- Title
- Valorisation of by-products from soy milk processing into marketable ingredients and functional foods
- Creator
- Davy, Philip
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2024
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- A large quantity of soy milk by-product (SMB) is generated from the commercial manufacture of this popular plant milk. This by-product is often treated as waste due to its short shelf life, low value, and limited applications. This leads to disposal via trade waste or utilisation as animal fodder. Research had shown it is a rich source of proteins and dietary fibre, fats, simple carbohydrates, vitamins, minerals, isoflavones and soyasaponins. Therefore, there is high potential to valorise this waste material to be used as a functional ingredient to formulate functional foods and nutraceuticals. It was noted however, that many recent studies require the use of complex modern techniques to stabilise this by-product, discounting simple preservation techniques. The overall aim of this project was to produce a nutritionally functional flour, primarily as a dietary fibre additive, utilising simple preservation techniques that retains bioactivity. The overall aim of this project was to produce a nutritionally functional flour, primarily as a dietary fibre additive. To accomplish this overall objective, three primary objectives were identified including: (1) to determine a rapid but simple drying method for the dehydration and preservation of wet soy milk by-product, (2) to evaluate the physicochemical properties and stability of the dried powdered soy milk by-product under different storage conditions, and (3) to investigate the potential application of the dried powdered soy milk byproduct as a high-fibre functional ingredient in bread to improve its nutritive content, while maintaining physical and sensory properties. The results (Chapter 4) showed that among the tested drying conditions, including vacuum oven drying and lyophilisation (control), drying in a fan forced oven at 100 °C did not significantly affect retention of phenolics, soyasaponins and antioxidant capacity, while it also produced higher concentration of daidzin and genistin. As such, fan forced drying at 100 °C was determined as the most suitable condition for drying soy milk by-product for further applications, with good recovery of soyasaponin (55.96 mg escin eq./g), daidzin (79.60 μg/g) and genistin (159.4 μg/g). Energy consumed was shown to be less than control, this further highlighting the benefits of this protocol. Following drying optimisation, the by-product was milled to produce a flour (SMB100) and the physicochemical and functional properties of the flour were quantified. The results (Chapter 5) indicated that this ingredient has good nutritional properties with 40.6% dietary fibre, 26.5% proteins, 31.4 mg soyasaponins (escin eq./g), and a total sum of isoflavones of 698 μg/g from daidzin, genistin, daidzein and genistein. This flour is light yellow with a hue angle of 83.3° and an 89.3 lightness index, a moisture content of 8.23% and water activity of 0.55, measured at room temperature (20°C). Additionally, this flour was shown to be stable at ambient storage conditions, as no quality change was observed at ambient conditions (20 °C) over a 10-week storage trial (Chapter 6). During the storage trial, it was determined that malonyl isoflavone were converted to their β-glycosidic form. This action is of particular interest to the project, as this conversion may increase bioavailability of isoflavones in the body. The SMB100 flour was further tested in bakery products through substituting in place of wheat flour when producing white bread. The results (Chapter 5) revealed that physical properties, such as volume, relative density and texture profile were significantly affected as compared to the control, when substituted with over 5% of SMB100 flour. However, bread substituted with 5% SMB100 flour exhibited minimal influence on all physical properties tested. The crumb colour was changed slightly, while no change was observed in crust colour. Interestingly, substitution of wheat flour with SMB100 flour can produce a high fibre bread at 7.5% and above. In conclusion, a new functional flour can be produced from the by-product of soy milk processing. This functional flour has good physical and nutritional properties, which can be used as a rich source of natural dietary fibre. Additionally, this flour is stable at ambient storage condition. To improve specific nutritional quality of this flour, future studies are recommended to increase protein content and convert insoluble fibre to a more soluble form. Additionally, concentration of isoflavone aglycones should also be elevated through solid-state biotransformation by food-safe microorganisms. Furthermore, applications of this flour and modified version of this flour in various food products should be tested to increase potential uses of this flour. Therefore, the value of this by-product can be increased to add more value to the food industry, while minimising its waste and environmental risks.
- Subject
- valorisation; soy milk by-product; food waste; isoflavones; bioactive compounds; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1510436
- Identifier
- uon:56401
- Rights
- Copyright 2024 Philip Davy
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT01 | Thesis | 26 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 219 KB | Adobe Acrobat PDF | View Details Download |