| Author | Jain, Surangna |
| Call Number | AIT Diss. no.FB-16-02 |
| Subject(s) | Protein hydrolysates
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| Note | A disse1iation submitted in pruiial fulfillment of the requirements for the degree of Doctor of Philosophy in Food Engineering and Bioprocess Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. FB-16-02 |
| Abstract | Food processing wastes, which are disposed off in huge amounts on a daily basis contributes to serious environmental pollution and severe health hazards. It is important to reuse and recycle these wastes for sustainable development of the society and for preserving the environment. Majority of the food processing wastes and by-products contain high amount of starch, lipids, proteins, peptides and various bioactive compounds having high potential to be utilized by the food, pharmaceutical and cosmetic industries and result in the value addition of the wastes. Eggs are one of the most popularly consumed food products in the world, which are gaining commercial importance due to their high nutritional values. Large amounts of by-products such as eggshells and eggshell membranes (ESM) are generated during the processing of eggs. These by-products are are underutilized and disposed off in landfills without any pretreatment. This contributes to environmental pollution and also results in economic losses. However, the eggshells and the ESM are a very good source of proteins which can be transformed to protein hydrolysates and peptides through various biotechnological processes. In this study, the ESM were peeled off from the eggshells and collected for the extraction of protein hydrolysates using ultrasonication, enzymatic hydrolysis, ultrasonic pretreatment followed by enzyme hydrolysis and fermentation. The ultrasonic assisted extraction (UAE) method was optimized by the Box-Behnken design by varying the amplitude, time and solid-to-solvent ratio. It was predicted that extraction at 100% amplitude at a solid-tosolvent ratio of 1 :30 (w/v) for 20 min resulted in maximum protein concentration of 90.2 mg/g and maximum degree of hydrolysis of 6.0 % and hence were determined as the optimum ultrasonication conditions. The optimum conditions were used as a pretreatment prior to enzymatic hydrolysis by alcalase and papain respectively. It was seen that this resulted in increased protein concentration and degree of hydrolysis of the protein hydrolysates and these values were found to be higher than that of the untreated hydrolysates (only enzyme hydrolysis). The hydrolysates obtained by ultrasonic pretreatment followed by papain hydrolysis demonstrated highest protein concentration of 257 .6 mg/g and hydrolysates obtained by ultrasonic pretreatment followed by alcalase hydrolysis demonstrated highest degree of hydrolysis of 21.9%. Fermentation with Lactobacillus plantarum was also conducted to produce protein hydrolysates from ESM by varying the initial pH of the culture media and fermentation time. Both time and initial pH were found to have a significant effect on protein concentration and degree of hydrolysis. Maximum protein concentration and degree of hydrolysis were observed at an initial pH of 8.0 after a fermentation period of 36 h which were 177.3 mg/g and 25.1 % respectively. These values were found to be lesser than that of pretreated enzyme hydrolysates. However, it can be suggested that fermentation of ESM using a probiotic microbial strain is an effective approach for recovering the protein hydrolysates from ESM and can be preferred due to their low costs and their easy scale-up. The protein hydrolysates obtained were analyzed for their physicochemical, functional and bioactive prope1ties. It was observed that both pretreated alcalase and papain hydrolysates demonstrated small molecular weight bands corresponding to 2 kDa which suggests the presence of peptides in the samples. On the other hand, fermented hydrolysates demonstrated multiple bands ranging from 50-10 kDa. These hydrolysates as well as peptides were also found to possess potential antioxidant, antibacterial and antihypertensive activities. Their hydrophobic and aromatic amino acid composition were also found to be high and known to contribute to their respective antioxidant and antihype1tensive activities. The pretreated alcalase hydrolysates (UA) and fermented hydrolysates (FH) demonstrated the strongest emulsifying properties with an emulsifying activity index (EAI) of 64.85 m2/g and 94.58 m2/g respectively and an emulsion stability of 22.31 min and 29.68 min. Hence, both these hydrolysates were used as emulsifiers for producing stable emulsions to be used in various food applications. It was observed that using these hydrolysates alone as emulsifiers resulted in emulsion instability after 3 days followed by phase separation. Hence, it can be said that they are not ideal emulsifiers on their own. Resistant starch (RS) isolated from culled banana pulp was used in combination with UA and FH respectively to stabilize the emulsions and were compared to that produced by the hydrolysates alone. Emulsions prepared using RS in combination with the protein hydrolysates were found to be more stable without any creaming or phase seperation up to 14 days. This is due to the interactions between RS and the protein hydrolysates that enhances the stability of the emul sions. The physical and oxidative stabilities of these emulsions were also found to be higher than the emulsions made by the protein hydrolysates alone. However, when comparing the emulsions prepared using RS and UA and RS and FH, it was seen that the emulsions prepared using RS and UA were found to be more stable along with demonstrating better flowability and encapsulation efficiency of their respective microcapsules. As the emulsions prepared using RS and UA were found to be most stable, their behaviour during their passage through the gastrointestinal system was studied and investigated. In the simulated mouth conditions, these emulsions were mixed with the artificial saliva and the effects of different concentrations of mucin were studied on their behaviour and stability. It was observed that the emulsions did not show considerable aggregation in the absence of mucin but at higher concentrations of mucin, they underwent flocculation and coalescence that resulted in reduced creaming stability and increased particle size and spotential of the emulsions. In the acidic conditions of the stomach phase, the presence or absence of pepsin on the behaviour of the emulsions was studied. The addition of pepsin resulted in larger flocculation and greater instability of emulsions as compared to that when pepsin was not added. This indicates that pepsin hydrolyzes the proteins stabilizing the emulsions which affect their stability. On the addition of the emulsions to the simulated intestinal fluid (SIF) containing bile salts and pancreatin, it was observed that larger aggregation, coalescence and fatty acid release was observed for the fed state in comparision with the fasted state which is attributed to the presence of higher concentrations of bile salts and pancreatin which ruptures the interfacial layer of the emulsions affecting their stability. |
| Year | 2016 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. FB-16-02 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Food Engineering and Bioprocess Technology (FB) |
| Chairperson(s) | Anal, Anil Kumar; |
| Examination Committee(s) | Athapol Noomhorm;Loc Thai Nguyen;Salin, Krishna R.; |
| Scholarship Donor(s) | Asian Institute of Technology fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2016 |