Asparagus Samples Research Articles

Saponin Profile of Green Asparagus Genotypes

Among the phytochemicals found in green asparagus, phenolics and saponins represent the major groups of bioactive compounds. The first are mainly related to the antioxidant activity of this product; and the distinct saponins detected in green (triguero) asparagus influence both its organoleptic and bioactive properties. The main objective of the present work is the characterisation of the saponins profile from distinct genotypes of the green asparagus. Their analysis by HPLC-MS (High Performance Liquid Chromatography-Mass Spectrometry) have revealed that the content and composition of saponins from green asparagus are significantly different from those of the commercial hybrids. Hence, in green asparagus, there have been identified several saponins that distinguish it from the rest and that can be an adequate parameter for the determination of not only its organoleptic properties but also its major or minor functional quality. Saponins total content was about ten times greater in the green asparagus than in the commercial hybrids. Besides, in the green asparagus there have been detected significant quantities of several saponins that are not present in commercial hybrids. Typical saponins from the green asparagus are steroidal saponins derived from diosgenin, and mostly consist of protodioscin. However, the analysis of the green asparagus samples has revealed the presence of six naturally occurring saponins, neither of them being diosgenin derivatives but sarsapogenin glycosides.

Characterization of Asparagus Lignin by HPLC

Lignin is the cell wall component most frequently associated with hardening. Its characterization and quantification are very important to understand the biochemical modifications related to the changes in texture of vegetables such as asparagus (Asparagus officinalis), in which this organoleptic attribute is a very important quality factor. In this study, asparagus lignin from the basal sections of fresh and stored spears was analyzed using 2 methods, the traditional (Klason lignin) and the recently developed derivatization, followed by reductive cleavage (DFRC) method. The latter is a simple and reproducible technique for lignin characterization based on a degradation procedure that produces analyzable monomers and dimers by cleaving alpha- and beta-aryl ethers in lignins. The primary monomers derived from DFRC degradation of lignins are essentially p-coumaryl peracetate, coniferyl peracetate, and sinapyl peracetate. To evaluate the efficiency of the DFRC method, our investigations have been carried on distinct sample types, including wood (data not shown), straw, and asparagus samples. The results have confirmed that lignin composition is affected by plant nature. It has been found that whereas wood samples mostly contain coniferyl units, plant foods, such as straw and asparagus, contain both coniferyl and guaiacyl units.

USE OF ONE STEP RT-PCR FOR DETECTION OF ASPARAGUS VIRUS 1

Two viruses are responsible for most of the decline in asparagus crops (Asparagus officinalis L.) in the world: Asparagus virus 1 (AV-1) and Asparagus virus 2 (AV-2). AV-1 is a member of genus Potyvirus and has so far been identified in plant and tissue-culture material of asparagus using biological assays on indicator plants, electron microscopy and, rarely, by serodiagnosis. In this study, degenerate potyvirus primers were used in RT-PCR to amplify a cDNA product from an asparagus potyvirus, previously identified as AV-1 on the basis of host range results. RT-PCR products were sequenced, and the nucleotide sequences obtained were aligned with those of other members of the genus Potyvirus to devise primer pairs specific for AV-1. The use of one primer pair in a one-step RT-PCR procedure was found to yield an amplicon with RNA from an AV-1 infected plant, but not with RNA from plants infected with Turnip mosaic virus (TuMV), Pea seed-borne mosaic virus (PSbMV), or Lettuce mosaic virus (LMV). The method was sensitive and reproducible for the detection of AV-1 in leaves and spears of asparagus samples collected from fields and from tissue-culture plantlets.

Identification of Marchfeld asparagus using Sr isotope ratio measurements by MC-ICP-MS

This work focuses on testing and application of Sr isotope signatures for the fast and reliable authentication and traceability of Asparagus officinalis originating from Marchfeld, Austria, using multicollector inductively coupled plasma mass spectrometry after optimised Rb/Sr separation. The major sample pool comprises freeze-dried and microwave-digested asparagus samples from Hungary and Slovakia which are compared with Austrian asparagus originating from the Marchfeld region, which is a protected geographical indication. Additional samples from Peru, The Netherlands and Germany were limited in number and allowed therefore only restricted statistical evaluation. Asparagus samples from Marchfeld were harvested within two subsequent years in order to investigate the annual variation. The results show that the Sr isotope ratio is consistent within these 2 years of investigation. Moreover, the Sr isotope ratio of total Sr in soil was found to be significantly higher than in an NH4NO3 extract, reflecting the mobile (bioavailable) phase. The isotope composition in the latter extract corresponds well to the range found in the asparagus samples in Marchfeld, even though the concentration of Sr in asparagus shows no direct correlation to the concentration of Sr in the mobile phase of the soil. The major question was whether the 'Marchfelder Spargel' can be distinguished from samples from the neighbouring countries of Hungary and Slovakia. According to our findings, they can be clearly (100%) singled out from the Hungarian samples and can be distinguished from the Slovakian asparagus samples with a probability of more than 80%.

Physical, chemical and microbiological changes in stored green asparagus spears as affected by coating of silver nanoparticles-PVP

Silver nanoparticles have recently gained increasing interests due to their antimicrobial activities in food processing applications. The aim of this study was to evaluate the effect of silver nanoparticles-PVP coating on weight loss, ascorbic acid, total chlorophyll, crude fiber, color, firmness and microbial qualities of asparagus spears stored at 2 and 10 °C. Asparagus samples were first sanitized with 100 mg l −1 sodium hypochloride solution for 15 min. They were then immersed in coating solution containing silver nanoparticles for 3 min at room temperature. During 25-day storage at 2 or 10 °C, the coated asparagus demonstrated lower weight loss, greener color and tender texture compared with the control samples. The growth of microorganism was significantly hindered by the coating. Based on comprehensive comparison and evaluation, asparagus spears coated by silver nanoparticles could be kept in good quality for 25 days at 2 °C and for 20 days at 10 °C.

Combined effect of mild heat and acetic acid treatment for inactivating Escherichia coli O157:H7, Listeria monocytogenes and Salmonella typhimurium in an asparagus puree

This study was conducted to validate combined heat and acid treatments for inactivating Escherichia coli O157:H7, Listeria monocytogenes and Salmonella typhimurium in an acidified brine containing, or pickled, asparagus model food. A mixture of three strains of E. coli O157:H7, L. monocytogenes and S. typhimurium were inoculated onto pickled asparagus samples. Combinations of various concentrations of acetic acid [0%, 0.25%, 0.5%, 0.75%, 1%, 1.5% and 2% (v/v)] and various temperatures (40 degrees C, 50 degrees C, 60 degrees C and 75 degrees C) were investigated. Following treatment, asparagus samples were stored at room temperature and enumerated at 0, 0.5, 1, 2 and 3 days. Heat and acetic acid treatments were synergistic. The inhibitory effects of these combined treatments on the tested foodborne pathogens were also effective during storage. Loss of green colour in the pickled asparagus significantly increased with increasing concentrations of acetic acid. Using a combination of mild heat and acetic acid treatments can successfully control E. coli O157:H7, L. monocytogenes and S. typhimurium in pickled asparagus, combinations of heat and acid are synergistic and effective treatments can be selected to reduce adverse effect on colour which occur during product storage. Mild heating plus acetic acid treatment are synergistic, so combined treatments can be developed, which would lower the temperature and amount of acetic acid required for minimally processed vegetables while maintaining pathogen control.

Fusarium Species Colonizing Spears and Forming Mycotoxins in Field Samples of Asparagus from Germany and Poland

AbstractThe occurrence of Fusarium spp. and associated mycotoxins in asparagus spears was evaluated in Poland in 2002 and 2003 and in Germany in 2002. Spears of two cultivars, Eposs and Gijnlim, were collected from two locations in Poland, Swidwowiec and Poznan, on sandy and sandy loam soil, respectively. Fusarium oxysporum and F. proliferatum were detected at an average incidence of 38.3% and 15.8% in the spear sections sampled, respectively. In stands of 11 (tested) cultivars of asparagus sampled in Germany on sandy soil, the same species dominated, however, they were less frequent than in Poland (26.6% and 5.6% of the spears infected with F. oxysporum and F. proliferatum, respectively). Chemical analyses revealed that fumonisin B1 (FB1) and moniliformin (MON) were present in some of the spears sampled in Poland. FB1 was not found and MON was not assessed in spears sampled in Germany in 2002, but F. proliferatum was able to form the toxin in vitro in the range from 101.4 up to 205.8 μg/kg maize kernel substrate. Asparagus samples in Poland contained FB1 at up to 5.6 μg/kg spear fresh weight. The highest MON concentration (1350 μg/kg) was detected in cultivar Eposs in Marcelin, Poland, in 2002. MON and FB1 were found in spears infected by both F. oxysporum and F. proliferatum, however, only the latter fungus was able to synthesize both toxins.

POTENTIAL NON-CHEMICAL METHODS FOR USE AGAINST THRIPS IN GREEN ASPARAGUS: QUALITY CHANGES IN RESPONSE TO HEAT TREATMENTS AND HIGH CONCENTRATIONS OF CARBON DIOXIDE

Quality changes induced in fresh green asparagus were determined after exposure to a combined post-harvest treatment of heat followed by high CO 2 atmospheres at low temperature. Asparagus samples obtained from Thailand were subjected to three heat treatments: control, hot water (45°C for 15 min) and hot air (45°C for 15 min). After that, they were transferred to sealed glass jars with atmospheres of low (1%) and high (52-83%) CO 2 concentrations at 4°C and 0°C for 24 h, followed by 10 days storage at the same temperature under air. Quality tests were performed, 1) before heat treatment, 2) after heat treatment, 3) after CO 2 treatment, 4) after 5 days storage and 5) after 10 days storage to evaluate weight loss, colour, overall appearance, decay, off-odour and texture. Hot air treatment significantly increased weight loss, reduced overall appearance, increased decay and caused softening. Significant, but much lower effects of hot water treatment were observed. High CO 2 atmospheres of 52-83% did not reduce the quality of asparagus at all. No difference was seen between the two storage temperatures.

Occurrence of fumonisins in asparagus (asparagus officinalis L.) and garlic (allium sativum L.) from Germany

Fusarium proliferatum is able to produce fumonisins and is considered a pathogen of many economically important plants (e.g. corn, rice, asparagus) [1]. The occurrence of fumonisin FB1 inF. proliferatum infected asparagus spears from Germany was investigated using a liquid chromatography/electrospray ionization-mass spectrometry (LC-ESI-MS) method with isotopically labeled fumonisin FB1-d6 as internal standard. Asparagus samples were harvested in July 2000 and screened forFusarium species. AltogetherF. oxysporum, F. proliferatum and F. sambucinum were isolated from the spears. The samples infected with F.proliferatum were subsequently analyzed for fumonisins. FB1 was detected in 9 of the 10 samples in amounts ranging from 36.4 ng/g to 4513.7 ng/g (based on dry weight). Fumonisins FB2 and FB3 were found in six samples in lower concentrations. In asparagus spears of June 2002 we could findF. proliferatum in 6% of the samples, however no fumonisins were detectable.Furthermore the capability of producing FB1 by the fungus in garlic bulbs was investigated. Therefore garlic was cultured inF. proliferatum contaminated soil and the bulbs were screened for infection with F.proliferatum and for the occurrence of fumonisins by LC-MS. F.proliferatum was detectable in the garlic tissue and all samples contained FB1 (26.0 ng/g to 94.6 ng/g).This is the first report of the natural occurrence of FB1 in German asparagus spears and furthermore our findings suggest a potential for natural contamination of garlic bulbs with fumonisins. For detailed results and methods see Ref. [2].

Determination of tribromophenol and pentachlorophenol and its metabolite pentachloroanisole in Asparagus officinalis by gas chromatography/mass spectrometry

AbstractA GC‐MS method was developed and optimized for simultaneous determination of pentachlorophenol (PCP), 2,4,6‐tribromophenol (TBP), and pentachloroanisole (PCA) residues in the edible part of Asparagus officinalis. For this purpose, two procedures were evaluated: the direct separation of PCP, TBP, and PCA and the separation of acetyl‐PCP, acetyl‐TBP, and non‐acetylated PCA. Better sensitivity and quantitative results, especially for PCP, were obtained after acetylation. The residues of PCP and TBP were extracted as phenolates and acetylated in a carbonate solution. Acetylated compounds were extracted by liquid‐liquid extraction with hexane, while PCA was directly leached with this solvent. The proposed method allows the rapid quantification of traces of PCP, TBP, and PCA in a concentration ranging between 1.0 and 8.0 ng mL–1 in solution (corresponding to 0.3 and 8.0 μg kg–1 in asparagus). In this concentration range, typical recoveries for PCA, TBP, and PCP from asparagus samples were 59%, 86%, and 97% respectively (RSDs 3–7%).

RT-PCR DETECTION OF ASPARAGUS 2 ILARVIRUS

Asparagus 2 ilarvirus (AV-2) is a major viral disease of asparagus that is transmitted through seed, sap and pollen. Therefore it is important for breeders to produce seed that is free of AV-2. In order to develop a more sensitive test for detection of AV-2, we designed PCR primers to amplify the coat protein gene and 3’ untranslated region of RNA3 of AV-2. RT-PCR produced a fragment of the expected size from template RNA isolated from a plant material known to be infected with AV-2. Cloning and sequencing showed that the RT-PCR product was more than 99% identical to the published sequence of RNA3 of AV-2. Double-stranded RNA analysis of asparagus samples revealed dsRNA molecules differing in size from those expected for AV-2 or other viruses known to infect asparagus in California. AV-2 could be detected by Northern blot analysis of dsRNA gels using the cloned RT-PCR product as probe.

THE INFLUENCE OF FROZEN STORAGE ON CHROMIUM AND NICKEL CONTENTS IN WHITE ASPARAGUS

ABSTRACTBatches of white asparagus (Asparagus officinalis, L. var Ciprés) were analyzed by flame atomic absorption spectrophotometry to investigate the variations in chromium and nickel contents caused by the freezing process and storage of spears at −18C for 45 and 90 days. Samples of asparagus were classified into two groups according to diameter, < 11 mm and > 14 mm spears. The spear was cut into two portions, the apical portion (7 cm from the spear tip) and the basal portion (14 cm of the remaining stem). Mean concentrations were 0.61 ± 0.18 and 4.23 ± 0.56 mg/kg (dry weight) for chromium and nickel, respectively. Three‐factor analysis of variance revealed statistically significant differences during frozen storage for both chromium and nickel content. Spear diameter had no statistically significant effect on chromium and nickel concentrations. Statistically significant interportion differences were found only for nickel levels, which were greater in the apical portion.

Incidence of Fusarium spp. in Asparagus Spears.

Fusarium proliferatum and F. oxysporum have been identified as causal agents of asparagus decline in the field and have been associated with reduction in spear quality (1,2). Our objective was to determine the origin and incidence of spear infection by these fungi during the cropping years 1994 to 1997. From 15 to 40 asparagus samples were randomly selected from the field, packing houses, and retail markets and assayed for Fusarium spp. Collections were made in California, Connecticut, Peru, Mexico, and Australia. The number of samples varied between sampling sites and for the time of harvest season. One Mexican collection site was sampled at the beginning, mid-point, and end of the harvest season to evaluate influence of decreasing carbohydrate levels and increasing temperatures on infection and growth of the fungi. Isolations included sections (5 to 6 cm) from the basal and terminal portions of the spear to evaluate postharvest growth in the spear. Fusarium spp. were recovered from spear samples that included all geographical sampling locations (mean 45%, range 20 to 90%). F. proliferatum was the dominant species isolated consistently from the desert areas regardless of harvest period. The frequency of F. oxysporum isolation ranged from 2 to 32% with no correlation to time or location of sampling. Basal sections were more frequently infected (94%) than terminal portions of the spear (less than 6%). No major differences in the percentage of infected spears were found in collection sites regardless of country sampled. There were differences in the incidence of infection between harvest sample dates. Spears sampled late in the harvest period were 57% more infected than spears of early or mid-season collections. Samples from the same fields, regardless of whether collected directly from the field, from packing sheds, or from the retail market, had higher infection rates later in the harvest season compared with earlier harvests. This may be attributable to warmer temperatures, changes in levels of carbohydrates, or other physiological factors. Spears harvested from the field that were infected with both Fusarium spp. had a greater incidence of infection than spears recovered from packing houses or from retail sources. This supports the theory that the source of spear infection is diseased crowns and not postharvest sources. Isolates from the spears of both Fusarium spp. were found to be pathogenic when challenged to asparagus seedlings.

Variations of chromium and nickel content during industrial processing of white asparagus

The influence of certain industrial processing operations of white asparagus ( Asparagus officinalis, L.) on concentrations of chromium and nickel was studied. Samples of white asparagus were taken during the following operations of the industrial processing: reception and selection of raw material (fresh asparagus), after machine-washing (washed asparagus), after peeling (peeled asparagus) and on completion of the blanching operation (blanched asparagus). Asparagus samples were selected for two varieties (‘Desto’ and ‘Sur’), four diameters (9–11 mm, 11–14 mm, 14–19 mm and > 19 mm) and three portions of spear (tip, middle and rest). The mean concentrations found for chromium and nickel were 1.37 ± 0.94 and 5.53 ± 1.17 (mg kg −1 dry weight), respectively. By means of analysis of variance, statistically significant differences ( P < 0.001) were determined between the different processing operations for the chromium and nickel ( P < 0.05) concentrations. Scheffé multiple range analyses ( P < 0.05) were applied for the processing, diameters and portion factors, separately, and homogeneous groups were formed which indicated the influence of each one of these factors on the contents of chromium and nickel.

Study of chromium and nickel content in white asparagus (Asparagus officinalis, L.)

The modifications in the chromium (Cr) and nickel (Ni) content and the distribution of these trace elements in white asparagus spears (Asparagus officinalis, L.) were investigated. Samples were taken of two varieties of white asparagus, Desto and Ciprés, and grouped in function of their thickness in spears of < 11 mm and of > 14 mm. All the asparagus samples were cut in lengths of 20 cm and divided into 10 portions of 2 cm each. The determinations of chromium and nickel were carried out by atomic absorption spectrophotometry with air-acetylene flame. The mean concentrations were 0.675 +/- 0.19 and 5.578 +/- 1.39 mg/kg dry weight for chromium and nickel, respectively. By means of three-factor analyses of variance (varieties, thickness and portions), statistically significant differences were determined between the concentrations of chromium and nickel and each one of the sources of variation established. The chromium content showed a variable distribution throughout the white asparagus portions as a result of the notable differences between varieties and thickness. In the case of nickel, its levels underwent a generalized decrease as the spear portions were further and further away from the apical area or tip of the white asparagus.

Mineral content modifications during ripening of asparagus (Asparagus officinalis, L.).

The essential elements: calcium (Ca), magnesium (Mg), sodium (Na) potassium (K) and phosphorus (P) were analyzed in fresh asparagus to determine the effect of the ripening of the asparagus on the mineral content. Asparagus samples were classified in two groups by diameter (< 11 mm and > 14 mm). Asparagus from a sample group with the same diameter were divided into two portions (apical and basal) according to distance from the tip. The concentrations of calcium, magnesium and phosphorus increased with the ripening process of the asparagus while the content of sodium decreased when the white asparagus turned into a green ripening state. No significant differences were established for potassium. The green ripening state was the group with the greater concentration of calcium, magnesium and phosphorus. Statistically significant differences (p < 0.001) were observed between portions of asparagus (tip and rest of stem) in the contents of the five mineral elements analyzed. The levels of mineral elements investigated increased notably in the tip of the asparagus with the exception of sodium and potassium of which the levels in the apical portion decreased or hardly modified. The variance analyses determined statistically significant differences (p < 0.001) in the concentration of magnesium, sodium and phosphorus between asparagus diameters (< 11 and > 14 mm) and no significant differences (p > 0.05) were found for calcium and potassium. The mean element levels were (mg/kg dry weight): Ca = 324 +/- 1186; Mg = 1818 +/- 490; Na = 368 +/- 86; K = 37297 +/- 4167 and P = 6809 +/- 2481.

Ascorbic Acid Stability in Ground Asparagus Samples and in Oxalic Acid Extracts

ABSTRACTTo establish the storage conditions for asparagus preparation before ascorbic acid determination, samples were ground, the mass was divided into three aliquots that were, respectively, stored at 4°C, – 18°C, or extracted with 1% oxalic acid. The extract was further split into aliquots and stored at 25°, 4°, –18° and ‐75°C. Ascorbic acid content was measured at different times of storage by a polarographic method. The rate of degradation increased with storage temperature; the degradation rate was higher in ground samples than in extracts; no significant changes in ascorbic acid content were observed in extracts stored for 7 days at ‐18° or for 90 days at ‐75°C.

Influence of vegetative cycle of asparagus (Asparagus officinalis L.) on copper, iron, zinc and manganese content

The essential elements copper (Cu), iron (Fe), zinc (Zn) and manganese (Mn) were analyzed in fresh asparagus to determine the effects of the vegetative cycle of the plant on the micronutrient content. Asparagus samples were classified in two groups by diameter (< 11 mm and > 14 mm). Asparagus from a sample group with the same diameter were divided into two portions (apical and basal) according to distance from the tip. The concentrations of copper, iron, zinc and manganese increased during the vegetative cycle of the asparagus, mainly in the apical portion which showed significantly greater concentrations with respect to the basal portion. The > 14 mm diameter asparagus presented higher levels of copper, zinc and manganese, whereas the concentration of iron was greater in the < 11 mm diameter asparagus. The mean element levels were (mg/kg dry weight): Cu, 18.9 +/- 3.9; Fe, 91.7 +/- 33.7; Zn, 69.5 +/- 24.6 and Mn, 20.9 +/- 5.0).

Mineral elements distribution in fresh asparagus

The essential elements calcium (Ca), copper (Cu), iron (Fe), magnesium (Mg), manganese (Mn), zinc (Zn), sodium (Na), and potassium (K) were analyzed in fresh asparagus to determine the effects of asparagus diameter and portion on the concentration of nutrients. Asparagus samples were divided into five groups by diameter. Asparagus from a sample group with the same diameter were divided into three portions (apical, middle, and basal), according to the distance from the tip. Nutrient concentration tended to decrease with the decrease in asparagus diameter, mainly for asparagus narrower than 9 mm in diameter. This group had significantly greater concentrations of Fe, Cu, Zn, Mn, Ca, Mg, and K in the asparagus apical portion. The asparagus mean nutrient levels were (μg/g fresh weight): Ca, 250; Cu, 1.50; Fe, 6.2; Mg, 180; Mn, 1.0; Zn, 3.7; Na, 4500; and K, 2000.

Effects of modified atmospheres on textural and cell wall changes of asparagus during shelf‐life

SummarySpears of asparagus cultivator (cv) Regal harvested from a commercial crop on 16 May, 30 May, and 6 June, 1989 were packaged in rigid PVC trays (300g per pack) over‐wrapped with non‐perforated 15 μ stretch PVC (Auto RMF‐A), a similar micro‐perforated film or with a highly perforated control film. Packs were held at 8°C for 1 d, then transferred to 20°C to simulate commercial cool chain distribution and ambient display. Respiration rates as mg CO2 production kg‐1h‐1 were determined for each harvest, and changes in the pack atmosphere composition and weight losses were monitored during shelf‐life. On the day of harvest, and after 3 and 6d shelf‐life, shear force's required to cut through spears and visual quality were determined, and cooked samples were assessed for tenderness, stringiness, flavour, and bitterness by a trained sensory panel. At these intervals, samples of asparagus from each treatment were also extracted for alcohol‐insoluble residues (AIR's), from which the composition of sugars and cell wall phenolics were also determined.Rates of respiration and the extent of pack atmosphere modification were similar for each harvest; in non‐perforated packs, CO2 increased to &gt; 11% and O2 fell to &lt; 2% and in microperforated packs, CO2 equilibrated to ca 5–6% and O2 decreased to a minimum of ca 6–7%. The shear forces needed to cut stems increased during 6 d shelf‐life; this increase was greatest for control‐packed spears and least for those from non‐perforated packs. Regrowth (elongation of the stem and opening of bracts) was almost eliminated in non‐perforated packs, and much reduced in micro‐perforated packs. Asparagus in micro‐perforated packs became slightly less tender and more stringy, whereas control‐packed spears became much tougher and stringier during shelf‐life; changes in flavour and bitterness were slight. Levels of most cell wallsugars changed little, although some obvious changes were detected during shelf‐life; galactose decreased in all treatments, arabinose decreased and xylose content increased considerably (67%) in control‐packed spears. Similarly, the lignin content of asparagus increased by &gt;400% in control, by 200% in micro‐perforated and by &lt; 100% in non‐perforated packs.The relationships between instrumental and sensory methods for assessing textural changes in asparagus and the changes in cell wall composition, and the effects of modified pack atmospheres on these changes are discussed. The possible benefits and limitations of modified atmosphere (MA) packaging to retard post‐harvest deterioration, particularly textural changes in asparagus are also discussed.