Document Type

Open Access Thesis

Embargo Period

8-31-2018

Degree Program

Food Science

Degree Type

Master of Science (M.S.)

Year Degree Awarded

2018

Month Degree Awarded

February

Abstract

Cancer is a global risk for human wellness and health. Dietary habits could profoundly affect the risk of certain cancer, such as colorectal cancer (CRC) (Platz, 2000). CRC has listed the third leading cancer among male and female in the United States (Stewart, 2014). Surprisingly, the consumption of dietary fiber has an inverse correlation with the mortality of CRC (Song, 2018). However, most Americans do not consume enough dietary fiber to meet the recommended level of dietary fiber intake (Clemens, 2012; Lee-Kwan, 2017). Hence, it is reasonable to increase the nutrient density, i.e., dietary fiber, of current food model. Xylo-oligosaccharides (XOS), an emerging prebiotics, showed multiple advantages over fructo-oligosaccharides (FOS) and inulin. For example, Hsu et al. (2004) reported XOS are more effective than FOS on increasing Bifidobacterium level in rat cecum (Hsu, 2004). It is also suggested that dietary fiber and phenolic compounds have synergistic effect on promoting gut health (Uehara, 2001; Matsukawa, 2009). Therefore, the application of XOS into a polyphenol-dense food vehicle (strawberry puree) could be a viable way to promote gastrointestinal health and help reduce CRC risk.

First, the effect of xylo-oligosaccharides (XOS) incorporation on the quality attributes of strawberry puree was investigated. Rheological properties, color and physicochemical characteristics and composition such as water activity, pH, and total soluble solids, were investigated to determine the maximum XOS content that can be incorporated into the strawberry pure without significantly altering the original properties of samples. Based on the collected data, adding xylo-oligosaccharides greater than 7.5% w/w will significantly change the quality attributes of the strawberry puree including its rheological characteristics, color profile, water activity, and total soluble solids. The addition of XOS at 2.5% and 5% w/w did not significantly alter overall quality attributes of strawberry puree.

Second, the effects of heat treatment (HTST, 75℃, 15s and UHT, 121℃, 2s) and storage condition (storage time: 1, 15, and 36 days; storage temperature: 4℃ and 55℃) on the quality attributes of xylo-oligosaccharides enhanced strawberry puree was studied (texture, color water activity, total soluble solids, and pH). In addition, the physicochemical (total phenolic, tannin, flavonoids contents, and antioxidant activity) evolution was studied. A 9-point Hedonic test was conducted to evaluate the sensory properties (overall, texture, color, appearance, sweetness, aroma, flavor) of purees (with and without XOS, 5%w/w) under different thermal treatments.

Briefly, all nutritional attributes were retained better under cold storage (4 ℃) as compared to high-temperature storage (55 ℃). The result revealed that thermal treatment and high storage temperature showed an inverse correlation with puree consistency. As for chemical analysis, intense thermal treatment (UHT) caused the most degradation in TPC, TFC and tannin level. However, such treatments (UHT) helped significantly increase the measurable antioxidant level. For other physicochemical properties, processing methods (HTST / UHT) and high storage temperature exhibited more significance in changing the color profiles of the specimen than XOS incorporation.

Overall, the addition of XOS up to 5% w/w could increase nutritional value of strawberry puree as well as consumer preference without significantly compromising quality attributes. Based on instrumental and sensory analysis, HTST treated strawberry puree with XOS incorporation (5% w/w) meet the standard of sensorial attributes of fresh puree with improved shelf-life stability and fiber concentration.

First Advisor

Amanda Kinchla

Second Advisor

Maria Corradini

Third Advisor

Hang Xiao

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