Changes In Titratable Acidity Research Articles

Temperature effects on fruit quality of mature green tomatoes during controlled atmosphere storage

Tomatoes were harvested at the mature green stage of maturity and stored at 13°C and 15°C for 60 days at three different combinations of CO2, all with 5.5% O2 compared with a control with 20.9% O2 with 0.3% O2/% CO2. Tomatoes were evaluated for changes in colour, titratable acidity, total soluble solids and decay appearance. In this experiment, the 'Criterium' variety of tomatoes was used and it was found that this variety was not suitable for storage at 13°C. Some chilling injury symptoms were observed during the storage period at 13°C, which did not occur at 15°C. Uneven colour development, irregular changes in titratable acidity and total soluble solids were observed during the storage period at 13°C, and the fruits did not ripen properly even after further 10 days ripening time in air at 20°C. Furthermore, the amount of decayed fruits was higher at 13°C than at 15°C, especially after 50 days of storage. In fruits stored for 60 days at 13°C, alterneria rot, blue mould rot and 'cottony leak' occurred that could be associated with chilling injury and increased during a further 10 days ripening at 20°C. It was concluded that the 'Criterium' variety is not suitable for storage at 13°C.

Efeito do fator de concentração do retentado na composição e proteólise de queijo minas frescal de baixo teor de gordura fabricado por ultrafiltração

O efeito da concentração do leite por ultrafiltração na composição e proteólise do queijo Minas Frescal de baixo teor de gordura durante o armazenamento refrigerado foi determinado. Três bateladas de queijo foram processadas em um dia, usando leite ultrafiltrado a três diferentes fatores de concentração (FC): 2:1, 3:1 e 4:1. A fabricação dos queijos foi realizada em duplicata. A evolução da proteólise foi acompanhada através da determinação do pH, acidez titulável e índices de proteólise nos dias 2, 10, 20 e 30 após a fabricação. Os fatores de concentração testados não afetaram significativamente a composição e a proteólise do queijo. Para todos os queijos, o pH diminuiu com o tempo, enquanto a acidez e os índices de extensão e profundidade de proteólise aumentaram. Portanto, a inclusão de proteínas do soro pela ultrafiltração não inibiu a ação proteolítica do coagulante. Para a faixa de FC estudada, os efeitos negativos associados ao aumento do teor de umidade dos queijos (maior intensidade de glicólise e proteólise e maior suscetibilidade a microrganismos contaminantes) predominaram sobre as potenciais vantagens tecnológicas do uso da técnica de ultrafiltração. Em função disso, observou-se uma tendência de diminuição da vida útil desses queijos, em relação aos queijos fabricados pelo método tradicional.

EFFECT OF PRESERVATION WITH SACCOGLOTTIS GABONENSIS ON THE BIOCHEMISTRY AND SENSORY ATTRIBUTES OF FERMENTING PALM WINE

Fresh palm-wine, from Raphia hookeri was treated with different amounts of Saccoglottis gabonensis. The alcohol content, refractive index, assimilation of sugars and assimilation of nitrates were monitored (for 4 days) in treated samples and untreated controls (containing no S. gabonensis). Fermentation rates were monitored by determining CO 2 production as well as pH and titratable acidity changes within the same period. Sensory attributes of fresh and treated palm wine were compared. Sensory evaluation studies were carried out on (1) The fresh palm wine, (2) Palm-wine stored for 4 days at ambient temperature (27C-29C) and (3) Palm-wine stored for 30 days at ambient temperature. Treatment with S. gabonensis led to increased alcohol content and CO 2 production with lower sugar content (sucrose, glucose and maltose) and pH, than in control samples. There were no significant variations in the refractive indices of treated and untreated samples. CO 2 production decreased with each successive fermentation day in both treated and untreated samples. Panelists preferred the sensory properties of fresh palm-wine to that of palm-wine treated with S. gabonensis. However, by the second day the sensory characteristics of treated palm-wine was preferred. Until the 4th day, the color and taste of treated palm-wine was acceptable while the untreated samples became unacceptable. By the 30th day both treated and untreated palm-wine samples became unacceptable. Pour prolonger la duree de conservation de la seve fraiche, les depots microbiens (Saccoglottis gabonensis) qui sont extraits avec celle-ci sont ajoutes au vin de palme. Cette etude compare les changements biochimiques dans les vins traites et non traites (sans depot microbien). La teneur en alcool, l'indice de refraction, l'assimilation des sucres et des nitrates sont controles pendant 4 jours. Les rendements de fermentation sont controles par la production de CO 2 , du pH et de l'acidite titrable. Des evaluations sensorielles sont menees sur le vin frais, apres 4 jours et 30 jours a temperature ambiante.

EFEITOS FÍSICO-QUÍMICOS DA ADIÇÃO DE LEITE RECONSTITUÍDO NA FABRICAÇÃO DE QUEIJO MINAS FRESCAL

Estudou-se a fabricacao do queijo Minas Frescal utilizando-se leite in natura adicionado de 10, 20 e 40% de leite reconstituido a partir de leite em po integral medium heat. Acompanhou-se a evolucao da proteolise dos queijos atraves da determinacao do pH, acidez titulavel e indices de proteolise em 1, 7, 14 e 21 dias. Determinou-se a transicao dos componentes do leite para o queijo, como forma de estimar o rendimento da fabricacao dos queijos. Os resultados demonstraram que nao houve diferencas marcantes nos parâmetros estudados. Observou-se que o teor de umidade dos queijos fabricados com adicao de leite reconstituido foi maior do que os queijos Minas Frescal tradicionais. Verificou-se que ate 7 dias apos a fabricacao os produtos mantiveram caracteristicas que os identificaram como aptos para o consumo. Concluiu-se que e possivel produzir queijos de boa qualidade usando ate 40% de leite reconstituido adicionado ao leite in natura.

The Under-Exploited Indigenous Alcoholic Beverages of Tanzania: Production,Consumption and Quality of the Undocumented "Denge

In Africa, then: are numerous traditional alcoholic beverages. Unavailability of literalllre on these beverages. particularly regarding their production, consumption and quality is a major constraint against industrial production. The rising prices of conventional alcoholic beverages call for more studies on these beverages. Denge, one such beverage, was studietl and analyzed in tenns of total soluble solids, specific gravity, pH and titratable acidity changes during fermentation. Result~ showed that Kigelia £1lricana and Aloe pluridens were used to prepare fermenting agents for subsequent production of ''denge. a.:ting primarily as a reservoir nf micro-organ­ isms fnr thi~ fermentation. Slime fom1ation in the raw cane juice was a common problem. Optimum time fur heat sterilisation of the juice. a possible method to he used by ordinary households need 10 be established. Types and numbers of microorganisms in the fermentation need idcnti tication. Types and levels of residual toxicants from K. a.fi'icana and A. pluridem in the wine need to be tlucurnented. The specific gravity. total soluble solids. pH and titrat­ able acidity studies have displayed the perishability of ''denge during storage. More shclftife studies arc recommended. Key \Vords: Dengc; Ail:oholi..: beverage; Tanzania: Kigelia africana: Aloe pluridens.

The xanthophyll cycle and energy dissipation in differently oriented faces of the cactus Opuntia macrorhiza.

Diurnal changes in titratable acidity, photosynthesis, energy dissipation activity, and the carotenoid composition of differently oriented cladodes of the cactus Opuntia macrorhiza were characterized during exposure to full sunlight in the field. Four cladode faces were chosen such that each was exposed to maximum photon flux densities (PFD) at different times of the day in addition to receiving different daily integrated PFDs. The sum of all carotenoids per chlorophyll was found to increase with increasing exposure to PFD, with the carotenoids of the xanthophyll cycle present in the most exposed face at more than twice the concentration found in the least exposed face. All faces exhibited large increases in xanthophyll cycle-dependent energy dissipation as the sun rose in the morning, even those receiving only minimal levels of diffuse radiation. The transient high levels of energy dissipation in those faces that did not receive direct sunlight in the morning may have been due to low temperature inhibition of photosynthesis (predawn low of 2°C). For the two faces receiving peak PFDs in the morning hours (north and east faces), the level of energy dissipation activity increased rapidly during exposure to direct sunlight in the early morning, gradually declining in the late morning under warm temperatures, and was negligible during the afternoon low light conditions. Changes in the xanthophyll cycle paralleled the changes in energy dissipation with the majority of the cycle present as violaxanthin (V) prior to sunrise, largely de-epoxidized to zeaxanthin (Z) and antheraxanthin (A) during exposure to direct sunlight, and reconverted to V during the afternoon. For the two faces receiving peak PFDs in the afternoon (south and west faces), energy dissipation activity increased dramatically during the early morning low light period, subsequently decreasing during midday as decarboxylation of malic acid proceeded maximally (providing a high concentration of CO2 for photosynthesis), and then increased to the highest level in the late afternoon as the supply of malic acid was depleted and rates of photosynthetic electron transport declined. The xanthophyll cycle, largely present as Z and A prior to sunrise in the south and west faces, was de-epoxidized to the greatest extent in the late afternoon, followed by epoxidation back to the predawn level by sunset. In all cladode faces high levels of energy dissipation activity were accompanied by decreases in the intrinsic efficiency of photosystem II (PSII), indicative of a regulatory process that diverted the excess energy away from the reaction centers during periods of excess light. Furthermore, the overnight retention of Z and A by the south and west faces was accompanied by a sustained reduction in PSII efficiency (i.e., "photoinhibition"). We suggest that this "photoinhibition" represents the sustained engagement of nocturnally retained Z and A in the photoprotective down-regulation of PSII.

Relationship between fern development and CAM in Pyrrosia piloselloides (L.) Price

Pyrrosia piloselloides (L.) Price is a constitutive CAM plant in the sporophytic phase of its life-cycle. Newly developed sporophytes, still attached to the gametophytes, showed signs of CAM expression in terms of diurnal changes in titratable acidity of the tissues. The gametophytes did not exhibit CAM.

Preservation of raw milk by activation of the natural lactoperoxidase systems

The preservation of raw ovine, bovine and caprine milks by activation of their natural lactoperoxidase (LP) systems was investigated. Milk samples with different concentrations of thiocyanate ions (SCN −) ranging from 15 to 150 mg/l and hydrogen peroxide (H 2O 2) ranging from 10 to 100 mg/l were stored at 4 °, 22 ° and 30 °C. Changes in titratable acidity, total colony counts and coliform counts of the milk samples were followed during storage. No significant differences were observed between samples with different concentrations of the added reagents, and this indicated that concentrations of 15 mg/l (SCN −) and 10 mg/l (H 2O 2) would be adequate for preserving milks of different mammals — at least at 4 °C. At higher temperatures, the effectiveness of the LP systems was, as monitored by the increases in acidity, of much shorter duration.

NonVolatile Organic Acids, pH and Titratable Acidity Changes in Pineapple Fruit Slices During Frozen Storage

NonVolatile Organic Acids, pH and Titratable Acidity Changes in Pineapple Fruit Slices During Frozen Storage

Inorganic carbon acquisition by Xiphophora chondrophylla (Phaeophyta, Fucales)

Abstract Measurements of parameters related to photosynthesis, with particular reference to the mechanism of inorganic C acquisition, were made on Xiphophora chondrophylla (R. Brown ex Turner) Montagne ex Harvey, an Australasian fucoid living in the upper subtidal and in low intertidal rock pools. Photosynthesis as a function of incident photon flux density and external inorganic C concentration, capacity to use HCO3−, diel changes in titratable acidity of cell contents (‘CAM-like’ behaviour), rates of dark inorganic 14C fixation and the δ13C values of plant organic C were similar to values previously found for emersed and submersed specimens of the sympatric Hormosira banksii (Turner) Decaisne. This is consistent with the proposed close relationship of the genera Hormosira and Xiphophora and with earlier work showing the phyletic, as well as ecologically adaptive, importance of certain characteristics of inorganic C acquisition in the Fucaceae and related fucoids. The N content of Xiphophora chondrophyll...

Inorganic carbon acquisition by Hormosira banksii (Phaeophyta: Fucales) and its epiphyte Notheia anomala (Phaeophyta: Fucales)

Abstract Measurements of parameters related to photosynthesis, with particular reference to the mechanism of inorganic C acquisition, were made on the obligate epiphyte Notheia anomala Harvey et Bailey (Phaeophyta: Fucales) and on its most usual basiphyte, Hormosira banksii (Turner) Decaisne (Phaeophyta: Fucales). The work on Hormosira banksii included a comparison of specimens which are normally emersed at low tide on rock platforms with specimens which are normally submersed in rockpools at low tide; the rockpool specimens are those which most commonly bear Notheia anomala. No significant differences were detected for any of the characteristics tested, i.e. photosynthetic rate as a function of incident photon flux density, external inorganic C concentration and plant N content; capacity to use HCO3−; diel changes in titratable acidity of cell contents (‘CAM-like’ behaviour); rates of dark 14C-inorganic C fixation; δ13C values of plant organic C. These data are consistent with there being no significant ...

Mozzarella Cheese: Impact of Rod:Coccus Ratio on Composition, Proteolysis, and Functional Properties

The impact of the rod:coccus ratio on chemical composition, proteolysis, and functional properties of Mozzarella during storage was determined. Three vats of cheese were made in 1 d using three rod:coccus ratios (9:1, 5:5, and 1:9). Cheese making was replicated on 3 different d using a 3×3 Latin square design. Changes in titratable acidity and pH during cheese making were slower with the 9:1 rod:coccus ratio. The viable count of both microorganisms increased during cheese making, but cocci were the dominant organism in the curd at milling, regardless of the initial rod:coccus ratio. Cocci remained viable during stretching at 57°C and during storage at 4°C. The rod:coccus ratio did not affect the initial composition of cheese. However, proteolysis of cheese, especially development of N that is soluble in 12% TCA, was faster with 9:1 rod:coccus ratio during storage. Hardness and cohesiveness of unmelted cheese, meltability, and free oil formation were unaffected, but springiness and apparent viscosity were lower with the 9:1 rod:coccus ratio. The amount of inoculation may have more impact on the functional properties of Mozzarella cheese than the rod:coccus ratio.

A one-year study on carbon, water and nutrient relationships in a tropical C3 -CAM hemi-epiphyte, Clusia uvitana Pittier.

Diel (24 h) courses of CO2 and water-vapour exchange of leaves of hemi-epiphytic plants of Clusia uvitana Pittier (Clusiaceae) were measured under natural tropical conditions in the semi-evergreen moist forest of Barro Colorado Island, Panama, from January 1991 until January 1992. Plants were studied at two sites, in the crown of a 47-m tall tree (Ceiba pentandra) and on the shore of Lake Gatun, at a height of about 2-4 m. The following results were obtained: (1) Diel carbon gain was mainly a function of photosynthetic photon fluence rate (PPFR) on individual days. PPFR also strongly affected CAM activity. A leafless period of the host tree Ceiba pentandra resulted in higher incident PPFRs and slightly lower nighttime temperatures in the canopy of C uvitana; this led to increases in both daytime and nighttime CO2 fixation. (2) In fully mature sun leaves from the two sites, nocturnal net uptake of atmospheric CO2 occurred on almost all of the 71 days measured and nocturnal carbon gain was enhanced during the dry season. (3) In C. uvitana at the Lake site, 24-h carbon gain during the wet and dry season was similar to C. uvitana at the Ceiba site during the leafless period of the host tree. Overall CAM activity was lower at the Lake site. (4) Recycling of respiratory CO2 was a major route for nocturnal acid synthesis. Nocturnal net uptake of atmospheric CO2 was closely correlated with changes in titratable acidity, but accounted for only about 30% of the nocturnal increase in organic acids. (5) Mature shade leaves performed CAM only during the dry season, whereas in the wet season they showed atmospheric CO2 uptake exclusively in the light. (6) Independent of exposure or season, leaves less than about 12 wk old showed a C3 pattern of diel gas exchange and the level of titratable acidity was high day and night. (7) The annual carbon budget of outer canopy leaves of C uvitana in the Ceiba site was 1780 g CO2 m-2 a-1 and the average long-term water-use efficiency was 23 × 10-3 g CO2 g-1 H2 O. (8) Vegetative growth was strongly seasonal. Branch length increment and leaf area development was much higher in the wet season. Mineral element contents in these evergreen plants showed no age-related changes, but a significant proportion of elements was retrieved before abscission.

Effects of light intensity, sugar and C02 concentrations on growth and mineral uptake of dendrobium plantlets

The effects of light intensity, sugar and C02 concentrations on nitrate and ammonium uptake, growth and photosynthetic activity of dendrobium plantlets grown on agar medium were studied. There was a preferential uptake of ammonium over nitrate. Uptake of nitrate was relatively low and increased with increase in light intensity or when the culture medium was supplemented with sugar. Ammonium uptake was also affected by Jight. However, the rates of ammonium and nitrate uptake were sluggish. The fresh weight of plantlets increased with the presence of sugar in the media but the relative growth rate decreased. C02 enrichment did not increase ion uptake or growth. The nutrition of plantlets in culture was mainly heterotrophic, as indicated by the changes in titratable acidity, 813C values and l4C02 fixation.

Patterns of gas exchange and organic acid oscillations in tropical trees of the genus Clusia.

Gas exchange patterns and nocturnal acid accumulation were examined in four species of Clusia under simulated field conditions in the laboratory. Clusia alata and C. major had midday stomatal closure, substantial net CO2 exchange ([Formula: see text]) during the night, and the highest water use efficiency (WUE). C. venosa showed a pattern similar to a C3 plant, with nighttime stomatal closure, while C. minor maintained positive [Formula: see text] continuously throughout a 24-h period. However, large changes in titratable acidity, which closely matched changes in citrate and malate levels, indicated that Crassulacean acid metabolism (CAM) is active in all four species. C. venosa showed dawn-dusk oscillations in titratable acidity that were higher than the values reported for other C3-CAM intermediates, while the nighttime acid accumulation of 998 mol m-3 observed in C. major is unsurpassed by any other CAM plant. Moreover, the dawn-dusk changes in citrate levels of over 65 mol m-3 in C. alata and C. minor, and over 120 mol m-3 in C. major, are 3-6 times higher than values reported for other CAM plants. Although these oscillations in citrate levels were quite large, and the nighttime dark respiration rates were high, the O2 budget analysis suggestes that only part of the reducing power generated by the synthesis of citric acid enters the respiratory chain. Dawn-dusk changes in malate levels were just over 50 mol m-3 for C. venosa but over 300 mol m-3 for C. major. Between 28% (C. major) and 89% (C. venosa) of the malate accumulated during the night was derived from recycled respiratory CO2. These daily changes in malate and citrate levels also contributed significantly to changes in leaf sap osmolality. This variability in CO2 uptake patterns, the recycling of nighttime respiratory CO2, and the high WUE may have contributed to the successful invasion of Clusia into a wide range of habitats in the tropics.

Effects of packaging materials following ethanol and benomyl treatments on chemical and microbiological changes in tomato (Lycopersicon esculentum) fruits

AbstractThe effects of various post‐harvest treatments on chemical changes, microbiological quality and occurrence of spoilage in ripe tomatoes (Lycopersicon esculentum L) were investigated. Fruits were pretreated in 70% ethanol or 0.2% benomyl before being packaged in low density polyethylene (LDPE), high density polyethylene (HDPE) or raffia palm basket. Fruit was stored at 27–32°C for up to 16 days. Control fruits (without pretreatment or packaging) showed the highest increase in pH; basket‐packaged fruits were erratic but LDPE‐ and HDPE‐packaged fruits showed gradual increases. Changes in titratable acidity were the inverse of those in pH. Among packagings, LDPE most effectively maintained total soluble solids (TSS) as compared with basket‐packaged fruits, and the control showed the lowest TSS. Of the pretreatments, benomyl‐treated fruits retained higher TSS. Aspergillus spp, Penicillium spp, Pseudomonas spp and Escherichia spp occurred most commonly in control and basket‐packaged fruits, but Rhizopus spp and Leuconostoc spp predominantly occurred in LDPE‐ and HDPE‐packaged fruits. Microbial load was lowest in benomyl‐treated fruits followed by ethanol‐treated and control fruits. Spoilage was higher (53.1%) in ethanol‐treated than in benomyl‐treated (43.8%) fruits.

INFLUENCE OF COMMERCIAL SHIPPING ON THE COLOR AND COMPOSITION OF APPLE JUICE CONCENTRATE1

ABSTRACTApple juice concentrate manufactured in Argentina was sampled before and after shipment to the USA and subjected to a number of color and compositional analyses. These included browning, haze, Hunter parameters, titratable acidity, hydroxymethylfurfural (HMF), and HPLC determination of sugars, nonvolatile acids, and chlorogenic acid. The primary objective was to determine those parameters which showed significant changes as a result of commercial transport. Browning significantly increased as did HMF and fumaric acid content. There was no evidence for sucrose inversion and there was no significant change in titratable acidity as a result of this 55 day commercial shipment.

Ecophysiology of xerophytic and halophytic vegetation of a coastal alluvial plain in northern Venezuela: III. Bromelia humilis Jacq., a terrestrial CAM bromeliad.

The terrestrial CAM plant Bromelia humilis was examined in the salinas of the Ciénega el Ostional, on the north coast of Venezuela, in the rainy and dry seasons. Three colour forms were distinguished; yellow (in full sun), green exposed (also in sun) and green shaded (beneath woodland). Plant size decreased with increasing irradiance. An examination was made of the three phenotypes in terms of CO2 exchange (Jco2 ), dawn-dusk changes in titratable acidity (ΔH+ ) and malate and citrate levels, osmotic pressure, xylem tension, sugar and amino acids levels, nitrogen and ion concentrations and ambient temperature fluorescence. All phenotypes exhibited lowered Jco2 and ΔH+ in the dry as compared to the rainy season. Citrate, as well as malate, showed dawn-dusk fluctuations. Soluble sugars were the major source of carbon skeletons for nocturnal organic acid production. The dawn-dusk changes in osmotic pressure were negligible. Yellow plants performed poorly in contrast to shaded plants in both seasons. The former showed higher dawn-dusk changes of citrate levels and contained much less nitrogen than shaded plants. Nocturnal recycling of respiratory CO2 was more important in yellow plants and, in the dry season, reached 87%. These differences were reflected in the overall productivity, shaded plants showing increases in size whereas yellow plants utilized energy mainly for leaf replacement. Water availability and nitrogen supply appear to be the overriding factors determining higher productivity and CO2 assimilation in partially shaded plants as compared with plants in full sun.

A preliminary survey for crassulacean acid metabolism (CAM) in submerged aquatic macrophytes in New Zealand

Abstract This preliminary survey covered 13 aquatic macrophytes present at two sites in Lake Taupo and two sites in the Auckland region (northern half of the North Island, New Zealand). Three species previously unrecorded as CAM plants, Isoetes kirkii A. Braun, Lilaeopsis lacustris Hill, and Vallisneria spiralis Graeb., exhibited diurnal fluctuations in titratable acidity and malic acid content. The changes in titratable acidity varied seasonally from 97 (Dec. 1985) to 46 (June 1986) microequivalents per gram fresh weight for I. kirkii, and from 40 to 23 and 51 to 26 microequivalents per gram fresh weight for L. lacustris and V. spiralis, respectively. The absence of CAM both in other members of the low mixed community and in other hydrocharitacean species at the same sites suggests that CAM can not be unequivocally regarded as conferring an ecological advantage to a species.

The Occurrence of diel changes in titratable acidity of plant Cell Contents: indications of CAM-like metabolism in plants native to Scotland and comparisons with plants from elsewhere

Summary The low-amplitude diel changes in titratable acidity previously reported for Ascophyllum nodosum (L.) Le Jolis, and in less detail for other members of the Fucaceae, has been confirmed for five intertidal members of the Fucaceae under both submersed and emersed conditions in a light-dark cycle. No significant change was found for five members of the Phaeophyta which normally live completely submerged (Halidrys siliquosa in the family Cystoseiraceae of the Fucales, and four members of the Laminariales). The diel changes in titratable acidity in the Fucaceae are consistent with a very low-amplitude Crassulacean Acid Metabolism in these organisms which can only contribute a few per cent at most to total inorganic C assimilation over a diel cycle. The taxonomic and ecological significance of the findings are discussed in the context of CAM in a world-wide and a Scottish context.