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In this study, the use of two modern portable blood glucose monitors (PBGMs) and a fruit juice-specific system (RQFlex) from Merck was evaluated for determination of glucose concentrations in potato juice, as a representation of the whole potato. The two PBGMs (LifeScan OneTouch Ultra Easy and Bayer Contour) both provided squared correlation coefficients (R 2, p

Summary We have studied mixing, rheology and stability of potato-cereal flour doughs. These were prepared using samples of two varieties of cooked and cold-stored potatoes. Dependent on variety a minimum duration of 24–48 h cold-storage was required. Dough mixing torque plateau was inversely related to potato water content. This should be 2 Nm at a specific total mechanical energy input of 18–22 kJ kg−1. The resting temperature of the dough was also inversely related to its strength (plateau elastic modulus at time zero). Target dough strength should be about 25 kPa in a bob-cup. Above 15 °C it decreased as a function of time and within 1 h it became too sticky for commercial processing. At 4 °C the dough remained stable. Sufficient potato starch retrogradation is a pre-requisite to make optimal potato-cereal flour dough for commercial processing.

The effect of different amounts of transmitted green light on photooxidation in pasteurized milk was studied. Five different green films produced with combinations of pigments and additives to minimize exposure to harmful wavelengths with regard to photosensitizers (400–450 and 600–650nm) were evaluated. In addition, a non-colored transparent film and an orange film were compared with 1 selected green film. Pasteurized milk (3.9% fat) was packed in an air atmosphere and exposed to light for 14, 20, 26, and 32h at 4°C under the different films. Samples stored in the dark were control samples. The results showed that the most-effective green film had low overall light transmission, and also almost completely blocked light wavelengths shorter than 450nm and wavelengths longer than 600nm, which prevented photooxidation of riboflavin and chlorophyllic compounds. Chlorophyll degradation was highly correlated with sensory properties (coefficient of determination=0.80–0.94). To preserve milk quality, total blocking of all visible light would be preferable. If total blocking is not feasible, then light transmission for wavelength below 450nm and above 650nm should be minimized (e.g., less than 5%). The newly developed green film can be used as a prototype for protection of dairy products to reduce the degradation of photosensitizers.

Norvegia cheese samples were packed in air and nitrogen atmospheres and exposed to light of different colours, blue (350–560 nm), green (450–620 nm) and red (580–700 nm). After 7 days of light exposure, each cheese was sliced, from the exposure surface and down, into eight slices of 3 mm thickness. The slices were analyzed by sensory analysis and fluorescence spectroscopy, enabling studies of how photo-oxidation progressed as a function of depth of the cheese. Green light gave the most oxidation at the surface for air stored samples. Oxidized flavours at depths down to 9 mm were more intense for exposure to red and green light. Blue light degraded riboflavin in the two upper layers (0–6 mm), whereas red and green light affected hematoporphyrin, protoporphyrin IX and chlorophyll as far as 21 mm into the cheese. The results suggest that tetrapyrroles are responsible for photo-oxidation at the surface and the interior of the cheese.

The aim of this study was to compare the digestion of milk proteins from different species using an in vitro gastrointestinal model. Raw and heated milks from bovine, caprine, human and equine species were digested by human digestive enzymes. Digestion was performed in two 30-min sequential steps by digestive juices from the stomach (pH 2.5/37 °C) and from the duodenum (pH 8.0/37 °C). The degradation patterns of the milk proteins were visualized by SDS-PAGE and quantified using the ImageQuant program. Caseins in the equine milk were rapidly digested by the gastric juice in contrast to the caseins from the other species. During the subsequent digestion by the duodenal juice most of the caseins from all species were degraded within 5 min, and within 30 min only traces of caseins were detected. The mean casein micellar size varied between species in the range of 146.0–311.5 nm (equine > caprine > bovine > human). The α-lactalbumin from all species appeared to be very resistant to both gastric and duodenal digestions. A similar trend was shown for β-lactoglobulin from bovine and caprine milks, of which ∼ 60% intact protein remained, while only 25% remained intact in equine milk after total digestion. Equine milk contained a high amount of lysozyme, of which 60% remained intact in the present study. In heated milks from all species, only α-lactalbumin degradation increased approximately 12–20% in comparison to the raw milk. This study shows that equine milk with fast digestible proteins could be considered as a replacement for bovine milk in the diet of people with special needs, such as infants and the elderly.

Prediction of dry matter content in whole potatoes is a desired capability in the processing industry. Accurate prediction of dry matter content may greatly reduce waste quantities and improve utilization of the raw material through sorting, hence also reducing the processing cost. The following study demonstrates the use of a low resolution, high speed NIR interactance instrument combined with partial least square regression for prediction of dry matter content in whole unpeeled potatoes. Three different measuring configurations were investigated: (1) off-line measurements with contact between the potato and the light collection tube; (2) off-line measurements without contact between the potato and the light collection tube; and (3) on-line measurements of the potatoes. The offline contact measurements gave a prediction performance of R(2)=0.89 and RMSECV=1.19. Similar prediction performance were obtained from the off-line non-contact measurements (R(2)=0.89, RMSECV=1.23). Significantly better (p=0.038) prediction performance (R(2)=0.92, RMSECV=1.06) was obtained with the on-line measuring configuration, thus showing the possibilities of using the instrument for on-line measurements. In addition it was shown that the dry matter distribution across the individual tuber could be predicted by the model obtained.

Two different types of pasture (cultivated and rangeland) and 2 different hay qualities (high and low quality) were examined for their effects on goat milk composition and rennet coagulation properties. Furthermore, the effect of dietary treatments in both the early and late grazing season was studied. As lactation stage is known to influence milk composition, the goats in the early and late grazing season were in the same lactation stage at the start of the experiment. The milk composition was influenced both by dietary treatment and season. Milk from goats on pasture was superior to those on hay by containing a higher content of protein and casein, and the goats on cultivated pasture had the highest milk yield. Casein composition was significantly influenced by forage treatment. Goats grazing on cultivated pasture had higher contents of αs1-casein and also of κ-casein compared with the other treatments, whereas goats grazing on rangeland had the highest content of β-casein. Factors such as milk yield, casein micelle size, αs2-casein, and calcium content were reduced in late compared with early season. More favorable rennet coagulation properties were achieved in milk from the early grazing season, with shorter firming time and higher curd firmness compared with milk from the late grazing season, but the firming time and curd firmness were not prominently influenced by forage treatment. The content of αs2-casein and calcium in the milk affected the firming time and the curd firmness positively. The influence of season and forage treatment on especially milk yield, casein content, and rennet coagulation properties is of economic importance for both the dairy industry and goat milk farmers.

A rapid spectroscopic method to determine total protein in bovine and buffalo milk using UV spectra of guanidine-hydrochloride mixed milk has previously been reported and validated. The method was based on mixed calibration samples and univariate calibrations of fourth derivative (4D) spectra. In this study the same method was compared and tested for determination of total protein in goat milk. Calculations based on multivariate calibration (partial least squares regression) on full spectra of goat milk were used. The method was tested on 2 UV instruments. The comparison resulted in a significantly more robust (i.e., better) transferability between UV instruments for the partial least squares regression method on full spectra compared with previous univariate calibration of 4D spectra. Local (1 instrument) calibrations gave similar, significantly not different (chi-squared test) cross-validated prediction error results for the 2 methods. It can be concluded that there is no need for fourth derivation. Partial least squares regression on full spectra was equal or superior to using the 4D spectra.

The dry matter is one of the main quality parameters of raw and processed potatoes. In the present study, the potential of utilizing high throughput commercially available NIR interactance systems for dry matter determination in whole unpeeled potato tubers is investigated. The performance of a 2D NIR interactance instrument was compared with that of a 1D NIR interactance instrument and a traditional underwater weight apparatus. A total of 114 tubers were assessed individually with both of the NIR instruments (760-1040 nm), the underwater weight and an external reference method (freeze drying). The 1D interactance instrument obtained better prediction results than what the 2D instrument could achieve (R2=0.95, RMSECV=0.91, and R2=0.83, RMSECV=1.65, respectively). The underwater weight obtained the highest explained variance (R2=0.97), but the estimation was biased by approximately 1.5% (by weight). The poorer prediction performance of the 2D NIR interactance system can be partly explained by the lower penetration depths of the light compared to the 1D NIR interactance systems.