Mexico is an important producer of fruit and vegetables which have a short shelf life because of their water content and are susceptible to physical, chemical and microbiological spoilage, which affects their sensory, hygienic and nutritional quality; this implies considerable economic losses. Instituto de Ingeniería at UNAM has developed a Geothermal Food Dehydrator (GFD) that uses low enthalpy geothermal energy (LEGE) installed in the geothermoelectric plant at San Pedro Lagunillas, Nayarit, México. It can process batches of 10 kg, using 11 kg s-1 of geothermal brine at 90 °C, each batch of dehydrated fruit prevents the release of 6 kg of CO2 to the atmosphere. Food and Biotechnology Department at Facultad de Química UNAM, developed sanitary instollation guides the GFD facility; Standardized Sanitation Procedures (SSP) for raw materials, utensils, workers, equipment and work areas were designed, tested and improved. Fruits processed are: tomato, guava, mango, papaya and pineapple. To assess Microbiological Quality, indicator microorganisms have been determined: mesophilic aerobes, total and fecal coliforms, molds and yeasts, as well as Salmonella spp. and E. coli. Over almost 4 years of analysis of microbiological results and process parameters, we propose microbiological specifications that can be applied to vegetables and fruits dehydrated by different methods, since there is no official regulation yet. Chemical composition analysis confirms larger reduction of humidity and concentration of solids compared to commercial samples obtained by different dehydration methods; greater firmness and roughness have best sensory impact. The attributes of the samples dehydrated with LEGE were very well evaluated in sensory quality, the notes of freshness, smell and taste were maintained; texture characteristics are superior to those of dehydrated fruits with other methodologies. It is possible to obtain an adequate hygienic quality and comply with the microbiological specifications proposed throughout the project, if SSP are applied and the critical parameters (temperature and time) are controlled in dehydration process. These results establish the possibility of taking advantage of geothermal energy to displace the consumption of fossil fuels.

Microbial and sensory quality of dried fruit processed in low enthalpy geothermal food dehydrator

2019 Spring National Meeting

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