Sensory evaluation and instrumental methods were applied to the evaluation of strawberry juice concentrate (68°Brix) stored at 20°C which had been produced both commercially (C-SJC) and in a pilot plant (SJC). Sensory evaluation included taste and aroma ratings by intensity scaling and time-intensity of taste, and visual colorimetry by matching Munsell color chips. Instrumental analyses included tristimulus colorimetry (i.e. Hunter colorimeter), spectrophotometric colorimetry for pigment analyses, titrametric analyses for acidity (pH and titratable acidity) and free α-amino acids (formol number), and headspace gas analyses for CO₂ and O₂. During six days storage of C-SJC, a decrease in concentration of anthocyanins and increase in polyphenolics (tannin) was associated with an increase in astringency. Free α-amino acids were observed to decrease, while CO₂ was released. These changes were associated with an increase in musty/moldy and pungent aromas. Free sugars and titratable acidity did not change. The pilot plant SJC was processed from blanched and unblanched fruit to evaluate the relative importance of oxidase activity (i.e. polyphenoloxidase) prior to pasteurization. The blanching treatment increased the astringency and sourness in unstored SJC. These affects were associated with an increase in concentration of polyphenolics (tannin). During storage, the blanch treatment decreased the rate of anthocyanin loss and decreased the release rate of CO₂, yet degradation rates were still high. The 0₂ concentration in headspace did not change significantly during storage indicating that polyphenoloxidase (PPO) activity during storage was low. The musty/moldy and pungent aromas increased similarly to C-SJC. A chemical mechanism accounting for these changes is proposed where products from the oxidative degradation of ascorbic acid contribute directly or indirectly to the degradation of anthocyanins to yield browning. Further, high initial concentrations and subsequent decreases during C-SJC storage of free α-amino acids indicate that Strecker degradation is a participating mechanism. Associations of browning with the development of off-flavors suggest this chemical mechanism forms odor-active volatile compounds. / Graduation date: 1989

Response Surface Methodology (RSM) was used to study the effect of two variables, sugar level (12-16 °Brix) and acid level (0.3-0.7 % T.A.) on sensory qualities and desirability of blackberry juice drinks. Three blackberry juice levels (10%, 15%, and 20%) were used to study the influence of juice flavor on sensory qualities and desirability of the juice drinks. A trained panel evaluated three attributes, blackberry flavor, sweetness, and sourness intensities, of the juice drinks. The consumer panel gave desirability and three attributes just-right ratings. A Balanced Complete Block Design was used. Blackberry flavor intensity was enhanced by sugar level. Blackberry flavor intensity was enhanced by acid level to a point about 0.5% T.A., and then decreased. Blackberry flavor intensity was not related to °Brix:acid ratio and was only related to the sweetness:sourness ratio at the 20% juice level. Sweetness and sourness intensities increased with increasing sugar and acid levels. There was a suppression effect of sugar and acid on each other in the juice drink. The relationships of sweetness, sourness, and sweetness:sourness ratios to °Brix:acid ratios were all linear. Desirability rating was related to °Brix:acid and sweetness:sourness ratios for the 10% and 20% juice levels, for 15% juice level no association was found. The formula which received the closest to "just right" ratings and highest overall desirability rating had in a °Brix of 15.4 and a % titratable acidity of 0.64, resulting in a °Brix:acid ratio of 24 and a corresponding sweetness:sourness ratio of slightly less than 1.0. In general, the 15% juice level was the best because of its sugar and acid tolerance and high desirability. / Graduation date: 1989

Fresh ripe, cantaloupes were processed into juice and juice concentrate. Processing trials were conducted on fresh and frozen fruits with and without rind. The effects of maceration enzymes and fining agents on yield and quality were investigated. Compositional measurement included °Brix, pH, titratable acidity, formol values, ascorbic acid content, total carotenoids, sugar and nonvolatile acid profiles, browning indices and Hunter color parameters. Considerable ascorbic acid degradation occurred during processing. The high juice yield (80%) and low acidity suggest its potential use as an alternate sweetener source. Sensory evaluation by a trained panel showed that concentrating the juice samples from flesh and rind can remove the rind aroma and flavor characteristics. Juices obtained from flesh and from flesh and rind were not significantly different (p [less than or equal to] 0.05) except for overall intensity and fresh fruit flavor characters. Single strength juice was significantly different (p [less than or equal to] 0.05) from concentrate on most aroma and flavor characters. / Graduation date: 1991

Graduation date: 1994