Robert Jackman - Academia.edu (original) (raw)
Papers by Robert Jackman
Http Dx Doi Org 10 1080 08905438709549666, Dec 9, 2009
HortScience: a publication of the American Society for Horticultural Science
Flat-plate compression, constant area compression, and puncture tests were examined for their sen... more Flat-plate compression, constant area compression, and puncture tests were examined for their sensitivity in differentiating the firmness of previously chilled (6C, 85% RH, 15 days) and nonchilled mature-green tomato (Lycopersicon esculentum Mill CV. Caruso) fruit during 10 days of ripening at 22C. Firmness, as measured by each of the three methods, progressively decreased (P < 0.001) with ripening. Previously chilled tomatoes were initially softer (P < 0.01) than nonchilled tomatoes, as measured by puncture of whole fruit and constant area compression of pericarp tissue sections, but not by flat-plate compression of whole fruit. Flat-plate compression was therefore found to be a relatively insensitive method by which to measure differences in tomato firmness that are characteristic of slightly chilling-injured fruit.
Canadian Institute of Food Science and Technology Journal, 1986
International journal of peptide and protein research, 1988
The rapid increase in sequence data in combination with a greater understanding of the forces reg... more The rapid increase in sequence data in combination with a greater understanding of the forces regulating protein structure has been the impetus for an upsurge in the development of theoretical prediction methods. These methods have afforded protein chemists the ability to identify and quantify the various secondary structures along the protein chain. Concurrently, various physico-chemical techniques have been developed such as nuclear Overhauser enhancement n.m.r. and laser Raman spectroscopy. In addition, traditional methods such as infrared and circular dichroism spectroscopy have been refined. Although both predictive and physico-chemical techniques are limited in the types of secondary structure they are capable of determining, they have provided valuable information with regards to protein folding and topology in the absence of X-ray data, and have formed the basis for the development of improved methods for secondary structure determination. This paper reviews some of the pred...
Several whey-potato and whey-pea protein composites were prepared by wet-blending and their ultra... more Several whey-potato and whey-pea protein composites were prepared by wet-blending and their ultraviolet (UV) absorption and fluorescence properties were measured at pH 4 to 8. A significant (p <0.05) interaction between the effects of pH and the proportion of vegetable proteins combined with acid whey proteins was observed for all UV absorption variables. In general, however, a blue shift and reduction of intensity of both UV absorption and fluorescence emission spectra occurred as pH decreased and the proportion of vegetable protein increased. Extrinsic fluorescence of proteins, measured at pH 6 to 8, also decreased with increasing proportions of vegetable protein. Increased protein-protein interaction and/or changes in protein conformation are implicated as proportions of vegetable protein in composites increased, and as pH decreased to near the pI of parent source proteins.
Physiologia Plantarum, 1992
. Effectsof chilling on tomato fruit texture. -Physiol, Plant. 86: «X)-6()8. The effects of chill... more . Effectsof chilling on tomato fruit texture. -Physiol, Plant. 86: «X)-6()8. The effects of chilling on totnato (Lycopersicon esctitentum Mill cv, Caruso) texture were investigated using fruit stored at 22°C (nonchilled) or 5°C (chilled) for IV, days, or at 5°C for !5 days before transfer to 22°C to facilitate ripening during an additional 13 days (prechilled). Prechilled fruit exhibited symptoms of shghl chiMing injury, i.e. development of mealiness, accelerated softening relative to that of nonchilled fruit and nonuniform surface colour development. The firmness of all fruit decreased during ripening and chilled storage when measured by flat plate compression and puncture, especially during the early stages of ripening of nonchilled and pFechilled fruit. The compression firmness of pericarp tissue similarly decreased during ripening of nonchilled and prechilled fruit, but was maintained during chilling. Total moisture content (ca 94%) of tissue, uronide content (,32-35% w/w) and extracted/?-galactosidase activity did not differ significantly (P>().05) among fruit during ripening and chilled storage. The degree of uronide methyl esterification in ethanol-insoluble solids prepared from pericarp tissue (EIS) was relatively low for all fruit, i.e. < 4cr'-;i. EIS from which greater levels of pectinesterase were extracted (i.e. non-chilled>chilled>prechilled) exhibited decreased levels of uronide methyl esterification. Markedly elevated levels of /3-glucosidase activity were extracted from prechilled EtS, Tota! polygalacturonase activity (mainly as PGI) and autolysis of enzyme-extracted EIS were inversely correlated (P'^().i)5) only uith the )o.ss of nonchilled fruit and tissue firmness and prechilled fruit firmness. Results suggest a possible role for ^-glucosidase in textural changes of prechilled fruit and tissue (e.g. loss of firmness, development of mealiness) and also implicate loss of skin strength in the softening of whole fruit during chilling.
LWT - Food Science and Technology, 1996
ABSTRACT
Journal of Texture Studies, 1992
Failure mechanisms of tomato pericalp tissue were investigated by measuring puncture and viscoela... more Failure mechanisms of tomato pericalp tissue were investigated by measuring puncture and viscoelastic properties of tissue from &it stored at 22C (nonchilled) or 5C (chilled) for 28 days, or at 5C for 15 days prior to transfer to 22C for an additional 13 days brechilled) to facilitate ripening. The puncture properties of tissue remained unchanged during 28 days of chilling. However, tissue shear strength and rigidity increased with chilling, as demonstrated by increases in storage and loss moduli, and decreases in oscillatory strain and the loss tangent. Puncture failure force, failure Jiimness and storage and loss moduli of nonchilled andprechilled tissues decreased to low, constant levels by 12 and 9 days, respectively. Simultaneously, pseudoplastic and failure strains and oscillatory strain each increased. These data suggest that the loss of tissue compressive strengths and transition in the dominant mode of failure from cell relaxation and rupture to cell debonding occurred at a faster rate during ripening of prechilled (i.e., chill-injured) compared to nonchilled fruit. 'Current affiliation: ORTECH International, Food
Journal of Texture Studies, 1996
ABSTRACT
Journal of Food Science, 1989
... System ROBERT L. JACKMAN and RICKEY Y. YADA ... protein. This has stemmed both from increased... more ... System ROBERT L. JACKMAN and RICKEY Y. YADA ... protein. This has stemmed both from increased use of nitrogen-fixing pea plants as a rotation crop and the advent of air classification technology (Bramsnaes and Olsen, 1979). ...
Journal of Food Science, 1988
Journal of Food Biochemistry, 1987
Methods of analysis for naturally occurring anthocyanins are described. The large number of chemi... more Methods of analysis for naturally occurring anthocyanins are described. The large number of chemical groups which may bind to t h e~a~l i u m molecule has contributed to a large variation in structure, making the qualitative analysis of anthocyanins diflcult. Qualitative analysis has generally involved preliminary solvent extraction followed by chromatographic separation and purijication of pigments. Individual anthocyanins are then characterized by their chromatographic mobility, absorption spectra, and by means of controlled hydrolysis and oxidation tests. Quantitative analysis of anthocyanins may be carried out using either differential or subtractive spectral methods. The validity of results obtained by either of these methods is dependent on the presence or absence of inteflering substances within the samples. Where the quantijication of individual anthocyanins is desired, their separation from a mixture, normally by means of column chromatography, is f'irst necessary. High resolution of microgram quantities of anthocyanin without the need for extensive sample purijication prior to analysis has led to an increase in the use of HPLC techniques for quantitative work.
Journal of Food Biochemistry, 1995
The extractability of polygalucturonase (PG) activity from alcohol-insoluble solids (AIS) prepare... more The extractability of polygalucturonase (PG) activity from alcohol-insoluble solids (AIS) prepared from red-ripe tomato pericarp tissue was investigated using acetate @H 4 . 3 , citrate @H 4.5) and MES @H 6.0) buffers. The acetate buffer was ako investigated with increasing concentrations of NaC1, G e l 2 , MgCI,, ethylenediaminetetc acid (EDTA) or ethyleneglycol-bis (/3-aminoethylether)-N,N'-tetraacetic acid (EGTA). Heat treatment of AIS to prepare control material suppressed PG extractability but nor in situ PG activity, as evidenced by the release of sign8cant quantities of soluble uronides into extraction media. With only a single extraction, acetate buffer containing > 1 M NaCl yielded the greatest amount of PG acrivity (> 50% of maximum extractability), with MES bufer being only marginally less eflcient. However: 3 successive extractions over a 2 h period yielded sign@cantly greater amounts of PG activity. The greatest yields of PG activity were obtained by successive extraction with parent MES and acetate buflers. There appeared to be little benejit in adding NaCl or a chelating agent to the extraction medium. Use of these extractants is suggested to have led to losses of PG activity during dialysis, via coprecipitation of PGprotein with otherwise soluble uronide material that was released in greater quantities when these extractants were used. Increasing CaC12 and MgC12 concentrations reduced the m u n t of extracted PG activity similarly, to about 50% of maximum levels with successive extractions.
Journal of Food Biochemistry, 1987
A number of factors affecting anthocyanin stability and color are discussed in this review. 13re ... more A number of factors affecting anthocyanin stability and color are discussed in this review. 13re anthocyanins are probably the most spectacular of plant pigments since they are responsible for most of the red, purple and bluepigmentation ofjlowers, h i t s and vegetables. However, because of their highly reactive nature, anthocyanins readily degrade, or react with other constituents in the media, to form colorless or brown colored compounds. lhe presence of an oxonium ion adjacent to carbon 2 makes the anthocyanins patticularly susceptible to nucleophilic attack by such compounds as sulfur dioxide, ascorbic acid, hydrogen peroxide and even water. Loss of anthocyanin pigmentation also occurs in the presence of oxygen and various enzymes, and as a result of high temperature processing. A certain degree ofpigment stabilization may be conferred by acylation with various organic acidr , copigmentation, self-association and/or metal chelation. In addition, pH has a marked effect on anthocyanin stability, and on the color of media containing these pigments. A number of anthocyanin-rich sources have been investigated for their potential as commercial pigment extracts. Although their application is primarily limited to acidic 'To whom correspondence should be directed.
Journal of Agricultural and Food Chemistry, 1989
... et al., 1982). Air-classified pea (Pisum satiuum) protein (53.8% protein, 27.5% carbohydrate,... more ... et al., 1982). Air-classified pea (Pisum satiuum) protein (53.8% protein, 27.5% carbohydrate, 8.2% moisture, 4.9% ash) was the generous gift of YJ Osuwu-Ansah (POS Pilot Plant Corp., Saskatoon, SK). A pea protein dispersion ...
Http Dx Doi Org 10 1080 08905438709549666, Dec 9, 2009
HortScience: a publication of the American Society for Horticultural Science
Flat-plate compression, constant area compression, and puncture tests were examined for their sen... more Flat-plate compression, constant area compression, and puncture tests were examined for their sensitivity in differentiating the firmness of previously chilled (6C, 85% RH, 15 days) and nonchilled mature-green tomato (Lycopersicon esculentum Mill CV. Caruso) fruit during 10 days of ripening at 22C. Firmness, as measured by each of the three methods, progressively decreased (P < 0.001) with ripening. Previously chilled tomatoes were initially softer (P < 0.01) than nonchilled tomatoes, as measured by puncture of whole fruit and constant area compression of pericarp tissue sections, but not by flat-plate compression of whole fruit. Flat-plate compression was therefore found to be a relatively insensitive method by which to measure differences in tomato firmness that are characteristic of slightly chilling-injured fruit.
Canadian Institute of Food Science and Technology Journal, 1986
International journal of peptide and protein research, 1988
The rapid increase in sequence data in combination with a greater understanding of the forces reg... more The rapid increase in sequence data in combination with a greater understanding of the forces regulating protein structure has been the impetus for an upsurge in the development of theoretical prediction methods. These methods have afforded protein chemists the ability to identify and quantify the various secondary structures along the protein chain. Concurrently, various physico-chemical techniques have been developed such as nuclear Overhauser enhancement n.m.r. and laser Raman spectroscopy. In addition, traditional methods such as infrared and circular dichroism spectroscopy have been refined. Although both predictive and physico-chemical techniques are limited in the types of secondary structure they are capable of determining, they have provided valuable information with regards to protein folding and topology in the absence of X-ray data, and have formed the basis for the development of improved methods for secondary structure determination. This paper reviews some of the pred...
Several whey-potato and whey-pea protein composites were prepared by wet-blending and their ultra... more Several whey-potato and whey-pea protein composites were prepared by wet-blending and their ultraviolet (UV) absorption and fluorescence properties were measured at pH 4 to 8. A significant (p <0.05) interaction between the effects of pH and the proportion of vegetable proteins combined with acid whey proteins was observed for all UV absorption variables. In general, however, a blue shift and reduction of intensity of both UV absorption and fluorescence emission spectra occurred as pH decreased and the proportion of vegetable protein increased. Extrinsic fluorescence of proteins, measured at pH 6 to 8, also decreased with increasing proportions of vegetable protein. Increased protein-protein interaction and/or changes in protein conformation are implicated as proportions of vegetable protein in composites increased, and as pH decreased to near the pI of parent source proteins.
Physiologia Plantarum, 1992
. Effectsof chilling on tomato fruit texture. -Physiol, Plant. 86: «X)-6()8. The effects of chill... more . Effectsof chilling on tomato fruit texture. -Physiol, Plant. 86: «X)-6()8. The effects of chilling on totnato (Lycopersicon esctitentum Mill cv, Caruso) texture were investigated using fruit stored at 22°C (nonchilled) or 5°C (chilled) for IV, days, or at 5°C for !5 days before transfer to 22°C to facilitate ripening during an additional 13 days (prechilled). Prechilled fruit exhibited symptoms of shghl chiMing injury, i.e. development of mealiness, accelerated softening relative to that of nonchilled fruit and nonuniform surface colour development. The firmness of all fruit decreased during ripening and chilled storage when measured by flat plate compression and puncture, especially during the early stages of ripening of nonchilled and pFechilled fruit. The compression firmness of pericarp tissue similarly decreased during ripening of nonchilled and prechilled fruit, but was maintained during chilling. Total moisture content (ca 94%) of tissue, uronide content (,32-35% w/w) and extracted/?-galactosidase activity did not differ significantly (P>().05) among fruit during ripening and chilled storage. The degree of uronide methyl esterification in ethanol-insoluble solids prepared from pericarp tissue (EIS) was relatively low for all fruit, i.e. < 4cr'-;i. EIS from which greater levels of pectinesterase were extracted (i.e. non-chilled>chilled>prechilled) exhibited decreased levels of uronide methyl esterification. Markedly elevated levels of /3-glucosidase activity were extracted from prechilled EtS, Tota! polygalacturonase activity (mainly as PGI) and autolysis of enzyme-extracted EIS were inversely correlated (P'^().i)5) only uith the )o.ss of nonchilled fruit and tissue firmness and prechilled fruit firmness. Results suggest a possible role for ^-glucosidase in textural changes of prechilled fruit and tissue (e.g. loss of firmness, development of mealiness) and also implicate loss of skin strength in the softening of whole fruit during chilling.
LWT - Food Science and Technology, 1996
ABSTRACT
Journal of Texture Studies, 1992
Failure mechanisms of tomato pericalp tissue were investigated by measuring puncture and viscoela... more Failure mechanisms of tomato pericalp tissue were investigated by measuring puncture and viscoelastic properties of tissue from &it stored at 22C (nonchilled) or 5C (chilled) for 28 days, or at 5C for 15 days prior to transfer to 22C for an additional 13 days brechilled) to facilitate ripening. The puncture properties of tissue remained unchanged during 28 days of chilling. However, tissue shear strength and rigidity increased with chilling, as demonstrated by increases in storage and loss moduli, and decreases in oscillatory strain and the loss tangent. Puncture failure force, failure Jiimness and storage and loss moduli of nonchilled andprechilled tissues decreased to low, constant levels by 12 and 9 days, respectively. Simultaneously, pseudoplastic and failure strains and oscillatory strain each increased. These data suggest that the loss of tissue compressive strengths and transition in the dominant mode of failure from cell relaxation and rupture to cell debonding occurred at a faster rate during ripening of prechilled (i.e., chill-injured) compared to nonchilled fruit. 'Current affiliation: ORTECH International, Food
Journal of Texture Studies, 1996
ABSTRACT
Journal of Food Science, 1989
... System ROBERT L. JACKMAN and RICKEY Y. YADA ... protein. This has stemmed both from increased... more ... System ROBERT L. JACKMAN and RICKEY Y. YADA ... protein. This has stemmed both from increased use of nitrogen-fixing pea plants as a rotation crop and the advent of air classification technology (Bramsnaes and Olsen, 1979). ...
Journal of Food Science, 1988
Journal of Food Biochemistry, 1987
Methods of analysis for naturally occurring anthocyanins are described. The large number of chemi... more Methods of analysis for naturally occurring anthocyanins are described. The large number of chemical groups which may bind to t h e~a~l i u m molecule has contributed to a large variation in structure, making the qualitative analysis of anthocyanins diflcult. Qualitative analysis has generally involved preliminary solvent extraction followed by chromatographic separation and purijication of pigments. Individual anthocyanins are then characterized by their chromatographic mobility, absorption spectra, and by means of controlled hydrolysis and oxidation tests. Quantitative analysis of anthocyanins may be carried out using either differential or subtractive spectral methods. The validity of results obtained by either of these methods is dependent on the presence or absence of inteflering substances within the samples. Where the quantijication of individual anthocyanins is desired, their separation from a mixture, normally by means of column chromatography, is f'irst necessary. High resolution of microgram quantities of anthocyanin without the need for extensive sample purijication prior to analysis has led to an increase in the use of HPLC techniques for quantitative work.
Journal of Food Biochemistry, 1995
The extractability of polygalucturonase (PG) activity from alcohol-insoluble solids (AIS) prepare... more The extractability of polygalucturonase (PG) activity from alcohol-insoluble solids (AIS) prepared from red-ripe tomato pericarp tissue was investigated using acetate @H 4 . 3 , citrate @H 4.5) and MES @H 6.0) buffers. The acetate buffer was ako investigated with increasing concentrations of NaC1, G e l 2 , MgCI,, ethylenediaminetetc acid (EDTA) or ethyleneglycol-bis (/3-aminoethylether)-N,N'-tetraacetic acid (EGTA). Heat treatment of AIS to prepare control material suppressed PG extractability but nor in situ PG activity, as evidenced by the release of sign8cant quantities of soluble uronides into extraction media. With only a single extraction, acetate buffer containing > 1 M NaCl yielded the greatest amount of PG acrivity (> 50% of maximum extractability), with MES bufer being only marginally less eflcient. However: 3 successive extractions over a 2 h period yielded sign@cantly greater amounts of PG activity. The greatest yields of PG activity were obtained by successive extraction with parent MES and acetate buflers. There appeared to be little benejit in adding NaCl or a chelating agent to the extraction medium. Use of these extractants is suggested to have led to losses of PG activity during dialysis, via coprecipitation of PGprotein with otherwise soluble uronide material that was released in greater quantities when these extractants were used. Increasing CaC12 and MgC12 concentrations reduced the m u n t of extracted PG activity similarly, to about 50% of maximum levels with successive extractions.
Journal of Food Biochemistry, 1987
A number of factors affecting anthocyanin stability and color are discussed in this review. 13re ... more A number of factors affecting anthocyanin stability and color are discussed in this review. 13re anthocyanins are probably the most spectacular of plant pigments since they are responsible for most of the red, purple and bluepigmentation ofjlowers, h i t s and vegetables. However, because of their highly reactive nature, anthocyanins readily degrade, or react with other constituents in the media, to form colorless or brown colored compounds. lhe presence of an oxonium ion adjacent to carbon 2 makes the anthocyanins patticularly susceptible to nucleophilic attack by such compounds as sulfur dioxide, ascorbic acid, hydrogen peroxide and even water. Loss of anthocyanin pigmentation also occurs in the presence of oxygen and various enzymes, and as a result of high temperature processing. A certain degree ofpigment stabilization may be conferred by acylation with various organic acidr , copigmentation, self-association and/or metal chelation. In addition, pH has a marked effect on anthocyanin stability, and on the color of media containing these pigments. A number of anthocyanin-rich sources have been investigated for their potential as commercial pigment extracts. Although their application is primarily limited to acidic 'To whom correspondence should be directed.
Journal of Agricultural and Food Chemistry, 1989
... et al., 1982). Air-classified pea (Pisum satiuum) protein (53.8% protein, 27.5% carbohydrate,... more ... et al., 1982). Air-classified pea (Pisum satiuum) protein (53.8% protein, 27.5% carbohydrate, 8.2% moisture, 4.9% ash) was the generous gift of YJ Osuwu-Ansah (POS Pilot Plant Corp., Saskatoon, SK). A pea protein dispersion ...