Showing papers by "Martina Lille published in 2006"

Impact of pretreatment and freezing conditions on the microstructure of frozen carrots: Quantification and relation to texture loss

Abstract: The textural quality of carrots subjected to pretreatments affecting the pectin structure in combination with different freezing conditions was studied. Carrot samples frozen under different conditions were extensively studied by light microscopy quantifying the freezing damage based on the analysis of different parameters (number, area, perimeter, and shape factor of tissue particles) associated with carrot tissue damage. The reduced texture loss of rapidly or cryogenically frozen carrots, compared to slowly frozen samples, was associated with the reduction in cell wall damage in the carrot tissue. In case no pretreatment was used, carrot texture was only slightly improved by using high-pressure shift freezing instead of slow freezing. Detailed analysis of the different steps involved showed that severe tissue damage occurred during the completion of the high-pressure freezing process at atmospheric pressure. However, tissue damage, and thus texture loss, of high-pressure frozen carrots could be minimized by applying pretreatments consisting of a thermal treatment at 60 °C and a high-pressure treatment at 300 MPa and 60 °C.

Combined Enzymatic and High-Pressure Processing Affect Cell Wall Polysaccharides in Berries

Abstract: The effect of high-pressure processing (HPP) on cell wall polysaccharides in berries was investigated. HPP decreased the degree of methyl esterification (DM), probably by activation of pectin methyl esterase (PME), and improved the extractability of pectins. When commercial enzyme mixtures were added to mashed berries, a synergistic effect was observed between treatment with commercial enzymes and HPP. Compared to treatment at atmospheric pressure, pectic polysaccharides were degraded to a larger extent when HPP was used. In contrast, hemicelluloses were hardly affected by the added enzymes when HPP was included, although they were degraded during similar treatment at atmospheric pressure. Additionally, the activity of rhamnose-releasing enzymes present in minor quantities might be enhanced after HPP, resulting in a decrease of rhamnose in the polymeric cell wall material. These results exploring the effect of HPP at representative conditions clearly point out the potential of HPP for polysaccharide modification.

Quality related aspects of high pressure low temperature processed whole potatoes

Abstract: The optimization of freezing and thawing paths for faster processes, leading to better quality and safety of processed food products, was studied with whole potatoes. Microstructure of processed products was examined through a light microscopy based method on the embedding of the samples in a resin. Colour of samples (visual appearance and spectrometric measurements) and drip loss after the thawing treatment were also examined. A processing time reduction for pressure-induced thawing at pressure levels of 290 MPa has been demonstrated, taking advantage of the existence of a solid ice I metastable phase in the domain of ice III. This time reduction is a direct consequence of the increase of the temperature gradient between sample and heating medium. Industrial relevance An already well established market for High-Pressure treated products, mainly concerning pasteurization, still shows no products commercialized for sub-zero temperature processes. High-Pressure Low-Temperature (HPLT) treatment of food products is still a non-industrialized technology. The quality and safety maintenance of treated foods (as shown in this paper), together with the existing High-Pressure industrial equipment and market (at room or high temperatures) clearly demonstrate the great opportunity of HPLT processing of foods. This paper shows an example of HPLT treated foods in a pilot scale, as a first scale-up attempt.

The effect of liquorice extract-containing starch gel on the amount and microbial composition of plaque

Abstract: The aim of this study was to find out whether liquorice-containing starch gel could affect plaque accumulation and its microbial composition. Sixteen healthy volunteers (mean age: 30.4±6.9 years) used 6 g of either control [8% acid-hydrolyzed corn starch, 25% maltitol syrup, water (w/w)] or liquorice gel (control + 2.5% liquorice extract), three times a day for 2 weeks. The gels were used in a random order with a 2-week washout period in between. At the end of each fortnight, plaque was allowed to accumulate for 2 days and all available plaque from the right side of the mouth was collected, weighed, and transferred to transport medium. The plaque on the left side was dyed and photographed in a standardized manner. Mutans streptococci, total streptococci, and facultative bacteria were assessed from the plaque using plate culturing. Plaque index (0−5) of incisors and canines on the left side was evaluated from the photographs. The clinical study was preceded by an in vivo acid production test. The acid production from gels containing 2.5–10% liquorice extract was monitored with a microelectrode. The in vivo acid production potential of the maltitol-containing starch gel was about 50% compared to the sucrose control. Liquorice inhibited acid production from the gel. In the clinical study, the weight of plaque after consumption of the liquorice gel did not differ from that of the control gel. No differences were found in the microbial counts nor in the plaque index between the two gels. In addition, the liquorice gel had no effect on the stability of the predominant bacterial populations of the plaque samples of 16 individuals as detected by PCR-denaturing gradient gel electrophoresis. In conclusion, an addition of liquorice extract to starch-containing gel with a low acid production potential had no effect on the plaque formed during a 2-week gel consumption period.