Table 1
Effect of storage in different packaging materials on the functional properties of C. lunatus seeds.
PACKAGING MATERIAL
|
BULK DENSITY (g/ml)
|
EMULSION CAPACITY (%)
|
EMULSION STABILITY (g/ml)
|
FOAM CAPACITY (%)
|
FOAM STABILITY (%)
|
HBB0
|
0.52a ± 0.00
|
50.12b ± 0.04
|
38.93e ± 0.03
|
13.66d ± 0.03
|
7.03e ± 0.04
|
GSB0
|
0.52a ± 0.03
|
50.16ab ± 0.01
|
38.72f ± 0.01
|
13.92b ± 0.01
|
7.16d ± 0.01
|
TPB0
|
0.52a ± 0.02
|
50.18a ± 0.02
|
39.17d ± 0.02
|
13.76c ± 0.02
|
6.93f ± 0.03
|
HBB3
|
0.50a ± 0.00
|
48.40c ± 0.01
|
39.44c ± 0.01
|
12.16e ± 0.03
|
7.73c ± 0.03
|
GSB3
|
0.50a ± 0.01
|
46.61e ± 0.01
|
39.90b ± 0.03
|
13.81c ± 0.01
|
8.44b ± 0.01
|
TPB3
|
0.51a ± 0.01
|
47.27d ± 0.02
|
40.19a ± 0.01
|
14.05a ± 0.03
|
8.93a ± 0.02
|
Values are mean ± standard deviation of duplicate determination. Means in the same column with different superscripts are significantly different at P < 0.05. HBB = Hessian Brown Bag; GSB = Propylene bag; TPB = Polyethylene bag; 0 = fresh sample; 3 = sample stored for 3 months |
Table 1 shows the functional properties of fresh and stored melon seeds in different packaging materials. Emulsion capacity was higher (P < 0.05) in fresh samples than in stored ones. Emulsion stability was higher in stored samples than in fresh ones (p < 0.05). Foam capacity and stability of stored samples were also higher than that of fresh samples (p < 0.05). TPB had the highest emulsion stability, foam capacity and foam stability (p < 0.05)
There were no significant differences in bulk density due to storage period or packaging materials. The differences in emulsion capacity (EC) emulsion stability (ES), foam capacity (FC) and foam stability (FS) were also statistically insignificant (P > 0.05). Functional properties express the complex interactions between the structures, molecular conformation, compositions, and physicochemical properties of food components with the nature of the environment and conditions in which these are measured and associated (Suresh and Samsher, 2013). They predict the behavior of food components in food systems. Obi and Offorha (2015) as well as Awuchi et al. (2019) had observed insignificant (p > 0.05) differences in functional properties of melon seeds and flours respectively.
Quality Indices of fat deterioration
Free fatty acid
Free fatty acid content of the samples in different packaging materials was significantly (p < 0.05) different after the 3-month storage period. TPB 3 were statistically higher (9.85%) in free fatty acid content indicating higher level of deterioration. Free fatty acid values ranged from 3.47–9.85 is like the free fatty acid (3.59–9.31) reported by Nwakaudu et al. (2017). High free fatty acid content of the samples after 3months suggest that the oil in the melon seeds might have gone rancid. Modern extraction methods conserve the oil quality of melon seeds (Olubi et al., 2019; Okolie et al., 2019).
3.2.2: Acid value: There was a significant difference in the acid value of samples after three months of storage. Acid values in the packaging materials after 3-month storage ranged from1.19–1.20 mg/KOH/g/mol/kg and correlates with the acid value observed by Nwakaudu et al. (2017) which was in the range of 1.12–1.88. Observed acid values in this study were higher than the acid value of melon seed oil (3.03) reported by Duru et al. (2019) but is within the recommended limit specified by FAO (1999). Acid value indicates age, edibility and suitability of oil (Nwakaudu et al., 2017). It measures the content of free fatty acids formed after the hydrolytic degradation of lipid molecules and indicates the degree of rancidity.
3.2.3: Peroxide value: There was a significant difference in the peroxide values of samples in different packaging materials after 3-month storage: GSB3 (20.04), TPB3 (19.57) and HBB3 (18.22 mg/KOH/g/mol/kg) respectively. After 3-month storage, the range (18.22–20.04) was higher than the peroxide value of melon seed (12.30–16.40) reported by Nwakaudu et al. (2017), but lower than the value reported by Duru et al. (2019) for melon seed oil (26.00).
Peroxide value is used as a measure of the extent to which rancidity have occurred during storage and as an indication of the quality and stability of fats and oils (Nwakaudu et al. 2017). High peroxide values are associated with higher rate of rancidity. Low peroxide values of oils may indicate lack of trace elements that trigger autoxidation (Adebisi and Olagunju, 2011). During storage, peroxide formation is slow at first during an induction phase which precedes the propagation phase (Duru et al.,2019). Peroxide value is the most common indicator of lipid oxidation, and the rancid taste begins to show up when the value is between 20 and 40mEq/kg (Duru et al., 2019).
2.2.4: Iodine value: There were significant differences (p < 0.05) in iodine values of fat from melon samples stored in different packaging materials after 3-months of storage (HBB3 (28.72), GSB3 (27.37) and TPB3 (25.86 g/100g). The iodine value observed in this study which ranged from 25.86-55.81g/100g correlate with the iodine value in melon seed (26.70–57.20 g/100g) as reported by Nwakaudu et al. (2017). Iodine value indicate the level of unsaturation of oils. The higher the iodine value, the more unsaturated fatty acid bonds in an oil or fat (Nwakaudu et al., 2017). Oils with iodine value less than I2g/100g of oil are non-drying oils, while good drying oil have iodine values of 130 and above.
2.2.5: Anisidine value: There was a significant difference in anisidine value after 3-month storage of samples and in the different packaging materials. Values were TPB3 (0.92), GSB3 (0.83) and HBB3 (0.71). Anisidine value (AV) measures the aldehyde levels in an oil or fat (especially the 2–alkenals). The P-anisidine value is a good measure of the secondary lipid oxidation of oil. Generally, aldehyde carbonyl bonds are formed during secondary lipid oxidation. There was 40–80% increase in anisidine value within the 3-month storage period. Lipid oxidation is one of the major causes of quality deterioration of many foods, leading to the rancid flavor of oil.
2.2.6: Saponification value: There were significant differences in saponification value based on storage period and on packaging materials GSB3 (189.30), TPB3 (189.15) and HBB3 (189.09) respectively. Saponification value from this study (189.19) was higher than the saponification value of melon seed oil (116.83) as reported by Duru et al. (2019). Saponification value is an indication of chain length and a measure of both free and combined acids (Duru et al., 2019). It is inversely related to the average molecular weight of the fatty acids in the oil fraction. During saponification, soap is usually formed, and a high saponification value indicates the suitability of an oil for industrial use (e.g., soap making) (Duru et al., 2019).
2.2.7: Total oxidation (totox) value:
The Totox value indicates the overall oxidation state of the sample and enables oxidative deterioration to be monitored. There was a statistically significant difference (p < 0.05) in Totox value between fresh and stored samples as well as packaging materials: HBB3- 37.15; TPB3-40.05 and GSB3-40.91 within the 3-month storage period. The oil in the melon seed stored in HBB package had the lowest Totox value indicating that it had better quality than oil from seeds stored in other packaging materials. The changes in the indices of fat quality are shown in Fig. 2
From Table 4.1 There was a significant decrease (p < 0.05) in the moisture content of samples after 3 months of storage (HBB3-3.96%; GSB3-4.08% and TPB3-4.53%. The moisture content of 5.7% before storage was lower than the recommended storage moisture content ranges (7–10%) of oilseeds (Nwakaudu et al., 2017). The moisture content in this study is significantly close to the moisture content in the Egusi (3.86%) as reported by Akusu et al. (2020). Low moisture content helps to improve shelf life.
Crude protein content was quite high in the fresh and stored samples irrespective of the packaging material. There was significant difference (p < 0.05) between the crude protein of Egusi based on packaging materials in HBB3 (23.61%), GSB3 (23.15%) and TPB3 (21.84%) respectively. The values are close to those observed for processed Egusi (22.98% and 24.60%) as reported by Akusu et al. (2020).
The least value for crude fibre was observed for samples stored in TPB after 3 months (3.56%). The fibre content in this study is significantly higher than that which was reported by Akusu et al. (2020). The fibre in this study is lower than that in Egusi (6.40%) as reported by Jacob et al. (2015).
There was a significant difference (p < 0.05) in the fat contents of the fresh and stored samples. For the samples stored for 3 months: TPB3 (39.20%) was significantly higher (p < 0.05) than GSB3 (38.3%) and HBB3 (37.29%) respectively. The fat content in this study is considerably lower than the fat content of processed Egusi as reported by Akusu et al. (2020) and Jacob et al. (2015) (49.05%). Fat provides the body with energy (Jacob et al., 2015).
Melon seeds contained 1.86–2.14% ash. Period of storage and packaging material affected the ash content. The ash content was highest in HBB3 (2.14%) and lower in GSB3 (2.03) and TPB3 (1.86) respectively. The Ash content in this study is significantly lower than that in Egusi (3.09%) as reported by Akusu et al. (2020) and Jacob et al. (2015 (6.7%).
Carbohydrate was most abundant (29.2%) in HBB3. There was a significant increase in carbohydrate content (p < 0.05) after 3-month storage period and there were significant differences in the packaging materials used. Carbohydrates increased possibly due to the decreases in other nutrients. Carbohydrate in this study was significantly higher than that which wis reported by Jacob et al., 2015 (7.22%). The energy value in this study was significantly high and decreased as storage period increased. Other researchers also found melon to be a good source of energy as comparably to other legumes (Akusu et al. 2020). Oluba et al. (2008) and Petkova et al. (2015), observed similar proximate composition for melon seeds. The changes in approximate nutrients and energy due to storge are shown in Fig. 3.
Mineral content.
Figure 4 shows the mineral content of melon seeds in different packaging materials.There were no significant differences in the magnesium content of fresh samples and after storage: HBB3 (24.83 mg/100g), TPB3 (24.64 mg/100g) and GSB3 (23.55 mg/100g) respectively). The magnesium content was statistically higher than the value (20.46 mg/100g) reported by Jacob et al. (2015). Magnesium deficiency leads to uncontrolled twisting of muscles and convulsion, which may result in death (Jacob et al., 2015). Magnesium is beneficial for blood pressure control, prevention of heart attack, and stroke. It contributes to the structural development of bones. While calcium stimulates muscles, magnesium relaxes the muscles (Jacob et al., 2015). zinc is vital in protein synthesis, cellular differentiation and replication, immunity and sexual functions (Pathak and Kapil, (2004).
There was significant difference in the zinc content of fresh samples and stored ones. There was a significant difference between HBB3 (28.37mg/100g) and GSB3 (28.26 mg/100g) but no significant difference between GSB3 (28.26 mg/100g) and TPB3 (28.30 mg/100g) respectively. Zinc concentration of the sample was higher (28.30mg/100g) than the zinc concentration of Egusi (21.05 mg/100g) reported by Jacob et al. (2015). Zinc promotes carbohydrate and protein metabolism, proper functioning of the senses of taste and smell, metabolism of vitamin A and health of the hair. It facilitates the synthesis of DNA and RNA (Jacob et al., 2015).
There were significant differences in the calcium contents of the fresh sample and those stored in different packaging materials after 3-month storage: HBB3 (8.78); G.S.B (8.45) and TPB3 (6.98) respectively. Calcium content value was statistically higher than that which was observed in Egusi (0.10 g/100g) as reported by Jacob et al. (2015). Calcium is essential for blood clotting, bone and teeth formation and enzyme function.
There were no significant differences in the iron content of fresh and stored samples: HBB3 (4.16), GSB3 (4.04) and TPB3 (3.90) after 3 months of storage. Iron is required for cognitive functions, oxygen transport, and some enzyme functions (Thomas and Krishnakumari, 2015; Jacob et al., 2015).
Figure 5 shows a marked decrease in magnesium and calcium, when compared with the other micronutrients.
Vitamin composition of Citrullus lunatus (Egusi).
Table 2
Effect of packaging materials on vitamin composition of freshly peeled and stored Egusi.
PACKAGING MATERIAL
|
vitamin B1(mg/100g)
|
vitamin B2 (mg/100mg)
|
vitamin B3 (mg/100g)
|
vitamin B6 (mg/100g)
|
vitamin E (mg/100g)
|
vitamin A (µg/100g)
|
vitamin D (µg/100g)
|
HBB0
|
1.12a ± 0.01
|
0.62b ± 0.01
|
0.81b ± 0.01
|
3.31a ± 0.01
|
15.93c ± 0.03
|
5.63a ± 0.04
|
0.53b ± 0.03
|
GSB0
|
1.11a ± 0.01
|
0.64ab ± 0.00
|
0.82ab ± 0.00
|
3.29a ± 0.00
|
18.8a ± 0.00
|
5.69a ± 0.00
|
0.61a ± 0.03
|
TPB0
|
1.13a ± 0.03
|
0.67a ± 0.01
|
0.85a ± 0.01
|
3.34a ± 0.01
|
16.92b ± 0.03
|
5.61a ± 0.04
|
0.60a ± 0.03
|
HBB3
|
1.09a ± 0.03
|
0.53c ± 0.01
|
0.72c ± 0.03
|
2.24c ± 0.02
|
12.64e ± 0.03
|
3.98c ± 0.02
|
0.31d ± 0.01
|
GSB3
|
0.98b ± 0.03
|
0.56c ± 0.01
|
0.70cd ± 0.00
|
3.05b ± 0.04
|
13.16d ± 0.03
|
4.08bc ± 0.04
|
0.34d ± 0.04
|
TPB3
|
0.92c ± 0.03
|
0.54c ± 0.03
|
0.67d ± 0.03
|
2.02d ± 0.02
|
12.57f ± 0.04
|
4.46b ± 0.04
|
0.42c ± 0.03
|
Values are mean ± standard deviation of duplicate determination. Means in the same column with different superscript are significantly different at P < 0.05. HBB = Hessian Brown Bag; GSB = Propylene bag; TPB = Polyethylene bag; 0 = fresh sample; 3 = sample stored for 3 months |
Table 2 shows the effects of packaging materials on the vitamin content of Citrullus lunatus.
There were no significant differences in vitamin B6 and E contents of fresh samples, but there was a significant difference after 3 months of storage in different packaging materials. The B6 value was significantly higher that obtained for Egusi (2.6) by Olumuyiwa et al. (2020). There was a significant difference in the vitamin E content of samples after 3 months storage different packaging materials: GSB3 (13.16), HBB3 (12.64) and TPB3 (12.57) respectively. Vitamin E content of the fresh sample (16.92) compared well with the raw Egusi sample (16.1) as reported by Ejoh and Ketiku (2013). There were no significant differences in vitamin A for samples stored in different packages. Figure 6 shows the changes in vitamin contents as the storge period increased.
Azuka et al. (2023), observed that laminated high density polyethylene (LHPE) was the best packaging material for storing ground melon seeds for 4 weeks. The samples showed the least changes in physicochemical properties: Free fatty acid (0.90–2.18 mg KOH/g), peroxide value (2.40–4.20 mEq kg 1) and water activity (0.31–0.49), compared to samples packaged in transparent high-density polyethylene (THPE) and amber coloured plastic bottle (APB).