This research investigated the chemical analysis and sensory evaluation of low-calorie formulated pumpkin jams after storage for six months and the effects of the consumption of low-calorie jams on diabetic rats. Pumpkin jam with sucrose, fructose, stevia, and aspartame sweeteners and soybean was prepared and stored at 10°C for six months. Rats were divided into group 1 (negative control), group 2 (positive diabetic groups), and groups 3, 4, and 5 (diabetic groups treated with 10% sucrose, fructose, and stevia soybean jam, respectively). The results indicated that the contents of protein, fat, ash, and fibre were increased in the low-calorie formulated pumpkin jams. The highest sensory scores were recorded for sucrose and fructose soybean jams and then for stevia soybean jam, while the aspartame soybean jam showed significantly lower scores after storage for 3 and 6 months. Rat groups 4 and 5 showed significant decreases in the glucose level, and liver function enzymes activity showed significant increases in insulin and glycogen levels compared to group 2.
Jams are produced mainly from fruits and sugar. Sugar (sucrose) derived from sugar cane or sugar beets is added to jams to produce a sweet taste and inhibit microbial growth by binding the water in the jam. However, a high sugar intake is associated with high energy intake, which can increase the risks for diabetes, obesity, and cardiovascular disease. In 2011, the American Diabetes Association recommended monitoring carbohydrate consumption by carbohydrate counting, making better food choices, or experience-based estimation to allow glycaemic control of diabetes, and this has increased the demand for the production of low-calorie foods and thus increased the market share of such foods. Low-calorie jams are produced from low-calorie sweeteners and low-calorie raw materials [
Pumpkin (
Therefore, the objectives of this study were to determine the chemical and sensory properties of low-calorie formulated pumpkin jams containing soybean and examine the effect of the storage period on the sensory properties of jams. Moreover, the possible effects of the consumption of low-calorie jams on diabetic rats were investigated.
A total of 20 kg of pumpkin fruits (
Pumpkin fruits were washed, peeled, and cut into small cubes. Soybean powder was soaked in water for 6 hours. Five jam formulations were prepared to select the best proportion of sweetener, as shown in Table
Ingredients used for preparing the five formulations of pumpkin jams with different sweeteners.
Formula | Pumpkin (g) | Sucrose (g) | HFCS (g) | Aspartame (g) | Stevia (g) | Citric acid (g) | Sodium benzoate (g/kg) | Polydextrose (g) | Soybean soaked (g) |
---|---|---|---|---|---|---|---|---|---|
Ordinary jam | 1000 | 1000 | — | — | — | 3.5 | — | — | — |
Sucrose soybean jam | 950 | 1000 | — | — | — | 3.5 | — | — | 50 |
Fructose soybean jam | 950 | — | 625 | — | — | 2.5 | — | — | 50 |
Aspartame soybean jam | 950 | — | — | 20 | — | 7 | 0.8 | 150 | 50 |
Stevia soybean jam | 950 | — | — | — | 4 | 7 | 0.8 | 150 | 50 |
Pumpkin fruit cubes were boiled. Sieved soybean and polydextrose were then added along with the sucrose, high-fructose corn syrup, aspartame, or stevioside. The mixture was boiled until the desired concentration was reached. Citric acid and sodium benzoate were added, and the mixture was stirred for an additional 1 min. Formulated jams were transferred to sterile jars. The evaluations were conducted immediately after production and after 6 and 12 months of storage at 10°C.
Protein, fat, ash, fibre, moisture, and carbohydrate contents of the different jam formulations were estimated according to AOAC [
Jam samples (30 g) after 0, 3, and 6 months of storage were randomly served in plastic containers to 15 trained panellists. Responses were recorded using a hedonic scale from 1 to 10 points for different attributes including colour, sweetness, texture, flavour, and overall acceptance according to a previous procedure [
The rats were fed a standard diet prepared according to Reeves et al. [ Group 2: positive diabetic control group fed a standard diet Group 3: fed a standard diet with 10% sucrose soybean jam Group 4: fed a standard diet with 10% fructose soybean jam Group 5: fed a standard diet with 10% stevia soybean jam
The choice of these jam formulations was based on the results of the sensory evaluation study prior to storage. The daily food intake and weekly body weight of the rats were recorded. The feed efficiency ratio (FER) was calculated. After completion of the experimental period (6 weeks), rats were fasted overnight and sacrificed to obtain blood and liver, which were perfused with 50 to 100 mL of ice-cold 0.9% NaCl solution for biochemical analyses.
Serum glucose and insulin were estimated after the second, fourth, and sixth weeks. Serum alanine and aspartate aminotransferase (ALT and AST) enzymes activity, liver cholesterol, total lipids, and glycogen were estimated enzymatically according to Henry [
Data were subjected to ANOVA. The means were compared using Duncan’s multiple-range test with a level of significance of 0.05, and this analysis was complemented by the Kruskal–Wallis correlation method to analyse the correlations between parameters at significance levels of 0.05.
The data presented in Table
Chemical compositions of the different formulations of pumpkin jam (g/100 g).
Sample | Protein | Fat | Ash | Fibre | Moisture | Carbohydrate |
---|---|---|---|---|---|---|
Ordinary jam | 3.88 ± 0.33c | 0.04 ± 0.01c | 3.11 ± 0.12cd | 4.66 ± 0.52cd | 20.65 ± 1.11bc | 67.66 ± 7.17a |
Sucrose soybean jam | 19.18 ± 2.41ab | 1.03 ± 0.21b | 4.03 ± 0.28bc | 5.01 ± 0.41c | 20.71 ± 2.14bc | 50.04 ± 5.07b |
Fructose soybean jam | 20.08 ± 2.46a | 1.11 ± 0.11ab | 5.09 ± 0.15b | 6.21 ± 0.31b | 23.31 ± 2.17b | 44.20 ± 4.11ac |
Stevia soybean jam | 20.11 ± 2.65a | 1.15 ± 0.02a | 10.69 ± 1.14a | 18.87 ± 1.33a | 33.96 ± 3.80a | 16.22 ± 1.14d |
Aspartame soybean jam | 20.05 ± 2.63a | 1.17 ± 0.07a | 10.89 ± 1.12a | 18.81 ± 1.22a | 31.01 ± 3.71a | 16.07 ± 1.11d |
Mean ± SD values in the same column with different letters indicate the values differ significantly (
The results of the statistical evaluation of the sensory properties of the different jam formulations prepared using different sweeteners are shown in Table
Sensory attributes of samples of the 5 different formulations of pumpkin jams in a hedonic test immediately after production (zero storage time).
Sample | Colour | Sweetness | Texture | Flavour | Overall acceptability | % |
---|---|---|---|---|---|---|
10 | 10 | 10 | 10 | 10 | 100 | |
Ordinary jam | 9.66 ± 0.45a | 9.57 ± 0.35a | 9.13 ± 0.56a | 9.70 ± 0.55a | 9.50 ± 0.42a | 95.12 ± 8.43a |
Sucrose soybean jam | 9.03 ± 0.40a | 9.44 ± 0.43a | 9.10 ± 0.53a | 8.90 ± 0.41b | 8.95 ± 0.30ab | 90.84 ± 7.46b |
Fructose soybean jam | 9.11 ± 0.36a | 9.34 ± 0.44a | 8.80 ± 0.45b | 8.78 ± 0.43bc | 8.93 ± 0.33b | 89.92 ± 7.35bc |
Stevia soybean jam | 9.21 ± 0.35a | 8.75 ± 0.34b | 7.41 ± 0.31c | 7.63 ± 0.32d | 7.71 ± 0.27c | 81.42 ± 6.37c |
Aspartame soybean jam | 7.22 ± 0.23b | 6.20 ± 0.20c | 5.78 ± 0.11d | 5.81 ± 0.21e | 5.11 ± 0.13d | 60.24 ± 6.15d |
Mean ± SD values in the same column with different letters are significantly different (
The results of the sensory analysis for the different pumpkin jam formulations after storage for 3 and 6 months are shown in Table
Effect of storage time on the sensory attributes of different pumpkin jam formulations.
Storage (months) | Ordinary jam | Sucrose soybean jam | Fructose soybean jam | Stevia soybean jam | Aspartame soybean jam | |
---|---|---|---|---|---|---|
Colour | 0 | 9.66 ± 0.45a | 9.03 ± 0.40a | 9.11 ± 0.36a | 9.21 ± 0.35a | 7.22 ± 0.23b |
3 | 9.01 ± 0.53a | 8.96 ± 0.54b | 8.77 ± 0.53b | 6.35 ± 0.55c | 5.67 ± 0.22cd | |
6 | 8.88 ± 0.44a | 8.66 ± 0.55b | 8.55 ± 0.85b | 5.76 ± 0.33c | 4.77 ± 0.40cd | |
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Texture | 0 | 9.13 ± 0.56a | 9.10 ± 0.53a | 8.80 ± 0.45b | 7.41 ± 0.31c | 5.78 ± 0.11d |
3 | 9.03 ± 0.84a | 8.96 ± 0.61ab | 8.51 ± 0.64b | 6.99 ± 0.67c | 5.17 ± 0.43d | |
6 | 8.98 ± 0.45a | 8.70 ± 0.71ab | 8.21 ± 0.76b | 6.51 ± 0.44c | 4.90 ± 0.49d | |
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Flavour | 0 | 9.70 ± 0.55a | 8.90 ± 0.41b | 8.78 ± 0.43bc | 7.63 ± 0.32d | 5.81 ± 0.21e |
3 | 9.61 ± 0.91a | 8.75 ± 0.55ab | 8.60 ± 0.83ab | 7.13 ± 0.53c | 5.40 ± 0.44d | |
6 | 9.58 ± 0.81a | 8.67 ± 0.63ab | 8.51 ± 0.77b | 6.98 ± 0.45c | 4.60 ± 0.56d | |
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Sweetness | 0 | 9.57 ± 0.35a | 9.44 ± 0.43a | 9.34 ± 0.44a | 8.75 ± 0.34b | 6.20 ± 0.20c |
3 | 9.38 ± 0.44a | 9.21 ± 0.66a | 9.10 ± 0.93ab | 7.70 ± 0.70c | 5.55 ± 0.40d | |
6 | 9.20 ± 0.63a | 9.11 ± 0.86a | 9.03 ± 0.74ab | 6.41 ± 0.43c | 4.88 ± 0.53d | |
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Overall acceptability | 0 | 9.50 ± 0.42a | 8.95 ± 0.30a | 8.93 ± 0.33b | 7.71 ± 0.27c | 5.11 ± 0.13d |
3 | 9.41 ± 0.55a | 8.94 ± 0.76ab | 8.92 ± 0.74ab | 7.21 ± 0.44c | 5.01 ± 0.42d | |
6 | 9.40 ± 0.55a | 8.90 ± 0.70ab | 8.93 ± 0.66ab | 7.01 ± 0.56c | 4.33 ± 0.44d | |
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% | 0 | 95.12 ± 8.43a | 90.84 ± 7.46a | 89.92 ± 7.35bc | 81.42 ± 6.37c | 60.24 ± 6.15d |
3 | 92.88 ± 6.99a | 89.70 ± 6.45ab | 87.80 ± 8.17bc | 70.76 ± 5.9d | 53.60 ± 0.41e | |
6 | 92.08 ± 7.11a | 88.08 ± 6.77b | 86.46 ± 8.11bc | 65.34 ± 5.10d | 47.08 ± 4.05e |
Mean ± SD values in the same row with different letters are significantly different (
As expected (Table
Effect of the consumption of different jam formulations on the nutritional indicators of diabetic rats.
BWG (g) | FI (g) | FER | |
---|---|---|---|
Group 1 | 75.66 ± 3.22a | 17.88 ± 1.10a | 0.094 ± 0.004a |
Group 2 | 45.33 ± 2.14e | 16.77 ± 1.3ab | 0.060 ± 0.001d |
Group 3 | 55.66 ± 2.65cd | 17.55 ± 1.05a | 0.070 ± 0.002c |
Group 4 | 57.70 ± 2.88c | 18.11 ± 1.11a | 0.070 ± 0.002c |
Group 5 | 63.77 ± 2.93b | 17.80 ± 1.03a | 0.079 ± 0.003b |
Group 1: negative control group; group 2: positive diabetic control group fed a standard diet; group 3: fed a standard diet with 10% sucrose soybean jam; group 4: fed a standard diet with 10% fructose soybean jam; group 5: fed a standard diet with 10% stevia soybean jam; BWG: body weight gain; FI: food intake; FER: feed efficiency ratio. Mean ± SD values in each column with different letters (a, b, and c) are significantly different at
After the injection of streptozotocin, significant hyperglycaemia and lower insulin values were observed at the beginning of the experiment (zero storage time) compared to normal rats (group 1). Positive diabetic control rats (group 2) and rats consuming 10% of the sucrose and fructose soybean jams (groups 3 and 4) had higher levels of glucose and lower levels of insulin after the second, fourth, and sixth weeks compared to group 1. Rats consuming 10% stevia soybean jam (group 5) showed a small improvement in their glucose levels and normal insulin levels after six weeks. Rats consuming 10% low-calorie jam with a nutrient sweetener (fructose) and nonnutrient sweetener (stevia) soybean jam (groups 4 and 5) showed significantly lower levels of glucose and significantly higher levels of insulin compared to the levels of group 2 as illustrated in Table
Effect of the consumption of different jam formulations on the glucose and insulin levels of diabetic rats.
Adaptation | Initially | Second week | Fourth week | Sixth week | ||||||
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Glucose (mg/dl) | Insulin (ng/dl) | Glucose (mg/dl) | Insulin (ng/dl) | Glucose (mg/dl) | Insulin (ng/dl) | Glucose (mg/dl) | Insulin (ng/dl) | Glucose (mg/dl) | Insulin (ng/dl) | |
Group 1 | 93.41 ± 4.11a | 3.66 ± 0.23a | 92.66 ± 5.11b | 3.65 ± 0.34a | 93.70 ± 4.76d | 3.63 ± 0.40a | 95.09 ± 5.07e | 3.64 ± 0.35a | 97.67 ± 6.35e | 3.64 ± 0.35a |
Group 2 | 92.45 ± 3.96a | 3.59 ± 0.22a | 291.88 ± 27.25a | 1.91±0.18b | 296.77 ± 31.65a | 1.88 ± 0.20d | 301.76 ± 35.69a | 1.78 ± .19d | 319.66 ± 33.99a | 1.53 ± 0.27d |
Group 3 | 90.51 ± 3.11a | 3.48 ± 0.25a | 297.61 ± 26.03a | 1.85 ± 0.26b | 280.67 ± 29.24ab | 1.99 ± 0.21cd | 270.60±30.11ab | 2.05 ± 0.23c | 240.33 ± 25.70b | 2.25 ± 0.33c |
Group 4 | 91.33 ± 3.22a | 3.43 ± 0.24a | 295.11 ± 28.31a | 1.84 ± 0.22b | 255.61 ± 28.20b | 2.01 ± 0.30bc | 240.31 ± 29.66c | 2.19 ± 0.26bc | 199.66 ± 19.68c | 2.39 ± 0.42bc |
Group 5 | 92.49 ± 3.17a | 3.50 ± 0.33a | 294.35 ± 25.99a | 1.83 ± 0.23b | 189.66 ± 25.11c | 2.46 ± 0.34b | 143.60 ± 10.22d | 2.85 ± 0.28b | 125.55 ± 12.13d | 2.90 ± 0.54ab |
Group 1: negative control group; group 2: positive diabetic control group fed a standard diet; group 3: fed a standard diet with 10% sucrose soybean jam; group 4: fed a standard diet with 10% fructose soybean jam; group 5: fed a standard diet with 10% stevia soybean jam. Mean ± SD values in each column with different letters (a, b, and c) are significantly different at
The most obvious changes in diabetic rats (group 2) were higher values of serum aminotransferase (ALT and AST), liver cholesterol, and total lipids and lower levels of liver glycogen compared to group 1. Diabetic rats consuming different pumpkin jam formulations (groups 3, 4, and 5) showed significantly higher levels of ALT activity and AST activity and liver cholesterol and an insignificant difference in the total liver lipids and glycogen compared to group 1. However, these groups showed significantly lower ALT and AST activities, liver cholesterol, and total liver lipids and significantly higher levels of glycogen compared to group 2, as shown in Table
Effect of the consumption of different jam formulations on liver function of diabetic rats.
ALT (IU/L) | AST (IU/L) | Cholesterol (mg/100 g) | Total lipids (mg/100 g) | Glucogen (mg/100 g) | |
---|---|---|---|---|---|
Group 1 | 13.25 ± 1.03d | 15.20 ± 1.15d | 3.50 ± 0.13c | 33.67 ± 3.18bc | 6.22 ± 1.66a |
Group 2 | 27.50 ± 2.99a | 30.65 ± 3.18a | 6.11 ± 1.21a | 41.22 ± 4.35a | 3.85 ± 0.43b |
Group 3 | 19.35 ± 1.41b | 21.11 ± 2.19bc | 4.11 ± 0.44b | 36.22 ± 3.07b | 5.31 ± 1.15a |
Group 4 | 18.51 ± 1.33bc | 22.05 ± 3.07b | 4.03 ± 0.34b | 35.71 ± 2.60b | 5.61 ± 1.17a |
Group 5 | 17.37 ± 1.15c | 19.11 ± 1.22c | 4.18 ± 0.40b | 36.27 ± 2.99b | 5.10 ± 1.14a |
Mean ± SD values in each column with different letters (a, b, and c) are significantly different at
These gross composition results as presented in Table
The sensory attributes of jams (Table
In view of the nutritive qualities of the formulated soybean jams with different sweeteners (Table
Results of the consumption of different jam formulations on the glucose and insulin levels of diabetic rats were agreed by Li et al. [
This study determined an acceptable formulation for jams made of pumpkin fruit and various low-calorie sweeteners, evaluated their composition (protein, fibre, fat, and minerals), and monitored the effects of six months of storage.
Consumption of low-calorie jams fortified with soybean improves nutritional indicators and serves as a beneficial natural remedy for hyperglycaemia and improving liver function in diabetic rats.
There have not been enough studies concerning the nutritional value and functional properties of low-calorie jams with different fruits and their shelf life. Further studies are recommended to determine the mechanism of action of low-calorie jams with different low-calorie sweeteners on diabetes in vitro especially on pancreatic and hepatic cells.
The data used to support the findings of this study are available from the corresponding author upon request.
The authors declare that they have no conflicts of interest.