Date of Award

5-2023

Document Type

Thesis

Degree Name

Master of Science (MS)

College/School

College of Education and Human Services

Department/Program

Nutrition and Food Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Adrian Kerrihard

Committee Member

John Specchio

Committee Member

Kristin Truglio

Abstract

Garlic, from the allium family, is known to contain organosulfur compounds. These compounds contain antioxidants, which provide a plethora of potential health benefits. Black garlic is created by processing regular garlic at temperatures ranging between 60-90°C, with high humidity for upwards of one month. The process of making black garlic alters these components, potentially increasing the antioxidant capacity. This end product yields a garlic that is a deep black color with a sweet flavor, pungent aroma, and a soft malleable texture. Black garlic is increasing popularity within the culinary world with more products making it to market shelves. PURPOSE: To determine the effects that time, temperature, and cooking vessel has on the antioxidant potential, PH, and Brix in the production of black garlic. MATERIALS AND METHODS: Garlic was processed in a sous vide, fermentation station, and dehydrator at 57°C, 63°C, and 68°C for 25 days, 30 days, 35 days, and 40 days. The antioxidant potential was assessed using a Trolox Equivalency Antioxidant Capacity (TEAC) Assay for all 36 samples. Samples were diluted with distilled water and homogenized for PH and Brix readings. A PH meter was used for PH assessment, and a refractometer was used for Brix assessment. An ANOVA analysis was performed to assess the results. RESULTS: The TEAC values observed for the samples prepared by sous vide (21.82 uMol Trolox/g wet weight black garlic sample) were significantly higher than those prepared by dehydrator 12.35 82 uMol Trolox/g wet weight black garlic sample) and fermentation station (7.24 82 uMol Trolox/g wet weight black garlic sample), see Figure 1. Temperature was also significant on TEAC values (p = 0.004), samples prepared at 68°C (18.60 82 uMol Trolox/g wet weight black garlic sample) were significantly higher than those prepared at 57°C (9.56 82 uMol Trolox/g wet weight black garlic sample), and those prepared at 63°C (13.23 82 uMol Trolox/g wet weight black garlic sample) were not significantly higher than those prepared at 57°C (9.56 82 uMol Trolox/g wet weight black garlic sample) (p= 0.325), and not statistically significant between those prepared at 63°C (13.23 82 uMol Trolox/g wet weight black garlic sample) and 68°C (18.60 82 uMol Trolox/g wet weight black garlic sample) (p= 0.096). There was no significant effect of time (p = 0.832), and no significance in any combination of time comparisons (all p values >0.05). There are also significant interaction effects between machine and time (p = 0.034). There is a positive correlation between temperature and TEAC value, showing that for every 1 °C increase in temperature, a prediction of an increase of 0. 812 TEAC value can be expected. The PH test resulted in a significant difference among temperature, time, and machine. For Temperature, the post-hoc tests show that of 57°C (5.01) was significantly higher than 68°C (4.74) (p < .001), 63°C (4.93) was significantly higher than 68°C (4.74) (p < .001), but not between 57°C (5.01) and 63°C (4.93) (p = .096). For time, 25 days (5.02) was significantly higher PH than 30 days (4.86) (p = .003), 25 days (5.02) was significantly higher than 35 days (4.87) (p = .006), 25 days (5.02) was significantly higher than 40 days (4.81) (p < .001). There was no significance found between 30 and 35 days (p = .995), or 30 and 40 days (p = .604), or between 35 and 40 days (p = .454). For machine, dehydrator and fermentation station, and sous vide (all p-values < .001). The fermentation station (5.15) showed significantly higher PH than both the dehydrator (4.87) and the sous vide (4.65). The dehydrator (4.87) showed significantly higher PH than then sous vide ( 4.65). It is predicted that for every 1 °C increase in temperature, there will be a -0.024 decrease in PH, and for every 1 day increase in time, there will be a -0.013 decrease in PH. The Brix tests resulted in a significant difference among time, temperature, and machine. For temperature, the post-hoc tests show that 57°C (52.81) was significantly lower than and 68°C (56.875) (p = 0.050), but not between 57°C (52.81) and 63°C (54.79) (p = 0.467), 63°C (54.79) and 68°C (56.875) (p = 0.431 ). For time, the post-hoc tests show that 25 days (52.94) was significantly lower than 30 days (58.19) (p = 0.013) only, but not between 25 days (52.94) and 35 days (53.75) (p = 0.784), 25 days (52.94) and 40 days (55.42) (p = 0.287), 30 days (58.19) and 35 days (53.75) (p = 0.114), or 30 days (58.19) and 40 days (55.42) (p = 0.480), or between 35 days and 40 days (p = 0.822). For machine, the dehydrator (83.96) was significantly higher than the fermentation station (51.04) (p < .001), the fermentation station (51.04) was significantly higher than the sous vide (29.48) (p < .001), and dehydrator (83.96) was significantly higher than the sous vide (29.48) (p < .001). The linear regression model for Brix had an R-squared value of 0.000, indicating that the model did not explain any of the variance in the data. CONCLUSION: Machine and temperature had the most significant effects on the TEAC values, though the fermentation station and dehydrator were not significantly different from one another's results. Time did not have a significant effect on TEAC values. Results predict that for every degree Celsius the temperature is increased, there will be a 0.812 increase in antioxidants. The test results indicate that the effects time, temperature, and machine have on PH are all significant variables. The results also indicate a correlation between temperature and PH, as well as time and temperature on PH. The Brix results indicate that time, temperature and machine all had a significant effect on the degrees Brix. However, there was no definitive correlation found between the variables.

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