❖ Total and water-soluble protein content of the sample
The results of total protein and water-soluble protein content of SBM and FSBM samples are shown in Tables 3.3, Table 3.4, Table 3.5, and Table 3.6.
20
Notation LM 3T LM 3K LM 0 LM 24 LM 48 LM 72 LM 96 LM 00 LM 024 LM 048 LM 072 LM 096 LM 3T1 LM 10 LM 124 LM 148 LM 172 LM 196 TT 50 TT 53 TT 55
Table 3. 5. Results of total protein and water-soluble protein content of SBM samples sterilized at condition 1 (Appendix 4).
LM 3T Sample
ARG LM 0 LM 24 LM 48 LM 72 LM 96
Different values printed in the same column indicate a statistically significant difference (p<0.05).
21
Table 3. 6. Results of total protein and water- soluble protein content of unsterilized SBM samples at condition 3 (Appendix 4).
LM 3K Sample
ARG LM 00 LM 024 LM 048 LM 072 LM 096
Different values printed in the same column indicate a statistically significant difference (p<0.05).
Table 3. 7. Results of total protein and water-soluble protein content of SBM samples sterilized at condition 2 (Appendix 4).
LM 3T1 Sample
ARG LM 10 LM 124 LM 148 LM 172 LM 196
Different values printed in the same column indicate a statistically significant difference (p<0.05).
Table 3. 8. Results of total protein and water-soluble protein content of marketed FSBM samples (Appendix 4).
Market FSBM Sample
TT 50 TT 53 TT 55
Different values printed in the same column indicate a statistically significant difference (p<0.05).
Percentage of total protein of ARG raw material SBM samples in conditions 1 and 2 are not the same, possibly due to not making the same batch of starting material leading to differences in data.
22
For the experiment of LM 3T samples (LM 0, LM 24, LM48, LM72, LM96), the total protein content was higher than water-soluble protein (Table 3.3). However, despite the difference in units in the final result, both show signs of increasing over time. Similar to the LM 3K sample (LM 00, LM 024, LM 048, LM 072, LM 096), the results measured by Kjeldahl and Lowry methods increased fermentation time (Table 3.4). In the same experiment as LM 3T but increased in weight from 10g to 1kg, the results show that LM 3T and LM 3T1 samples have a difference in the final total protein content because the LM 3T sample has a small weight, so it should be mixed evenly, and microorganisms are dispersed more evenly. But for sample LM3T1, the larger mass makes it difficult to mix by hand, resulting in uneven distribution of microorganisms resulting in lower final results.
The total protein content of the sterilized samples (LM 96: 53.58 ± 0.13d) was higher than that of the non-sterilized samples (LM 096: 52.90 ± 0.13d). In contrast, the soluble protein content of the unsterilized samples (LM 096: 16.45 ± 0.00e) was higher than that of the sterilized samples (LM 96: 9.14 ± 0.01f). One of the first noticeable protein changes upon heating (even to around 100°C) is the loss of labile amino acids such as cysteine and lysine. Lysine is one of the most temperature-sensitive amino acids, and the destruction of lysine is typically 5 to 15 times greater than other amino acids as heat denatures protein and reduces its solubility. However, the gradual increase in fermentation time is due to hydrolysis, which decreases the molecular weight of the protein [43].
Compared with market samples, the total protein content of TT 55 was lowest (56.31 ± 1.26a) compared to the other two samples, TT 50 (60.14 ± 0.13b) and TT 53 (63.49 ± 0.35c). The total protein content is the same, but the water-soluble protein content is higher than TT 50 (TT 53/TT 50: 7.85 ± 0.01c/4.92 ± 0.01a). However, TT 53 still ranked first in total and water-soluble protein content with measured results of 63.49 ± 0.35c and 8.74 ± 0.02b.
Whether the LM 3T sterilized samples or the LM 3K unsterilized samples, the total protein results are still less than the TT market samples. However, the water-soluble protein content with the highest market sample TT 53 (8.74 ± 0.02b) is still lower than that of the general unsterilized samples (LM 024: 10.18 ± 0.00b, LM 048: 13.13 ± 0.02c, LM 072: 13.06 ± 0.00d, LM 096: 16.45
± 0.00e) except LM 00 (5.12 ± 0.00a). Compared with the sterilized sample, the water-soluble protein content of the TT 53 sample was lower than that of the LM 96 sample (9.14 ± 0.01f).
Despite the difference between the two methods, the results showed that during the fermentation time from 0 h to 96 h, the total protein and water-soluble protein increased.
Apparently, carbohydrates are used by bacteria during growth for cellular respiration to generate energy for life activities. Respiration, in addition to creating energy, also converts carbohydrates into CO2 and H2O, thereby reducing the carbohydrate content in the FSBM compared to the starting material (SBM). Next, due to a decrease in the amount of carbohydrates (the percentage of carbohydrates decreases), the consequent increase in the percentage of crude protein in the sample [33].
23
From this, it can be seen that the results obtained by the Kjeldahl method and the Lowry method agree with each other; from 0 h to 96h, the protein content will increase with the fermentation time [44].