Oxidative stability of snack and cereal products in relation to moisture sorption

Assessment of Textural Properties of Puffed Corn Cakes during Storage at Different Relative Humidity

Moisture adsorption is considered a critical factor during production and shelf-life of puffed corn cakes (PCC). This study aims to develop and validate an instrumental method and a mathematical model for the characterization of the textural modifications caused by the moisture adsorption in PCC. For that purpose, PCC were stored at different relative humidities to achieve a wide range of water activities (from 0.1 to 0.8 at 22 ± 1 °C). A flexion-compression test was successfully validated in order to characterize the average textural properties of a PCC batch. A mathematical model considering consecutive elastic and plastic zones satisfactorily fitted (average VAR 99.65% and MRE 3.29%) the average stress-strain profiles of PCC and reported useful textural parameters, such as the deformability modulus (E), critical strain (ε_c), and n curvature parameter. The structural modifications caused by moisture adsorption led to the reduction in E and n and the increase in ε_c. Even minor changes on the PCC moisture content involve remarkable modifications of the textural properties, which has to be considered for industry and retail distribution.

Delayed Quality Deterioration of Low-Moisture Cereal-Based Snack by Storing in an Active Filler-Embedded LDPE Zipper Bag

This study focused on controlling the vapor permeability of an active zipper bag and preserving the quality of cereal-based snacks during the storage period at home. The active zipper bag was prepared by extruding low-density polyethylene with active fillers obtained from natural mineral materials. The active zipper bag showed the same transparent appearance as the existing one but showed 21% lower water vapor capability. As a result, during a 20-day storage period, three types of grain-based snacks (biscuits, shortbread cookies, and puffed snacks) showed delayed increases in weight, moisture content, and moisture activity when stored in an active zipper bag. In addition, this also affected the texture of the biscuits and shortbread cookies, in which the area under the curve was reduced significantly after appearing at a peak during the hardness measurement. On the other hand, the decrease in the number of air cell fracture events in puffed snacks was remarkable. This result suggests that the inner microstructure is preserved better when stored in an active zipper bag. In conclusion, the active zipper bag showed poor water vapor permeability, suggesting that the prepared zipper bag can be developed as snack packaging.

The Study of Thermal Properties of Blackberry, Chokeberry and Raspberry Seeds and Oils

The seeds of berry fruits are a component of fruit waste occurring in the production process. Circular economy rules focus on decreasing the amount of waste produced and reusing by-products when it is possible. To determine the possible applications of the studied fruit industry wastes, the thermal properties of berry seeds and of oil extracted from the tested material were examined. Differential scanning calorimetry (DSC), modulated differential scanning calorimetry (MDSC), and thermogravimetry (TG) of blackberry, chokeberry, and raspberry seeds were carried out. The properties of oil extracted in the Soxhlet apparatus were studied by pressure differential scanning calorimetry (PDSC), TG, and gas chromatography (GC) measurements. The results show that berry seeds lipids are from different melting fraction groups with a dominance of low-melting fraction, which consists of mono- and polyunsaturated fatty acids. There are also occurring residues of carbohydrates and inorganic, thermostable substances in the studied seeds. A GC analysis of oil confirms that the polyunsaturated fatty acids (PUFA) are most abundant and amount to 78.72 ± 0.06% in blackberry seed oil, 73.79 ± 0.14% in chokeberry seed oil, and 82.74 ± 0.03% in raspberry seed oil. The PDSC study showed that the most oxidative stable oil is blackberry seed oil, followed by raspberry and chokeberry seed oils. According to the obtained results, berry seeds can be used as a source of oil in food or other production chains. However, more detailed characteristics of berry seed oils are needed to determine their applicability.

Lipid Oxidation in Low-moisture Food: A Review

Overly high intake of saturated fat is an international problem contributing to global health issues. Low-moisture snacks account for a nutritionally significant proportion of the saturated fat in the diet, making these foods a key target for improving consumers' health. However, it is not currently feasible to maintain the same oxidative shelf life when replacing saturated fats with unsaturated fats, which are generally perceived to be more heart-healthy. This article summarizes current theories and available research on lipid oxidation in low-moisture foods in order to lay the groundwork for new lipid oxidation rate-reduction strategies. Research deficits needing attention and new methods for assessing lipid oxidation in low-moisture foods are also discussed.

Moisture adsorption behaviour of biscuit during storage investigated by using a new Dynamic Dewpoint method

The changes in moisture adsorption isotherms of commercial biscuits during storage were investigated by means of a rapid Dynamic Dewpoint Isotherms (DDIs) method. Moreover, the relationships between the changes in moisture content and some quality characteristics of biscuits (moisture, aw, peroxide value - PV and texture) were studied during 92 days of storage at 35 °C. GAB model was used to fit the experimental sorption behaviours. During storage, moisture content and aw of biscuits increased and the obtained isotherms showed modifications in behaviour and shape. Significant changes were observed in PV values and texture, particularly during the first 40 days of storage. The monolayer moisture content, obtained by the BET equation, significantly increased during storage from 1.473 to 2.080 g water 100 g db(-1), probably because of the increase in the active sites for water binding due to the chemical and physical changes of the main components, induced by product ageing.

Effect of flameless catalytic infrared treatment on rancidity and bioactive compounds in wheat germ oil

FCIR was used to inhibit lipase and lipoxygenase activities of WG to extend its shelf life. FCIR inhibits rapid hydrolytic and oxidative rancidity of WG in minutes. The optimum water activity for inhibiting both hydrolytic and oxidative rancidity of WG is about 0.186.

Preservation engineering assets developed from an oxidation predictive model

A previously developed model which effectively predicts the probability of olive oil reaching the end of its shelf-life within a certain time frame was tested for its response when the convective diffusion of oxygen through packaging material is taken in account. Darcy’s Law was used to correlate the packaging permeability with the oxygen flow through the packaging materials. Mass transport within the food-packaging system was considered transient and the relative one-dimensional differential equations along with appropriate initial and boundary conditions were numerically solved. When the Peclet (Pe) number was used to validate the significance of the oxygen transport mechanism through packaging, the model results confirmed the Arrhenius type dependency of diffusion, where the slope of the line per material actually indicated their –Ea/R. Furthermore, Pe could not be correlated to the hexanal produced in samples stored under light. Photo-oxidation has a significant role in the oxidative degradation of olive oil confirmed by the shelf-assessing test. The validity of our model for the oxygen diffusion driven systems, was also confirmed, for that reason the predictive boundaries were set. Results safely indicated the significance of applying a self-assessing process to confirm the packaging selection process for oxygen sensitive food via this model.

Effect of different new packaging materials on biscuit quality during accelerated storage

BACKGROUND

The effect of innovative multilayer packaging materials versus a standard one on biscuit quality was studied during accelerated storage at 25, 35, 45 °C and 50% relative humidity for 92 days. Three different packaging materials were used: metalized orientated polypropylene (OPP)/paper (control); metalized poly-lactic acid (PLA)/paper; metalized OPP with ethylene vinyl acetate pro-oxidant additive (EVA-POA)/paper. EVA-POA additive is used to make the plastic layer biodegradable. Various quality sample parameters (moisture, water activity (aw ), texture, peroxide value (PV), hexanal) were analysed during storage. Rate constants (k) and activation energies (Ea ) of hydration reactions and hexanal formation were calculated.

RESULTS

No remarkable differences in the evolution of primary and secondary lipid oxidation were observed among differently packed biscuits during storage. All samples maintained PV levels between 4 and 14 meq O2 kg(-1) oil. The product in flexible packaging with PLA reached the highest moisture and aw levels, but they did not significantly and adversely affect the other quality characteristics.

CONCLUSION

The obtained results demonstrate that the new tested packaging materials were suitable for commercial biscuit storage, having similar performance and preservation effects on the overall product quality to those of the standard one. Furthermore, these results could make a contribution to the food industry, encouraging the use of packaging materials with a negligible environmental impact as an alternative to petroleum-based ones.

Physicochemical Properties of Flaxseed Fortified Extruded Bean Snack

Milled flaxseed was incorporated (0–20%) into a combination of bean-corn flours and extruded in a twin screw extruder using corn curl method. Physicochemical parameters such as water activity, color, expansion ratio, bulk density, lipid content, and peroxide values of extruded snack were analyzed. Scanning electron micrographs were taken. Peroxide values and propanal contents were measured over four months of storage. Rancidity scores of extruded snack were measured using a trained panel. As expected, omega-3 fatty acids and bulk density increased with increasing flaxseed fortification levels. Extrudates with more flaxseed had decreased lightness values and expansion ratios. However, only the 15 and 20% flaxseed containing extrudates had expansion ratios that were significantly (P ≤ 0.05) different from the control. In general, no significant difference (P > 0.05) in water activity values was observed in the flaxseed fortified extrudates, except in the navy-corn based extrudates. Peroxide values increased with increased flaxseed levels and over a storage period. However, propanal values did not change significantly in the 5–10% flaxseed fortified extrudates but increased in extrudates with higher levels of flaxseed. Rancidity scores were correlated with peroxide values and did not increase significantly during storage under nitrogen flushed conditions.

Autoxidation of unsaturated lipids in food emulsion

Unsaturated lipids having various physiological roles are of significance in biochemistry, nutrition, medicine, and food. However, the susceptibility of lipids to oxidation is a major cause of quality deterioration in food emulsions. The reaction mechanism and factors that influence oxidation are appreciably different for emulsified lipids and bulk lipids. This article gives a brief overview of the current knowledge on autoxidation of oil-in-water food emulsions, especially those that contain unsaturated lipids, which are important in the food industry. Autoxidation of unsaturated lipids in oil-in-water emulsion is discussed, and so also their oxidation mechanism, the major factors influencing oxidation, determination measures, research status, and the problems encountered in recent years. Some effective strategies for controlling lipid oxidation in food emulsion have been presented in this review.

Effect of relative humidity on oxidation of flaxseed oil in spray dried whey protein emulsions

Flaxseed oil was emulsified in whey protein isolate (WPI) and spray-dried. Powder characteristics and oxidative stability of oil at relative humidities (RH) from RH approximately 0% to RH 91% at 37 degrees C were analyzed. Oil droplets retained their forms in drying and reconstitution, but the original droplet size of the emulsion was not restored when the powder was dispersed in water. The particles seemed to be covered by a protein-rich surface layer as analyzed by electron spectroscopy for chemical analysis (ESCA). Oxidation of flaxseed oil dispersed in the WPI matrix was retarded from that of bulk oil but followed the same pattern as bulk oil with respect to humidity. A high rate of oxidation was found for both low and high humidity conditions. The lowest rate of oxidation as followed by peroxide values was found at RH 75%, a condition that is likely to diverge significantly from the monolayer moisture value. A weak baseline transition observed for the WPI matrix in a differential scanning calorimetry (DSC) thermogram suggested a glassy state of the matrix at all storage conditions. This was not consistent with the observed caking of the powder at RH 91%. Scanning electron microscopy (SEM) images revealed a considerable structural change in the WPI matrix in these conditions, which was suggested to be linked with a higher rate of oxygen transport. Possible mechanisms for oxygen transport in the whey protein matrix under variable RHs are discussed.