Physico-chemical properties
pH
The pH values differed significantly (P<0.01) (Table 1) among the treatment groups and also in the storage days with a slow but gradual decreasing trend irrespective of different formulations and days of storage. The lowest pH values were recorded in the C group as compared to others in all the storage days. However, the interaction between the treatment groups and storage days was non-significant. The relatively higher pH values recorded initially in the treatment groups as compared to the C formulation might be due to the fact that all the treated formulations had high content of rice flours, a very rich source of carbohydrate and also oat flours added in fresh during EAP preparation. But during the storage days these carbohydrate were slowly acted by different lipolytic enzymes (
Buege et al. 1978) (Saccharolytic/Glycolytic) resulting in the production of different acids, thus lowering the pH values (high acidity) slowly and gradually till the end of storage period. A slightly lower pH value reported by
Deepthi et al. (2011a) might be related to the difference in varieties of RF and oat flour incorporated in EAP production.
Thiobarbituric acid (TBA) values
The TBA values showed a gradual increasing trend irrespective of treatment groups and days of storage, however itwas within the permissible limit of 2 mg malonaldehyde/kg of food product. On day-1, the highest TBARS value was recorded in T
4 while it was lowest in T
1 group (Table 2). However, on 90
th day the highest TBARS value was recorded in C and the lowest in T
2 formulation. The gradual increase in TBARS values of EAP might be related to the lipid oxidation caused by different lipolytic enzymes (
Buege et al. 1978) present in EAP for which there were gradual increase in malonaldehyde values during the storage days. Moreover, albumen has high foaming property that entraps oxygen within it and this might have also contributed in oxidation of lipid
Deepthi et al. (2011a). Considering the fact that the lipid content of egg albumen is very less
i.e.,1.09% (
Bashir et al.2015) as compared to the flours incorporated in EAP and this could be the possible reasons for very slow but gradual rise in TBARS values during the storage days. The TBARS values recorded for C formulation in the study was nearer to the ones reported by
Deepthi et al. (2011a) who also reported TBARS values that varies from 0.66±0.04 to 1.24±0.07 in EAP during the storage period of 6 months. Several other investigators also reported an increase in TBARS values along with the increase in storage period although most of them had worked on certain meat products (
Jebin 2011;
Sebranek et al. 2005).
Tyrosine value
Tyrosine values of EAP increased gradually irrespective of the treatment groups and days of storage. The lowest Tyrosine values were recorded on day-1, having lowest value in T
3 and highest in C formulation (Table 3). A very similar trend was also observed on 90
th day of storage with highest value in C and lowest in T
3 formulations. The gradual increase in Tyrosine values of EAP might be related to the continuous protein denaturation by the different proteolytic enzymes
i.e. Proteases/Cathepsins and others present in EAP. Moreover, egg albumen is very rich in protein content
i.e., 3.48% (
Bashir et al. 2015) which might have facilitated the proteolysis process during the storage days resulting in a gradual rise of tyrosine values of EAP. Several other workers also reported increase in Tyrosine values of their meat food products during the storage period (
Mahmmod et al. 2014).
Water activity (aw)
Water activity (aw) of EAP revealed a gradual decrease in values irrespective of treatment groups and the days of storage and varies between 0.5795±0.005 to 0.7357±0.004 during storage (Table 4). On day-1, the T
3 formulation recorded highest and T
1 formulation recorded lowest aw. However, on 90
th day of storage, the T
3 and C formulation registered highest and lowest aw values respectively. The gradual fall in aw values of EAP might be a corollary to the continuous drop in pH values during the storage days and vacuum packaging of EAPs with high density polyethylene (HDPE) packaging material. This gradual fall in aw values of EAP during their storage time might have resulted in the absence of microbial count as observed in the present study. The aw values recorded for the C formulation were at variance with the ones reported by
Deepthi et al. (2011a) for EAPs prepared with same incorporation levels of WF and RFs. This discrepancy could be attributed to the vacuum packaging of EAP with HDPE packaging material, besides, storing of the product (EAP) at refrigeration temperature (5 -7
oC).
Increase in volume on rehydration
The increase in volume on rehydration values of EAP ranges between 120.69±1.57 to 153.07±7.00. There was no significant differences in increase in volume on rehydration among the T
3 and T
4 groups whereas the other formulations recorded a significant difference (P<0.05) (Table 5). The highest increase in volume on rehydration value recorded in T
1 formulation might be due to incorporation of only rice flours (10% GRF and 10% JRF) in EAP preparation since rice flours has higher water binding capacity as compared to wheat and oat flours. The lowest increase in volume value recorded in the control group might be a reflection of incorporation of high percentages of wheat flour (15%) which has poor water absorption capacity. The results obtained in the study for increase in volume on rehydration were in contrast to that of
Deepthi et al. (2011b). The higher increase in volume on rehydration values recorded in the present studies might be due to the differences in the product formulation,
i.e. incorporation of GRF and JRF, besides oat flour.
Coefficient of rehydration
No significant differences in coefficient of rehydration were found among the T
1, T
2, T
3 and T
4 groups, however, the control group showed a significant difference (P<0.05) (Table 5) with the other formulations. The highest coefficient of rehydration recorded in T
1 formulation might be due to incorporation of only rice flours having higher water binding capacity. A much lower coefficient of rehydration registered in the control group might be due to the same explanation as has been given for rehydration of EAP. Lower coefficient of rehydration value as reported by
Deepthi et al. (2011a) might be due to their evaluation of EAP at monthly intervals and also on storage of the product at 27±2
oC which was much higher than the one followed in the present study
i.e. 5-7
oC.
Rehydration ratio
There was no significant differences in rehydration ratios among the control and T
4 groups whereas, the T
1, T
2, T
3 groups recorded a significant difference (P<0.05) (Table 5) with the other formulations. The highest rehydration ratio recorded in T
2 formulation might be a reflection of much higher fiber content in oat flour (3.53-5.87% fiber,
Youssef et al., 2016) that was added at 12
% along with 8% level GRF (0.9%,
Itthivadhanapong and Sangnark, 2016). The study further revealed almost equal rehydration ratio of EAP in Control and T
4 formulations. This could be attributed to much lower fiber content in JRF (0.25-0.75%,
Roy et al., 2010) and slightly higher fiber content in oat and wheat flours incorporated in T
4 and Control formulations of EAP.
Rehydration percentage
The rehydration percentage of different formulations of EAP varies between 87.06±2.31 to 104.92±5.38 per cent. No significant differences in rehydration percentages were observed between the T
3 and T
4 groups. On the contrary, the C, T
1 and T
2 groups revealed significant differences (P<0.05) (Table 5) with the other two formulations. The highest rehydration percentage recorded in T
2 formulation might again be a reflection of high fiber content in GRF while the lowest in control group might be ascribed to incorporation of 15% wheat flour (low in fiber content) and only 5% rice flour (RF).
The results for Rehydration percentage recorded in the study for the control group was almost in conformity with the findings of
Deepthi et al. (2011a) who also recorded (84.10±5.35) rehydration percentage on ‘0’ day of storage of EAP prepared by incorporation of same levels of WF and RF as followed in the control formulation of EAP in the present study.