Gunnar B. Bengtsson

Sensory quality of ethylene-exposed carrots (Daucus carota L, cv 'Yukon') related to the contents of 6-methoxymellein, terpenes and sugars

Carrots were analysed for taste and odour and for contents of terpenes, 6-methoxymellein and sugars during 3 weeks storage at 15 °C in an atmosphere containing ethylene (1 µl l−1). The ethylene treatment caused an increase in 6-methoxymellein and the conversion of higher amounts of sucrose to fructose and glucose compared to control carrots stored in air. This corresponded to higher sensory scores for bitterness and terpene flavour and a lower score for sweetness, as measured by an expert taste panel. Principal component analysis showed a more expressed bitter taste, earthy flavour, green flavour, terpene flavour and aftertaste in the ethylene-treated carrots. Correlations were found between sweet taste and the content of sucrose (r  = 0.91, p < 0.005) and between the contents of various terpenes (particularly γ-terpinene, limonene and caryophyllene) and terpene flavour, green flavour, aftertaste and bitter taste (r ≥ 0.72, p < 0.05). In the air-stored carrots these off-flavours seemed to be masked by a high sucrose content. © 2000 Society of Chemical Industry

Drying Kinetics and Allicin Potential in Garlic Slices during Different Methods of Drying

Drying kinetics of garlic cloves was investigated by drying 5 mm thick slices in air, vacuum, and nitrogen atmosphere. The drying coefficient and lag factor were estimated from the slope and intercept of the moisture ratio time plot based on a model by Dincer-Hussain. Both drying coefficient and lag factor increased with increasing drying temperature. The diffusivity estimated from the Ficks law of diffusion and Dincer-Hussains model differed, because Ficks law assumes negligible external mass transfer, whereas Dincer-Hussains model considers both internal and external mass transfer resistance. Allicin, which is rapidly produced by the action of alliinase on alliin when fresh tissue is crushed, is the main biologically active phytochemical of garlic. Air drying at 50°C, vacuum drying at 50 and 60°C, nitrogen atmosphere drying at 40°C gave lowest losses of allicin potential. In general, the loss of allicin potential increased with increasing drying temperature, and drying below 50°C should be the best drying condition for the retention of allicin potential. This could be due to higher retention of alliinase activity during lower temperature drying. The loss of allicin potential decreased with the increase of slice thickness. This may be explained by lower structural damage and by lower shrinkage in the case of thicker slices.

Effects of temperature and photoperiod on sensory quality and contents of glucosinolates, flavonols and vitamin C in broccoli florets

Broccoli is grown around the world at a wide range of photoperiods and temperatures, which may influence both sensory quality and phytochemical contents. Florets produced in phytotron and at two semi-field sites (70 °N and 58 °N) were examined for effects of contrasting temperatures and photoperiods on sensory quality and contents of glucosinolates, flavonols and vitamin C. Growth conditions associated with high northern latitudes of low temperature and long photoperiods, produced bigger floral buds, and florets with sweeter taste and less colour hue than more southern conditions. The contents of vitamin C did not vary, while the response of individual glucosinolates varied with temperature and day length, and contents of quercetin and kaempferol were lower in phytotron than under semi-field conditions. Thus, our results show that contrasting temperatures and photoperiods influence the sensory quality of broccoli florets, while contents of different bioactive phytochemicals are not influenced in a unidirectional pattern.

Influence of day length and temperature on the content of health-related compounds in broccoli (Brassica oleracea L. var. italica).

Vegetables grown at different latitudes are exposed to various temperatures and day lengths, which can affect the content of health- and sensory-related compounds in broccoli florets. A 2 × 2 factorial experiment was conducted under controlled growth conditions, with contrasting temperatures (15/9 and 21/15 °C) and day lengths (12 and 24 h), to investigate the effect on glucosinolates, vitamin C, flavonols, and soluble sugars. Aliphatic glucosinolates, quercetin, and kaempferol were at their highest levels at high temperatures combined with a 12 h day. Levels of total glucosinolates, d-glucose, and d-fructose were elevated by high temperatures. Conversely, the content of vitamin C was highest with a 12 h day length combined with 15/9 °C. Our results indicate that temperature and day length influence the contents of health-related compounds in broccoli florets in a complex way, suggesting no general superiority of any of the contrasting growth conditions.

Effects of genotype, soil type, year and fertilisation on sensory and morphological attributes of carrots (Daucus carota L.)†

BACKGROUND The aim of the study was to investigate the effects of variety, soil type and fertilisation, and the interactions between these factors, on yield and quality traits of carrots. RESULTS Optimum fertilisation levels for yield and quality of grade one roots were found to be between 80 and 160 kg ha(-1) for nitrogen and between 0 and 120 kg ha(-1) for potassium depending on soil type and precipitation. Carrots grown in peat soil had the highest score for sweetness and the lowest scores for negatively associated characteristics such as bitterness, earthy flavour, terpene flavour and firmness. Nitrate content and the amounts of splitted and forked roots were lowest on sandy soil. Variety significantly affected number of grade 1 roots, dry matter, nitrate content and most of the sensory attributes tested. Interactions between variety, soil type and nitrogen fertilisation were found for most of the tested quality characteristics. CONCLUSION The investigations showed that year and variety had the highest impact on the carrot quality attributes studied, whereas soil type and fertilisation had less influence. Peat soil and moderate fertilisation with N and K gave optimal sensory quality while sand soil gave optimal quality as regards morphological characters like splitting and forking of roots as well as nitrate content.

Assessment of the Anti-Microbial Activity of Dried Garlic Powders Produced by Different Methods of Drying

The anti-microbial activity of a range of garlic products including dried garlic powder produced by different methods, commercial garlic products, and garlic oil was determined against a range of selected bacteria. The bacteria included food borne pathogens, spoilage agents, and health-beneficial agents, namely Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, Bacillus cereus, and a mixed lactic culture consisting of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus. The dried powders were produced using air-drying at both 60 and 80°C, vacuum-drying at 50 and 60°C, and freeze-drying at −20°C. In addition, five commercial products were tested, two of which are used as spices, and three as food supplements. Before testing, the moisture content of the dried garlic powders was raised to that of fresh garlic before drying. Garlic oil was used without any addition of water. In general, the results showed that the lactic culture was the most sensitive to the growth inhibitory active compound of garlic used in this study, followed by Staphylococcus aureus. In contrast Salmonella typhimurium and Bacillus cereus demonstrated the greatest resistance to garlic. Generally, fresh garlic produced the greatest inhibition followed by freeze-dried powder. The anti-microbial activity decreased with decreasing dried garlic powder concentration. The results showed that both drying temperature and time have major effects on retaining the active components responsible for the inhibition of microbial growth. The anti-microbial substances in the moist fresh garlic were also affected by moist-heating temperatures and time. Higher heating temperatures caused faster loss of anti-microbial activity. The decrease in growth-inhibition zones for moist-heated fresh garlic followed zero-order kinetics.

Rapid analysis of 6-methoxymellein in carrots by boiling water extraction, solid phase extraction and HPLC

Abstract By modification and combination of existing methods we have developed a rapid method for quantification of 6-methoxymellein in carrot roots by means of boiling water and solid phase extraction, followed by high performance liquid chromatography (HPLC). The performance of the method was found to be acceptable, when tested by three consecutive boiling water extractions from carrot samples with different levels of 6-methoxymellein. The recovery was 96–99% after one extraction. With this method it was possible for one person to extract 20 samples during a working day and further quantify the amount of 6-methoxymellein by automatic HPLC the following night.

Growth temperature affects sensory quality and contents of glucosinolates, vitamin C and sugars in swede roots (Brassica napus L. ssp. rapifera Metzg.).

Swede is a root vegetable grown under a range of growth conditions that may influence the product quality. The objective of this controlled climate study was to find the effect of growth temperature on sensory quality and the contents of glucosinolates, vitamin C and soluble sugars. High temperature (21 °C) enhanced the intensities of sensory attributes like pungent odour, bitterness, astringency and fibrousness, while low temperature (9 °C) was associated with acidic odour, sweet taste, crispiness and juiciness. Ten glucosinolates were quantified, with progoitrin as the dominant component followed by glucoberteroin, both with highest content at 21 °C. Vitamin C also had its highest content at 21 °C, while the total sugar content was lowest at this temperature. In conclusion, the study demonstrated clear effects of growth temperature on sensory quality and some chemical properties of swede and indicated a good eating quality of swedes grown at low temperatures.

Effects of Organic and Waste-Derived Fertilizers on Yield, Nitrogen and Glucosinolate Contents, and Sensory Quality of Broccoli (Brassica oleracea L. var. italica)

Organic vegetable production attempts to pursue multiple goals concerning influence on environment, production resources, and human health. In areas with limited availability of animal manure, there is a need for considering various off-farm nutrient resources for such production. Different organic and waste-derived fertilizer materials were used for broccoli production at two latitudes (58° and 67°) in Norway during two years. The fertilizer materials were applied at two rates of total N (80 and 170 kg ha(-1)) and compared with mineral fertilizer (170 kg ha(-1)) and no fertilizer. Broccoli yield was strongly influenced by fertilizer materials (algae meal < unfertilized control < sheep manure < extruded shrimp shell < anaerobically digested food waste < mineral fertilizer). Yield, but not glucosinolate content, was linearly correlated with estimated potentially plant-available N. However, extruded shrimp shell and mineral NPK fertilizer gave higher glucosinolate contents than sheep manure and no fertilizer. Sensory attributes were less affected by fertilizer material and plant-available N.

Stability of Prussian blue bound to anion-exchange resin beads for radiocaesium reduction in foodstuffs

Emergency decontamination of foodstuffs may be necessary after an extensive radioactive fallout causing food shortages. Prussian blue bound to spherical inert beads would be suitable for radiocaesium reduction if leaching of Prussian blue components could be minimized. Prussian blue was synthesized by consecutive binding of its constituents to macroreticular anion-exchange resin beads. After various incomplete synthesis cycles (i.e. [Fe(CN)6]4− binding last), the beads (designated RCF1.5, RCF2.5, RCF3.5) leached significantly larger amounts of soluble iron than beads of complete synthesis cycles (Fe3+ binding last; beads designated RCF1, RCF2, RCF3, RCF4). Most of the release from RCF1.5-RCF3.5 beads could be accounted for as [Fe(CN)6]3−, whereas RCF1-RCF4 beads did not leach this substance. Repeated rinsing of RCF3 beads reduced the leach to a minimum. The same extent of leach reduction was also accomplished by treatment with KH2PO4, water-glass, a meat extract or an artificial meat fluid. Treatment with P2O4−7 or P3O5−10 destabilized the RCF3 beads. Properly prepared composite beads after complete cycles of Prussian blue synthesis may be usable for safe reduction of radiocaesium in foodstuffs, at least in meat.