Influence of moisture content on the degradation of waxy and normal corn starches acid-treated in methanol

Waxy and normal corn starches with different moisture contents, 5.1-16.9% and 4.8-15.9%, respectively, were prepared and treated in methanol containing 0.36% HCl at 45 °C for 1 h. Recovery of all the treated starches was found to be above 90%. Peak viscosity, gelatinization temperature and enthalpy change of gelatinization of waxy and normal corn starches decreased after treatment and this decrement was found to be more in treated starches having lower initial moisture content. The weight-average degree of polymerization and chain length (CL) of waxy and normal corn starches decreased upon acid-methanol treatment. The decrement ratio of molecular weight of modified starches was found to be negatively correlated with the initial moisture content of the starches. The decrement ratio of normal corn starch was higher than waxy corn starch with similar moisture content of starch. The content and CL of long chain fraction of amylopectin for waxy corn starch slightly decreased after treatment, while no obvious trend was found among starches with different moisture contents. CL of amylose for acid-methanol-treated normal corn starch decreased and this change was found to be higher in starches with lower initial moisture contents. Results demonstrated that the initial moisture content of starch granules strongly influenced the functional properties and degradation of starch treated by acid in methanol.     

Detection of cheese packaging containment failures using reversible optical oxygen sensors

This study investigated the capacity of optical oxygen sensors to nondestructively detect containment packaging failures in commercial vacuum packed cheddar cheese. Unacceptable oxygen levels in packs lead to product deterioration and can significantly reduce shelf life. Vacuum packed cheddar cheese was monitored for oxygen levels over time at 4 °C with optical sensors prefitted to packaging laminates polyethyleneterephthalate/polypropylene. Oxygen levels present in packs immediately after packaging were 3% on average. Further ingress of oxygen into all packs occurred over storage time and levels ranged from 3.6% to 8.2% after 6 days. Information obtained using oxygen sensors led to further assessments and identification of the causes of packaging containment failure.     

储粮环境中米象发生与CO2含量变化的关系研究

为阐明储粮环境中害虫发生与CO_2气体含量变化的关系,研究不同含水量的小麦感染不同虫口密度(0、2、5、10、20、30头/kg)米象后储藏环境中CO_2气体体积分数变化的情况。结果表明:对于含水量相同的储藏小麦,储藏环境中CO_2气体体积分数随虫口密度的增加和储藏时间的延长而显著增加。对于含水量12%的小麦,初始感染虫口密度为30头/kg的储粮环境中CO_2气体体积分数最初为0.413%,在第30天达到最大值为14.777%。对于含水量14%的小麦,初始感染虫口密度为30头/kg的储粮环境中CO_2气体体积分数最初为0.720%,在第15天达到最大值为17.197%。本研究结果为今后通过检测CO_2体积分数变化来监测粮堆中虫害发生情况提供了可靠信息。     

On-line carbon balance of yeast fermentations using miniaturized optical sensors

Monitoring of microbiological processes using optical sensors and spectrometers has gained in importance over the past few years due to its advantage in enabling non-invasive on-line analysis. Near-infrared (NIR) and mid-infrared (MIR) spectrometer set-ups in combination with multivariate calibrations have already been successfully employed for the simultaneous determination of different metabolites in microbiological processes. Photometric sensors, in addition to their low price compared to spectrometer set-ups, have the advantage of being compact and are easy to calibrate and operate. In this work, the detection of ethanol and CO(2) in the exhaust gas during aerobic yeast fermentation was performed by two photometric gas analyzers, and dry yeast biomass was monitored using a fiber optic backscatter set-up. The optical sensors could be easily fitted to the bioreactor and exhibited high robustness during measuring. The ethanol content of the fermentation broth was monitored on-line by measuring the ethanol concentration in the fermentation exhaust and applying a conversion factor. The vapor/liquid equilibrium and the associated conversion factor strongly depend on the process parameter temperature but not on aeration and stirring rate. Dry yeast biomass was determined in-line by a backscattering signal applying a linear calibration. An on-line balance with a recovery rate of 95-97% for carbon was achieved with the use of three optical sensors (two infrared gas analyzers and one fiber optic backscatter set-up).     

Effect of hyperbaric pressure and temperature on respiration rates and quality attributes of Boston lettuce

A study was conducted to determine whether hyperbaric treatment has an effect on the shelf life of lettuce during short‐term storage. Lettuce was treated with different pressure and temperature conditions (100–850 kPa at 20 °C and 100 kPa at 4 °C). A preliminary experiment was performed with different treatment periods, that is, 3, 5 and 7 days. Hyperbaric treatment of lettuces at 20 °C caused noticeable changes in sensory quality, but the product was still marketable after 3 days. On the other hand, the cold‐stored lettuce showed little degradation even after 7 days of treatment, at which time all the lettuce treated at 20 °C was unmarketable. At 5 days of treatment, the respiration rate of hyperbaric‐treated lettuces at 625 and 850 kPa remained fairly stable, while that of the lower‐pressure‐treated lettuce began to increase, indicating the initiation of decay. The 850‐kPa hyperbaric treatment showed better quality results than the 100 kPa, 20 °C treatment. Overall, hyperbaric treatment has the potential of being used as an alternative technique for short‐term storage of lettuce without refrigeration.     

The use of peroxide value as a measure of quality for walnut flour stored at five different temperatures using three different types of packaging

Walnut flour, a by-product from the production of cold-pressed walnut oil, can contain up to 20% oil, which contains high levels of polyunsaturated fatty acids and is, therefore, potentially unstable. In this experiment, ground walnut flour was stored in three types of container, polypropylene plastic containers, multi-walled plastic-lined paper bags and manila (brown) paper bags. These containers were stored at mean temperatures of −24.6, 3.3, 10.4, 14.3 and 23.0 °C for 26 weeks. The moisture content and the peroxide value of the oil extracted from the flour were determined every four weeks for 26 weeks. The initial peroxide value of the freshly ground flour was 0.01 ± 0.008 meq O₂/kg oil.     

Sorption isotherm of corn distillers dried grains with solubles (DDGS) and its prediction using chemical composition

Corn distillers dried grains with solubles (DDGS) has high feed value due to its nutritive contents. The ratio of wet distillers grains (WDG) and condensed distillers solubles (CDS) added during the production process determines the chemical composition of DDGS. Effect of changing this ratio on water sorption behaviour of DDGS, at different temperature, was studied. Five mathematical models were evaluated to explain the sorption behaviour of DDGS. Prediction of sorption isotherm from chemical composition using a four-component model was also investigated. DDGS followed a BET Type III isotherm with higher equilibrium moisture content at increasing relative humidity. Difference in the sorption isotherm curves of DDGS samples reduced as equilibrium relative humidity increased. Equilibrium moisture content of DDGS samples reduced with lowering of CDS quantity added during production process. Modified Halsey equation was found suitable for mathematically explaining the sorption behaviour of DDGS. Binding energy of water molecule with DDGS increased with lowering of CDS level. Sorption behaviour of DDGS can be predicted from the chemical composition of protein, sugar, minerals, starch, fibre and glycerol. Increase in CDS level increased the percent relative deviation of predicted values calculated using the modified four-component model and might be due to the interaction between the chemical compounds present in the samples.     

Controlling deterioration of high-moisture maize with ozone treatment

Two experiments were conducted to determine the effect of ozone treatment on controlling deterioration of high-moisture maize under extreme and moderate environmental conditions experienced during harvest. In the first experiment, 0.77-kg maize samples held at 22% moisture content were treated with ozone at 0.08, 0.16, 0.31, 0.62, 0.94, 1.25 and 1.56 mg kg maize⁻¹ min⁻¹ (60-1120 ppm ozone in air during application) for periods of 5 or 24 h, with an additional treatment of 1.56 mg min⁻¹ repeated every 3 d, and stored at 32 °C for 9 d under continuous aeration. Ozone treatment decreased dry matter loss compared to the control, but not to a level that would likely justify ozone treatment at the rates and treatment times used. In the second experiment, 2.43-kg maize samples held at 26% moisture content were treated with ozonation rates of 0.25, 0.5, 1, and 2 mg kg maize⁻¹ min⁻¹ (1090-8680 ppm ozone during application) for 24 h, stored at 15.5 °C for 30 d and passively aerated every 3 d. Additional ozone treatments at the 2 mg kg maize⁻¹ min⁻¹ rate were applied for 1 h on 3-, 6-, and 12-d intervals throughout the experiment. Single ozone treatments of 1 and 2 mg kg maize⁻¹ min⁻¹ were equally effective, reducing dry matter loss by 1.3 percentage points compared to the control after 30 d of storage. Repeat treatments at 2 mg kg maize⁻¹ min⁻¹ did not reduce dry matter loss compared to the single treatment.     

Oxygen transfer in foods using oxygen luminescence sensors: Influence of oxygen partial pressure and food nature and composition

A rapid and easy to handle (on-line monitoring) method to achieve oxygen sorption kinetics was developed and tested on a large range of food products. Measurements were performed using luminescence sensors placed into of a thin layer of food material exposed to increasing oxygen contents in the atmosphere. From oxygen sorption kinetics diffusivity values could be calculated using a mathematical model based on Fick’s second law. A large range of model and real food were studied: water, agar gel, orange juice, mashed apple, mashed tomato, miglyol, olive oil and copra oil.     

Movement of Cryptolestes ferrugineus (Coleoptera: Cucujidae) in grain columns containing pockets of high moisture content wheat and carbon dioxide gradients

The movement of the adult rusty grain beetle, Cryptolestes ferrugineus (Stephens), in 100 cm long, 10 cm diameter columns, filled with wheat of uniform or non-uniform moisture content (m.c.), was determined for horizontal and vertical placement of columns at 30°C.In horizontal columns filled with wheat of 13.5% uniform m.c., adult C. ferrugineus exhibited a trend of distributing themselves uniformly in the columns after 5 d. In the vertical columns filled with 14.7% uniform m.c. wheat, 44% of the insects moved downward after 7 d showing positive geotaxism. In the horizontal or vertical columns containing pockets of high m.c. wheat, 43-48% of the beetles aggregated in the region of high m.c. after 7 d exhibiting a hygrotactic response. Under CO₂ gradients in the columns filled with uniform m.c. wheat, 65% of C. ferrugineus moved towards higher levels of CO₂ after 1 and 5 d. Also, high levels of CO₂ were more influential in attracting C. ferrugineus (60%) after 1 d in horizontal columns containing high m.c. wheat at one end and high CO₂ levels at the other. In the vertical columns filled with pockets of high m.c. wheat and subjected to CO₂ gradients, movement of C. ferrugineus was more influenced by the combined effects of any two factors out of the three, viz., gravity, higher levels of CO₂ and high m.c. than a single factor.     

Production of enniatins A,A1, B,B1, B4, J1 by Fusarium tricinctum in solid corn culture: Structural analysis and effects on mitochondrial respiration

Enniatins (ENs) are secondary fungal metabolites with hexadepsipeptidic chemical structure and they possess a number of potent biological activities that can contaminate several kind of food and foodstuffs increasing the exposure risk for consumers. ENs are produced by several Fusariun strains including Fusarium subglutinans, Fusarium proliferatum and Fusarium tricinctum. Production of a mixture of ENs was performed by culturing F. tricinctum ITEM 9496 on white corn as substrate. The solid culture components were dried and subsequently extracted with water/methanol (50/50 v/v, 0.5% NaCl), homogenised, filtered, extracted by ethyl acetate and analysed by liquid chromatography with diode array detection (LC-DAD). The crude extract was first separated by low pressure liquid chromatography (LPLC) and then further purified by liquid chromatography (LC), resulting in six compounds with a purity higher than 95% as calculated by ¹H NMR, and with a yield of 30–300 mg per compound. The chemical structures of the ENs were determined by liquid chromatography coupled to mass spectrometry (LC–MS) and nuclear magnetic resonance (NMR). The biological activity of the resulting ENs was determined using a mitochondrial respiration test. We discovered that all the ENs studied induced an increase in the mitochondrial respiration resulting in uncoupling of the oxidative phosphorylation. This effect was most likely due to flux of K⁺ ions into the mitochondrial matrix. The order of potency of the ENs derivatives was: A₁ > B₁ > B > A > B₄ > J₁. These results suggest a correlation between the chemical structures and bioactivity and confirm the severe risks for human associated with consumption of enniatins.