Date of Award

8-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Committee Member

Dr. John McGregor, Committee Chair

Committee Member

Dr. Paul Dawson

Committee Member

Dr. Scott Whiteside

Abstract

Coffee is a globally popular beverage – it is the second most consumed beverage in the world after tea (Petracco, 2001). According to a report from the National Coffee Association (NCA), in 2018, 64% of US consumers drink coffee daily. The same NCA report in 2017 shows that 59% of all coffee consumed in the US is specialty or gourmet coffee. Within this trend of specialty coffee, a product with rapidly growing market share is cold brew coffee. Cold brew coffee can offer the potential for a unique flavor profile, a position within the growing specialty coffee world, and RTD (ready-to-drink) convenience (Sisel, 2016). Products touted as cold brew coffee are coffee beverages that are extracted using low temperature and longer time than traditional hot brewed drip coffee or espresso (Hwang, and others, 2014). This can give cold water extracted (CWE) coffee an entirely different extraction profile, as different compounds are extracted at different rates, and many coffee constituents have temperature dependent solubility (Bladyka, 2014). Many producers are now selling cold brew coffee in a canned or bottled RTD (ready-to-drink) format to be consumed at a later date (Sisel, 2016). This presents the potential problem of microbial and sensorial deterioration. However, there is little published information around the exact chemical characteristics of cold brew to verify producers’ claims and allow for prediction of shelf life. In this study, the shelf-life of refrigerated cold and hot brewed coffees were investigated based on sensory and chemical profile and microbial growth, while also examining the influence of extraction temperature on the chemical and sensorial profile of cold water extraction coffee. Based on the results, the refrigerated shelf life of bottled hot and cold brewed coffee is limited not by microbial stability, but rather by deterioration in sensory attributes. Further work is recommended to elucidate the mechanisms of coffee staling in a refrigerated environment, with particular interest in the degradation products of chlorogenic acid, as a significant decline in chlorogenic acid concentration was found over the storage period. Cold extracted coffees were found to be chemically and organoleptically different beverages from coffees extracted at high temperature, specifically, the cold brewed coffees had higher sweetness and lower bitterness than the hot extracted coffee, supporting claims made by producers of cold brew. Additionally, the cold brewed coffees had greater flavor stability over the storage time than the hot brewed treatment.

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