Karl Kaack

The effect of asparaginase on acrylamide formation in French fries

Acrylamide formation in French fries was investigated in relation to blanching and asparaginase soaking treatments before final frying. Par-fried potatoes of Bintje variety were prepared by cutting strips (0.8×0.8×5cm) which were blanched at 75°C for 10min. Unblanched strips were used as the control. Control or blanched strips were then dried at 85°C for 10min and immediately partially fried at 175°C for 1min. Finally, frozen par-fried potatoes were fried at 175°C for 3min to obtain French fries. Pre-drying of raw or blanched potato strips did not generate acrylamide formation as expected. Partial frying of pre-dried control potato strips generated 370μg/kg of acrylamide and the final frying determined French fries with 2075μg/kg of acrylamide. When control potato strips were treated with a 10000 ASNU/l asparaginase solution at 40°C for 20min, the acrylamide formation in French fries was reduced by 30%. When blanched potato strips were treated in the same way, the produced French fries have 60% less acrylamide content than blanched strips without the enzyme treatment. Soaking of blanched potato strips (75°C, 10min) in an 10000 ASNU/l asparaginase solution at 40°C for 20min is an effective way to reduce acrylamide formation after frying by reducing the amount of one of its important precursors such as asparagine.

Rheological properties of biscuit dough from different cultivars, and relationship to baking characteristics

Abstract Rheological properties of semi-sweet biscuit doughs from eight wheat cultivars were studied, and related to the dimensional changes of biscuits after cutting and baking. The tested cultivars were selected in order to represent a wide diversity in biscuit baking performance, and were grown with low use of N-fertiliser in three successive years. A standard recipe for semi-sweet biscuit dough was used, and the amount of water added was adjusted to the water absorption capacity. The rheological properties of the dough were characterised by creep recovery and oscillation. The fundamental methods showed that maximum strain at creep, recovery, storage modulus G ′, and phase angle δ were significantly influenced by the tested cultivars. The ranking of the cultivars according to phase angle δ was identical in each of the years investigated 3 which indicates that phase angle δ reflects differences in structural properties with genetic control. Multivariate regression of flour physiochemical, dough rheological, and biscuit baking characteristics showed that a decrease in biscuit length was correlated under several rheological parameters, including phase angle δ , Farinograph and creep recovery parameters. Sedimentation value was the only physiochemical flour characteristic with considerable influence on the model. Validation of the partial least squares-model including all samples from the 3 years gave only a weak correlation ( r =0.58), whereas when each single year was evaluated separately, the correlation increased considerably ( r =0.71 and 0.87).

Olfactory and quantitative analysis of volatiles in elderberry (Sambucus nigra L) juice processed from seven cultivars

Aroma compounds emitted from elderberry juices processed from seven cultivars were collected by the dynamic headspace technique and analysed by GC–FID and GC–MS. Forty aroma compounds were identified and quantified, including nine compounds which had not previously been detected in elderberry juice. Significant differences were found among cultivars in the concentration levels of 30 compounds. The sensory characteristics of the individual aroma compounds in elderberry juice were determined by a GC-sniffing technique, and the compounds were grouped according to their odour. The characteristic elderberry odour is due to dihydroedulan and β-damascenone, of which the former occurs in relatively high concentrations in the headspace of elderberry juice. The fruity group consisted of aliphatic alcohols and aldehydes and aromatic esters, of which 1-pentanal, 2-methyl-1-propanol, 2- and 3-methyl-1-butanol, 1-octanal, 1-octanol and methyl and ethyl benzoate contributed with fruity notes. In the flowery group, 1-nonanal, nerol oxide and (Z)- and (E)-rose oxide contributed with characteristic elder flower odour, whereas other flowery notes were associated with hotrienol, linalool and α-terpineol. Fresh and grassy odours were correlated with 1-hexanal, (E)-2-hexen-1-al, (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol and (E)-2-octen-1-al of the grassy group, whereas 1-octen-3-ol and 1-octen-3-one of the agrestic group contributed significantly with the characteristic aroma of mushrooms. © 2000 Society of Chemical Industry

Nutritionally Important Chemical Constituents and Yield of Carrot ( Daucus carota L.) Roots Grown Organically Using Ten Levels of Green Manure

In a field experiment carried out over two years (1995, 1996) carrots were grown organically on a sandy loam soil. A broad range of mineral nitrogen (N-min) levels at carrot emergence was obtained by depleting or amending the soil by removing or supplying different amounts of green manure. With N-min values ranging from 22 to 162 kg N ha -1 at carrot emergence, the N uptake of the carrot crop increased linearly from 70 to 200 kg N ha -1 . The yield increased with N-min at lower levels of N, but levelled off above 90-100 kg N ha -1 . In fresh carrot roots the concentrations of total N, ten individual amino acids, total sum of amino acids, two amides, asparagine and glutamine, and g -carotene increased linearly with the soil concentration of N-min at carrot emergence. Nitrate N increased exponentially with N-min, reaching levels of 340 mg NO 3 kg -1 fresh weight under some conditions. The concentrations of potassium, calcium, glucose, fructose, sucrose and six individual free amino acids were unaffected by the N-min level. Magnesium was decreased at the lowest deliberately depleted N-min levels, whereas the concentration of dry matter and vitamin C decreased linearly with increasing N-min levels. Significantly lower concentrations of dry matter, total N, nitrate N, vitamin C and total sum of free amino acids were found in the warm and sunny year 1995 with the highest yield of carrot roots, whereas the contrary was found for g -carotene.

Modelling of the optimum harvest time for long-term storage of ‘Elstar’ and ‘Aroma’ (Malus domestica) apples at low oxygen concentration

Abstract Research evaluated modelling of optimum harvest time for long-term storage of ‘Aroma’ and ‘Elstar’ apples at 1 °C in three low-oxygen air compositions: (1) 1.5/1.5% O2/CO2 throughout the storage period; (2) 0.25/0.25% O2/CO2 for seven days, and then at 1.5/1.5% O2/CO2 for the remaining storage period; and (3) 1.5/1.5% O2/CO2 until the final three weeks of the storage period where it changed to 2.0/2.0% O2/CO2. The differences between measured and predicted fruit weight of ‘Aroma’ apples varied by 0–4 g during the six harvesting dates in 2005, whereas the differences for ‘Elstar’ apples were 1–10 g. Measured and predicted Streif index for ‘Aroma’ and ‘Elstar’ apples varied between 0.01 and 0.07 g/w/w%*index and from 0.04 to 0.10 kg/w/w%*index, respectively. For ‘Aroma’ the Streif index was 0.16 kg/w/w%*index at the beginning of the storage period and 0.04 kg/w/w*index at the end; whereas the Streif indexes were 0.16 and 0.05 kg/w/w*index for ‘Elstar’. The highest and the lowest levels of the gas compositions resulted in the least and most mature apples, respectively. Apple colour was unaffected by air composition. Improved prediction of fruit weight and Streif index for ‘Aroma’ and ‘Elstar’ may be obtained using four linear equations and degree days without a reference temperature and improvement in prediction of apple fruit diameter may be obtained using degree days and two exponential equations. The quality characteristics of both cultivars were extremely high after storage in controlled atmosphere for 204 days and the analytical data including the low weight losses indicate that the storage time for ‘Aroma’ and ‘Elstar’ may be extended by at least two and three more months, respectively. The highest level of the gas compositions resulted in the least mature apples and may therefore be recommended for storage of ‘Aroma’ and ‘Elstar’.

Effects Of Potassium, Phosphorus And Nitrogen Fertilization On Endogenous Ethylene And Quality Characteristics Of Apples (Malus Domestica L.)

Factor analysis of the data from experiment one with fertilization of ‘Spartan’ apples using various levels of nitrogen, phosphorus, and potassium and their interactions showed significances between ethylene and potassium, soluble solids and potassium, acidity and phosphorus, ethylene and phosphorus, and between ethylene and nitrogen. Factor analysis of data from experiment two with twenty apple cultivars showed that maturation time and ethylene were positively associated, whereas ethylene was inversely related to acidity that is reduced during the apple fruit maturation, and soluble solids are produced during apple fruit maturation. The effects of potassium on ethylene could be through promotion of enzyme activation, promotion of protein synthesis and increased solute transport in the xylem and phloem. Production of ethylene through soluble solids could be due to increased synthesis of the amino acid cysteine that is precursor of ethylene that may be extended to synthesis of other amino acids. The decreasing concentration of malic acid during fruit maturation may be due to increasing rates of several enzymes involved in the citric acid and glyoxylate cycles that are delivering precursors to synthesis of amino acids and porphyrins. The significant relationships between soluble solids and potassium and between acidity and phosphorus may increase the synthesis of nucleic acids and improve energy supply through adenosine phosphates. The significance between ethylene and nitrogen may also increase synthesis of amino acids, proteins and enzymes. On this basis it may be concluded that the three major minerals nitrogen, phosphorus and potassium are very important for apple fruit maturation because they may be involved in several biochemical processes.

Growing and picking of green beans

This research was initiated with an experiment regarding the importance of a corn shelter in order to improve the yield and quality characteristics of green beans with a minimum of mechanical damage of the bean pods. That was followed by studies in bean pod distribution in order to optimize bean pod composition towards the most delicious texture, colour, and flavour. The obtained data showed that the bean pod distribution was skew with a non-normal left part due to the continuously supply of new thin pods in the left part of the pod distribution and a normal distribution in the right part of the diauxi pod growth. The solution was to remove pods in sizes below five mm and avoiding pods with diameter above 11 mm, b ecause that included pods with delicious sensory quality characteristics. Evaluation of this hypothesis by growing and processing of ten cultivars showed possibilities for improvements of the sensory properties in sweetness, texture, mealiness and firmness of blanched and frozen green pods. Taking optimum degree days from 761 to 1046 resulted in improvements of the sensory properties of the pods from ten fields with areas from 2.2 to 11.3 ha. The applied statistical analyses showed very strong relationships between quality characteristics and the sum of degree days from sowing the seed to picking of the bean pods.

Quality Characteristics of Jam and Whole Destoned Cherries Processed Using Sour and Sweet Cherries

This research includes the steps from selection of raw to industrial processing of jam, and whole destoned cherries using high quality raw materials from seven cultivars including ʽStevnsbær clone 23ʼ and ʽKelleris 16ʼ as representatives for sour and sweet cherries, respectively. The six cultivars applied for processing of cherry fruit jam varies significantly in fruit weight, stone, acidity, soluble solids and especially the contents of colorants. Equilibrium in weight, brine and fruit were obtained after storage at 20oC for six days. Acidity in brine and fruit increased and decreased significantly in 73 days, respectively. Increasing content of sugar resulted in significantly increases in net weight, brine and cherries, whereas weight of cherries and acidity were constant and cherry volume decreased significantly. During pasteurization for up to 73 days were the weight was stable, while brine increased, cherries, volume and anthocyanin decreased significantly and benzaldehyde was unaffected by pasteurization. Lightness decreased, redness increased, yellowness decreased and anthocyanin increased with storage time. Increasing brix resulted in increasing cherry brix, density, fruit weight, brine weight, while fruit cherry weight and berries weight were unaffected by the brix level. Acidity and cherry increased and cherry fruit volume decreased significantly. During pasteurization was cherry weight constant, brine increased, cherry decreased, percentage cherries decreased, volume, benzaldehyde and anthocyanine decreased significantly.