Master of Science / Food Science / J. Scott Smith / The objective of this study was to observe the effect of natural cocoa powder versus 200 ppm of tocopherols on delaying the onset of oxidative rancidity in peanuts, peanut butter, and peanut oil. The samples were obtained from a single lot of blended Runner peanuts after roasting, grinding, and pressing. The samples were treated within a week of initial roasting with either 200 ppm of mixed tocopherols or 2.5% cocoa powder. The development of oxidation was monitored by peroxide value (PV) and gas chromatography monitoring of hexanal development. The peanut butter samples were assessed by a professional sensory panel using descriptive analysis for the development of rancidity. The data was analyzed using JMP SAS software. In peanuts, the cocoa powder sample developed significantly lower levels of oxidation identifiers than the tocopherol or control samples. In peanut oil, there was no significant difference in levels of oxidation identifiers between the treatments. In peanut butter, the PV was significantly higher in the tocopherol sample than the cocoa powder or control samples, but no significant difference was observed in hexanal. The results of the sensory analysis indicated that the cocoa powder depressed the perception of both positive and negative attributes compared to the tocopherol and control samples. This study showed that cocoa powder may be a more effective preservative than an untreated sample or a sample treated with 200 ppm of tocopherols in peanuts and peanut butter; however, cocoa powder at 2.5% w/w basis did not perform as a significant antioxidant in peanut oil.

Digitized by Kansas Correctional Industries

Peanuts contribute significantly to food security in western Kenya due to their high nutritional value and cash crop potential. However, the crop is highly susceptible to aflatoxin contamination. Yet little information is available on the extent of contamination in the region. This study explores the level and extent of contamination of peanuts by aflatoxins, Aspergillus section Flavi, Rhizopus and Penicillium spp. in western Kenya. A survey of 769 households was carried out in the Busia and Homa bay districts of Kenya. Information on peanut pre- and post-harvest practices was collected through person-to-person interviews. Aflatoxin levels of samples collected from each household were determined by indirect competitive ELISA method. Isolation of Aspergillus section Flavi, Penicillium and Rhizopus spp. was done on Modified Dichloran Rose Bengal (MDRB) agar, while identification of specific fungal species was done on Czapek yeast extract agar (CYA). Screening isolates of A. flavus and A. parasiticus for aflatoxin production was done in high sucrose yeast extract (YES) liquid medium, and the aflatoxin types identified on TLC plates, using analytical grades of aflatoxin B1, B2, G1 and G2 as reference standards. Common household preparation techniques (roasting, making peanut paste and boiling peanuts) were evaluated for effectiveness in reducing aflatoxin levels in peanuts. The boiling procedure was modified to test the effect of magadi (locally available salt used mainly to soften legumes, vegetables or maize while cooking), ammonium persulphate and sodium hypochlorite during soaking. Magadi, sodium bicarbonate and locally prepared ash was subsequently used to boil the nuts after soaking. Aflatoxin levels ranged from zero to 7525 ìg/kg. Most samples were safe to consume, based on the European Union and Kenya Bureau of Standards tolerance levels, with 63.7 per cent of all samples having undetectable levels, and only 7.54 per cent being contaminated based on KEBS standards. Peanuts from the Busia district, which has more of Lower Midland 1 (mean annual rainfall of 1600-1800 mm) and Lower Midland 2 (mean annual rainfall of 1300-1700 mm) agro-ecological zones had significantly (÷2=14.172; P=0.0002) higher levels of aflatoxin compared to the Homa bay district, that has more of the drier Lower Midland 3 agroecological zone (mean annual rainfall of 900-1500mm). Improved cultivars had significantly (÷2=9.748; P=0.0018) lower levels of aflatoxin compared to local cultivars. Over 60 per cent of all samples had A. flavus S-strain, A. flavus L-strain and A. niger. A. flavus S-strain was positively correlated with aflatoxin levels. As expected, grading of peanuts post-harvest significantly reduced the incidence of A. flavus S- and L-strains, while peanuts collected from farmers who belonged to producer marketing groups had a significantly lower incidence of A. flavus S- and L-strains, A. niger and Rhizopus spp. The incidence of A. flavus L-strain, A. niger and Rhizopus spp. was significantly higher in local landraces compared to the improved cultivars. Over 60 per cent of isolates produced Aflatoxin B1. Intermediate processes such as sorting and dehusking led to a significant decline in levels of aflatoxin. Soaking peanuts in water, magadi, NaOCl and ammonium persulphate significantly reduced aflatoxin levels by 27.7, 18.4, 18.3 and 1.6 per cent respectively; while boiling the peanuts in magadi, local ash, baking powder and water reduced aflatoxin levels by 43.8, 41.8, 28.9 and 11.7 per cent respectively. Using magadi during boiling increased the acceptability of the boiled peanuts while reducing the aflatoxin levels. The impact of aflatoxin levels in peanuts studied in this research is within safe limits except a few samples, and therefore aflatoxin contamination of peanuts at household level is not a serious threat. Contamination by aflatoxin and post-harvest fungi can be reduced by focusing on improved control strategies for wetter and more humid zones such as planting improved peanut cultivars and controlling pre-harvest pest damage. Conventional household peanut preparation techniques should be explored as possible aflatoxin management strategies in Kenya. The aflatoxin binding properties of locally available salts such as magadi and locally prepared ash should be further investigated. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 54-59).

Dissertation (Ph.D.)--Auburn University,2009. / Abstract. Includes bibliographic references (p.94-104).

Thesis (Ph. D.)--Auburn University. / Abstract. Vita. Includes bibliographical references.

Ph. D.

The peanut is an important crop in most countries due to its industrial, nutritional, and pedological potential. It grows well in subtropical areas. This study was planned based on the weather characteristics of the Yungas and the St. Felix community. A completely randomized block design with 6 treatments and 3 repetitions was used. An analysis of variance and a Tukey test were used for statistical analysis of the variables. With respect to time required for maturation, the Coloradito Palmar variety was most premature with a time of 134 days while the Local variety took 177 days to mature, which is considered late. With respect to plant height during the different stages (establishment, vegetative, flowering, fructification, and maturation), the Local variety grew the most with a value of 64.23 cm during physiological maturity. The Local variety also had the largest number of pods per plant with a value of 49.50. On the other hand, the Coloradito Palmar variety had the lowest value with 17.07. The largest number of grains per pod was reached by the Coloradito Palmar variety with a value of 2.35 and the smallest number was reached by the Colorado Gigante variety with a value of 1.66. The Overo Gigante variety had the largest values for pod and grain weight with 4.54 g and 1.77 g respectively. The smallest pod weight was obtained by the Coloradito Palmar variety with a value of 2.47 g while the smallest grain weight was obtained by the Local variety with a value of 0.78 g. With respect to pod length, the Colorado Gigante variety was longest at 4.25 cm and the Virginia variety was shortest with a measurement of 3.27 cm. The varieties that had the largest seed or grain size were Colorado Gigante and Overo Gigante with a size of 2.04 cm while the Coloradito Palmar variety had the smallest measurement of only 1.52 cm. Furthermore, the Virginia variety had the highest yield at 2.89 t/ha and the Coloradito Palmar variety had the lowest at 0.71 t/ha. After analysis, the total cost of production for each variety is 8,620 Bolivianos/hectare. The analysis of the cost-benefit ratio showed that only the Virginia (1.58) and Local (1.30) varieties would be profitable due to their higher yields. Thus, these varieties can be considered as an economic alternative for farmers in the area.

A deep-bed drying model simulating the drying of peanuts in a fixed bed is required for designing energy-efficient and automatically controlled dryers. A deep-bed drying model consists of a thin-layer drying model to calculate the moisture release from the material and a set of mass and energy balances. An experimental setup was constructed to determine drying rates of Virginia-type peanuts under 14 different drying air conditions. Selected empirical and semi-theoretical models available for modeling thin-layer drying rates were fitted to the collected data using nonlinear regression techniques. The modified Page's model and the two-term exponential model fitted the data better than other models considered. A deep-bed drying model PEATECH based on four coupled partial differential equations consisting of four variables, air temperature, peanut temperature, air humidity, and peanut moisture content was developed. Validation of the model was accomplished by using the data collected from 36 deep-bed drying experiments conducted using three laboratory dryers during 1987, 1988, and 1989. PEATECH predicted the variables within a peanut bed with an accuracy of less than ± 6%. The energy saving potential of exhaust-air recirculation was established by conducting simulated experiments using a modified version of PEATECH. / Ph. D.

Preventing flavor fade requires an understanding of the relationship between carbonyl amine and lipid oxidation reactions. The polyunsaturated fatty acid content of lipids in peanuts makes them more susceptible to lipid oxidation. The major by-products of the oxidation reaction are nonanal, hexanal, octanal, and decanal. These chemicals are associated with cardboardy, painty, and oxidized flavors associated with flavor fade. The carbonyl-amine reaction yields a variety of pyrazines with positive flavor attributes. Initial flavor notes were explored through sensory work, Gas Chromatography-Olfactometry, and chemical analysis. The fresh roasted volatiles produced from roasted peanuts and the aldehydes resulting from oxidation were also evaluated using GC-FID to quantify and identify the pyrazines and hexanal over a 21 day storage period. Electronic Nose was used to determine differences between storage periods. Gas chromatography-Olfactometry identified potent pyrazines contributing to fresh roasted peanutty aroma in fresh peanuts. Using GC-FID a significant decrease (p<.05) in 2-ethylpyrazine and 2,3-diethylpyrazine concentration was found over a 21-day period. No significant difference (p>0.05) was noted in the other pyrazines evaluated. A significant increase (p<0.05) was noted in the hexanal concentration over a 21-day period. The peroxide values and sensory analysis correlated directly with the GC-FID results with a significant increase (p<0.05) in peroxide value at Day 14 and Day 21, and a significant decrease (p<0.05) in fresh roasted peanuty flavor from days 0-21 and a significant increase (p<.05) in painty, cardboardy and bitter from days 7-21. The electronic nose successfully separated Day 0 and Day 21 samples from Day 7 and 14, which were also separated, but with minimal overlap. / Ph. D.