Effect of the incorporation of antioxidants on physicochemical and antioxidant properties of wheat starch–chitosan films

Blend edible films were prepared from wheat starch (WS) and chitosan (CH) with glycerol as plasticizer. Four active ingredients (antioxidants) were added, namely basil essential oil, thyme essential oil, citric acid and α-tocopherol. The starch:antioxidant mass ratio was 1:0.1. Prior to characterisation, the films were conditioned at 25 °C–53%RH as to their structural, mechanical, optical and barrier properties. The antioxidant capacity of the active ingredients was determined by means of a spectrophotometric method. The incorporation of antioxidants led to a heterogeneous film microstructure, mainly in those containing α-tocopherol, which affected the surface roughness. Yellowness was induced in films when α-tocopherol was added and no notable colour changes were observed in the other cases, although all the antioxidants increased the transparency of the films. Despite of the fact that the mechanical properties were barely affected by the incorporation of antioxidants, citric acid promoted an increase in the elastic modulus but a decrease in film stretchability. The water vapour barrier properties of the films were only slightly improved when citric acid and α-tocopherol were added, whereas the oxygen barrier properties were significantly improved in all cases. The greatest antioxidant capacity of the films was reported for films containing α-tocopherol, which exhibited the highest antioxidant power.     

Influence of kappa-carrageenan on the gel properties of auricularia auricular-judae during freeze–thaw cycles

The effect of kappa-carrageenan (kC) on the properties of AAJ gel during freeze–thaw cycles (FTC) was investigated in this paper. The results showed that a greater amount of kC significantly increased the storage modulus to a greater extent for cycling 1–7 times, indicating kC enhanced the gel-like properties of AAJ supported by TPA during FTC. Moreover, reducing the amount of freezable water and enhancing the water holding capacity of AAJ gel demonstrated by the shorter relaxation times and strengthened hydrogen bonding after the addition of kC were determined by LF-NMR and FT-IR. In addition, more crystallites and higher peak intensity based on DSC and XRD, as well as more uniform and ordered honeycomb-like holes in AAJ gel observed by SEM formed by the addition of kC helped for reducing damages from FTC. The findings suggested that 20% kC was significant for developing and improving novel AAJ-based foods.     

Effects of heat moisture treatment on the structural,physicochemical and digestibility properties of potato starch–soybean peptide complexes

In this study, potato starch (PS) was complexed with soybean peptides (SPTs) with different molecular weights under heat moisture treatment (HMT) at different moisture contents. The results showed that PSSPT complexes formed under HMT were characterised by weaker and fuzzier polarised cross patterns, and more agglomerates. After HMT, higher gelatinisation temperatures and lower enthalpies were observed for PSSPT complexes. In particular, higher gelatinisation temperatures were observed when moisture levels were higher during HMT. Compared with physically mixed counterparts, the PSSPT complexes under HMT displayed higher pasting temperatures and lower swelling power, and peak viscosity. Higher moisture content during HMT led to a less thermodynamically stable B-polymorphic structure converting to a more stable A-type polymorph. Higher SDS content was found in the PSSPT complexes subjected to HMT with lower moisture content, while relatively higher RS content was associated with higher moisture content of HMT. These results could be attributed to restructuring of the amylose/amylopectin chains, the physical barrier of SPT and interactions between the negatively charged groups in PS and the side chains in SPT. This study will advance our understanding of food multicomponent interactions, as well as guidance for the application development of low-glycaemic index foods containing SDS and RS in the field of fine food processing.     

Effect of autoclave–cooling cycles combined pullulanase on the physicochemical and structural properties of resistant starch from black Tartary buckwheat

A starch-rich portion is produced as a by-product of black Tartary buckwheat processing. The effect of enzymatic combined with autoclaving–cooling cycles (one, two, or three times) on the physicochemical and structural properties of black Tartary buckwheat type 3 resistant starch (BRS) was evaluated. The autoclaving–cooling cycles enhanced solubility and reduced swelling, with the BRS content increasing from 14.12% to 25.18%. The high crystallinity of the BRS reflected a high molecular order. However, increasing the number of autoclaving–cooling cycles did not result in higher BRS content. The highest BRS yield in the autoclaved starch samples was 25.18% after double-autoclaving–cooling cycles. Furthermore, the autoclaving–cooling cycles altered the crystalline structure of black Tartary buckwheat, and the subsequent crystallinity changed from 36.33% to 42.05% to 38.27%. Fourier-transform infrared spectroscopy shows that the number of cycles results in more efficient double-helical packing within the crystalline lamella. Principal component analysis showed that the autoclaving–cooling cycle treatment leads to significant changes in the molecular structure of resistant starch (RS). These results indicated that autoclaving–cooling cycles might be a feasible way for producing RS from black Tartary buckwheat starch with better structural stability to expand their application range.     

Influence of ι-carrageenan, pectin, and gelatin on the physicochemical properties and stability of milk protein-stabilized emulsions

This study evaluated the stability of bilayer emulsions as a function of secondary layer composition and pH. Primary emulsions were formulated with 5% soybean oil, 1% protein from nonfat dry milk (NDM) powder as emulsifier and ι-carrageenan (ι-carr), low-methoxyl pectin (LMp), high-methoxyl pectin (HMp), or gelatin as secondary layers. ζ-Potential values increased for each emulsion as the pH decreased, with ι-carr emulsions being consistently more negatively charged than primary emulsions and significantly more stable. ζ-Potential values were not always correlated to emulsion stability. Gelatin secondary emulsions at pH 3 and HMp secondary emulsions at pH 7 were unstable due to the presence of depletion flocculation. In addition, LMp secondary emulsions stability at pH 7 might be due to calcium bridging, which increased the emulsion's viscosity. Overall, the stability of NDM emulsions was improved when ι-carr and LMp were used as secondary layers at pH 7 and 5, and when ι-carr and HMp were used as secondary layers at pH 3. Increased stability of these systems can be attributed to a second homogenization step used to formulate the secondary emulsions and to the presence of Ca(+2) in the NDM. Results from this research show that the stability of bilayer emulsions is driven by the presence of depletion flocculation, droplet charge, droplet size and distribution and viscosity. PRACTICAL APPLICATION: The use of everyday ingredients (nonfat dry milk powder, gelatin, pectin, and carrageenan), which are understood and accepted by the average consumer, creates label-friendly products that are the wave of the future. Stable emulsions can be formed using these ingredients at various pH. Understanding the stability and how the pH impacts the physicochemical characteristics and stability of these emulsions will enable manufactures to use ordinary ingredients to create healthier products (for example, low-fat dressings, sauces, dips, and beverages).     

Effect of high pressure processing on the gel properties of salt-soluble meat protein containing CaCl2 and κ-carrageenan

The effects of high pressure processing (HPP) on the water-binding capacity and texture profile (TPA) of salt-soluble meat protein (SSMP) containing 0.2% CaCl₂ and 0.6% κ-carrageenan (SSMP-CK) gels were investigated. The results showed that 300–400 MPa improved water-binding capacity and decreased TPA parameters of SSMP-CK gels (P < 0.05), while 100 MPa could increase hardness and chewiness of the gels. The thermal transition temperature peak for the myosin head (T_peak1) of SSMP disappeared on addition of CaCl₂ and κ-carrageenan. 300 MPa produced a new peak, and caused a shift of the NH-stretching left peak and amide I and the disappearance of NH-stretching right peak. The destruction of network structure and the weakening of molecular interaction within the pressurized gels could result in the decrease of TPA parameters. Thus gelling properties could be modified by HPP, κ-carrageenan and Ca^2 +. It is of interest to develop low-fat and sodium-reduced meat products.     

Effects of high hydrostatic pressure on microstructure,physicochemical properties and in vitro digestibility of oat starch/β-glucan mixtures

Oats do not contain gluten protein, and oat dough structure is formed mainly through the hydrogen bonding of starch and β-glucan. As a non-thermal processing technology, high hydrostatic pressure (HHP) is mainly used to modify starch and protein in food processing. This study investigated the effects of HHP treatment on the morphological, structural, thermal, pasting and in vitro digestion properties of oat starch/β-glucan mixtures. Results showed that β-glucan interconnects with amylose through hydrogen bonding and has a protective effect on the crystalline region of oat starch. Effect of HHP treatment on the crystal structure of mixture system goes through crystal structure perfection stage, crystallisation disintegration and gelatinisation stage. After 300–400 MPa treatment, the changes in particle surface were not obvious, the phase transition temperature, the ΔH_gel and the PT of mixtures increased, while the particle size, viscosity and BD values decreased. After 500–600 MPa treatment, mixtures were completely gelatinised, most of the particles swelled and deformed, the particle size increased significantly. The principal component analysis results show that the complexes were distributed in the same region with similar properties after the 300–400 MPa and 500–600 MPa treatments, respectively.     

Effect of γ-irradiation on the physicochemical and sensory properties of cashew nuts (Anacardium occidentale L.)

The present study evaluated cashew nuts' quality as a function of γ-irradiation dose in order to determine dose levels causing minimal undesirable changes to the product. Physicochemical (colour, peroxide value, hexanal content, fatty acid composition, volatile compounds) and sensory (colour, texture, odor, taste) properties of cashew nuts were determined after irradiation at doses up to 7 kGy. Results showed a five-fold increase in peroxide value (PV) and a two-fold increase in hexanal content after irradiation at a dose of 7 kGy. Of the fatty acids determined, stearic acid concentration increased while oleic acid decreased with irradiation dose. PUFA were unaffected by irradiation. Volatile compounds such as aldehydes, ketones and alcohols increased after irradiation indicating enhanced lipid oxidation. Colour parameter a∗ increased (p < 0.05) at doses >3 kGy while colour parameters L∗ and b∗ remained unaffected by irradiation. Sensory analysis showed that cashew nuts remained organoleptically acceptable at doses <3 kGy.     

Modifications in the physicochemical properties of flour “fractions” after Pulsed Electric Fields treatment of thermally processed oat

This research aimed to investigate the physicochemical properties of thermally processed oat flour (TPOF) “fractions” (Supernatant, Top/S1, Middle/S2, Bottom/S3) after Pulsed Electric Fields (PEF) treatment of TPOF at 2 and 4 kV/cm between 50 and 451 kJ/kg. Supernatant from PEF-treated TPOF displayed a generally higher β-glucan content than untreated TPOF. No major changes were observed in chemical composition (in terms of total starch, protein, and fat contents) amongst “fractions”. However, S1 obtained from PEF-treated TPOF exhibited an increase in particle size, while both gelatinisation enthalpy and percent relative crystallinity were significantly lower compared to untreated counterpart. S1 from PEF-treated TPOF at 422–451 kJ/kg also manifested severe changes in granule morphology. S2 exhibited the highest gelatinisation enthalpy and S3 registered the least degree of observed changes in particle size. Findings of this study suggest the potential of PEF treatment application to produce oat “fractions” with varying physicochemical properties.Industrial relevanceThis study provides indispensable scientific information that could be utilised to further investigate industrial production of customised fractionation of oat flour with targeted physicochemical properties through PEF treatment. This opens new opportunities to strategically diversify the range of oat flour ingredients based on their targeted unique properties in the food industry.     

Influence of storage period and packaging method on sliced dry cured beef “Cecina de Leon”: Effects on microbiological,physicochemical and sensory quality

Quality aspects of sliced dry-cured beef “Cecina de León” preserved in vacuum and gas mixtures (20%/80% CO₂/N₂ and 80%/20% CO₂/N₂) were studied. The evolution of microbiological, physicochemical and sensory parameters were analysed during storage (210 days) at 6 °C. Although microbial counts at 60 days of the gas-packaged samples were lower than the vacuum-packed ones, they were never higher than the spoilage limit (7 log ufc/g). A slight increase (p < 0.05) in pH was observed throughout storage of “Cecina de León” packaged under vacuum and in gas mixtures. However, a decrease (p < 0.05) in a_w was observed during storage of “Cecina de León” packaged under vacuum but a_w did not vary (p > 0.05) during storage in the gas-packaged samples. No changes were observed (p > 0.05) in lightness (L¹), redness (a¹) and yellowness (b¹) in vacuum and gas packaged samples during storage. However, sensorially evaluated colour showed lower values in gas packaged samples during 30 days storage. This difference was decisive in establishing the shelf-life of “Cecina de León” slices preserved in gas mixtures (20%/80% CO₂/N₂ and 80%/20% CO₂/N₂). Therefore, from a microbiological point of view, gas mixtures are more effective in extending the shelf-life of “Cecina de León” slices. It is concluded that vacuum packaging allows longer storage than gas-packaging as it maintains a good visual appearance of “Cecina de León”, the main parameter in consumers’ perception of meat quality.     

Influence of heat shrink treatments on the onset of clostridial “blown pack” spoilage of vacuum packed chilled meat

Storage trials were conducted to determine if short duration high temperature treatments applied in commercial heat shrinking of vacuum barrier packs affect the onset of clostridial blown pack spoilage. Spore suspensions of six significant gas producers were used: Clostridium estertheticum NCIMB 12511, and five local psychrotolerant clostridial isolates. Beef striploins, pH 5.5 and 6.0, were cut into steaks and placed into vacuum pouches. Duplicate pouches were inoculated with each test spore suspension for each meat pH/heat treatment/storage temperature combination. After vacuum packaging and heat shrinking, packs were stored at −1.5, 1 or 4°C. Based on time to first-phase gas production (small bubbles in drip), the test strains were considered statistically as representing two groups. With both groups, post-packaging heat treatment had a significant effect on time to gas production. Mean times, pooled for the three storage temperatures, to gas production with Group A were 49, 39, 36 and 35 days for the no heat, 70, 80 and 90°C treatments, respectively. With Group B these times were 77, 42, 39 and 36 days, respectively. Post-packaging heat shrink treatments of vacuum packaged meat accelerate the onset of Clostridium spp. mediated blown pack spoilage during chilled storage. Possible mechanisms for accelerated onset of blown pack spoilage following heat shrinking of vacuum packs are discussed.