The potential of different spectroscopic techniques for evaluating potato (Solanum tuberosum L.) quality was investigated. Spectral data in the wavelength range of 400-1750 nm were used to develop quality prediction models. The Partial Least Squares (PLS) regression was used for predicting the water content in potato samples. Water content was predicted with R2 ≥ 0.938. / A further study was conducted to find the best wavelengths for predicting water content using two methods, PLS and multiple linear regression. Wavelength ranges of 910-1020, 1129-1211, 1363-1403 nm were selected for samples without skin, while 700-900, 930-1050, 1100-1300, 1400-1550 nm were selected for samples with-skin. Weight prediction models were established using the predicted water content. / Visible spectroscopy was used for classifying shriveled and non-shriveled potatoes. The wavelength ranges best suited to such a classification were those of 442-452, 456-466, 641-651, and 684-694 nm, with accuracies as high as 94.28% and as low as 80%.

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Chipping varieties and model systems were used to determine the role of potato constituents on chip color. Composition was evaluated by HPLC and chip color measured using a ColorQuest colorimeter. Reducing sugar (RS) content did not completely explain color quality when present in low concentrations (<60 mg/lOOg). Levels of ascorbic acid, glutamine and a chlorogenic acid isomer, along with RS, showed high correlation with color. Sucrose was a poor estimator of chip color. Model systems used leached potato slices infiltrated with solutions containing sucrose, RS, ascorbic, chlorogenic and amino acids. Linear association of RS with L* and hue angle and quadratic relationship with chroma of chips were found. Ascorbic acid affected chroma and hue at low RS levels while chlorogenic acid was not involved in color development. Red potatoes {Solarium tuberosum and Solarium stenotomum) were evaluated as potential source of natural red colorant. Cultivars (33) were screened for anthocyanin content and qualitative composition. Monomeric anthocyanin content, determined by pH differential, ranged between 4 and 40 mg/lOOg fresh weight (fw) tuber. Varieties 5847-1 and ND04069-4 showed high anthocyanin content (>35 mg/lOOg). Anthocyanin composition was characterized by HPLC, spectral analysis and Mass Spectroscopy (MS). The major anthocyanin was pelargonidin-3-rutinoside-5-glucoside acylated with p-coumaric acid. The presence of glycoalkaloids (α-solanine and α-chaconine) was detected by MS and quantified by HPLC. Varieties NDO4069-4 and 5847-1 showed glycoalkaloid levels of 13 and 7 mg/lOOg fw, respectively. Glycoalkaloids were precipitated from pigment concentrates by alkaline treatment. The best results were obtained at pH 8.0 with 30% monomeric anthocyanin degradation and 90% glycoalkaloid precipitation. The color and pigment stability of chemically related anthocyanin extracts (red-fleshed potatoes and radishes), the effect of pigment purity, and temperature were evaluated in model juices (pH 3.5). Color (CIELch) and anthocyanin degradation was monitored for 65 wks of storage. All model juices showed color similar to FD&C Red # 40. Excellent stability was obtained with all treatments in refrigeration. Anthocyanin structure and extraction method affected pigment stability. At 25°C, higher stability was obtained on juices colored with chemically purified radish anthocyanins (22 wk half-life) and lowest with potato vegetable juice (10 wk half-life). / Graduation date: 1999

The composition of the non-starch polysaccharides in sweet potato was determined and their flatulence-inducing potential evaluated. A preparative adaptation of the AOAC enzymatic method was used to isolate the insoluble and soluble non-starch polysaccharides. The insoluble non-starch fraction was mainly cellulose, but contained a substantial amount of hemicellulosic glucose, suggesting the presence of an independent glucan fraction. Relatively small amounts of xylose, galactose, arabinose, mannose, rhamnose and fucose were present. Galactose was the predominant sugar in the soluble non-starch polysaccharide fraction, although substantial quantities of arabinose and mannose were also present. Xylose, rhamnose, glucose and fucose were also present in small quantities. Uronic acids also made up a substantial portion of the soluble non-starch polysaccharides. Appreciable protein and ash were present in both the insoluble and soluble NSP fractions. The in vitro test for gas production using Clostridium perfringens as a test organism showed that both the insoluble and soluble non-starch polysaccharides are potential flatulence-inducers in sweet potato. However, the presence of the hemicellulosic glucans in the insoluble fraction make the latter a more likely candidate for flatus-inducer. / Master of Science