Loren Gautz

Isotopes as tracers of the Hawaiian coffee-producing regions

Green coffee bean isotopes have been used to trace the effects of different climatic and geological characteristics associated with the Hawaii islands. Isotope ratio mass spectrometry (IRMS) and inductively coupled plasma mass spectrometry ((MC)-ICP-SFMS and ICP-QMS) were applied to determine the isotopic composition of carbon (δ13C), nitrogen (δ15N), sulfur (δ34S), and oxygen (δ18O), the isotope abundance of strontium (87Sr/86Sr), and the concentrations of 30 different elements in 47 green coffees. The coffees were produced in five Hawaii regions: Hawaii, Kauai, Maui, Molokai, and Oahu. Results indicate that coffee plant seed isotopes reflect interactions between the coffee plant and the local environment. Accordingly, the obtained analytical fingerprinting could be used to discriminate between the different Hawaii regions studied.

Chapter 22 - Coffee

In this chapter, it is shown how spectroscopic techniques can be applied for the discrimination of different types of coffee and of their geographical origin. In a first approach, a study on the application of Raman spectroscopy to the differentiation of coffee type (Arabica vs. Robusta) is described, based on the determination of kahweol content, wherein the results obtained allowed coffee type discrimination. Then, isotope ratio mass spectrometry (IRMS) is addressed as a tool for the determination of the isotopic composition of carbon (C), nitrogen (N) and oxygen (O) of the green coffee bean, allowing coffee differentiation at continental level. Studies involving isotope analysis of the coffee bean have shown that oxygen is a fundamental element to achieve this differentiation, reflecting the hydrology of the coffee-producing regions. Subsequently, IRMS has been combined with inductively coupled plasma mass spectrometry, to determine the isotopic composition of strontium (Sr) in the coffee bean, in particular the ratio of the isotopes 87 and 86 (87Sr/86Sr). The study demonstrated that the isotope ratios of Sr and O can be promising for coffee authenticity, as these elements reflect the local geology and hydrology. However, in order to expand the understanding of how environmental factors determine the isotopic composition of the different elements in the green coffee bean, it may be necessary to study a model region of production, such as Hawai’i. A study performed at microscale, with coffees from different Hawai’i islands, allowed the detail analysis of how the various environmental factors prevailing in the location and time of coffee production were reflected in the elemental isotopic composition of the coffee beans. This approach allowed the discrimination of coffees from the different islands of Hawai’i. It has also revealed that the isotopic composition of O, Sr and S in the green coffee beans is related to known environmental factors, namely, the isotopic composition of the O of local precipitation (δ18Oprec), the distance to the coast and the volcanic activity characteristic of that region. In short, this chapter describes the various tentative approaches to coffee geographical origin discrimination where isotope analysis may play an important role and also, how this tool can bring an additional value to each coffee (or provenance), an ecological value.

Direct Contact Heating of Fermentors by Rotational Hot Gas Discharge System

In order to develop economical methane fermentation systems, a pilot scale fermentor with a rotational gas discharge system composed of a pivot and a rotational bar was constructed. The heat exchange is accomplished by direct contact between the hot biogas from the bar and the slurry in the fermentor. Water and air instead of waste slurry and biogas were used in this study. Energy and material balance analysis were used to investigate the rotational and heating characteristics of the system. Airflow rate from the rotational bar and heat transfer from the inlet air to the water were first observed in the system without the gasbag. The enclosed fermentor with the gas bag was heated to obtain the water temperature increase that was used to develop a heating model. Data obtained seems to indicate that the new heating system is feasible for practical use.