•The effect of film multi-structure on selective barrier property was proposed.•SiO2 content was effective to regulate film multi-structure.•The increase of micro-ordered region size favored H2O barrier property.•The higher compactness of micro-ordered region contributed to O2 barrier property.In order to control H2O/O2 selective permeability of starch based nanocompsites for food packaging, the addition of SiO2 nanoparticles was proven to be an effective method. The results suggested that the SiO2/hydroxypropyl starch (HPS) ratio was a feasible approach to regulate the film multi-scale structure. The H2O/O2 selective permeability was influenced by comprehensive factors including film short-range molecular conformation, crystalline structure and aggregated structure. The increase of micro-ordered region size was likely to favor the improvement of water vapor barrier property and the rise of compactness in this region seems to contribute to the oxygen prevention. Notably, the effect of film multi-scale structure on H2O/O2 selective permeability could be a supplement to conventional “tortuous path” theory for the explanation of barrier property improvement. This study could significantly guide to the rational design of H2O/O2 selective biodegradable food packaging in order to meet the requirement for different food systems.

•This review summarized the pathogenic features of biofilm.•The principle of biofilm biomass, viability and matrix is presented.•Three features were further compared with its particular benefits in specific application.Biofilm is a ubiquitous growth pattern of bacterial species survival but is notorious for its threat on public health and food contamination. Extensive studies of the biofilm structure, formation, quantification, quorum sensing system and underlying control strategies have been reported during the past decades. Insightful elucidation of the pathogenic features and characteristic of bacterial biofilm can facilitate in devising appropriate control strategies for biofilm eradication. Therefore, this review mainly summarized the pathogenic features of biofilms from food borne microorganisms, including the biomass (which could be quantified using crystal violet and fluorogenic dye Syto9 assays), viability (which could be determined by tetrazolium salts, fluorescein diacetate, resazurin staining and alamar blue assays) and matrix (which are commonly detected by dimethyl methylene blue and wheat germ agglutinin assays). In addition, three features were further compared with its particular benefits in specific application.

•The lowest WVP came at Na-MMT/HPS ratio of 3%.•The addition of Na-MMT changed the multi-scale structure of the films.•Multi-scale structures of the films influenced the WVP.•A good balance of structure in multi-scale was required for lower WVP.To improve the water vapor resistance of starch-based films, Na-MMT (Na-montmorillonite) as nanofillers were fabricated into hydroxypropyl starch and the multi-scale structural changes (including intermolecular interaction, short-range conformation, long-range ordered structure and the aggregated structure of the film) were revealed. The elongation of the water vapor molecule pathway by tortuous path is generally recognized as the main reason for the improvement of water resistance. However this study observed the lowest water vapor permeability (WVP) was at the 3% Na-MMT/hydroxypropyl starch (HPS) ratio instead of 5% even nanofillers were partially exfoliated at both ratio. Except for the “tortuous path” caused by nanofillers, this observation proposed that the short-range conformation of HPS chains, long-range ordered structure and the aggregated structure likely influenced the water barrier property. The relationship between WVP and multi-scale structure of the film was investigated. The results suggested that a good balance of short-range conformationin the amorphous region, long-range ordered structure and the aggregated structure of the film was required for the improvement of water vapor barrier property.

Retrogradation is the process of starch recrystallization, and it profoundly affects the quality, acceptability and shelf-life of starch-containing foods. The influence of glutelin on the wheat starch retrogradation was studied in this paper. Glutenin was isolated from wheat flour, and its effect on retrogradation of wheat starch, amylose and amylopectin was investigated with UV–Vis (starch-iodine), IR and 13C NMR. The results showed that glutenin probably interacted with amylose during gelation and retrogradation of starch. The results of IR showed that the addition of glutenin to wheat starch reduced the number of hydrogen bonds formed between amyloses during retrogradation. The 13C NMR results suggested that tyrosine (Tyr) of glutenin might combine with amylose at the first carbon atom when they were mixed homogeneously and such combination was strengthened during retrogradation. Glutenin and amylose formed double helix with each other completely and hindered amylose–amylose short-term retrogradation of wheat starch, and glutenin would no longer inhibit the retrogradation of starch when all of the Tyr formed hydrogen bond with amylose. These results suggest that glutenin could play a powerful role in retarding the retrogradation of amylose, which is very important for the food industry.

The retrogradation of rice in shelf life is the biggest barrier to the industrial production of traditional foods using rice as material. Many rice breeders have tried their best to screen low-retrogradation rice cultivars without a specific indicator. To identify the main retrogradation-related properties of rice, the starch, amylose, and amylopectin from 16 rice cultivars were extracted from rice powder and their physicochemical properties, such as visible absorbance, infrared, average molecule weight (amylopectin), chain-length distribution (amylopectin), X-ray diffraction, and differential scanning calorimetry, were determined. The correlation between starch retrogradation rates and those physicochemical properties was investigated. The results show that a significant positive correlation (R2 = 0.85; r = 0.926; p < 0.01) exists only between proportions of the chains [degree of polymerization (DP) > 10] in amylopectin and the retrogradation rates of different rice starches. The findings in the paper offer a shortcut for rice breeders to screen cultivars with a low retrogradation rate. Because the genes related to the branching enzyme control the DP of amylopectin, they can be exploited as molecular markers to screen low-retrogradation rice cultivars.

•The macromolecular interaction was enhanced to form more compact amorphous regions.•The crystallites were formed interference and further aggregation.•The mobility of macromolecular chain, triacetin and water molecules was restricted.•The relaxation caused the subsequent triacetin migration to deviate from Fick's law.•Aggregation structural modification of the film could restrain plasticizer migration.This work studied the structural changes and the migration of triacetin plasticizer in starch acetate films in the presence of distilled water as food simulant. Fourier-transform infrared spectroscopy result showed that the macromolecular interaction was enhanced to form compact aggregation of amorphous chains. The characterization of aggregation structures via wide and small angle X-ray scattering techniques indicated that the orderly microregion was compressed and the crystallites inside were “squeezed” to form interference and further aggregation. The compact aggregation structures restricted the mobility of macromolecules, triacetin and water molecules. The overall kinetic and the diffusion model analysis manifested that Fick's second law was the predominant mechanism for the short-term migration of triacetin. The increasing relaxation within film matrix caused the subsequent migration to deviate from Fick's law. The safe and reasonable application of the starch-based materials with restrained plasticizer migration could be accomplished by controlling the molecular interaction and aggregation structures.

The aim of this work was to evaluate the plasticizing effect of triacetin on the structure and properties of starch ester film and further establish the structure–property relationships. The presence of triacetin resulted in multiple structure changes of the film. The mobility of macromolecular chain was increased to form scattered crystallite during the film formation process. The amorphous region was enlarged to contain more triacetin squeezed from crystalline region. The plasticization of triacetin and restriction of crystallite oppositely influenced the mobility of macromolecular chains in different regions. The thermal stability of triacetin changed along with its fluctuant interaction with macromolecules. Comparatively, the enhanced ether bond and the restriction from crystalline regions on the mobility of the amorphous chain consequently improved the thermal stability of the film matrix. The interaction between triacetin and starch ester was essential to film forming but unexpectedly lowered the triacetin stability.Highlights► New interaction between triacetin and starch ester enhanced CO in alcoxyl group. ► Increased mobility of macromolecules facilitated crystallite formation. ► Increased triacetin enlarged amorphous region with less effect on crystalline part. ► The thermal stability of triacetin and film matrix was influenced discriminately. ► Crystallite restricted the mobility of macromolecules in different scale and regions.