Optimizing the Formulation and Processing Conditions of Gulab Jamun: A Statistical Design

Abstract

Increasing demand for the traditional dairy products presents immense opportunity for the organized dairies in India to modernize and scale-up their production. The objective of the present study was to use L₂₅ orthogonal array to predict the quality of gulab jamun -an indigenous product, and optimizing the processing conditions. Gulab jamun was prepared by frying balls made by kneading a heat-dessicated intermediary milk product (khoa), refined wheat flour (maida), baking powder and water, in butter oil (ghee) and dipping in sugar syrup. Optimization of the formulation was carried out in terms of khoa:maida ratio (70:30–90:10), level of baking powder (0.2–1% of the khoa:maida mixture), frying time (7–11 min), sugar syrup concentration (50–70° Brix), temperature of sugar syrup (30–70°C) and soaking time (2–10 h). These parameters were evaluated in terms of weight change and volume expansion on frying and soaking, and porosity. Instrumental texture profile analysis (TPA) of gulab jamun at different stages (raw, fried, and soaked) was measured via TAXT2i Texture Analyzer. The sensory acceptability of soaked gulab jamun was evaluated by a panel of judges using 9-point hedonic scale and statistically analyzed. The overall acceptability of the gulab jamun sample had an edge over the market sample.

Keywords:

• Gulab jamun
• Volume expansion
• Porosity
• Texture
• Sensory acceptability
• Hedonic scale

INTRODUCTION

Among the milk-based sweets, gulab jamun occupies a prominent place as a popular delicacy throughout Indian subcontinent. It may be round or cylindrical in shape, is golden to dark brown in color, has a soft to firm body, and smooth texture. Traditionally, gulab jamun is prepared from a mixture of khoa (a heat-desiccated intermediary milk product), refined wheat flour (maida) and baking powder. Khoa is a base for preparation of many Indian indigenous sweets. It refers to partially dehydrated whole milk product prepared by the continuous heating of milk in a frying pan, while also constantly stirring-cum-scraping by using steel or wooden spoon till it reaches a semi-solid consistency. The semi-solid mass is transformed to solid consistency known as khoa, having typically a fat, moisture, and total solid content of 20–23%, 37–44%, and 56–63% respectively, and is used as an ingredient for the preparation of gulab jamun. The mixture is kneaded to get uniform consistency of dough by addition of appropriate quantity of water, and then rolled into small round or cylindrical shape. Finally the round or cylindrically shaped balls were deep-fried in ghee until golden brown followed by dipping into a sugar solution of 62.5°Brix for few hours before serving either hot or cold.

Technology for industrial production of gulab jamun has been developed using an assembly line system and is in operation commercially. Canned gulab jamun is mostly exported. Currently, gulab jamun is made commercially.[1] The formulation for gulab jamun is still empirical, and varies widely, both at the domestic and industrial level. In one study, gulab jamun prepared from 80% khoa and 20% wheat flour showed excellent consumer acceptability. Increasing the flour to 30% hardened the texture, while 10% flour softened it to an extent that was not received well by the consumers. Deep fat frying of gulab jamun at 130°C for 15 min followed by soaking of the fried gulab jamun in sugar syrup of 50° Brix at 70°C for 4 h is reported to give excellent sensory quality.[2] The effect of formulation on chemical composition of gulab jamun in terms of protein, fat and total carbohydrate content has been determined.[3]

Refined wheat flour or maida is generally used as a binder for preparation of gulab jamun. The type of binder and content play an important role in deciding the composition, rheology and sensory attributes of gulab jamun. In another study, semolina (suji) was used as a binder. Each lot of khoa was kneaded with simultaneous mixing with 10% suji either as such or presoaked (suji was mixed with thrice the quantity of skim milk and allowed to soak overnight at refrigerator temperature). The presoaked suji was slightly better as a binder as compared to dry suji, which manifested itself as improved textural attributes of gulab jamun. Examination of a cross section of gulab jamun prepared with pre-soaked suji revealed greater porosity as compared to the product prepared with dry suji. Significantly higher sugar absorption from the sugar syrup during soaking stage was observed in gulab jamun prepared using pre-soaked suji as compared to dry suji.[4] Addition of trisodium citrate addition (0.5 and 0.8% w/w of milk solids) is also reported to give better softness and springiness to gulab jamun, as a consequence of which the product also had higher sugar absorption.[5] gulab jamun from khoa prepared from unhomogenized milk showed an acceptability as good as that from unhomogenized milk, suggesting homogenization to be inconsequential for textural quality of gulab jamun.[6] Interrelationships among Instron textural parameters, composition and microstructure of khoa and gulab jamun made from buffalo milk have also been investigated. While Instron hardness, gumminess, and chewiness were positively correlated with moisture and fat contents, it was positively correlated with protein, lactose, added carbohydrates, ash and calcium contents for both khoa and gulab jamun.[7] Transmission electron microscopy (TEM) of khoa showed complete loss of natural entities of protein and lactose, but no change in fat moieties. Microstructure of gulab jamun revealed a loose protein matrix with carded-cotton appearance, while the starch particles had either thread or petal-like structure, interspersed loosely in the protein matrix.[7] Instron textural values of khoa and gulab jamun revealed higher hardness, gumminess and chewiness of khoa than those of gulab jamun, in contrast to higher springiness in gulab jamun[7]. Formulations for ready-to-use gulab jamun mix based on defatted skim milk powder (SMP) and roller dried whole milk powder (WMP) have also been developed.[8] Soy flour enriched gulab jamun premixes and ready-to-serve soy flour gulab jamun prepared from admixture of soy flour (partially deoiled or full fat) and milk solids (khoa, whole milk powder, or skim milk powder) in different proportions are also reported.[9]

The quality of gulab jamun depends upon a number of factors such as type of khoa, ingredients, manufacturing technique, type of binder and pretreatments used, and use of other additives among many others. The present work deals with optimization of various process parameters such as khoa to maida ratio, baking powder level, frying time, sugar syrup concentration, temperature of sugar syrup and duration of soaking time to manufacture gulab jamun using L₂₅ orthogonal array. Effect of these parameters was evaluated in terms of weight change, volume expansion, textural properties and sensory characteristics.

MATERIALS AND METHODS

Materials

Commercial dairy cow milk (Gokul Satvik, Kolhapur, Maharashtra) was used for the preparation of khoa. Sugar and refined wheat flour (maida) (Sahakari Bhandar Brand, Mumbai, Maharashtra; sieve size of 80 mesh, and moisture content 13.6% as determined by drying at 102°C to constant weight) were procured locally. Baking powder (Blue Bird brand, Mumbai, Maharashtra; composition: edible maize starch, sodium bicarbonate, sodium aluminium sulphate), and butter oil (ghee, Dynamix brand, Baramati, Maharashtra) used for the work were procured locally.

Preparation of Gulab jamun

Milk used for preparation of khoa was analysed for moisture content by oven drying at 102°C, fat content by Gerber's method, and solids-non-fat. Khoa was prepared by heating milk. Moisture content of this khoa was determined by drying a pre-weighed sample in khoa in hot air oven at 102°C until constant weight. To the known quantity of khoa, maida and baking powder were added as per the proportion for the different experimental batches. To the above mixture, calculated amount of water was added to achieve 40% moisture content in the resulting dough. Balls were made by hand, each weighing 7 g. They were fried in ghee at 135–140°C for specific duration of time. Temperature was monitored using a K-Type thermocouple (model, DIT 720, Libatherm, Mumbai, India), having a temperature range of −50 to 1200^oC. These balls were soaked in sugar syrup of specific concentration at a particular temperature for specific duration of time. Ratio of gulab jamun to sugar solution was kept constant as 1:5 (weight of raw gulab jamun: volume of sugar syrup).

Optimization of the Formulation for Gulab jamun

Khoa % (rest being maida), baking powder level, frying time, sugar syrup concentration, temperature of sugar syrup and duration of soaking were selected as variables. L₂₅ orthogonal matrix was developed using Minitab 13.3 software (Table 1). The levels of variables were fixed by conducting experiments with one-factor at a time approach, so that in each case gulab jamun is well formed. The values for overall acceptability of gulab jamun were fed to Minitab 13.30 software and the response was analyzed.

Table 1 L₂₅ orthogonal design of experiments for optimization of gulab jamun preparation

No.	A	B	C	D	E	F	A	B	C	D	E	F	OA ^a
1	1	1	1	1	1	1	70	0.2	7	50	30	2	2.58
2	1	2	2	2	2	2	70	0.4	8	55	40	4	3.67
3	1	3	3	3	3	3	70	0.6	9	60	50	6	5.37
4	1	4	4	4	4	4	70	0.8	10	65	60	8	6.42
5	1	5	5	5	5	5	70	1	11	70	70	10	5.25
6	2	1	2	3	4	5	75	0.2	8	60	60	10	3.67
7	2	2	3	4	5	1	75	0.4	9	65	70	2	3.92
8	2	3	4	5	1	2	75	0.6	10	70	30	4	2.67
9	2	4	5	1	2	3	75	0.8	11	50	40	6	6.42
10	2	5	1	2	3	4	75	1	7	55	50	8	5.83
11	3	1	3	5	2	4	80	0.2	9	70	40	8	4.17
12	3	2	4	1	3	5	80	0.4	10	50	50	10	6.47
13	3	3	5	2	4	1	80	0.6	11	55	60	2	6.58
14	3	4	1	3	5	2	80	0.8	7	60	70	4	5.25
15	3	5	2	4	1	3	80	1	8	65	30	6	5
16	4	1	4	2	5	3	85	0.2	10	55	70	6	5.25
17	4	2	5	3	1	4	85	0.4	11	60	30	8	5.5
18	4	3	1	4	2	5	85	0.6	7	65	40	10	6.58
19	4	4	2	5	3	1	85	0.8	8	70	50	2	5.67
20	4	5	3	1	4	2	85	1	9	50	60	4	7.03
21	5	1	5	4	3	2	90	0.2	11	65	50	4	6.08
22	5	2	1	5	4	3	90	0.4	7	70	60	6	6.75
23	5	3	2	1	5	4	90	0.6	8	50	70	8	6.17
24	5	4	3	2	1	5	90	0.8	9	55	30	10	7
25	5	5	4	3	2	1	90	1	10	60	40	2	6.17
a: Results are mean ± S.D. of 6 determinations. A: khoa%; B: baking powder %; C: frying time in minutes; D: Sugar syrup concentration in °Brix; E: temperature of sugar syrup; F: duration of soaking in hours; and OA: overall acceptability score.

For optimization, Khoa:maida ratio was varied as 70:30, 75:25, 80:20, 85:15 and 90:10; baking powder was added at 0.2%, 0.4%, 0.6%, 0.8% and 1% of the khoa + maida mixture; frying time was varied as 7, 8, 9, 10, and 11 min; sugar syrup of different concentrations as 50, 55, 60, 65, and 70° Brix was used for soaking the gulab jamun; temperature of sugar syrup was varied as 30, 40, 50, 60, and 70°C; Gulab jamun were soaked for different duration as 2, 4, 6, 8, and 10 h.

Analysis of the Gulab jamun

Determination of change in weight on frying and soaking

Weight of gulab jamun, at various stages (raw, after frying and soaking) were recorded and percent weight loss on frying and percent weight gain on soaking were calculated. The weight change after frying was due to the combined, but opposite effects of moisture loss and oil uptake during frying of gulab jamun balls. The weight increase after soaking determines the sugar syrup uptake of the fried gulab jamun balls.

Determination of volume expansion on frying and soaking

Diameter (d), of gulab jamun was determined using vernier caliper (A. V. Enterprises, Thane, Maharashtra) after wiping with a tissue paper. Observations were recorded on each sample at four points without disturbing the shape of the ball. The percent volume expansion of gulab jamun on frying and soaking were calculated by measuring the volume, V, at different stages of processing.

(1)

Determination of porosity

Diameter of fried gulab jamun was measured using a vernier caliper. Volume of gulab jamun (V₁) was then calculated using following formula:

(3)

where ‘d’ is the diameter of fried gulab jamun. This fried gulab jamun was then macerated in mortar and pestle. Ground material was added to known volume of water and increase in volume was recorded as V₂. The percentage porosity was calculated as:

(4)

Evaluation of Texture

Stable Micro System TAXT2i Texture Analyzer (Mode TPA2) was used for texture profile analysis (TPA) of gulab jamun at different stages. A P36R cylindrical probe with 5mm/s of pre-test, test and post-test speeds; and 50% compression was taken for TPA analysis. TPA is a “two-bite” test, which includes the first and second compression cycles. The first and second compression cycles indicate the force vs. time data during the first and second compression of the product by the instrument probe. Representative graphs for texture of raw, fried and soaked gulab jamun are as shown in Figures 1, 2, and 3, respectively. The parameters recorded were fracturability, hardness, cohesiveness, adhesiveness, springiness, gumminess, and chewiness.

Figure 1 Representative graph of texture of raw gulab jamun.

Figure 2 Representative graph of texture of fried gulab jamun.

Figure 3 Representative graph of texture of soaked gulab jamun.

Sensory Evaluation

The sensory acceptability of the soaked gulab jamun was evaluated in terms of appearance, color, flavor, taste, and overall acceptability by a six-member panel on 9-point hedonic scale. The panel members were all graduate students of food science and technology at University of Mumbai, and familiar with the product since their childhood. The analysis was carried out under natural daylight during the warm sunny days of Mumbai during the months of October to Januray. The panel members evaluated the product by taking one gulab jamun each, and rinsing the mouth with water after each evaluation. Allowance for given for fatigue experienced by the members, and the analysis was continued as soon as the panel members were ready for further evaluation. The time for rest was generally about 30 min after 10 – 15 evaluations.

Statistical Interpretation of Data

A full factorial design results in a large number of experiments. To reduce the number of experiments to a practical level, only a small set from all possibilities is selected. Taguchi constructs a special set of arrays called orthogonal arrays, which stipulate the way of conducting minimum number of experiments and give the full information of all the parameters that affect the performance Taguchi orthogonal arrays were selected to optimize formulation and process parameters that affect gulab jamun quality such as khoa:maida ratio, baking powder level, frying time, sugar syrup concentration, temperature of sugar syrup, and soaking time. While there are many standard orthogonal arrays available, each of the arrays is meant for a specific number of independent design variables and levels. The additive design of the Taguchi design implies that the individual or main effects of the independent variables on the performance parameter are separable. Under this assumption, the effect of each factor can be linear, quadratic or may have higher order, but the model assumes absence of any cross product interaction among the individual factors.

RESULTS AND DISCUSSION

The moisture, fat and solids-non-fat content of the milk used for preparing khoa were 86.8, 4.6 and 8.6%, respectively. The yield of khoa prepared from the milk was 20% (w/v). The levels of variables for optimization of gulab jamun making were selected on the basis of one-factor-at-a-time approach. The parameters optimized using the L₂₅ orthogonal approach were khoa:maida ratio, baking powder levels, frying time, sugar syrup concentration, temperature of sugar syrup and duration of soaking (Table 1). The weight changes on frying and subsequent soaking of the gulab jamun, as well as the porosity of the fried gulab jamun are shown in Table 2. The representative plots for texture at different stages are presented in Figures 1, 2, and 3, respectively, while the actual values of the textural attributes are recoded in Tables 3, 4, and 5, respectively. Table 6 represents the sensory scores of the gulab jamun prepared in the different batches. It can be seen that batches 1, 6, 11, 16, and 21 which had maida levels of 30, 25, 20, 20, 15, and 10%, respectively, showed a better sensory score at 10% maida than at 30% maida. The sensory scores for the other batches were in between. These batches had a fixed level of baking powder at 0.2%. (Table 6). The porosity and % volume expansion after frying also correlated with the level of maida in the formulation. The % volume expansion increased with a decease in the content of maida in the formulation. It ranged from 42.68% for formulation containing 30% maida to 93.24% in the formulation containing 10% maida. Simlarly, the porosity of the fried gulab jamun also increased from 21.48% to 39.54%, when the maida in the formulation decreased from 30 to 10% (Table 2). These differences in porosity and % volume expansion affected the texture of the fried (Table 4) and soaked gulab jamun (Table 5) more than the raw version (Table 3). For instance, in batches 1 and 21, which had maida at 30 and 10% level, a hardness value of 1401 and 1336 g for the soaked gulab jamun was observed. The hardness of the fried versions of same batches were 1718 and 1384 g, respectively. It is difficult to interpret the values of other batches in this regard, since the level of baking powder in these are different and it has an important bearing on the texture of both fried and soaked gulab jamun. The texture profiles of raw, fried, and soaked gulab jamun, as shown in Figures 1, 2, and 3, respectively, indicate hardness to be the most prominent variable, and is seen as the peak in the relevant graphs.

Table 2  % Weight change, % volume expansion on frying and soaking of gulab jamuns, and % porosity ^a

Batch no.	% Weight loss on frying	% Weight gain on soaking	% Volume expansion on frying	% Volume expansion on soaking	% Porosity
1	10.55 ± 0.40	49.26 ± 4.43	42.68 ± 0.80	−1.11 ± 2.90	21.48 ± 2.78
2	9.93 ± 0.39	65.5 ± 1.3	54.20 ± 2.00	16.07 ± 3.56	28.33 ± 1.06
3	7.14 ± 0.27	118.51 ± 2.56	43.99 ± 5.19	36.20 ± 1.22	33.00 ± 4.05
4	11.03 ± 0.25	127.95 ± 10.84	57.99 ± 8.03	33.89 ± 2.03	34.25 ± 4.56
5	9.08 ± 0.39	163.01 ± 8.05	65.44 ± 4.40	37.14 ± 0.93	39.60 ± 2.24
6	9.01 ± 0.22	105.75 ± 1.82	49.37 ± 4.28	35.35 ± 2.06	29.46 ± 0.40
7	15.51 ± 0.13	57.68 ± 12.15	45.90 ± 0.78	−4.17 ± 2.79	35.98 ± 3.20
8	10.77 ± 0.65	48.72 ± 2.45	52.77 ± 0.90	4.32 ± 1.76	32.44 ± 3.82
9	13.88 ± 0.40	157.04 ± 7.57	59.64 ± 0.66	41.20 ± 0.59	33.10 ± 3.69
10	5.58 ± 0.20	138.35 ± 5.26	66.61 ± 1.93	37.50 ± 3.49	43.73 ± 5.50
11	11.14 ± 0.15	99.52 ± 0.67	60.25 ± 2.51	22.48 ± 4.54	36.12 ± 2.20
12	13.10 ± 0.09	130.02 ± 6.78	55.57 ± 1.00	38.42 ± 2.39	37.38 ± 1.24
13	11.39 ± 0.07	141.31 ± 14.15	77.12 ± 1.27	24.32 ± 3.33	32.35 ± 0.65
14	6.91 ± 0.41	141.85 ± 7.37	74.03 ± 1.71	30.05 ± 1.68	32.20 ± 1.25
15	9.75 ± 0.37	92.71 ± 3.36	59.26 ± 1.79	10.57 ± 1.58	38.78 ± 3.04
16	12.40 ± 0.23	126.16 ± 7.34	61.58 ± 6.42	34.79 ± 2.23	31.88 ± 3.44
17	10.19 ± 0.11	82.19 ± 3.54	60.25 ± 1.64	19.17 ± 1.20	35.72 ± 3.21
18	7.31 ± 0.20	117.77 ± 0.27	65.57 ± 1.76	17.49 ± 1.17	37.22 ± 0.90
19	6.49 ± 0.12	111.75 ± 7.88	86.27 ± 0.91	14.42 ± 0.59	41.37 ± 1.01
20	8.19 ± 0.22	157.85 ± 1.81	63.27 ± 2.99	35.74 ± 2.68	33.73 ± 3.57
21	10.11 ± 0.32	107.72 ± 10.13	93.24 ± 3.57	10.58 ± 3.47	39.54 ± 2.38
22	8.84 ± 0.68	117.01 ± 8.09	66.42 ± 1.30	20.30 ± 0.67	44.65 ± 6.01
23	6.43 ± 0.22	129.94 ± 0.27	75.68 ± 2.87	13.30 ± 1.76	41.04 ± 0.80
24	4.97 ± 0.15	112.29 ± 4.98	67.97 ± 2.42	22.10 ± 0.21	36.56 ± 1.91
25	7.36 ± 0.89	106.41 ± 1.76	67.43 ± 4.00	12.67 ± 1.11	40.23 ± 1.84
Pr ^b	13.93 ± 0.45	142.55 ± 4.35	74.87 ± 2.17	10.74 ± 3.58	48.54 ± 3.19
a: Results are mean ± S.D. of 3 determinations; and, b: Pr means the combination of variables predicted by Minitab 13.

Table 3 Texture of raw gulab jamun ^a

Batch no.	Hardness (g)	Cohesiveness	Adhesiveness (g-s)	Adhesive force (g)	Springiness (s)	Gumminess (g)	Chewiness (g-s)
1	447.20 ± 12.92	0.34 ± 0.01	−9.34 ± 2.16	−38.40 ± 4.22	0.60 ± 0.03	151.20 ± 8.17	90.56 ± 7.34
2	438.40 ± 23.79	0.35 ± 0.02	−10.05 ± 4.50	−38.50 ± 10.51	0.62 ± 0.03	154.49 ± 12.95	95.31 ± 6.97
3	285.73 ± 22.40	0.38 ± 0.01	−11.75 ± 2.60	−33.50 ± 2.81	0.67 ± 0.03	109.41 ± 8.00	72.76 ± 3.75
4	408.63 ± 31.45	0.40 ± 0.01	−11.23 ± 1.02	−39.53 ± 3.15	0.68 ± 0.03	163.41 ± 9.02	110.08 ± 4.23
5	386.37 ± 22.70	0.38 ± 0.02	−10.34 ± 3.80	−37.50 ± 6.59	0.61 ± 0.03	145.06 ± 9.04	89.28 ± 7.72
6	325.27 ± 8.15	0.39 ± 0.01	−12.57 ± 0.62	−37.57 ± 0.79	0.65 ± 0.01	125.51 ± 1.28	81.37 ± 1.11
7	300.33 ± 11.83	0.39 ± 0.01	−13.12 ± 0.26	−36.60 ± 2.98	0.67 ± 0.03	116.97 ± 4.17	78.21 ± 4.95
8	384.37 ± 18.64	0.36 ± 0.01	−8.86 ± 1.68	−35.67 ± 3.31	0.62 ± 0.02	139.30 ± 4.24	86.20 ± 5.07
9	326.93 ± 37.25	0.37 ± 0.00	−14.19 ± 2.34	−42.20 ± 5.88	0.60 ± 0.05	120.18 ± 13.63	72.09 ± 6.41
10	315.10 ± 15.27	0.34 ± 0.01	−10.87 ± 1.70	−37.83 ± 3.43	0.59 ± 0.02	108.10 ± 4.91	63.19 ± 2.77
11	333.47 ± 14.68	0.38 ± 0.01	−12.12 ± 0.35	−37.60 ± 0.43	0.64 ± 0.01	127.09 ± 7.10	81.62 ± 5.90
12	288.13 ± 24.49	0.37 ± 0.00	−10.91 ± 2.10	−33.03 ± 3.46	0.65 ± 0.01	107.22 ± 10.22	69.32 ± 6.40
13	280.33 ± 9.83	0.38 ± 0.00	−12.24 ± 0.23	−34.10 ± 0.08	0.66 ± 0.01	105.69 ± 2.84	69.59 ± 2.20
14	322.70 ± 11.34	0.37 ± 0.00	−13.60 ± 1.02	−38.77 ± 2.86	0.64 ± 0.02	120.64 ± 3.33	77.15 ± 0.55
15	342.83 ± 32.89	0.37 ± 0.01	−15.16 ± 1.78	−43.47 ± 3.33	0.62 ± 0.01	125.39 ± 14.15	78.52 ± 10.03
16	408.33 ± 36.75	0.38 ± 0.01	−12.20 ± 2.15	−41.67 ± 2.67	0.65 ± 0.01	153.35 ± 9.00	100.35 ± 4.18
17	432.30 ± 13.44	0.37 ± 0.01	−10.40 ± 0.94	−39.77 ± 1.57	0.62 ± 0.01	161.03 ± 8.98	100.17 ± 6.78
18	374.00 ± 5.43	0.38 ± 0.01	−11.92 ± 0.83	−39.07 ± 0.39	0.63 ± 0.01	142.92 ± 1.92	89.78 ± 0.76
19	369.73 ± 27.10	0.35 ± 0.01	−10.26 ± 0.60	−39.50 ± 3.31	0.59 ± 0.05	128.05 ± 6.44	76.03 ± 5.31
20	362.17 ± 5.23	0.33 ± 0.00	−10.76 ± 0.89	−40.77 ± 1.51	0.57 ± 0.02	119.29 ± 3.17	67.63 ± 3.55
21	335.67 ± 24.71	0.36 ± 0.00	−12.06 ± 0.22	−36.20 ± 2.43	0.64 ± 0.02	120.10 ± 8.42	76.11 ± 3.50
22	326.53 ± 5.44	0.35 ± 0.01	−11.13 ± 0.76	−36.63 ± 1.46	0.60 ± 0.02	114.41 ± 4.75	68.73 ± 4.98
23	365.10 ± 13.97	0.33 ± 0.02	−9.56 ± 2.02	−33.00 ± 1.81	0.58 ± 0.01	122.12 ± 4.87	70.48 ± 4.27
24	348.13 ± 0.85	0.35 ± 0.00	−11.92 ± 1.21	−39.87 ± 0.94	0.58 ± 0.01	122.32 ± 0.69	70.53 ± 1.15
25	411.43 ± 28.33	0.32 ± 0.00	−8.54 ± 0.23	−37.17 ± 1.69	0.54 ± 0.01	131.42 ± 9.78	71.36 ± 5.10
Pr ^b	355.50 ± 25.99	0.33 ± 0.00	−8.77 ± 2.08	−35.43 ± 1.11	0.62 ± 0.03	111.92 ± 9.45	69.91 ± 6.35
a: results are mean ± S.D. of 3 determinations; and b: Pr means the combination of variables predicted by Minitab 13.

Table 4 Texture of fried gulab jamun ^a

Batch no.	Fracturability (g)	Hardness (g)	Cohesiveness	Springiness (s)	Gumminess (g)	Chewiness (g-s)
1	Na	1718.77 ± 109.41	0.28 ± 0.02	1.82 ± 0.06	484.23 ± 10.13	881.42 ± 36.93
2	Na	1452.57 ± 129.17	0.28 ± 0.02	1.79 ± 0.01	410.15 ± 33.56	734.68 ± 59.65
3	Na	1470.27 ± 178.39	0.30 ± 0.02	1.81 ± 0.03	443.31 ± 46.91	802.66 ± 95.36
4	Na	1788.43 ± 118.87	0.31 ± 0.01	1.92 ± 0.01	554.04 ± 25.96	1061.73 ± 46.24
5	Na	1424.80 ± 53.47	0.31 ± 0.02	1.95 ± 0.01	443.93 ± 23.43	864.86 ± 44.49
6	Na	1432.57 ± 144.60	0.28 ± 0.00	1.82± 0.02	403.20 ± 37.58	733.27 ± 62.25
7	Na	1326.60 ± 129.02	0.29 ± 0.00	1.84 ± 0.02	378.48 ± 31.82	694.98 ± 57.19
8	Na	2375.83 ± 39.87	0.27 ± 0.02	1.66 ± 0.01	633.01 ± 47.40	1051.87 ± 78.97
9	Na	1061.73 ± 46.20	0.31 ± 0.01	1.87 ± 0.01	325.56 ± 14.49	608.93 ± 30.05
10	Na	982.93 ± 120.93	0.25 ± 0.01	1.84 ± 0.01	249.30 ± 37.63	458.73 ± 72.37
11	712.53 ± 241.31	935.53 ± 71.40	0.36 ± 0.01	1.93 ± 0.01	340.94 ± 38.42	656.46 ± 70.41
12	Na	1073.37 ± 220.94	0.41 ± 0.17	1.78 ± 0.03	409.22 ± 92.60	728.15 ± 161.49
13	Na	917.10 ± 32.10	0.30 ± 0.01	1.88 ± 0.01	275.34 ± 3.73	518.57 ± 8.07
14	Na	713.80 ± 173.68	0.34 ± 0.01	1.94 ± 0.03	245.77 ± 70.17	477.08 ± 140.17
15	Na	907.80 ± 145.39	0.26 ± 0.02	1.79 ± 0.02	231.56 ± 31.89	415.43 ± 31.38
16	Na	2082.37 ± 310.60	0.39 ± 0.01	1.89 ± 0.01	821.16 ± 107.71	1554.78 ± 193.93
17	1013.90 ± 193.98	1479.20 ± 102.27	0.31 ± 0.02	1.96 ± 0.03	459.68 ± 42.57	902.95 ± 97.20
18	658.57 ± 147.03	832.37 ± 45.61	0.33 ± 0.01	1.97 ± 0.01	277.27 ± 10.74	545.67 ± 18.86
19	Na	908.10 ± 53.13	0.28 ± 0.01	1.76 ± 0.01	253.77 ± 11.11	445.84 ± 20.87
20	Na	1082.07 ± 53.44	0.27 ± 0.00	1.90 ± 0.03	290.43 ± 12.61	551.93 ± 15.31
21	1250.63 ± 246.12	1384.00 ± 357.23	0.31 ± 0.01	2.00 ± 0.03	435.61 ± 126.49	868.33 ± 240.66
22	544.17 ± 51.40	789.27 ± 62.72	0.26 ± 0.04	1.87 ± 0.06	202.75 ± 35.95	380.74 ± 78.34
23	488.37 ± 56.38	652.83 ± 28.01	0.28 ± 0.02	1.84 ± 0.09	181.85 ± 17.28	335.48 ± 46.71
24	Na	897.97 ± 54.52	0.28 ± 0.01	1.79 ± 0.05	253.62 ± 21.00	453.80 ± 48.28
25	727.73 ± 280.23	999.67 ± 34.13	0.20 ± 0.01	1.61 ± 0.03	198.96 ± 11.29	320.56 ± 17.66
Pr ^b	Na	840.00 ± 27.38	0.31 ± 0.03	1.90 ± 0.02	257.69 ± 27.49	489.07 ± 55.36
a: results are mean ± S.D. of 3 determinations; b: Pr means the combination of variables predicted by Minitab 13.3; and Na : Not available.

Table 5 Texture of soaked gulab jamun ^a

Batch no.	Hardness (g)	Cohesiveness	Adhesiveness (g-s)	Adhesive force (g)	Springiness (s)	Gumminess (g)	Chewiness (g-s)
1	1401.03 ± 60.67	0.77 ± 0.01	−1.32 ± 1.06	−14.63 ± 7.08	1.29 ± 0.06	1079.98 ± 40.02	1397.034 ± 111.73
2	1424.77 ± 48.80	0.62 ± 0.02	−9.79 ± 4.07	−32.97 ± 2.56	1.47 ± 0.06	944.06 ± 44.78	1381.89 ± 13.84
3	1656.77 ± 153.06	0.47 ± 0.03	−11.72 ± 6.05	−23.23 ± 12.24	1.95 ± 0.08	778.25 ± 62.31	1523.04 ± 168.21
4	2135.10 ± 335.43	0.48 ± 0.03	−15.17 ± 2.39	−32.63 ± 10.03	1.92 ± 0.04	1031.36 ±220.92	1988.60 ± 467.98
5	1552.97 ± 138.96	0.36 ± 0.01	−35.83 ± 9.43	−41.13 ± 4.71	2.07 ± 0.08	555.25 ± 72.29	1152.52 ± 190.56
6	2269.10 ± 236.55	0.52 ± 0.03	−15.85 ± 6.68	−41.87 ± 16.86	1.82 ± 0.24	1181.70 ±182.86	2114.22 ± 181.45
7	1227.33 ± 67.85	0.74 ± 0.03	−2.40 ± 2.05	−19.23 ± 9.67	1.11 ± 0.04	915.41 ± 80.37	1014.86 ± 82.49
8	1841.30 ± 23.41	0.61 ± 0.02	−4.30 ± 1.49	−28.07 ± 4.30	1.56 ± 0.03	1117.55 ± 48.72	1743.10 ± 111.90
9	1007.80 ± 40.49	0.57 ± 0.06	−4.01 ± 0.62	−17.30 ± 1.13	1.83 ± 0.11	576.37 ± 80.24	1054.11 ± 155.46
10	1215.10 ± 98.05	0.42 ± 0.06	−25.43±10.70	−29.73 ± 12.45	1.95 ± 0.21	520.27 ± 115.01	993.34 ± 130.59
11	1592.30 ± 75.72	0.65 ± 0.02	−3.87 ± 2.29	−23.30 ± 9.06	1.56 ± 0.05	1031.84 ± 42.44	1610.74 ± 72.57
12	1518.77 ± 164.48	0.56 ± 0.05	−12.57 ± 2.07	−29.00 ± 12.45	1.78 ± 0.09	854.37 ± 111.52	1513.67 ± 161.80
13	1112.97 ± 129.12	0.44 ± 0.05	−5.51 ± 2.19	−12.70 ± 8.14	1.98 ± 0.15	490.91 ± 112.14	956.34 ± 144.13
14	805.23 ± 138.96	0.36 ± 0.04	−19.37 ± 4.63	−19.67 ± 3.21	1.94 ± 0.15	299.52 ± 85.43	570.02 ± 121.12
15	1232.13 ± 45.91	0.61 ± 0.00	−20.85 ± 4.94	−37.33 ± 6.55	1.62 ± 0.02	746.96 ± 33.81	1212.09 ± 46.54
16	582.13 ± 61.17	0.41 ± 0.01	−12.49 ± 1.84	−15.60 ± 4.38	1.70 ± 0.10	240.32 ± 33.98	412.02 ± 81.72
17	1306.47 ± 59.13	0.68 ± 0.01	−8.76 ± 5.83	−26.37 ± 13.52	1.60 ± 0.03	887.79 ± 41.54	1421.41 ± 87.40
18	1222.77 ± 81.48	0.56 ± .003	−28.33 ± 2.88	−60.13 ± 3.09	1.53 ± 0.04	689.07 ± 35.47	1059.26 ± 83.21
19	1536.53 ± 135.31	0.42 ± 0.02	−7.22 ± 2.31	−22.40 ± 5.23	1.96 ± 0.02	650.27 ± 84.54	1272.03 ± 164.11
20	566.10 ± 22.38	0.40 ± 0.02	−5.65 ± 1.47	−12.13 ± 1.79	1.89 ± 0.15	226.91 ± 16.78	426.75 ± 4.27
21	1336.30 ± 130.14	0.47 ± 0.07	−3.35 ± 4.39	−13.97 ± 11.64	1.84 ± 0.12	643.25 ± 157.17	1164.06 ± 209.05
22	1010.67 ± 40.19	0.39 ± 0.03	−6.72 ± 4.06	−18.90 ± 4.43	1.75 ± 0.06	398.22 ± 44.42	697.02 ± 68.67
23	804.10 ± 17.38	0.44 ± 0.02	−20.10 ± 7.08	−28.10 ± 3.97	1.52 ± 0.09	356.34 ± 6.53	541.16 ± 26.57
24	794.97 ± 62.69	0.55 ± 0.01	−7.68 ± 0.92	−18.80 ± 2.14	1.73 ± 0.03	439.13 ± 24.60	759.32 ± 50.35
25	533.50 ± 17.31	0.41 ± 0.03	−1.79 ± 14.42	−8.37 ± 1.06	1.79 ± 0.09	216.92 ± 20.42	386.90 ± 16.69
m1 ^b	560.57 ± 48.48	0.36 ±0.03	−20.06 ± 3.24	−18.37 ± 3.73	1.80 ± 0.16	200.45 ± 7.88	362.98 ± 45.86
m2 ^b	810.97 ± 180.84	0.29 ± 0.02	−65.34 ±14.09	−73.50 ± 21.78	1.35 ± 0.13	228.53 ± 39.50	306.51 ± 42.84
m3 ^b	767.83 ± 114.64	0.35 ± 0.05	−36.18 ±19.36	−30.80 ± 1.98	1.90 ± 0.22	267.48 ± 33.28	504.00 ± 51.10
Pr ^c	410.33 ± 20.92	0.44 ± 0.10	−4.78 ± 0.78	−8.70 ± 1.85	1.76 ± 0.09	183.17 ± 48.35	320.47 ± 80.23
a: results are mean ± S.D. of 3 determinations; b: m1, m2, m3 represent market samples of gulabjamun; and c: Pr means the combination of variables predicted by Minitab 13.3.

Table 6 Sensory evaluation of gulab jamun ^a

Batch no.	Appearance	Colour	Taste	Flavour	Firmness	Crumbliness	Sponginess	Gumminess	Chewiness	Juiciness	Overall acceptability
1	3.83 ± 1.57	3.33 ± 1.11	3.50 ± 1.38	3.50 ± 1.38	3.50 ± 1.61	3.17 ± 1.34	3.33 ± 1.89	3.75 ± 1.82	3.17 ± 1.07	1.83 ± 1.07	2.58 ± 1.37
2	5.67 ± 2.13	5.33 ± 1.97	4.50 ± 1.71	4.50 ± 1.50	5.33 ± 2.43	4.83 ± 2.54	4.67 ± 2.36	5.83 ± 1.77	5.33 ± 1.25	2.50 ± 1.12	3.67 ± 1.49
3	6.47 ± 1.25	6.33 ± 1.25	5.97 ± 2.05	5.50 ± 2.14	5.42 ± 1.79	5.08 ± 2.01	5.67 ± 1.80	5.83 ± 0.90	5.33 ± 1.25	4.33 ± 1.89	5.37 ± 2.00
4	7.00 ± 0.82	6.75 ± 0.80	6.83 ± 0.69	6.58 ± 1.02	6.20 ± 1.10	6.33 ± 0.47	6.17 ± 1.21	6.87 ± 0.65	6.58 ± 0.93	6.25 ± 1.41	6.42 ± 1.24
5	6.67 ± 0.94	7.25 ± 0.69	5.83 ± 1.07	5.83± 0.69	5.33 ± 1.80	5.00 ± 1.53	5.17 ± 1.57	5.92 ± 0.61	5.25 ± 0.80	4.50 ± 1.61	5.25 ± 1.07
6	5.92 ± 1.48	6.50 ± 0.76	4.42 ± 1.48	3.83 ± 1.86	3.83 ± 1.67	3.33 ± 1.49	3.33 ± 1.37	4.17 ± 1.57	3.50 ± 1.26	3.50 ± 1.71	3.67 ± 1.46
7	5.83 ± 1.34	6.17 ± 1.07	4.83 ± 1.86	4.42 ± 1.79	4.17 ± 1.86	4.33 ± 1.80	4.50 ± 2.36	5.67 ± 0.47	4.50 ± 1.26	3.67 ± 1.70	3.92 ± 1.17
8	5.00 ± 1.91	5.00 ± 1.53	3.50 ± 1.80	4.17 ± 1.46	3.33 ± 1.60	3.00 ± 1.63	3.83 ± 1.77	3.00 ± 1.00	2.17 ± 1.21	2.08 ± 1.10	2.67 ± 1.28
9	7.17 ± 0.69	7.33 ± 0.75	6.17 ± 0.90	6.17 ± 0.69	6.75 ± 0.56	6.83 ± 0.69	6.50 ± 1.12	6.08 ± 1.24	5.50 ± 1.61	5.67 ± 1.25	6.42 ± 1.02
10	5.17 ± 1.67	3.17 ± 1.67	6.17 ± 1.34	5.17 ± 1.07	6.00 ± 1.91	6.58 ± 1.10	6.00 ± 0.58	6.50 ± 1.71	6.17 ± 1.77	6.08 ± 1.43	5.83 ± 1.37
11	6.67 ± 0.94	6.67 ± 0.94	4.83 ± 1.34	4.83 ± 1.46	5.33 ± 1.60	4.50 ± 1.26	4.83 ± 1.57	4.67 ± 1.25	4.00 ± 1.15	4.00 ± 0.82	4.17 ± 1.25
12	6.70 ± 1.15	6.58 ± 1.02	5.75 ± 1.46	5.67 ± 1.97	7.33 ± 0.75	7.08 ± 0.84	7.00 ± 0.82	6.00 ± 1.73	6.17 ± 1.67	7.17 ± 1.03	6.47 ± 1.55
13	7.17 ± 0.90	7.25 ± 0.69	6.25 ± 1.35	6.25 ± 0.99	6.67 ± 0.47	5.83 ± 1.07	6.17 ± 1.07	6.67 ± 0.47	6.50 ± 0.50	6.00 ± 1.15	6.58 ± 0.84
14	6.08 ± 1.48	6.17 ± 0.69	5.00 ± 1.63	5.08 ± 2.05	5.33 ± 1.25	5.67 ± 1.25	6.08 ± 0.73	6.17 ± 0.37	5.83 ± 0.69	4.67 ± 1.37	5.25 ± 1.28
15	6.50 ± 0.76	4.67 ± 1.37	5.17 ± 1.07	5.17 ± 0.69	6.08 ± 1.02	5.67 ± 1.46	6.08 ± 1.24	5.58 ± 1.02	5.00 ± 1.29	4.33 ± 1.70	5.00 ± 1.26
16	7.03 ± 0.82	7.17 ± 0.69	5.83 ± 1.34	5.00 ± 1.73	5.67 ± 1.60	5.00 ± 1.53	5.33 ± 1.11	5.50 ± 0.96	5.00 ± 1.41	4.67 ± 1.60	5.25 ± 1.73
17	6.83 ± 1.03	6.92 ± 0.73	5.08 ± 1.02	5.33 ± 0.75	6.17 ± 0.85	6.17 ± 1.07	6.33 ± 1.46	5.42 ± 1.17	4.67 ± 1.60	5.00 ± 1.41	5.50 ± 0.91
18	6.83 ± 0.90	6.67 ± 0.94	6.33 ± 0.94	5.83 ± 0.90	6.33 ± 0.47	6.83 ± 0.69	6.42 ± 0.45	5.83 ± 1.07	6.33 ± 1.11	6.33 ± 1.11	6.58 ± 1.02
19	5.50 ± 1.61	5.42 ± 1.64	5.92 ± 1.17	6.33 ± 1.11	5.67 ± 1.25	6.50 ± 0.50	5.75 ± 1.28	6.08 ± 0.73	5.25 ± 1.41	6.42 ± 1.88	5.67 ± 1.37
20	7.08 ± 0.84	6.75 ± 1.41	7.42 ± 0.45	7.17 ± 0.69	6.67 ± 1.25	6.67 ± 1.25	6.83 ± 1.34	7.00 ± 1.15	7.17 ± 0.90	7.17 ± 1.07	7.03 ± 1.16
21	6.25 ± 1.41	6.08 ± 1.59	6.53 ± 1.64	5.83 ± 1.67	6.03 ± 1.00	5.67 ± 0.94	5.17 ± 0.90	5.25 ± 1.28	5.00 ± 1.53	5.50 ± 1.71	6.08 ± 0.84
22	6.92 ± 0.93	6.83 ± 0.90	7.00 ± 0.58	6.33 ± 0.94	6.33 ± 0.94	5.83 ± 1.07	6.33 ± 1.25	6.63 ± 0.45	5.33 ± 1.49	6.75 ± 0.99	6.75 ± 0.56
23	7.00 ± 1.00	6.67 ± 1.37	6.83 ± 0.90	5.83 ± 0.69	6.17 ± 1.67	5.83 ± 1.95	6.00 ± 1.83	6.00 ± 1.63	6.17 ± 1.34	7.00 ± 1.15	6.17 ± 1.07
24	7.42 ± 0.73	7.42 ± 0.45	6.92 ± 0.61	5.83 ± 0.90	7.00 ± 0.76	6.58 ± 1.02	6.92 ± 1.17	6.25 ± 1.22	6.42 ± 1.37	7.42 ± 0.84	7.00 ± 0.87
25	6.83 ± 0.69	7.08 ± 0.61	6.00 ± 1.83	6.17 ± 1.46	6.17 ± 1.46	6.00 ± 1.00	4.83 ± 0.69	5.67 ± 1.37	5.33 ± 0.94	6.50 ± 0.96	6.17 ± 1.11
m1 ^b	6.83 ± 0.69	7.08 ± 1.02	6.67 ± 0.94	7.17 ± 0.69	6.33 ± 1.37	5.50 ± 1.38	5.92 ± 0.73	6.50 ± 1.12	6.67 ± 0.94	5.92 ± 1.17	6.33 ± 0.75
m2 ^b	7.25 ± 1.15	6.25 ± 1.28	6.08 ± 1.37	5.33 ± 1.37	5.83 ± 1.21	5.92 ± 0.73	6.42 ± 1.59	6.83 ± 1.07	7.17 ± 0.37	6.75 ± 0.90	6.58 ± 1.17
m3 ^b	6.75 ± 0.69	7.00 ± 0.82	6.42 ± 0.84	6.42 ± 0.61	6.08 ± 1.43	6.08 ± 0.84	6.50 ± 0.76	6.92 ± 0.45	6.42 ± 0.84	7.00 ± 0.82	6.25 ± 0.69
Pr ^c	7.42 ± 1.24	7.42 ± 1.24	6.58 ± 1.10	6.33 ± 1.11	7.17 ± 0.94	6.92 ± 1.54	6.58 ± 1.59	7.08 ± 0.93	7.25 ± 0.80	7.97 ± 0.52	7.52 ± 0.61
a: results are mean ± S.D. of 6 determinations; b: m1, m2, m3 represent market samples of gulabjamun; and c: Pr means the combination of variables predicted by Minitab 13.3.

The maximum weight loss was 15.51% after frying (batch no. 7), while it was 13.93% in optimized batch. The highest weight gain on soaking was 163.01% for batch 5 and that for optimized batch was 142.55%. Highest volume expansion on frying was 93.24% in case of batch no. 21, probably due to higher proportion of khoa in the formulation. Batches with lower khoa proportion showed lower values of % volume expansion on frying probably due to more binding of moisture by the gluten in the maida. Highest volume expansion on soaking was observed to be 41.20% in batch 9, while for the optimized batch it was 10.74%. In batch 1 and 7, shrinkage was observed in some gulab jamun, which could not be explained. Batch 22 showed highest porosity of 44.65% for fried gulab jamun, while optimized batch showed 48.54% porosity.

Batches containing higher proportion of maida showed higher values of hardness in soaked gulab jamuns, owing to higher proportion of gluten. Higher gumminess and chewiness were also obtained in batches with higher proportion of maida (Table 6) as per sensory analysis. This could be due to stickiness imparted by gluten present therein. The sensory score for batches 1, 6, 11, 16, and 21 containing 30, 25, 20, 15, and 10% maida were 2.58, 3.67, 4.17, 5.25, and 6.08, respectively. This correlates inversely with the gluten content, which would increase with an increase in the content of maida used in the formulation. Gluten is well known to have viscoelastic property, which in turn contributes to chewiness and gumminess in wheat based products such as bread. The sensory values for gumminess for gulab jamun containing 30, 25, and 20% maida were 3.75, 5.92, and 6.50, while for chewiness they were 3.17, 5.25, and 6.17, respectively. These values did not change much, when the maida was lower at 15 and 10%. This could be due to the effect of soaking, which may have counteracted the effect of gluten in the maida. The extent of starch gelatinization could also be a contributing factor. However, their individual contribution towards these textural attributes need further investigation. The values for chewiness (as obtained from texture analyzer) of soaked gulab jamun prepared from 30 and 10% maida was 1080 and 1164 g-s (Table 5), with intermediate levels showing both higher and lower values. This is attributed to the differences in the level of baking powder used in the batches. Hence, the differences in the texture of raw and soaked gulab jamum may be due to the gelatinization of starch in the maida during frying, and also due to the uptake of sugar syrup during soaking. A detailed investigation on the extent of starch gelatinization, sugar uptake, and texture could be undertaken.

Table 7 represents the response table for means (larger is better) and signal to noise ratio obtained with L₂₅ orthogonal array. The last two rows indicate the delta values and ranks for the system. Rank and delta values help to assess which factors have the greatest effect on the response characteristic of interest. Delta measures the size of effect by taking the difference between the highest and lowest characteristic average for a factor. A higher delta value indicates greater effect of the component. Rank orders the factors from the greatest effect (based on delta values) to the least effect on the response characteristic. The order in which the variables selected in the current study influence the quality of gulab jamun in terms of overall acceptability can be ranked (based on mean) as khoa:maida ratio > baking powder level > temperature of sugar syrup > frying time > sugar syrup concentration > soaking time. This indicates khoa:maida ratio had a major effect while soaking time had the least effect on the overall acceptability of gulab jamun.

Table 7 Response table for mean and S/N ratios

Levels	A		B		C		D		E		F
	Mean	S/N	Mean	S/N	Mean	S/N	Mean	S/N	Mean	S/N	Mean	S/N
1	4.66	12.95	4.29	12.25	5.40	14.18	5.73	14.67	4.55	12.49	4.98	13.47
2	4.44	12.48	5.26	14.15	4.78	13.34	5.67	14.85	5.40	14.40	4.94	13.37
3	5.49	14.67	5.47	14.33	5.50	14.54	5.13	14.034	5.88	15.38	5.76	15.14
4	6.01	15.52	6.15	15.74	5.40	14.22	5.60	14.81	6.03	15.32	5.62	14.90
5	6.43	16.15	5.86	15.29	5.97	15.48	4.90	13.40	5.17	14.18	5.73	14.89
Delta	1.99	3.48	1.86	3.48	1.19	2.14	0.83	1.46	1.48	2.89	0.82	1.77
Rank	1	1	2	2	4	4	5	6	3	3	6	5

Minitab provides main effects plots by plotting the characteristic average for each variable level. Main effect plots show how each variable affects the response characteristic. These averages are same as those displayed in response in Table 7. A line connects the points for each factor. When the line is horizontal, i.e., parallel to x-axis, there is no main effect present. Each level of the variable affects the characteristic in the same way and the characteristic average is the same across all variable levels. When the line is not horizontal, i.e., not parallel to x-axis, then there is a main effect present. Different levels of variable affect the characteristic differently. The greater the difference in the vertical position of the plotted points, the greater is the magnitude of the main effect. In case of all the variables, the line does not go parallel to x-axis in both mean and S/N ratio plots, indicating that each of the variables has significant effect on the quality of gulab jamun.

Response table can also be used to predict the optimum levels of each variable used in the study. To obtain the optimized levels, the predictive analysis based on statistical calculations is shown in Table 7. The optimized levels of the parameters are khoa:maida ratio 90:10, baking powder 0.8%, frying time 11 min, sugar syrup concentration 50° Brix, temperature of sugar syrup 60°C, and soaking time 6 h. To confirm these results, experiments were carried out using these parameters. A mean value of 7.52 was obtained for overall acceptability of gulab jamun as compared to 9.04 predicted using Minitab. The highest sensory score for overall acceptability of market sample of gulab jamun was observed to be 6.58, while for the gulab jamun with Minitab optimized parameters was 7.52.

CONCLUSIONS

The ingredient formulation and processing conditions undoubtedly affect the sensory characteristics of gulab jamun. Optimizing by orthogonal matrix showed a 90:10 khoa:maida ratio, 0.8% baking powder, frying time of 11 min, and soaking in 50°Brix sugar syrup, at 60°C for 6 h to give best overall acceptability to gulab jamun.