Effect of soil temperatures at harvest on the bruise resistance of potatoes

The effect of soil temperature at harvest time on the bruise resistance of potatoes was determined by dropping a weight onto tubers, by dropping tubers, and by sampling commercially harvested potatoes. The results show that a positive linear relationship exists with bruise resistance increasing as soil temperature increases. Shifts in the regression function during the one season studied suggest that some factor or factors which were influenced by time also affected the bruise resistance rating. However temperature of the tubers (and hence, of the soil) at harvest remains the major determinant of the resistance of potato tubers to bruising. Correlation between the bruise rating and soil temperature, as found in the commercial operation, indicates that the relationship is of a magnitude to be of economic importance. An average of 20% of the Katahdin tubers sampled were bruised in the harvesting process and were a potential loss from marketing channels.     

Rates of internal blackspot bruise development in potato tubers under conditions of elevated temperatures and gas pressures

Internal blackspot bruising was produced in Russet Burbank tubers by dropping a 150 g weight 40 cm through a slotted guide tube and incubating the tubers for varying time periods at temperatures ranging from 10 to 80 C. When potatoes were bruised following 1 to 5 months storage, those tubers incubated at 10 C required 48 hr for maximum blackspot development. Increasing the incubation temperature accelerated blackspot formation with an optimum response at 36 to 40 C. At 40 C tubers reached maximum discoloration within 6 hr. Bruised tubers were also exposed to combinations of varied temperatures and varied gas pressures of 0.3 to 2.1 kg/cm² using air, O₂, CO₂, and N₂. Pressurized air slightly enhanced the temperature effect at 40 C; pressurized O₂ had no significant effect upon blackspot development, while CO₂ and N₂ inhibited blackspot formation. Blackspot bruises incurred in the field during harvest required a longer incubation period at a lower temperature than did bruises inflicted on tubers held in storage for 1 to 5 months.     

Determination of thiabendazole residues in potatoes using high pressure liquid chromatography

Summary This paper describes a method for the extraction, purification and quantification by high pressure liquid chromatography using fluorimetric detection, of thiabendazole residues from potatoes. Bonded silica sorbent extraction columns (diol phase) are used for sample clean up, resulting in a rapid and accurate analysis. The average recovery was 93.8%±2.1%. Levels of about 0.0004μg of TBZ, equivalent to 0.033 mg kg⁻¹ in potatoes (on fresh weight basis), were readily detected from deliberately contaminted potatoes.     

Inheritance of blackspot bruise resistance in potato

Inheritance of blackspot bruise reaction in tetraploid potato was studied using a five-parent half-diallel, including parental selfs. The parents were chosen to represent the full range of blackspot reactions. Four 12-plant replications of each family were grown at Aberdeen, Idaho and at Prosser, Washington. The abrasive-peel method was used to evaluate the blackspot reaction. Highly significant general combining ability (GCA) effects and specific combining ability (SCA) effects were observed for this trait. The GCA and SCA variances represented 59% and 9%, respectively, of the total variance. GCA effects are presented for the parents. The narrow sense heritability was 0.85. These results indicate that breeding for resistance to blackspot should be successful if resistant parents are used; backcrossing may be needed.     

Suberization and periderm development in Norchief and Red Pontiac potatoes

The largest difference in the rate of wound healing (suberization and periderm development) of cut tubers was attributable to the difference in temperatures (15.5 vs 23.8 C) tubers were stored at after cutting. Lesser differences were found between the Red Pontiac and Norchief cultivars and between the various regions of the tuber. The least difference was found between the different sources of Norchief. Wound healing occurred most rapidly at 23.8 C, in Red Pontiac and in the cortical region of the tuber. It seems probable that a major cause of the high incidence of seed piece decay and poor stands found in Norchief is due to slow wound healing.     

Comparison of inoculation methods on ring rot development in potatoes

Symptoms of bacterial ring rot (Corynebacterium sepedonicum) developed earlier and were more severe in root-inoculated potato plants grown from stem cuttings treated with indole-3-butyric acid (IBA) than in those grown from stem cuttings not so treated or from tuber seed pieces. Disease expression was more rapid and severe in root-inoculated plants than in plants from inoculated seed pieces. The use of IBA-treated stem cuttings provided uniform plant material for ring-rot studies.     

Friction force and pressure causing “skinning” of potatoes

American Journal of Potato Research - A technique for measurement of frictional force and pressure required to cause skinning of potatoes is described. The technique yields data which include...     

Double-dip caustic peeling of potatoes I: Laboratory-scale development

A modified caustic peeling process for potatoes was developed and evaluated. The process, called the double-dip process, comprises two separate caustic applications with an intervening holding period. Results on Russet Burbank potatoes showed that tissue removal was enhanced for the double-dip process when compared to the standard single dip process and that the double-dip process can effect reduction in caustic usage without requiring additional heat input.     

Composition of sulfited potatoes: Comparision with fresh and frozen potatoes

The content in moisture, fat, protein, carbohydrate, fibre and vitamin C was analyzed in three commercial types of potatoes: sulfited (treated with E223), frozen potatoes (pre-fried) and fresh potatoes (not processed). The composition of sulfited potatoes does not usually appear in food composition tables. Our results showed significant differences in the content of carbohydrates and fibre between sulfited and fresh potatoes. The content of vitamin C in sulfited potatoes, which is similar to that of frozen potatoes, was shown to be approximately half of that found in fresh potatoes.     

Harvesting potatoes with minimum damage

Temperature, tuber condition and harvester operation must be considered if potatoes are to be harvested with minimum damage. In general, total damage increased as temperature decreased; however, the type of damage resulting from impact was influenced by temperature and tuber condition. The data indicate that a tuber turgidity level occurs wherein total damage susceptibility level is minimal for a given tuber temperature and that the proper tuber turgidity level changes as temperature changes. A tuber hydration level which produces little damage when bruised at a flesh temperature of 65–70 F results in severe damage (shatter bruise) when subjected to the same force at 45–50 F. Conversely, a hydration level which results in severe blackspot at 65–70 F may result in slight to moderate total damage when subjected to the same impact at 50–55 F. Data from several commercial harvester studies indicate that damage may increase rather than decrease with a reduction of harvester speed. The ratio of chain speeds to forward speed was found to be more important than forward speed alone. The optimum ratios varied and were dependent on potato yield. Theoretical ratios based on the volume of tubers at different yield levels and harvester chain capacities were calculated and compared with actual ratios of commercial harvest operation. Harvesters operated with chain speed to forward speed ratios near the theoretical ratios resulted in low tuber damage (25%) with forward speed ranges of 1.60 to 3.25 mph. Harvesters operating with ratios differing considerably from theoretical ratios resulted in a high level of damage (66%). The catechol test identified shatter bruise damage which ruptured the skin, but did not detect internal blackspot. Therefore, the catechol test should be used with discretion when attempting to determine the total damage level. Lye peeling and abrasive peeling identified both blackspot and severe shatter bruise damage and should be used when determining harvester operation speeds when both types of damage occur.