Water-insoluble Solids Content Research Articles

Characterization of Zygophyllum album L Monofloral Honey from El-Oued, Algeria

Background: Honey is generally evaluated by physicochemical analysis of its constituents. The manipulation of honey and its possible adulteration is reflected in many of its physicochemical properties. Objective: In this study, samples of Zygophyllum album L honey produced in El-Oued, Algeria, were characterized based on their melissopalynology, physicochemical and antioxidant properties, also polyphenol content. Methods: The physicochemical parameters of honey, such as density, moisture content, pH, free acidity, electrical conductivity (EC), total sugar content, color intensity, water insoluble solids content, hydroxymethylfurfural (HMF), ash, specific rotation, were measured. A number of antioxidant tests were performed to determine the antioxidant properties of Zygophyllum album L honey samples. The polyphenol in the Zygophyllum album L honey was measured by spectrometric determination based on folin-ciocalteu’s method. The identification and quantification of phenolic compounds were carried out by RP-HPLC (high-performance liquid chromatography). Results: All honey samples contained monofloral (67.83-91.89%) pollen belonging to Zygophyllum album L. The results of physicochemical parameters of analyzed honeys were: pH 4.33, moisture 17.2%, free acidity 41.96 meq/kg, electrical conductivity 0.408 mS/cm, HMF 11.89 mg/kg, Ash 0.246 (%), specific rotation -8.21. The Zygophyllum album L honey was extra white amber. The total sugar content ranged from 81.5 to 83. Honey samples contain high levels of gallic acid (252.53±15.56 mg/kg honey), chlorogenic acid (124.71±10.09 mg/kg) and low amounts of total polyphenol (467.82±46,98 mg GAE/kg). Conclusion: Physicochemical parameters (total acidity, pH, moisture, dry matter, ash, and qualitative hydroxymethylfurfural) were within the approved limits established by International Honey Commission.

Meliponiculture and physicochemical properties of honey produced by the African stingless bee Plebeina hildebrandti Friese in Kalakamati village, Botswana

This study was conducted to assess the harvesting practices in Kalakamati village of honey produced by the African stingless bee Plebeina hildebrandti Friese and to determine the physicochemical properties of this honey. To understand stingless bee honey harvesting practices, a semi-structured questionnaire was prepared and 15 individuals who have experience in collecting stingless bee honey were interviewed. The physicochemical properties of four honey samples were analysed following standard procedures. The stingless bee honey had average moisture (28.4%), reducing sugar (61%), apparent sucrose (2.4%), free acidity (36 meq/kg), pH (4.77), total ash (0.42%), hydroxymethylfurfural (HMF) (17.82 mg/kg) and water-insoluble solids content of 0.07%. All the parameters comply with the Tanzanian standard for stingless bee honey whereas all but moisture content agrees with the European standard for honey from Apis mellifera. Moisture content of the stingless bee honey in the present study is higher than the 21% EU standard for Apis mellifera honey. In Kalakamati village, honey from stingless bees is collected from the bush and stingless bees are not kept by farmers. According to the respondents, honey from stingless bees is consumed as it is, is used as a substitute for sugar in tea and for its medicinal value to treat cough, stomach ache and flu. The results suggest that honey produced by stingless bees in Kalakamati village is of good quality as it generally meets international quality standards. Honey production from stingless bees could contribute to poverty alleviation and food security in the study area if appropriate interventions are made.

Combined production of biogas and ethanol at high solids loading from wheat straw impregnated with acetic acid: experimental study and techno-economic evaluation

Production of ethanol and biogas from acetic acid-impregnated steam-pretreated wheat straw was investigated. The solid fraction after pretreatment was used at high solids concentrations to generate ethanol by simultaneous saccharification and fermentation (SSF). The residual streams were evaluated with regard to biogas production. The experimental results were used to perform a techno-economic evaluation of a biorefinery concerning ethanol, raw biogas, pellet, and electricity production at various solid contents and residence times in the fermentation step. The configurations were also altered to include biogas upgrading to vehicle fuel quality or fermentation of xylose to ethanol. At a water-insoluble solids (WIS) content in the SSF of between 10 and 20 %, the ethanol yields exceeded 80 %, the highest being 86 % at 12.5 % WIS, expressed as % of the theoretical maximum, based on the glucan content in SSF. Anaerobic digestion of wheat straw hydrolysate and stillage yielded 4.8 and 1.0–1.2 g methane/100 g dry straw, respectively, in 7-day experiments. Maximum recovery of overall product was achieved when SSF was run at between 10 and 15 % initial WIS content, for which the product yields from 100 g dry wheat straw were 16.1–16.3 g ethanol, 5.8–6.0 g methane, and 25 g lignin-rich solid residue. The net present value (NPV) was negative at discount rate of 11 % but positive at 5 % discount rate for all configurations. The 20 % WIS configuration with a residence time of 96 h in the fermentation stage attained the highest NPV. The minimum ethanol selling price varied between 0.72 and 0.87 EUR/L ethanol when the biogas was unchanged and it decreased to between 0.46 and 0.60 EUR/L ethanol when the biogas was upgraded to vehicle fuel quality or when xylose was converted to ethanol. According to the techno-economic assessment, a process that is based on the fermentation of only hexoses to ethanol, and production of raw biogas from xylose is not profitable under the economic assumptions including 11 % discount rate in the evaluation. However, the profitability of a plant can be improved by biogas upgrading to vehicle fuel quality or fermentation of xylose to ethanol.

Model-based optimization and scale-up of multi-feed simultaneous saccharification and co-fermentation of steam pre-treated lignocellulose enables high gravity ethanol production.

BackgroundHigh content of water-insoluble solids (WIS) is required for simultaneous saccharification and co-fermentation (SSCF) operations to reach the high ethanol concentrations that meet the techno-economic requirements of industrial-scale production. The fundamental challenges of such processes are related to the high viscosity and inhibitor contents of the medium. Poor mass transfer and inhibition of the yeast lead to decreased ethanol yield, titre and productivity. In the present work, high-solid SSCF of pre-treated wheat straw was carried out by multi-feed SSCF which is a fed-batch process with additions of substrate, enzymes and cells, integrated with yeast propagation and adaptation on the pre-treatment liquor. The combined feeding strategies were systematically compared and optimized using experiments and simulations.ResultsFor high-solid SSCF process of SO2-catalyzed steam pre-treated wheat straw, the boosted solubilisation of WIS achieved by having all enzyme loaded at the beginning of the process is crucial for increased rates of both enzymatic hydrolysis and SSCF. A kinetic model was adapted to simulate the release of sugars during separate hydrolysis as well as during SSCF. Feeding of solid substrate to reach the instantaneous WIS content of 13 % (w/w) was carried out when 60 % of the cellulose was hydrolysed, according to simulation results. With this approach, accumulated WIS additions reached more than 20 % (w/w) without encountering mixing problems in a standard bioreactor. Feeding fresh cells to the SSCF reactor maintained the fermentation activity, which otherwise ceased when the ethanol concentration reached 40–45 g L−1. In lab scale, the optimized multi-feed SSCF produced 57 g L−1 ethanol in 72 h. The process was reproducible and resulted in 52 g L−1 ethanol in 10 m3 scale at the SP Biorefinery Demo Plant.ConclusionsSSCF of WIS content up to 22 % (w/w) is reproducible and scalable with the multi-feed SSCF configuration and model-aided process design. For simultaneous saccharification and fermentation, the overall efficiency relies on balanced rates of substrate feeding and conversion. Multi-feed SSCF provides the possibilities to balance interdependent rates by systematic optimization of the feeding strategies. The optimization routine presented in this work can easily be adapted for optimization of other lignocellulose-based fermentation systems.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0500-7) contains supplementary material, which is available to authorized users.

Combined substrate, enzyme and yeast feed in simultaneous saccharification and fermentation allow bioethanol production from pretreated spruce biomass at high solids loadings

BackgroundEconomically feasible cellulosic ethanol production requires that the process can be operated at high solid loadings, which currently imparts technical challenges including inefficient mixing leading to heat and mass transfer limitations and high concentrations of inhibitory compounds hindering microbial activity during simultaneous saccharification and fermentation (SSF) process. Consequently, there is a need to develop cost effective processes overcoming the challenges when working at high solid loadings.ResultsIn this study we have modified the yeast cultivation procedure and designed a SSF process to address some of the challenges at high water insoluble solids (WIS) content. The slurry of non-detoxified pretreated spruce when used in a batch SSF at 19% (w/w) WIS was found to be inhibitory to Saccharomyces cerevisiae Thermosacc that produced 2 g l-1 of ethanol. In order to reduce the inhibitory effect, the non-washed solid fraction containing reduced amount of inhibitors compared to the slurry was used in the SSF. Further, the cells were cultivated in the liquid fraction of pretreated spruce in a continuous culture wherein the outflow of cell suspension was used as cell feed to the SSF reactor in order to maintain the metabolic state of the cell. Enhanced cell viability was observed with cell, enzyme and substrate feed in a SSF producing 40 g l-1 ethanol after 96 h corresponding to 53% of theoretical yield based on available hexose sugars compared to 28 g l-1 ethanol in SSF with enzyme and substrate feed but no cell feed resulting in 37% of theoretical yield at a high solids loading of 20% (w/w) WIS content. The fed-batch SSF also significantly eased the mixing, which is usually challenging in batch SSF at high solids loading.ConclusionsA simple modification of the cell cultivation procedure together with a combination of yeast, enzyme and substrate feed in a fed-batch SSF process, made it possible to operate at high solids loadings in a conventional bioreactor. The proposed process strategy significantly increased the yeast cell viability and overall ethanol yield. It was also possible to obtain 4% (w/v) ethanol concentration, which is a minimum requirement for an economical distillation process.

Effects of agitation on particle-size distribution and enzymatic hydrolysis of pretreated spruce and giant reed.

BackgroundMixing is an energy demanding process which has been previously shown to affect enzymatic hydrolysis. Concentrated biomass slurries are associated with high and non-Newtonian viscosities and mixing in these systems is a complex task. Poor mixing can lead to mass and/or heat transfer problems as well as inhomogeneous enzyme distribution, both of which can cause possible yield reduction. Furthermore the stirring energy dissipation may impact the particle size which in turn may affect the enzymatic hydrolysis. The objective of the current work was to specifically quantify the effects of mixing on particle-size distribution (PSD) and relate this to changes in the enzymatic hydrolysis. Two rather different materials were investigated, namely pretreated Norway spruce and giant reed.ResultsChanges in glucan hydrolysis and PSD were measured as a function of agitation during enzymatic hydrolysis at fiber loadings of 7 or 13% water-insoluble solids (WIS). Enzymatic conversion of pretreated spruce was strongly affected by agitation rates at the higher WIS content. However, at low WIS content the agitation had almost no effect on hydrolysis. There was some effect of agitation on the hydrolysis of giant reed at high WIS loading, but it was smaller than that for spruce, and there was no measurable effect at low WIS loading. In the case of spruce, intense agitation clearly affected the PSD and resulted in a reduced mean particle size, whereas for giant reed the decrease in particle size was mainly driven by enzymatic action. However, the rate of enzymatic hydrolysis was not increased after size reduction by agitation.ConclusionsThe impact of agitation on the enzymatic hydrolysis clearly depends not only on feedstock but also on the solids loading. Agitation was found to affect the PSD differently for the examined pretreated materials spruce and giant reed. The fact that the reduced mean particle diameter could not explain the enhanced hydrolysis rates found for spruce at an elevated agitation suggests that mass transfer at sustained high viscosities plays an important role in determining the rate of enzymatic hydrolysis.

Dietary fiber, fructooligosaccharides, and physicochemical properties of homogenized aqueous suspensions of yacon (Smallanthus sonchifolius)

Yacon roots are a promising source of inulin­type fructans (35g/100g dry matter) with a total amount of dietary fiber of about 45g/100g dry matter. The polydispersity of the particle size distribution of yacon aqueous suspension was reduced with increasing the degree of homogenization due to two phenomena: aggregation of particles, and disruption of large particles. Non­homogenized yacon suspensions exhibited large cell clusters that were disrupted into small cell clusters, single cells, and aggregates. The most concentrated suspension exhibited mainly aggregates.The volume fraction of the suspensions decreased significantly with increasing the degree of homogenization. This was attributed to a denser packing of small particles and aggregates in between large particles thus allowing the water within the structure to be released.Yacon suspensions exhibited high elastic modulus (750Pa) at low water insoluble solids content (0.9% WIS). Additional results suggested that inulin­type fructans contributed to the elastic properties of yacon suspensions.The yacon suspensions studied in this work can be considered as semi­concentrated suspensions, i.e. the plot elastic modulus of the suspensions versus concentration exhibited a region immediately after the transition region. Particle interactions seem to be of great importance in this region in the particular case of yacon suspension since the elastic modulus (G′) reached 750Pa at low water insoluble solids content (<1%).

Feasibility of simultaneous saccharification and juice co-fermentation on hydrothermal pretreated sweet sorghum bagasse for ethanol production

For a commercial breakthrough of ethanol production from lignocelluloses, one main challenge still exists in achieving high ethanol concentrations during fermentation. Using sweet sorghum as a feedstock for ethanol production has the advantage to have both, directly fermentable sugars in the juice as well as sugars from lignocellulose of the plant fibers. A novel concept is presented, which combines the fermentation of dewatered sweet sorghum bagasse after hydrothermal pretreatment and sweet sorghum juice in one process step. For the pretreatment of sweet sorghum bagasse, liquid hot water was used as a reagent. Combinations of different retention times and target temperatures (170–200°C) were investigated for severities between logR0=3.51 and 4.09. Further, a mathematical function of first order was established to describe the solubility of hemicellulose with reference to the severity. The highest solubilization of hemicellulose obtained was 85% with the highest severity applied (logR0=4.09, target temperature 200°C). Additionally the cellulose content was enriched from an initial 36% DM (raw bagasse) to 59% DM. For almost all the pretreatment conditions the pH in the supernatant remained higher than or equal to the critical value of 4. For simultaneous saccharification and fermentation trials of the dewatered pretreated but non-washed material, a maximum convertibility of cellulose of 74% was obtained at a severity of logR0=4.02 (190°C). When sweet sorghum juice with a sugar concentration of 100g/L was mixed with the pretreated and dewatered bagasse (logR0=4.0, 190°C) to a water-insoluble solids content of 7.5%, 53g/L ethanol was achieved after 168h of fermentation. The convertibility of cellulose after this time remained unaffected by the juice addition.

Torque measurements reveal large process differences between materials during high solid enzymatic hydrolysis of pretreated lignocellulose

BackgroundA common trend in the research on 2nd generation bioethanol is the focus on intensifying the process and increasing the concentration of water insoluble solids (WIS) throughout the process. However, increasing the WIS content is not without problems. For example, the viscosity of pretreated lignocellulosic materials is known to increase drastically with increasing WIS content. Further, at elevated viscosities, problems arise related to poor mixing of the material, such as poor distribution of the enzymes and/or difficulties with temperature and pH control, which results in possible yield reduction. Achieving good mixing is unfortunately not without cost, since the power requirements needed to operate the impeller at high viscosities can be substantial. This highly important scale-up problem can easily be overlooked.ResultsIn this work, we monitor the impeller torque (and hence power input) in a stirred tank reactor throughout high solid enzymatic hydrolysis (< 20% WIS) of steam-pretreated Arundo donax and spruce. Two different process modes were evaluated, where either the impeller speed or the impeller power input was kept constant. Results from hydrolysis experiments at a fixed impeller speed of 10 rpm show that a very rapid decrease in impeller torque is experienced during hydrolysis of pretreated arundo (i.e. it loses its fiber network strength), whereas the fiber strength is retained for a longer time within the spruce material. This translates into a relatively low, rather WIS independent, energy input for arundo whereas the stirring power demand for spruce is substantially larger and quite WIS dependent. By operating the impeller at a constant power input (instead of a constant impeller speed) it is shown that power input greatly affects the glucose yield of pretreated spruce whereas the hydrolysis of arundo seems unaffected.ConclusionsThe results clearly highlight the large differences between the arundo and spruce materials, both in terms of needed energy input, and glucose yields. The impact of power input on glucose yield is furthermore shown to vary significantly between the materials, with spruce being very affected while arundo is not. These findings emphasize the need for substrate specific process solutions, where a short pre-hydrolysis (or viscosity reduction) might be favorable for arundo whereas fed-batch might be a better solution for spruce.

Rheological characterization of dilute acid pretreated softwood

Large-scale bioethanol production from lignocellulosic biomass will require high solids loading in the enzymatic hydrolysis step. However, slurries of pretreated lignocelluloses are complex fluids due to the fibrous nature, especially at high concentrations of water insoluble solids (WIS). A prerequisite for dealing with transport issues and for developing efficient full-scale processes is a fundamental understanding of the flow properties of pretreated lignocellulose. A comprehensive rheological characterization of dilute acid pretreated spruce has been carried out in this study, accounting for the effects of WIS concentration, particle size distribution (PSD), and the degree of enzymatic hydrolysis. The rheology of pretreated spruce slurries was found to be strongly dependent on the WIS concentration. The storage modulus (G'(LVR)) and yield stress showed typical power-law dependencies on volume fraction and WIS content. Milling of the pretreated material resulted in significantly higher yield stress and viscosity, likely due to narrower PSD, which suggests that the strength of the network of the coarsest fibers determines the rheology of these materials to a large extent. During enzymatic hydrolysis, yield stress and viscosity decreased dramatically, partly due to decreasing WIS content, but possibly also due to changes in fiber properties such as the chemical composition.

Steam pretreatment and fermentation of the straw material “Paja Brava” using simultaneous saccharification and co-fermentation

Pretreatment, enzymatic hydrolysis and simultaneous saccharification and fermentation (SSF) of the South American straw material Paja Brava were investigated. Suitable process conditions for an SO₂-catalyzed steam pretreatment of the material were determined and assessed by enzymatic digestibility of obtained fiber slurries for 72 h at a water insoluble solids (WIS) content of 2%. The best pretreatment conditions obtained (200 °C, 5 min holding time and 2.5% SO₂) gave an overall glucose yield following enzymatic hydrolysis of more than 90%, and a xylose yield of about 70%. Simultaneous saccharification and co-fermentation of glucose and xylose (SSCF) of the pretreated material using the xylose-fermenting strain Saccharomyces cerevisiae TMB3400 was examined at WIS contents between 5% and 10%. In agreement with previous studies on other materials, the overall ethanol yield and also the xylose conversion decreased somewhat with increasing WIS content in the SSCF. In batch SSCF, the xylose conversion obtained was almost 100% at 5% WIS content, but decreased to 69% at 10% WIS. The highest ethanol concentration obtained for a WIS content of 10% was about 40 g/L, corresponding to a yield of 0.41 g/g in a fed-batch SSCF. The Paja Brava material has previously been found difficult to hydrolyze in a dilute-acid process. However, the SSCF results obtained here show that similar sugar yields and fermentation performance can be expected from Paja Brava as from materials such as wheat straw, corn stover or sugarcane bagasse.

Improving simultaneous saccharification and co-fermentation of pretreated wheat straw using both enzyme and substrate feeding

BackgroundSimultaneous saccharification and co-fermentation (SSCF) has been recognized as a feasible option for ethanol production from xylose-rich lignocellulosic materials. To reach high ethanol concentration in the broth, a high content of water-insoluble solids (WIS) is needed, which creates mixing problems and, furthermore, may decrease xylose uptake. Feeding of substrate has already been proven to give a higher xylose conversion than a batch SSCF. In the current work, enzyme feeding, in addition to substrate feeding, was investigated as a means of enabling a higher WIS content with a high xylose conversion in SSCF of a xylose-rich material. A recombinant xylose-fermenting strain of Saccharomyces cerevisiae (TMB3400) was used for this purpose in fed-batch SSCF experiments of steam-pretreated wheat straw.ResultsBy using both enzyme and substrate feeding, the xylose conversion in SSCF could be increased from 40% to 50% in comparison to substrate feeding only. In addition, by this design of the feeding strategy, it was possible to process a WIS content corresponding to 11% in SSCF and obtain an ethanol yield on fermentable sugars of 0.35 g g-1.ConclusionA combination of enzyme and substrate feeding was shown to enhance xylose uptake by yeast and increase overall ethanol yield in SSCF. This is conceptually important for the design of novel SSCF processes aiming at high-ethanol titers. Substrate feeding prevents viscosity from becoming too high and thereby allows a higher total amount of WIS to be added in the process. The enzyme feeding, furthermore, enables keeping the glucose concentration low, which kinetically favors xylose uptake and results in a higher xylose conversion.

Bioethanol production from wheat straw by the thermotolerant yeast Kluyveromyces marxianus CECT 10875 in a simultaneous saccharification and fermentation fed-batch process

Solid content in the simultaneous saccharification and fermentation (SSF) broth should be as high as possible in order to reach higher ethanol concentration. In this work, several feeding strategies for ethanol production from steam-exploded wheat straw by Kluyveromyces marxianus CECT 10875 have been studied with the aim of obtaining higher ethanol concentrations. Previous fermentability tests as well as SSF processes showed the difficulty of using the slurry for ethanol production under the studied conditions. Notwithstanding, fed-batch SSF processes with water-insoluble solids (WIS) fraction resulted in better configuration, reaching the highest ethanol concentration (36.2 g/L) with an initial WIS content of 10% (w/v) and 4% (w/v) of substrate addition at 12 h, which meant 20% more ethanol when compared with batch SSF.

Influence of Tomato Paste Processing on the Linear Viscoelasticity of Tomato Ketchup

Tomato paste is used as an ingredient for the manufacture of tomato ketchup. This paper deals with the influence that some tomato paste processing variables (finisher screen opening and breaking temperature) and tomato variety exert on the linear viscoelastic properties of tomato ketchup. Two tomato varieties (H-282 and H-282F) were used. H-282 is a commercial variety whilst H-282F is a variety with a lower content in polygalacturonase (PG). Dynamic viscoelastic tests and particle size distribution measurements were carried out. Viscoelastic properties of tomato ketchup were mainly related to their mean volume diameter, tomato paste water-insoluble solids content (that depended on the tomato paste processing) and tomato variety.

Evaluation of in-line absorption photometry to predict consistency of concentrated tomato products

This study evaluated the correlation between optical density as measured by absorption photometry, water-insoluble solids (WIS) and consistency as measured by the Bostwick consistometer for a variety of concentrated tomato products. Linear regression analysis indicated a linear correlation ( R 2=0.97) between optical density and WIS content in diluted tomato paste, a linear correlation ( R 2⩾0.92) between optical density and consistency in various commercial tomato products and a linear correlation ( R 2=0.93) between optical density and consistency during commercial production of tomato puree made from ripe tomatoes. The optical density appeared to be unaffected by product temperature and flow rate. Potential limitations of in-line absorption photometry to monitor and control tomato product consistency are briefly discussed.

Linear viscoelasticity of tomato sauce products: influence of previous tomato paste processing

Tomato paste is used as an ingredient for the manufacture of tomato sauce products. This work deals with the influence that some tomato paste processing variables (finisher screen opening and breaking temperature) and tomato variety exert on the linear viscoelastic properties of tomato sauce products. Four tomato varieties (two commercial varieties, one with a lower content of polygalacturonase enzyme, and one with a low content in pectin methylesterase enzyme) have therefore been used. Dynamic viscoelastic tests and particle size distribution (PSD) measurements have been carried out. From the experimental results obtained, we may conclude that the dependence of the linear viscoelastic properties of tomato sauce on the above-mentioned variables is very complex. Nevertheless, the evolution of the viscoelastic characteristics of these products is mainly related to their mean volume diameter and tomato paste water insoluble solids content (WIS). This solid content is mainly controlled by tomato variety and tomato paste processing conditions.

Effect of storage of apple on the enzymatic hydrolysis of cell wall polysaccharides

Cell wall materials in the form of water-insoluble solids (WIS) and water-soluble fractions (WSF) were prepared from apples stored at 4 °C for 30 weeks. During storage, the WIS content decreased whereas the WSF content remained unchanged. The total amount of polysaccharides decreased, in particular the pectic polymers which decreased by 10%. In contrast, the soluble pectic fraction increased by 40% whilst its degree of methoxylation remained constant. The arabinose and galactose content progressively declined. The enzymatic treatment of the apple tissues was more effective the longer the storage; yields correlated well with the enzyme hydrolysis of WIS. The accessibility of pectin to poly-galacturonases in apple tissues is discussed since it was higher at the end of storage, whereas the solubilisation of pectins from WIS by polygalacturonases remained constant. On the other hand, with liquefying enzymes, the yield of pectin solubilisation from apple tissues or WIS were well correlated and increased with storage time.

Factors Influencing Serum Separation of Tomato Ketchup

ABSTRACTThe effect of tomato cultivar, breaking procedure, starting tomato paste concentration, reconstituted paste, homogenization treatment, percent total and water insoluble solids, and pH on serum separation of tomato ketchup was investigated. Homogenization, as well as increasing the total and/or the water insoluble solids of the ketchup reduced separation. Increasing the total solids of the starting tomato paste decreased the rate of separation, but increased the final amount of serum loss from the resulting ketchup. Among tomato cultivars and breaking procedures included in this study, the Peto 98 cultivar (high water insoluble solids content) and the medium break procedure (at 107.2°C after a 10 min hold at room temperature) gave ketchups with the least serum separation.

Tomato Anatomy: Solids: Consistency Relationships. Influence of Fruit Anatomy and Solids Composition of Tomatoes on Product Consistency

The anatomy and solids composition of fresh tomato outer pericarp were studied in relation to consistency of the finished product prepared as puree. Twelve cultivars that produced a wide range in puree consistency were used in the study and the results correlated. Fresh fruit properties that correlated with thicker (desirable) consistency were: a gradual, rather than abrupt, gradient in cell size; the presence of small cells interspersed in the mesocarp; thickened mesocarp cell walls as revealed by their intermittent-staining with toluidine blue; high water-insoluble solids content; and less starch in the cells of young fruit along with its early disappearance during fruit development. All of these properties, except the one involving starch, pointed to the significance of the cell walls in determining product consistency. The results are discussed in relation to the literature on cell wall composition, changes on processing, and commercial implications.

TOMATO FRUIT PROPERTIES AFFECTING CONSISTENCY OF CONCENTRATED PRODUCT

Fruit properties of tomato (Lycopersicon esculentum Mill.) that determine the flow characteristics of the concentrated product were associated mainly with water-insoluble solids content and serum viscosity. Levels of total (mostly soluble) solids had much less effect on product flowability. Soluble and total solids levels fluctuated widely between and within seasons, increasing during periods of low rainfall and vice versa. Water-insoluble solids content appeared to be mainly cultivar-dependent, and only minimally influenced by moisture and other climatic conditions. Levels of all three solids fractions and serum viscosity differed characteristically from one cultivar to another. Cultivars also differed with respect to apparent loss of water-insoluble solids and serum viscosity during the concentration process.Key words: Tomato, product, consistency, viscosity, solids, serum