3种蛋白膜包裹对核桃仁脂质过氧化作用的比较研究

对于大豆蛋白、蛋清蛋白和乳清蛋白的成膜性及其膜特性研究已有一些报道,但对于这3种蛋白膜特性的分析和比较则未见报道。在3种蛋白最佳成膜条件下分别制备大豆蛋白膜、蛋清蛋白膜和乳清蛋白膜,分析比较其水蒸气透过率,来考察其膜特性;观察3种蛋白膜包裹对核桃仁在贮藏条件下的酸价、过氧化值和TBA值等的影响,来考察其对核桃仁脂质过氧化的影响。结果表明,在与大豆蛋白和蛋清蛋白相同蛋白浓度下,乳清蛋白需要较高甘油浓度才具有较好的成膜性,这使得乳清蛋白膜具有较高的水蒸气透过率。在贮藏过程中,核桃仁的酸价、过氧化值和TBA值均上升。但应用3种蛋白膜包裹均可使核桃仁的酸价显著降低,可降低约24.9%,3种蛋白膜包裹的核桃仁的酸价之间没有明显差异;3种蛋白膜包裹均可使核桃仁的过氧化值显著降低,其降低的程度依次为:大豆蛋白膜>蛋清蛋白膜>乳清蛋白膜,且3种蛋白膜包裹之间有明显差异;3种蛋白膜包裹均可使核桃仁的TBA值显著降低,其降低的程度依次为:大豆蛋白膜>蛋清蛋白膜>乳清蛋白膜,且3种蛋白膜包裹之间有明显差异。由上述结果可见,3种蛋白均能延缓核桃仁的脂质过氧化,其中效果最好的是大豆蛋白,其次是蛋清蛋白,最后是乳清蛋白。     

Quality changes during the storage of dehydrated chicken kebab mix

The level of binders (starch, refined wheat flour and milk powder) was optimised with respect to sensory quality of ready‐to‐eat kebab made from a dehydrated mix using the experiment based on the Box–Behnken design. The optimised levels (as % of cooked meat) were 4.5% starch, 9.5% refined wheat flour and 2% milk powder. Dehydrated chicken kebab mix prepared with optimised quantities of binders and spices was packed in metalised polyester pouches, stored at ambient temperature (27 ± 2 °C) for 6 months and sampled periodically for quality evaluation. A gradual decrease (P ≤ 0.05) in pH from 5.8 to 5.5, increases (P ≤ 0.05) in a_w from 0.31% to 0.42%, in moisture from 5.4% to 6.2%, in free fatty acid values from 0.99 to 1.74 as per cent oleic acid and in thiobarbituric acid numbers from 2.9 to 5.3 mg malonaldehyde kg^?1 were observed during storage. Hunter colour a values increased (P ≤ 0.05) from 0.30 to 1.29, whereas changes in Hunter L (51.8–53.4) and in Hunter b (19.0–19.5) values were marginal (P ≥ 0.05) during storage. The chicken kebab mix was microbiologically safe as indicated by low bacterial counts and absence of coliforms throughout the storage period of 6 months. Fried chicken kebabs prepared from mix stored for up to 6 months were acceptable.     

Droplet composition affects the rate of oxidation of emulsified ethyl linoleate

Our objective was to study the influence of droplet composition on the rate of lipid oxidation in emulsions. A series of oil-in-water emulsions stabilized by a nonionic surfactant (Tween 20) was studied. These emulsions had the same total oil concentration (5 wt%) and initial droplet diameter (0.3 μm), but contained droplets with different ratios of ethyl linoleate (substrate) andn-tetradecane (inert diluent). Lipid oxidation was measured as a function of time by three different methods: gas-chromatographic determination of residual substrate; ultraviolet-visible spectrophotometric determination of conjugated dienes; and measurement of aqueous thiobarbituric acid-reactive substances. All three methods showed similar trends for emulsions of similar composition. The progress of lipid oxidation in the emulsions was dependent on the concentration of ethyl linoleate in the emulsion droplets. At low concentrations (1% oil as substrate), oxidation proceeded at a relatively slow and constant rate. At intermediate concentrations (20%), the oxidation rate was rapid initially and then slowed down with time. At high concentrations (100%), the oxidation rate was slow at first, and then increased with time. An explanation of our results is proposed in terms of the distribution of substrate molecules between the droplet interior and interface, and the ingress of aqueous radicals into the emulsion droplets.     

Small-scale production and storage quality of dry-milled degermed maize products for tropical countries

Summary A small‐scale, single operation, dry degerminator, originating from Brazil was tested on six maize samples (from France and Mali) at two moisture contents (10 and 15% wb). The yield of brewery maize grits (<1% lipids) was higher for extensively dry (10% mc) and hard grains. It ranged from 50 to 70% for four cultivars, which was equivalent or higher than for industrial plants. The rancidity of the products was controlled by the fat acidity level, which was 40–60 mg KOH 100 g^?1db, after 4 months storage of degermed flour. This indicates that degermed products can be stored at 35 °C for up to 6 months without developing significant rancid off‐flavour. Thus the Brazilian dry degerminator appears suitable for the treatment of maize in the tropical zone of Africa.     

Sensory quality of marinated frozen stored chicken thighs as affected by dietary fish fat and vitamin E

The effects of diets containing fish meal (0 or 4%), fish silage (0 or 4%) and vitamin E (60 or 200 mg kg^–1) and the processing effect of marinating with sodium citrate (0.24 or 0.48%) or ascorbate (0.31 or 0.62%) have been studied to test the hypothesis that oxidative stability of frozen stored chicken thighs can be improved by such treatments. A trained sensory panel assessed the samples after storage at –25 °C for 1 week, 3 and 6 months. Feed with 4% fish meal resulted in increased fish flavour and odour of the thighs while 4% fish silage had a smaller effect on these attributes. Fish meal and fish silage added together into the feed by an amount of 4% each, caused strong fish flavour and odour in the product and accelerated the rancidity process. High concentration of vitamin E (200 mg kg^–1) in the feed reduced rancidity when 4% fish products had been added to the feed, but no effect was noted when 4% fish meal plus 4% fish silage had been added together. High concentration of ascorbate in the brine (0.62%) decreased sensory score for rancidity attributes (hay, grass, soap and paint), while high concentration of citrate (0.48%) increased these parameters in frozen stored chicken thighs.     

Lipid Oxidation in Microsomal Fraction of Squid Muscle (Loligo peali)

Frozen squid is susceptible to both lipid oxidation and yellow/brown discoloration during frozen storage. The involvement of lipid oxidation in the microsomal fraction of squid muscle on oxidative rancidity and discoloration was investigated using iron and either enzymatic or non‐enzymatic redox cycling pathways. Lipid oxidation was measured by thiobarbituric acid‐reactive substances (TBARS), and color changes were measured spectrophotometrically using an integrating sphere. The lipid oxidation was not observed in the squid microsomes in the presence of Fe³⁺ and β‐nicotinamide adenine dinucleotide disodium salt (NADH) or β‐nicotinamide adenine dinucleotide phosphate, reduced (NADPH), suggesting that the enzymatic redox cycling pathway was not active. Iron‐promoted TBARS formation was observed in the non‐enzymatic pathway when ascorbic acid was used as a reducing compound. Non‐enzymatic lipid oxidation increased with increasing temperature (4 °C to 37 °C), iron (0 to 100 μM), and ascorbic acid (0 to 200 μM) concentrations. As lipid oxidation in the microsomes or isolated microsomal lipids increased, color changes were observed as could be seen by an increase in b* values (yellowness) and a decrease in a* (redness) values. The ability of iron and ascorbate to promote both lipid oxidation and pigment formation in the microsomal fraction suggests that this pathway could be responsible for quality deterioration of squid muscle during storage.     

Film preparation with high protein defatted peanut flour: characterisation and potential use as food packaging

The purpose of this study was to prepare a defatted peanut flour‐based film (DPFF); to characterise their physicochemical, optical, barrier and mechanical properties; and to evaluate the defatted peanut flour package efficacy to preserve the chemical quality of sunflower oil during storage. The film presented high lightness values (L* = 86.83). The water vapour permeability was 5.44 × 10^?11 g m^?1 s^?1 Pa^?1. Tensile strength and percentage of elongation were 1.01 MPa and 84.01%, respectively. Sunflower oil samples packaged in defatted peanut flour packages (DPFP) were stored during 67 days at room temperature. Peroxide value and conjugated dienes increased less for sunflower oil conditioned in DPFP and high barrier plastic pouches (EVOH) during storage than sunflower oil conditioned in Petri dishes (C). The use of DPFP improved the chemical stability of sunflower oil during storage. The DPFF showed suitable film properties, and also, the capacity to be incorporated in food packaging applications.     

Effect of Oxygen-Absorbing Packaging on the Shelf Life of a Liquid-Based Component of Military Operational Rations

ABSTRACT: Oxygen within the sealed package can reduce the quality of liquid‐based food products with high oil content such as hot‐filled meal‐ready‐to‐eat (MRE) cheese spread, a component of military operational rations. The aim of this study was to test a novel oxygen absorber‐containing laminate material and its ability to maintain and/or extend shelf life of a cheese‐spread MRE item. An iron‐based oxygen absorber (ABSO₂RB®) activated by moisture was incorporated into the laminate and used to pack hot‐filled cheese spread MREs. The kinetics of oxygen absorption due to humidity and temperature were characterized and peel tests performed to ensure pouch seal integrity. Accelerated shelf‐life tests of ABSO₂RB and regular MRE pouches without the O₂‐absorber were conducted for 3 mo at 51.7 °C (125 °F), and 6 mo at 37.8 °C (100 °F) by measuring oxygen concentration (Mocon O₂‐analyzer), microbiological, and physicochemical quality characteristics, including color, texture, moisture, free fatty acid (FFA), pH, water activity, and vitamins and A. Pouches stored at 26.7 °C (80 °F) for 12 mo served as calibrated controls. Consumer tests were conducted in‐house and a confirmatory sensory test was conducted at Natick by a trained panel using a 9‐point hedonic scale. ABSO₂RB‐laminates maintain the same seal integrity and strength as those of the control samples. The headspace oxygen concentrations in these pouches reached (P < 0.05) < 0.5% in 11 d of storage at 26.7 °C (80 °F) and remained below this level throughout the storage period (1 y). No microbial growth (aerobic, coliforms, yeast, and molds) was detected (P < 0.05) for both packages. Overall, the ABSO₂RB‐pouches indicate an improved reduction in oxygen and vitamin C retention compared with MRE controls and maintained product quality (physicochemical and organoleptic). ABSO₂RB‐laminates met the accelerated shelf‐life requirement of 1 mo at 51.7 °C (125 °F), and 6 mo at 37.8 °C (100 °F). This study clearly shows the benefits of using active packaging technology on retaining nutrition and prolonging shelf life of high‐fat, liquid content MRE items.