Oxidative Stability of Frozen Pork Patties. Effect of Light and Added Salt

Salt (1%) and light effects on oxidative deterioration were followed during freezer storage (?18°C) in a display cabinet. Oxymyoglobin oxidation and lipid oxidation were strongly accelerated by added salt and more moderately by exposure to fluorescent light. The light-dependent lipid oxidation was prevented by using packaging material with incorporated UV-light absorber. However, a UV-light absorber only yielded partial protection against discoloration. The two oxidation processes showed similarities in progression. In contrast to color deterioration, lipid oxidation showed an initial lag period in agreement with previous indications that pigment oxidation was an initiator of lipid oxidation in beef during freezer storage.     

Atlantic Salmon Average Fat Content Estimated by Near-Infrared Transmittance Spectroscopy

Near-infrared transmittance spectroscopy was used to determine the average fat content in farmed Atlantic salmon fillets with skin and scales. The fat content was 5.7–17.6% and weight range 1.0–5.4 kg. A partial least square regression including 43 salmon resulted in a multivariate prediction correlation of 0.97 and a root mean square error of cross validation of 0.75%. Regression models using 6 to 9 wavelengths in the 850–1048 nm range gave somewhat lower prediction errors than a model using 100 wavelengths. Results showed that NIR transmittance was suited to determine fat content nondestructively in whole salmon fillets with skin and scales.     

Biochemical Changes and Sensory Quality of Shredded and MA-Packaged Iceberg Lettuce

Cultivars of shredded iceberg lettuce (Lactuca sativu L.) ‘Saladin’, ‘Santis’, ‘Telda’ and ‘Roxette’ responded in a parallel way to four modified atmosphere (MA) packaging treatments. Moderate vacuum packaging (mvp) in 80 μm polyethylene (PE) inhibited enzymatic browning over 10-day storage at 5°C. When lettuce was packaged in 80% O₂, 20% CO₂ (80/20), more browning occured in SL3-bags (59 μm multilayer coextruded film) than in PE-bags. Polyphenol oxidase activity declined during storage in all 4 atmospheres, with lowest activity in PE-80/20. Endogenous ascorbic acid (AA) did not act as an efficient antioxidant in delaying browning. Total carbohydrate content (TC) declined slightly during storage. Tristimulus color measurements correlated highly with visual ratings.     

Determination of Iron-Binding Phenolic Groups in Foods

A spectrophotometric assay was developed with the specific aim of determining the content in foods of iron-binding phenolic compounds. Foods were extracted with dimethylformamide (50%) and an ironcontaining reagent was added. The resulting color was due to formation of Fe-galloyl and Fe-catechol complexes. These complexes had different absorbance maxima and could thus be separately determined by readings at two wavelengths. The method was simple and had good precision, accuracy and analytical recovery. The new method was compared with two commonly used methods for determination of phenolic content in cereals, fruits, vegetables, spices and beverages.     

CHEMICAL AND SENSORY QUALITY OF BROCCOLI (BRASSICA OLERACEA L. VAR ITALICA)

Five cultivars of broccoli (Brassica oleracea L. var. italica) were analyzed for individual glucosinolates, S-methylcysteine sulfoxide (SMCSO), aroma volatiles and sensory quality. Total glucosinolate content ranged from 47 to 93 μmol μmol·g dry weight¹, and SMCSO ranged from 22 to 57 μmol μmol·g dry weight¹. A total of 11 glucosinolates were identified in the broccoli cultivars. The major glucosinolates were: progoitrin, glucoiberin, glucoraphanin, glucobrassicin and neo-glucobrassicin and they accounted for more than 95% of the total content. Glucoiberin was only found in appreciable amounts in purple-headed broccoli. Pentanol, pentanal, hexanal, heptanal and nonanal were the most abundant higher boiling volatiles isolated from cooked broccoli using dynamic headspace trapping on Porapak and solvent desorption with diethyl ether. Sensory analysis by a trained panel showed that scores for cooked vegetable odor (‘hay’ and ‘green peapod’) were significantly different between cultivars. In contrast, scores related to Brassica odor (‘cauliflower’ and ‘mustard’) were not significantly different. The content of individual glucosinolates, SMCSO and higher boiling volatiles in the cultivars is discussed in relation to the sensory quality of the cooked product.     

QUANTIFICATION OF RADICAL FORMATION IN OIL-IN-WATER FOOD EMULSIONS BY ELECTRON SPIN RESONANCE SPECTROSCOPY

The tendency of formation of radicals in an oil-in-water food emulsion (a mayonnaise partly based on fish-oil) was quantified by electron spin resonance (ESR) spectroscopy using the spin trapping technique. Among the spin traps examined, N-tert-butyl-α-phenylnitrone (PBN) was preferred for this type of product. Under mildly accelerated conditions (i.e. heating to 37C, a spin trap concentration of 2 mM ensured pseudo-first order conditions for trapping of radicals in the assay for up to 36 h of thermal treatment. The resulting linearity between ESR-signals and rate of radical formation allows a direct quantification by standardization against stable radicals dissolved in the product. The hydrophobic spin-probe 12-doxylstearic acid (in contrast to the hydrophilic 2,2,6,6-tetramethyl-l-piperidinyl-oxyl) gave a stable signal and a linearity existed between signal intensity and probe concentration.