 minutes at 100 °C to achieve the desired cooking quality. Data analysis was carried out using SPSS statistical software version 24.0, and the sample with the best sensory acceptability was identified by using the Friedman test. C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 171 2.7 Proximate composition analysis The AOAC (Association of Analytical Communities) official method 2000 was used to determine the moisture, ash, and crude protein content. The fat content was analyzed according to (Sanchez-Machado et al. 2004) with slight modifications. Initially, 2:1 chloroform: methanol solution was used to extract lipids included in the samples. Then, 2 g of the sample (already dried, grounded) was weighed into a centrifuge tube. Under the fume hood, 14 ml of the initially prepared solution mixture was added into the centrifuge tube and the centrifuge tube was closed. Tubes were vortexed for 2 min in a vortex mixer. Then the content of the tube was filtered through Whatman No. 41 paper. The residue was re-extracted by using 5 ml of the solvent mixture and vortexed for 30 s. Then the extract was filtered through Whatman No. 41 paper. The filtrates were allowed to dry under the fume hood. When drying was completed, the final residue was measured and taken as the total lipid content of the sample. 2.8 Analysis of total carbohydrate content Total carbohydrate content was measured by the Dubois method (Dubois et al. 1956) with slight modifications. Initially, a beaker was placed on an analytical balance and approximately 100 mg of grounded jackfruit bulb sample powder was transferred into the beaker. Then, 50 ml of 2 M HCl solution was added to the beaker. The mixture was boiled at 100 °C for about 2 h in a water bath. After that beaker was taken out from the hot water bath and neutralized with 50 ml of 2 M NaOH. Then the mixture was filtered by using Whatman filter paper. A test tube was filled with 0.5 ml of filtrate and 0.5 ml of 20% phenol. Afterwards, 2.5 ml of Conc. H2SO4 acid was added rapidly. Then the mixtures of solutions were kept at room temperature for 30 min. The absorbance was measured at 490 nm by using a UV Mini Spectrophotometer. Blank solutions were prepared by using distilled water without jackfruit bulb samples. The amount of sugar in the sample was found with the help of the D-Glucose reference curve. The same procedure used to prepare the D-Glucose standard curve was used to test D-Glucose solutions at concentrations of 1, 0.5, 0.25, 0.125, 0.0625, 0.03125, and 0.015625 mg/ml. Triplicate solutions were used to minimize the errors in the results. 2.9 Analysis of the mineral content (AAS method) Sample preparation for metal analysis using the Atomic Absorption Spectrometer was done as per guidelines provided in the AOAC official method (AOAC 2000). 2.10 Determination of titratable acidity for Jackfruit bulbs The titratable acidity (TA) was determined according to Jagadeesh et al. 2007 with some modifications. Accordingly, 5 g of sample was measured using an analytical C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 172 balance and transferred to a vortex tube. Then 100 ml of distilled water was added to the tube and the tube was vortexed for 5 min. After that, the mixture was filtered through Whatman 41 filter paper and 10 ml of the filtered sample was transferred into a conical flask. As an indicator 4 drops of phenolphthalein were added. The mixture was titrated against 0.1 N NaOH until the pink colour endpoint was reached, and TA% was calculated as follows: TA% = Normality of NaOH ∗ Volume of NaOH ∗ 192.124 3 ∗ Weight of the sample 2.11 Determination of antioxidant properties of jackfruit bulbs The dried jackfruit bulb sample was mixed with methanol at 1:40 (g/ml). The sample mixture was allowed to stand at room temperature for 6 h in a shaker and filtered through Whatman 41 filter paper. The above mixture was used for the phytochemical composition analysis. DPPH radical scavenging activity The free radical activity of the jackfruit bulb sample was measured by DPPH following the method of (Gunathilake and Ranaweera 2016) with some modifications. Hence, 6.309 mg DPPH was dissolved in 100 ml of methanol solution. Next, 2 ml of DPPH methanol solution and 2 ml of the diluted solution were transferred into a test tube by using a micro pipet. The solutions were mixed for 1 min by using a vortex mixer. Afterwards, the mixture was kept in a dark place for 30 min and the absorbance was measured at 517 nm. Absorbance was calculated by using the following equitation. % of inhibition = (A control – A sample) 𝐴 𝑐𝑜𝑛𝑡𝑟𝑜𝑙 ∗ 100 where A control equals to absorbance of the pure DPPH methanol solution. Total phenolic content Total phenolic content was measured according to the Folin – Ciocalteu reagent assay method described by Lim et al. 2002 with some modifications. 2.5 ml of Folin – Ciocalteu reagent was mixed with 25 ml of distilled water. The final solution was diluted up to 10 folds and allowed to stand at room temperature for 5 min. Then l ml of methanol extracted sample and 5 ml of Folin – Ciocalteu reagent was added to a test tube. The solutions were allowed to stand for 10 min at room temperature. Then, 4 ml of 7.5% sodium carbonate solution was added and the mixture was mixed thoroughly. The solutions were kept for 30 min in a dark place at room temperature. Absorbance was measured at 765 nm. The standard curve of Gallic acid was used to compare the absorbance reading. Nine different concentrations (10, 20, 30, 40, 50, 60, 70, 80, and 90 mg/l) of Gallic acid solutions were made from 1000 mg/l stock solution. The C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 173 standard curve was constructed from regression analysis using the software MINITAB (R17). TPC was expressed as Gallic acid equivalent in mg/l of jackfruit bulb extract. 2.12 Color values for easy-to-cook jackfruit bulb pieces L*, a*, and b* values of dehydrated jackfruit bulb samples were measured by using a chronometer (Lovibond® LC100). L* reflects brightness ranging from black to white, a* denotes green to red values, and b* represents blue to yellow values. Colour values were taken as replicates (n=3) on different areas of the sample. 2.13 Data analysis The collected data were analyzed using Minitab 17 statistical software with a 95% confidence interval using One-way ANOVA. The Friedman test was used to analyze the sensory evaluation data at a 95% confidence interval using SPSS software. 3 Results and Discussion In the present study, a new product formulation was developed using a two-factor factorial design. As factors, freezing and dipping variables were used. Hot water extracts of A. heterophyllus and T. ammi leaves were used as dipping variables. A sensory test range was carried out to determine the best dipping treatment and concentration. Hot water extract from the leaves of A. heterophyllus was occupied because of its antioxidant properties, (Loizzo et al. 2010) whereas hot water extract from the leaves of T. ammi was used because it acts as a digestive stimulant by promoting the enzyme reactions that are responsible for bile secretion, digestion, or both. (Prakash et al. 2009) The jackfruit bulb pieces were precooked before dehydrating because it takes considerably more time for the developed product to achieve the desired cooking quality without precooking. The cooking time evaluation test was conducted to determine the pre-cooked time. The biochemical analysis was performed on the sample that was perceived as the most acceptable sensory sample. 3.1 Sensory evaluation for optimization of dipping treatment of Jackfruit bulb Figure 1 illustrates the radar charts used to get an insight into the best sensory quality sample, from the two basic dipping treatments using A. heterophyllus and T. ammi leaves extracts applied to jackfruit bulbs. According to Figure 1, the sample code-100, i.e., jackfruit bulb pieces dipped in 1/10 dilution factor of A. heterophyllus leaves hot water extract, and the sample Code-500, i.e., jackfruit bulb pieces dipped in 2/10 dilution factor of T. ammi leaves hot water extract was selected from the dilution factor C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 174 series based on the results of sensory evaluation tests. The jackfruit bulb pieces dipped in a 2/10 dilution factor of T. ammi leaves hot water extract was the best sensory quality sample in terms of appearance, texture, odour, taste, and overall acceptability, according to the results of the sensory evaluation tests conducted for the above-selected samples (code 100 and code 500). Fig 1. Optimization of the sensory treatments in jackfruit bulbs. (Note: The codes 100, 200, and 300 represent 1/10, 2/10 and 4/10 dilution factors of hot water extract of A. heterophyllus leaves, respectively. Similarly, 400, 500, and 600 represent 1/10, 2/10 and 4/10 dilution factors of hot water extract of T. ammi leaves, respectively.) 3.2 Evaluation of cooking time Fig 2. The effect of cooking time on rehydration, freezing, and pre-cooked time C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 175 According to Figure 2, with the optimization of the pre-cooking time of jackfruit bulb pieces, the frozen treatment has reduced the cooking time of the processed jackfruit bulbs. According to the results, 6 min pre-cooking, and 10 min rehydration was selected to reduce the final cooking time of the developed sample. According to Kuna A et al. (2019), the frozen operation reduced the cooking time significantly in the red gram dhal. When the pre-cooked time increased, the cooking time was reduced accordingly. According to Ghadge et al. (2008), the pre-cooking and freezing operation reduced the cooking time of the instant whole legume. 3.3 Final sensory evaluation Fig 3. Radar chart for the sensory evaluation of the final processed jackfruit bulb samples. (The codes 103, 203, 303 and 403 represent non-frozen and non-dipped samples, frozen and non-dipped samples, non-frozen and dipped samples, and frozen and dipped samples respectively). According to the radar chart (Figure 3), the sample containing frozen jackfruit bulbs, without T. ammi leaves hot water extract was the best sensory quality sample concerning the appearance, texture, odour, taste and overall acceptability. 3.4 Proximate composition The proximate composition of the best sensory-acceptable sample (the frozen jackfruit sample without T. ammi leaves hot water extract) is given in Table 2. Moisture content Opkala (2010) reported that 5 mins steamed blanched, 0.1% sodium sulfate treated, 55 °C dried jackfruit bulb flour contains 15.19 ± 0.01 % moisture content. Similarly, Yi et al. (2016) reported the influence of pre-drying treatments on the physicochemical C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 176 and organoleptic properties of explosion puff dried jackfruit chips. According to a study at 65 °C hot air-dried jackfruit bulb pieces contained 6.13 ± 0.12 % moisture content. The results of the current study showed 8.08 ± 0.28 % moisture content at 60 °C and which is less than the moisture content of the dried jackfruit bulbs at 55 °C and greater than the dried jackfruit bulbs at 65 °C. Table 2: Proximate composition of the jackfruit sample with the best sensory quality. Variable Value Moisture 8.08 ± 0.28 % Ash 0.88 ± 0.01% Total Fat 0.31 ± 0.03% Crude Protein 3.93 ± 0.06% Total Carbohydrate 81.09 ± 0.54% [Data presented as mean ± S.D. (n = 3) Ash content Goswami et al. (2011) stated that the biochemical parameters of fresh jackfruit bulbs changed according to the growing area and the ash content of fresh jackfruit bulbs can be ranged from 1.11 to 0.70%. The current study demonstrated 0.88 ± 0.01% ash content which is comparable to Goswami et al. (2011). Fat content Opkala (2010) reported that 5 mins of steamed blanched, 0.1 % sodium sulfate treated, 55 °C dried jackfruit bulb flour contains 0.20 ± 0.04 % fat content. However, according to the variety, growing region (Goswami et al. 2011), and maturity stage (Maheswari and Valsan 2020), the biochemical parameters of jackfruit can vary. Ranasinghe et al. (2019) reported that the fat content of young jackfruit can vary between 0.1 and 0.6 % while the fat content of ripened jackfruit can vary between 0.1 and 0.4 %. The present study reported 0.31 ± 0.03 % fat content and it was in the range of the above studies. Crude protein content Maheswari and Valsan (2020) stated that the crude protein content of jackfruit can vary from 1.61 ± 0.02 % to 4.36 ± 0.06 % depending on the maturity stage of the jackfruit bulbs. The current study reported 3.93 ± 0.06 % of crude protein content and it complies with the above range reported in the previous study. 3.5 Mineral content analysis Maheswari and Valsan (2020) further reported 44.67 ± 0.50 % of Calcium to be present in raw mature jackfruit bulbs while Ranasinghe et al. (2019) reported 2.0 - 41.0 % of Sodium content to be available in raw jackfruit bulbs. The mineral composition of the C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 177 best sensory-acceptable sample with respective to Na, Ca, Mg, K, and P is given in Table 3. Table 3: Mineral content of the jackfruit sample with the best sensory quality. Mineral Type Na Ca Mg K P Concentration (mg/100g) 8.47 ± 0.04 43.88 ± 0.25 61.49 ± 0.47 709.65 ± 0.46 48.76 ± 0.21 [ Data presented as mean ± S.D. (n = 3) ] 3.6 Titratable acidity Titratable acidity of jackfruit sample with the best sensory acceptability, i.e. frozen without dipping in T. ammi leaves extract was 0.29 ± 0.01 % (mean ± SD; n = 3). Yi et al. (2016) reported 0.30 ± 0.02 % titratable acidity in dehydrated jackfruit bulbs at 65 °C. Yi, Wang et al. (2016) reported 0.38 ± 0.04 % titratable acidity for freeze-dried jackfruit bulb pieces. Results of the current study were much lower compared to those. According to the (Opkala 2010) study, 0.81 ± 0.28 % titratable acidity was reported in jackfruit bulb flour made out of 5 min steamed blanched, 0.1 % sodium sulfate treated and 55 °C dried in a conventional hot-air drier. The variations may be due to the variety, growing condition and maturity stage of the jackfruit. 3.7 Antioxidant properties of easy-to-cook jackfruit bulb DPPH (1-1-diphenyl 1-2-picrylhydrazyl) radical scavenging activity assay Jagtap et al. (2010) reported that radical scavenging activity for the ethanolic extract of raw jackfruit bulb concentration ranged from 1, 2, 3, 4, and 5 mg/ml was in between 55% and 65%. The obtained value in this study (38.43 ± 0.12%) was less than the previously reported values, and it may be due to heating of the bulbs at 100 °C for 6 mins and dehydration at 60 °C. Total Phenolic Content Yi, Zhou et al. (2016) stated that the total phenolic content of hot air-dried jackfruit bulb was 0.84 ± 0.06 (mg GAE / g). According to (Yi, Zhou et al. 2016) the total phenolic content of the fresh jackfruit bulb was 1.8 ± 0.1 (mg GAE / g) and after freeze- drying, it was decreased up to 1.6 ± 0.1 mg GAE / g. According to the (Jagtap et al. 2010) study, the total phenolic content of the fresh jackfruit bulbs was 0.46 ± 0.014 mg GAE/ g. The value obtained for phenolic content in the present study (0.38 ± 0.04%) is lower than the above-reported values. This may be due to the pre-cooking of the bulbs for 6 mins at 100 °C, frozen treatment, thawing for 15 mins and drying treatment carried out at 60 °C. C. Akmeemana et al. Process optimization for easy-to-cook jackfruit bulbs Ruhuna Journal of Science Vol 13 (2): 167-180, December 2022 178 3.8 Colour values of easy-to-cook jackfruit bulb Table 4 indicates the colourimetric values of the best sensory-acceptable jackfruit bulb sample. Table 4. Colour values of best sensory quality sample. L* a* b* c* 79.40 ± 0.61 1.87 ± 0.35 25.43 ± 1.33 25.50 ± 1.35 * Data presented as mean ± S.D. (n = 3) The L* value is a measure of the lightness of the product colour. It ranges from 100 to 0. a* and b* values indicate the redness/greenness and yellowness/blueness respectively (Swami et al. 2016). 4 Conclusions Four different formulations were developed by jackfruit bulbs following a two-factor factorial design, dipping or non-dipping and frozen or non-frozen as the variables. Among the three sensory tests conducted, the best sensory quality sample concerning appearance, texture, odour, taste and overall acceptability was the 2/10 dilution factor of hot water extract of T. ammi leaves dipped jackfruit bulb pieces sample. The results revealed that the frozen operation, pre-cooked time and rehydration significantly reduce the cooking time of jackfruit bulbs. To reduce the final cooking time of the developed product, 6 minutes of pre-cooking and 10 minutes of rehydration were selected based on the results of the cooking time evaluation. Final sensory evaluation indicates frozen non-dipped sample as the most sensory-acceptable sample. Furthermore, the final processed product possesses a good nutritional profile concerning the ash, fat, crude protein, carbohydrate, mineral content, DPPH and total phenolic acid content. 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