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The possibility of evaluating the quality of blueberry fruit in chemical terms rather than by color or organoleptic methods was considered. The fruit of three varieties of commercial highbush blueberries at four stages of physiological maturity was analysed for total solids, water-insoluble solids, soluble solids, titratable acids, total acids, volatile acids, reducing sugars, total sugars and sugar-acid ratios. Differences among varieties and stages of physiological maturity were sought by use of the above measurements supplemented by a study of the individual organic acid patterns of the fruit. Meaningful differences were evident among the four stages of physiological maturity for all measurements except volatile acids and total solids. Varietal differences were evident from measurements of the pH, soluble solids, sugar-acid ratios, and a number of the individual organic acids. / Land and Food Systems, Faculty of / Graduate

No description available.

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: By world standards South Africa’s contribution to fresh blueberry production is very small, a mere 0.25 %. This seemingly insignificant and unimpressive statistic is, however, by no means indicative of the impending impressive potential the South African blueberry industry holds. South Africa is encountering a rapid growth phase off a very small base and the current 100-150 ton export crop is expected to increase to a range of 500 to 600 tons or more in the next five years. Consequently, export by sea must be considered as a logistic alternative. Seafreight success relies on controlled atmosphere storage which in turn relies on berries of exceptional quality. To achieve this, fundamental differences between blueberry cultivars must be examined and blueberry handling and storage regimes must be assessed and optimised. This study investigates the storage potential of certain rabbiteye blueberries relative to controlled atmospheres and short pre-cooling delays. Quality assessments were based on external colour, soluble solids, titratible acidity, firmness and decay development. Furthermore, the respiration and ethylene production rates as well as moisture loss, of various cultivars were determined to characterize fundamental differences amongst cultivars and to gain insight into their postharvest behaviour. Lastly the effect of infection on pigment levels of blueberry flesh and peel was examined for the purpose of laboratory experience. Controlled atmosphere storage had the greatest impact on berry firmness and percentage decay. No off flavours were detected during sensory analysis at the CA levels tested. CAstored berries were firmer and incidence of decay was reduced significantly. Significant decay reduction was challenged by the market tolerance of no more than 2 %. Decay suppression and storage extension was insufficient (for the set period), particularly after the shelf life period. Cultivar and seasonal differences as well as picking maturity and inoculum pressure determine blueberry CA storability. CA may be a valuable technology, however advances must first be made in ensuring optimal blueberry quality to warrant export by sea. Short pre-cooling delays (0, 2, 4, 6 h) at 20 ºC had no effect on colour (L, C, H), total soluble solids, titratable acidity and firmness of blueberry cultivars, ‘Centurion’, ‘Premier’ and ‘Tifblue’. Results for percentage decay indicate that prompt cooling becomes more critical as the duration of storage increases, particularly when market specification of no more than 2 % decay must be met. Berries subjected to longer delays appear to be more susceptible to decay. Differences exist among cultivars and knowledge gained from this research can be used to adapt handling and cooling regimes. Information generated will benefit cultivar selection for marketing (local vs. export), storage (short vs. long term) and logistics (air vs. seafreight). Rabbiteye blueberry cultivars differ considerably in terms of their respiration rate, ethylene production and moisture loss. These quality parameters were evaluated for various cultivars at 15 ºC. ‘Climax’ appears to have the highest respiration rate, ethylene production and moisture loss, whilst ‘Premier’ has the lowest respiration rate and ethylene production was too low to be detected by gas chromatography. The lowest moisture loss proportionality constant was found for ‘Tifblue’ and ‘Centurion’. A change in blueberry flesh colour from white to dark red was noted in infected berries. Artificial inoculation with Botrytis cinerea showed a similar result. The colour change was evaluated by comparing anthocyanin pigment levels (determined by spectrophotometry and HPLC) of the peel and flesh. Anthocyanin content of infected flesh doubled, whilst that of infected peel was less than 50 % of the control. Pigment leakage has been reported in blueberries. It would appear that cell disruption, induced by infection may facilitate migration of anthocyanin from the peel to the flesh. The storage potential of blueberries depends on cultivar, maturity at harvest, climatic conditions as well as the inoculum pressure. Under favourable conditions storage life of blueberries can be manipulated effectively. Further cultivar specific research that targets relevant quality issues should be investigated. Reliable techniques should be developed to quantify blueberry firmness changes. Research on inoculum levels may give insight into the reduction of decay pressure and decay suppressing alternatives such as antibacterial pads can be examined. Peel integrity relative to decay susceptibility can also be researched on a cellular level. / AFRIKAANSE OPSOMMING: Suid-Afrika se bydrae tot wêreld bloubessie produksie is baie klein, ‘n skrale 0.25 %. Hierdie onindrukwekkende statistiek weerspieel egter glad nie die indrukwekkende potensiaal van die Suid-Afrikaanse bloubessie bedryf nie. Die bedryf ondervind tans ‘n dramatiese groei met ‘n klein begin vanaf die huidige 100-150 ton opbrengs tot wat volgens verwagting binne die volgende vyf jaar sal styg tot in die orde van 500-600 ton. Na aanleiding van die verwagte toename in produksie, sal seevrag verskeping oorweeg moet word as alternatief vir uitvoer eerder as lugvrag. Die sukses van seevrag lê in die gebruik van beheerde atmosfeer opberging (BA), waarvan die sukses op sy beurt bepaal word deur bessies van hoogstaande kwaliteit. Om steeds aan die verwagtings van die oorsese mark te voldoen moet grondliggende verskille tussen bloubessie kultivars ondersoek word en daaropvolgend moet hantering en opbergingstelsels aangepas en geoptimeer word. Die navorsing bestudeer die opbergingspotensiaal van verskeie rabbiteye bloubessies relatief tot beheerde atmosfere en kort vertragings in verkoeling. Kwaliteit, gebasseer op eksterne kleur, oplosbare deeltjies, titreerbare sure, fermheid en persentasie bederf, is ondersoek. Die respirasie en etileenproduksie tempos sowel as vogverlies van verskeie kultivars was verder bepaal om die fundamentele verskille tussen kultivars te bepaal, sowel as insig te verwerf in na-oes gedrag. Die effek van infeksie op pigment vlakke van bloubessie vlees en skil was ondersoek vir die doel van laboratorium ondervinding. Beheerde atmosfeer opberging het die grootste effek getoon op bessie fermheid en persentasie bederf. Na aanleiding van sensoriese toetse is daar geen wansmaake aangeteken ten op sigte van die BA vlakke wat getoets is nie. Bessies onderworpe aan beheerde atmosfeeriese toestande was fermer en bederfonderdrukking was beduidend. Die markverdraagsaamheid ten opsigte van bessiebederf, is egter 2 %. Hiervolgens was onderdrukking van verval asook opbergingsvermoë, onvoldoende (spesifiek na die rakleeftyd). Kultivar en seisoenale verskille asook plukrypheid en inokulum druk, bepaal ook die sukses van BA opberging. BA word beskou as ‘n waardevolle tegnologie vir verlenging van opberging. Dit blyk egter dat daar eers ‘n vooruitgang gemaak moet word in die versekering van optimale bessie kwaliteit voordat verskeping oorweeg kan word. Kort vertragings (0, 2, 4, 6 uur by 20 ºC) in verkoeling, het geen invloed gehad op kleur, (L, C, H), totale oplosbare vastestowwe, titreerbare suur en fermheid van bloubessie kultivars ‘Centurion’, ‘Premier’ en ‘Tifblue’ nie. Bederfresultate dui daarop dat onmiddelike verkoeling krities is, veral by verlengde opberging, om aan die 2 % bederf drempelwaarde te voldoen. Bessies onderhewig aan langer vertragings voor verkoeling, blyk meer vatbaar te wees vir bederf. Verskille bestaan tussen kultivars en kennis ingewin tydens hierdie navorsing kan toegepas word om hanteringsprosedures en verkoeling aan te pas. Ingeligte besluitneming kan dus ten opsigte van kultivarspesifieke bemarking (plaaslik en uitvoer), opberging (kort- en langtermyn) en vervoer (lug- en seevrag) gemaak word. Rabbiteye bloubessie kultivars verskil aansienlik ten opsigte van hul respirasietempo, etileenproduksie en vogverlies. Laasgenoemde kwaliteitsbepalers is by verskillende kultivars ondersoek by 15 ºC. ‘Climax’ het die hoogste respirasietempo, etileenproduksie en vogverlies getoon, terwyl ‘Premier’ die laagste respirasietempo gehad het, en die etileenproduksie te laag was om met die gaschromatograaf te bepaal. Die laagste vogverlies proporsionaliteitskonstante is waargeneem tussen ‘Tifblue’ en ‘Centurion’. ‘n Verandering is waargeneem in bloubessie vrugvleeskleur van wit tot donkerrooi by besmette bessies. ‘n Soortgelyke resultaat is verkry met kunsmatige inokulering met Botrytis cinerea. Die kleurverskil is geëvalueer deur vergelyking te tref met die antosianienpigment vlakke tussen die skil en die vlees (bepaal deur spektrofotometrie en HPLC). Antosianieninhoud van besmette vrugvlees het verdubbel, terwyl die van besmette vrugskil minder as 50 % van die kontrole groep was. Pigmentlekkasie is al vermeld by bloubessies. Dit wil voorkom of selskade veroorsaak deur infeksie beweging van antosianien vanaf die skil na die vlees kan aanhelp. Die opbergingspotensiaal van bloubessies hang af van kultivar, rypheid by oes, omgewings toestande sowel as inokulum druk. Onder gunstige toestande kan bloubessies se opbergingsvermoë effektief gemanipuleer word. Verder kultivar-spesifieke navorsing wat relevante kwaliteits kwessies aanspreek, kan gedoen word. Verder kan betroubare tegnieke in die meting van bloubessie fermheid veranderinge ondersoek word. Navorsing ten opsigte van inokulum vlakke mag insig gee in terme van bederf-druk vermindering en die gebruik van bederf-onderdrukking alternatiewe soos anti-bakteriese lappies. Skil integriteit relatief tot bederf-vatbaarheid kan ook op sellulere vlak ondersoek word.

Seediness and other differences between rabbiteye-RB (Vaccinium ashei), southern highbush-SHB (Vaccinium darrowii), and commercial market equivalent, highbush-HB (Vaccinium corymbosum) varieties/lines were determined. Forty six selections of rabbiteye and southern highbush blueberries, and three highbush varieties, were analyzed for seediness (seeds per berry volume, SPV). There were no differences (p > 0.05) in SPV between SHB and RB selections, but differences (p < 0.05) existed within species. Berries were assigned to 8 groups based on SPV to conduct sensory panels and chemical analysis. Consumers perceived RB more different than SHB from HB blueberries. In the descriptive panel, differences (p < 0.05) were found in shriveling, skin intactness, grittiness, seediness, and tartness. The soluble solids to acid ratio of HB, SHB, and RB averaged 16.05, 9.60, and 11.05%, respectively. Some consumers and trained panelists can discern differences due to seediness and other traits between blueberry species.

Thesis (M.S.) in Food Science and Human Nutrition--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 45-48).

Thesis (Ph. D.)--Cornell University, 1930. / Cover title. Published also as Bulletin 356 of the Maine Agricultural experiment station. "Literature cited": p. 219-221.

Thesis (M.S.)--Rutgers University, 2009. / "Graduate Program in Biology." Includes bibliographical references (p. 25-27).

This work was aimed at obtaining high quality dried strawberries using microwaves to assist convection air of 2 m/s at 30--45°C. Preliminary trials with whole strawberries were unsuccessful. Fruits would cook rather than dry at low microwave power levels, and burst at higher powers. This was due to the inhibition of moisture movement by the waxy cuticle. Slice and pureed strawberries dried, but were of lower quality than freeze-dried / A treatment consisting of dipping the berries in a solution of ethyl oleate and sodium hydroxide was studied. Such treatments are used in industry to reduce the skin resistance to moisture diffusion. Result showed that the treatment greatly enhanced the drying rates of whole berries in convection and microwave regimes. A 1% concentration of ethyl oleate was sufficient for maximum reduction of drying time, and it is possible that even lower concentrations could be used for strawberries. Rehydration was similar to that of the dipped and freeze-dried samples, but the microwaved samples were a bit softer, and had less aroma, colour and flavour. / Osmotic dehydration was then studied as a technique of binding flavours and aromas and of reducing the time required for finish drying with microwaves. These studies were performed on strawberries and blueberries. Results showed berries that were dipped and then osmotically dehydrated for 24 h in sucrose, yielded a microwave-dried final product that was equal to the freeze-dried one in terms of quality, and this, with a much lower time for finish drying. / The shrinkage ratio of strawberries has a straight line relation to the moisture ratio. The reduction in equivalent diameter is well-described by a reciprocal logarithmic function. / The results of these major aspects of the research suggest that microwave-drying could be a viable and more rapid alternative to freeze-drying when berries are first subjected to a pretreatement of ethyl oleate and partial dehydration by osmosis. It was also found that if microwave energy is applied in continuous mode, the initial applied power should not exceed 0.2 W g--1, otherwise burning may occur. It is also recommended that osmotic dehydration be limited to not much longer than 24 hours, since off-odours, develop. The results apply to convective regimes with inlet air temperatures of 45°C and inlet velocity of 2 m/s.