Recent reports, especially those of Russian scientists, have emphasized that application of stimulatory concentrations of naphthenates (Naps) induced greater and better growth and productivity of a number of species of plants. This stimulatory action of Naps has been found to result from seed soaking and spraying seeds or developing plants once or repeatedly. However, no systematic attempt has so far been made to investigate physiological and biochemical changes induced in a relative short period following immediately these treatments. A correlation of such changes with final improvements in growth and yield may provide a better understanding of the mechanism of action of Naps It was therefore essential and significant to investigate these aspects. Seeds of tomato (Lycopersicum esculentum var. Bonny Best) were germinated in wooden flats containing sterilized soil and were transplanted when 10 days old to plastic pots of 6 inche diameter containing sterilized soil. The plants were grown in a growth room. In separate experiments, potassium naphthenate (KNap) aqueous solutions, 2,500 ppm and 5,000 ppm, were sprayed onto tomato leaves when plants were 2, 3, and 4 weeks old. Measurements of vegetative growth, based on fresh and dry weights of plant tops, indicated that maximum stimulation was induced by the 5,000 ppm KNap solution applied to plants when 3 weeks old. It was then decided to investigate the biochemical and physiological responses of the tomato plants to 5,000 ppm KNap when treated at the age of 3 weeks. Determinations of pigment content, intensities of photosynthesis and respiration, activity of enzymes involved in nitrogen metabolism, such as nitrate reductase (NRase) and glutamic-pyruvic transaminase (transaminase), and of enzymes involved in carbohydrate metabolism, such as succinic dehydrogenase, phosphorylase, and phosphoglyceryl kinase were made three times at 2-week intervals, beginning 2 weeks after the spraying. Number and fresh weight of tomato fruits, quality of tomato fruits in terms of sugars, titratable acidity and ascorbic acid were also investigated at scheduled intervals. Results indicated the following: (1) In the treated plants, the content of the pigments chlorophyll a and b, and especially carotenoid, in the leaf blades was higher than in control plants, (2) Measurements made with intact plants using an infrared CO₂ analyzer revealed increases in intensities of photosynthesis and respiration of the aerial portions 4 weeks after treatment but the opposite was true 2 weeks after treatment, (3) Under the influence of KNap, of the 5 enzymes examined only phosphorylase activity was found to be stimulated at all three observation times. Transaminase activity was greater 6 weeks after treatment. Activities of succinic dehydrogenase, NRase, and phosphoglyceryl kinase were all reduced by treatments, (4) In a subsequent experiment, leaf blades of plants treated when 2 weeks old were analyzed for succinic dehydrogenase activity 4, 8, 12, 16, 20, and 24 days after spraying. The effect on succinic dehydrogenase activity fluctuated with the age of the plant. Parallel changes in the protein content of the enzyme extract could not be detected, (5) Tomato fruit yield, based on number and fresh weight, was decreased by 2,500 ppm KNap treatment but increased by 5,000 ppm KNap. In addition, 5,000 ppm KNap-treated plants were more resistant to blossom-end rot and showed better and quicker recovery when the deficiency disease was treated with CaCl₂. Earlier maturity was found in 5,000 ppm KNap-treated plants, (6) The mature tomato fruits from 5,000 ppm KNap-treated plants contained larger amounts of sugars (reducing sugar and sucrose) than the controls, and the sugars in mature tomato fruits were lost at a lower rate during the storage period. The treatment resulted in decreased titratable acid and ascorbic acid content. It afforded no protection against loss of titratable acid and ascorbic acid during storage. / Science, Faculty of / Botany, Department of / Graduate

In the modern era consumer awareness on quality aspects has been a growing concern for the fresh produce market due to the fact that consumer perspective defines the bottom line of all agricultural businesses. External damage to produce does not only render fruit less attractive but damaged locations serve as entry points for pathogens resulting is food safety issues. Because tomatoes have a limited shelf life, it is vital to control the factors that lead to earlier deterioration of the quality of the product. Shipping, handling and distribution can cause numerous forms of cuts and bruises on harvested tomatoes which compromise their quality and appearance. Furthermore the economic value to the retailer and grower is reduced (Chonhenchob et al., 2009). Post-harvest science focus mainly on the quality of fresh produce. One of the areas of interest is the shipment of tomatoes using road transport. Trucks are one of the best methods for transporting perishable products because of shorter transport times and the ability to reach more inland destinations than any other mode of transport (Jarimopas et al., 2005; Chonhenchob et al., 2009). Although the flexibility of road transport is an advantage, previous studies have indicated that fruit and vegetables suffer mechanical damage due to in-transit vibrations which is caused by the road condition (Jarimopas et al., 2005). The condition of roads in South Africa is dependent on the management plan execution by the managing agent. The National Road Network, maintained by SANRAL is predominantly in a good condition (Ittmann, 2013). In contrast, condition assessment data for provincial roads indicate that roads are deteriorating at an alarming pace, not to mention that the majority of road networks under municipal authorities have no data at all (SAICE, 2011). To date there is no model that relates tomato damage and loss in shelf life to the road condition, fruit maturity and position in the container. For this experiment the in-transit conditions were monitored on trucks travelling from three farms in Limpopo, owned by the ZZ2 group, to the fresh produce market in Pietermaritzburg. These trucks drive on a variety of roads including gravel or rural roads where higher roughness values are probable along with more produce damage. The experimental setup consisted of two phases. The first phase was the in-transit monitoring of the conditions to which tomatoes are exposed when shipped from grower to the farmers market. The second phase was the laboratory simulation of in-transit conditions to create a model for the prediction of shelf-life under controlled conditions. Equipment for the field experiment included a profilometer to determine road conditions, accelerometers to determine in-transit vibrations, pressure sensors to determine in-transit pressures. Equipment for the laboratory experiment included a vibration table to simulate different road conditions, pressure sensors to measure pressures that can be related to in-transit pressures and a colour meter to measure colour changes in damaged and control tomatoes. From the in-transit pressure analysis it was concluded that the amount of pressure cycles that a tomato experience increase as the roughness of the road increase and the force distribution that is applied to the tomatoes becomes wider to include forces larger in magnitude. Good correlations existed between in-transit and laboratory pressures. Colour measurements had no strong trends that could be related to damage and an experimental model based on consumer perspective was developed. The experimental model was designed based on a marketability matrix that models the decision of the consumer on whether to purchase a tomato or not. Ultimately it is a subjective matter and each consumer would react differently towards the colour and firmness of the tomato in question. The model indicated that for roads with high roughness values (International Roughness Index (IRI) > 8 m/km), which mostly consist of farm roads that are poorly maintained, all tomatoes in the first and second layers would acquire significant damage irrespective of the maturity of the fruit. On well-maintained roads with roughness values less than 3.5 m/km red tomatoes in the top layers tend to damage more with an increase in time as compared to tomatoes in the lower layers. Green and pink tomatoes are more resistant to damage in the top layers than the red tomatoes. From the damage models it is apparent that as the roughness of the road increases the damage to tomatoes increase as well. Tomato maturity and the position of the tomatoes in a container also influence the amount of damage to the fruit. With this information in hand, logistic planners can make informed decisions during route planning in weighing transportation costs to the cost of losses to produce during transportation. Similar models can be developed to include other fruits and vegetables. / Dissertation (MEng)--University of Pretoria, 2017. / Tamatie Produsente Organisasie (TPO) / ZZ2 / Post-Harvest Innovation Program (PHI) / Civil Engineering / MEng / Unrestricted

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

Fresh and fresh-cut tomatoes have been associated with numerous outbreaks of salmonellosis in recent years. While the exact routes of contamination are unknown, high pressure processing (HPP) is being evaluated as a post harvest treatment to eliminate Salmonella enterica from tomatoes. The objectives of the study were to determine the potential for of HPP to reduce S. enterica serovars Newport, Javiana, Braenderup and Anatum (clinical isolates from tomato outbreaks) in tryptic soy broth (TSB) and to determine the effect of HPP to reduce the most pressure resistant S. enterica serovar from fresh diced and whole tomatoes. Five ml portions of broth containing 8 log CFU/ml of one of the four serovars (nalidixic acid resistant) were packaged in sterile stomacher bags and subjected to one of three different pressures (350, 450, or 550 MPa) for 120s. Samples were enumerated by surface plating onto tryptic soy agar supplemented with 50 ppm nalidixic acid (TSAN) and incubated at 35°C for 48 hours. The most pressure resistant S. enterica serovar evaluated was Braenderup. Subjecting the broth culture to 350, 450 and 550 MPa resulted in a 4.53, 5.74 and 7.09 log reduction in S. Braenderup, respectively. Diced tomatoes (150g) and whole red round tomatoes (150g; packaged in 350ml of 1% CaCl2) were inoculated with S. Braenderup, to obtain 6 log CFU/g throughout the sample and subjected to the same pressure treatments as described above. After HPP, diced tomatoes were homogenized for 1 minute and then plated on TSAN. Whole tomatoes were surface sampled, and then homogenized for 1 minute. Surface and homogenate samples were plated on TSAN supplemented with 1% pyruvic acid (TSANP). Significant reductions of S. Braenderup concentrations in diced tomatoes (P < 0.05) were seen after processing at 350 (0.46 CFU/g), 450 (1.44 log CFU/g), and 550 MPa (3.67 log CFU/g). In whole tomatoes, significant reductions (P < 0.05) were also seen at 350 (1.41 log CFU/g), 450 (2.25 log CFU/g) and 550 MPa (3.35 log CFU/g). There were no differences in visual appearance between fresh and HPP diced and whole tomatoes. HPP may be an effective post harvest strategy to reduce low levels of S. enterica contamination in diced tomatoes. / Master of Science in Life Sciences