Development of reduced-fat halal chicken sausages using emulsion gels containing whey protein isolate and guar gum / Hajah Nur Hamizah Haji Abd Hamid

Submitted in fulfilment of the requirements for the Doctor of Philosophy

ABSTRACT
The study was conducted to evaluate the effect of whey protein isolate (WPI) and guar gum (GG) in emulsion gels on chemical, physical, antioxidant activity, and technological and sensory evaluation of chicken sausages. Nine different formulations of oil-in-water emulsion gels with three levels of inclusions (2%, 5%, 10 %) of fat substitute were prepared, analysed and compared with the control (CON - 100% chicken breasts) sample (without any fats). Three of the formulations are made up of PI only and six of the formulations are WPI and GG combinations, E treatments having 50% WPI and 50 % GG and GM treatments having 70% WPI and 30% GG.
The physical properties of the chicken sausages studied were shown to be the most important for understanding sensory properties. The modified chicken sausages had high moisture, fat and ash content (p < 0.05) but low protein content (p < 0.05) compared to the control sausage. The protein, fat, ash, and carbohydrate contents for the formulated chicken sausages were significantly (p < 0.05) different, in the range from 15.58% to 20.71%, 11.59% to 16.83%, 4.88% to 6.61% and 27.86% to 34.77% respectively.
The formulated sausages exhibited elevated average cooking losses of 13.26% (p <
0.05). Treatment E10 (50% WPI, 50% GG with 10% fats) had the highest cooking yield out of all treatments. Furthermore, the increase of WPI and GG mixture in the formulation was observed to improve the cooking yield (p <0.05) and showed to decrease the total expressible fluid (TEF%) significantly (p <0.05). The incorporation of WPI and GG, both alone and combined significantly increased (p < 0.05) moisture retention values of chicken sausages. The moisture retention of the sausages incorporated with WPI and GG ranged from 27.86% to 34.77%. Additionally, the results found that the addition of WPI and GG increased the percentage water-holding capacity (%WHC) but the values were lower than the control chicken sausages.
Our results demonstrated that the pH values of the chicken sausages exhibited a significant upward trend (p < 0.05) during refrigeration and frozen storage. Water activity (Aw) decreased (p <0.05) during the 60-day storage period. Desirable ideal conditions for the treated sausages lie within freezer storage, with GM5 (70% WPI, 30% GG with 5% fats) having the lowest value of 0.33 Aw.
Moreover,
the sausage has higher total phenolic contents and high antioxidant
capacities in DPPH (1,1-diphenyl-2-picrylhydrazyl (DPPH) Free Scavenging Method), which contributes to reducing lipid oxidations in sausages during storage. Although peroxide values remained below the acceptable threshold for oily food, the TBARS (Thiobarbituric Acid Reactive Substance (TBARS) Assay) value exceeded the permissible limit for lipid oxidation for both refrigerated and frozen storage, indicating that the products developed off-odour and flavour for both storage conditions.
Additionally, the total viable count was not significantly affected (p > 0.05) by the addition of WPI and GG under freezer conditions. Consequently, it can be inferred that the cooked chicken sausages can be safely stored under frozen conditions for an extended period of 120 days. Similarly, the yeast and mould count increased (p > 0.05) in refrigerated storage and frozen storage. The modified chicken sausages had no apparent impact on the yeast and mould count for up to 60 days in frozen condition.
The inclusion of WPI and GG changed the antioxidant activity of the chicken sausages differently. E treatments with greater GG concentration had higher total phenolic content than GM (70% WPI, 30% GG) treatments. In this study, a decreasing trend of total flavonoid content was demonstrated as the concentration of WPI alone and WPI/GG combinations increased, along with during the storage (p > 0.05). GM2 (70% WPI, 30% GG with 2% fats) recorded the highest percentage inhibition of DPPH in the whole treatment (68.64% on day 1, 60.45% on day 15 and 45.48% on day 60). Furthermore, E2 (50% WPI, 50% GG with 2% fats) exhibited the highest lethality value towards brine shrimp with LC50 (Lethal Concentration 50) of 1696 ug/mL, but it can be inferred that there are no active compounds that were found to be hazardous or induce the mortality of the brine shrimps.
Textural properties
decreased significantly (P < 0.05) throughout both storage
conditions. The concentration of PI increased the firmness of the chicken sausages (p < 0.05). The addition of GG in WPI resulted in products with lower firmness, less elasticity, less cohesive and less gummy compared to other samples in refrigerated storage.
Sensory evaluation showed that the panelists regarded the CON samples as being acceptable overall. Despite having the lowest texture scores, the panelists showed no significant preference, indicating that the addition of chicken sausage and the reduction of fat did not compromise the overall acceptability of chicken sausages. Overall, the chicken sausages treated had acceptable sensory scores independently of the added
Overall, this study added to the scientific understanding of the inclusion and usefulness of WPI and GG as fat replacers in chicken sausage product developments. The combination of both WPI and GG has significant benefits in terms of WHC, CL (cooking loss), cooking yield and moisture retention. Further enhancement could be achieved through proper, better and optimized packaging strategies.
Keywords: whey protein isolate, guar gum, sensory perception, antioxidants,
chicken sausages, textural changes, cytotoxicity, emulsion gel

Dissertation (Doctor of Philosophy) - Universiti Teknologi Brunei (2025)

Includes references pages 237-276