| Spice essential oils,as the highly concentrated products of flavor and active substances in natural spices,have strong aroma-adding,taste-rectifying,and color-giving effects,outstanding antimicrobial and antioxidant activities,and ideal safety for food consumption,thus having great potential for application in the food seasoning and preservative industries.However,the universal application of spice essential oils in these industries is still severely limited by the “pain points” of poor sensory quality stability(especially poor sensory quality thermal stability)and low compatibility with preservative objects due to the quality defects of high volatility and heat sensitivity,strong hydrophobicity and sensory stimulation.Taking the quality defects of spice essential oils as the entry point,this project selected spice essential oils with typical characteristics as the research objects,firstly studied the point-to-point control effect and mechanism of the quality control means such as high-efficiency antioxidant intervention,novel delivery system construction,and synergistic sterilization strategy application on the above quality defects;then overcame the quality defects in a targeted manner to broke through the application problems of spice essential oil industry one by one,through the combined treatment of the above control means;finally,the 3D printing film preparation technology was introduced to construct a multiple control mean for comprehensively improving the quality defects of essential oils.After the universal evaluation in a variety of application scenarios,the fully quality-modified spice essential oils were found to have good application advantages in improving food flavor and inhibiting food spoilage.The details are as follows:(1)Taking the essential oils of Sichuan pepper and chili pepper,which had typical taste and color characteristics,as the research objects,the effects of antioxidants on the contents of the taste and color presenting substances contained therein during thermal processing and storage were investigated,and the actual stabilizing effects of antioxidants on the taste and color of the two essential oils were determined to elucidate the mechanisms and effects of antioxidants on the stability of taste and color of typical spice essential oils.The results showed that the fat-soluble antioxidants—tea polyphenol palmitate(TPP),ascorbyl palmitate(AP),and rosemary extract(RE)—were well compatible with two essential oils,produced a significant retention effect on the taste and color presenting substances by blocking their oxidative pathway,simultaneously stabilized the flavor and color qualities of the essential oils,and the effect of TPP was the most prominent.Among the taste and color presenting substances,hydroxy-α-sanshool,capsaicin,and capsanthin were the main objects of action of the stability enhancement of the pungency of Sichuan pepper essential oil,as well as the spiciness and red color of chili pepper essential oil.(2)Aiming at the quality defects of volatility and high-heat sensitivity of spice essential oils,the essential oils of Sichuan pepper,star anise,and ginger with typical aroma characteristics were chosen,and the quinoa protein isolate(QPI)-gum Arabic(GA)complex coacervated microcapsules were constructed to improve the odor quality stability of the spice essential oils and the related control mechanisms were analyzed.The results showed that the optimal preparation conditions of QPI-GA coacervates were QPI:GA=4:1(w/w),p H=3.6.The optimally prepared coacervates had good encapsulating effects on three spice essential oils(encapsulation efficiency: 82.53%～88.19%),and the main aroma substances were well preserved after encapsulation.The encapsulated essential oils showed significantly reduced volatility,enhanced thermal stability and storage stability.According to the results of scanning electron microscopy and infrared spectrum analysis,coacervated microcapsules effectively retained the aroma of spice essential oils through the continuous dense wall layer formed by QPI-GA coacervates and strong hydrogen bonding interaction between the coacervates and essential oils.(3)The antimicrobial ability of ten spice essential oils was firstly compared while the bacteria(Escherichia coli,Staphylococcus aureus)and molds(Penicillium citrinum and Aspergillus niger)common in foods were served as testing microbes.Then,the sterilization effect and lethal mechanism of essential oil and high-voltage electrostatic filed(HVEF)used either individually or in combination on the testing microbes were investigated to enhance the antimicrobial ability of the essential oil while reducing the dosage,so as to avoid the negative sensory impact of the strong odor of the essential oils on the added foods.The results showed that cinnamon essential oil(CEO)had the strongest antimicrobial ability and the widest antimicrobial spectrum,its antimicrobial effect was dramatically enhanced by combining with HVEF,and the required concentration for the same sterilization effect was only 1/4～1/3 of that when used alone.Both CEO and HVEF treatments could alter the permeability of the microbial cell wall as well as the permeability and integrity of the cell membrane,result in the change in chemical structure of microbes,lead to the increase in content of reactive oxygen species in the microbial cells.Moreover,CEO+HVEF caused the significantly greater effect on microbes than two treatments applied alone.(4)The essential oils of cinnamon,oregano,and litsea cubeba with the same high hydrophobicity and different properties(p H,relative density,viscosity,and oil/water partition coefficient)were selected to systematically investigate the regulating effect of Pickering emulsion stabilized by QPI-GA conjugates on the water solubility of spice essential oils and the related mechanisms.Based on the optimization by BP artificial neural network-genetic algorithm model,the optimal conditions for the preparation of QPI-GA conjugates were:heating temperature of 72℃,ultrasonic power of 450 W,and reaction time of 46 min.The grafting reaction increased the water solubility and surface hydrophobicity of QPI,and the obtained conjugates were able to rapidly absorb and form thicker interfacial layers on the surface of essential oil droplets.Therefore,the QPI-GA conjugates showed good emulsification ability(emulsification efficiency: 88.29%～95.03%)to three spice essential oils.With the stabilization of the conjugates-based Pickering emulsion,the water solubility of essential oils was well maintained at different p H,salt concentration,and storage time.Meanwhile,the improvement of the water solubility of spice essential oils by the Pickering emulsion served to enhance their antibacterial ability.(5)Based on the studies of part 1 and 2,the spicy essential oil with good color and flavor was formulated with essential oils of chili pepper,Sichuan pepper,star anise,and ginger.Then,the effect of combined treatment of TPP and M(TPP+M)on the stability of the sensory qualities(odor,taste,and color)of spicy essential oil during thermal processing and storage was investigated.Then,the broad applicability of quality modified spicy essential oil for food flavor improvement was assessed through three application scenarios(steamed twisted roll,fried crispy meat,as well as high temperature and high pressure sterilized fava bean)with different thermal processing environments.The results showed that TPP+M had a comprehensive and efficient effect on the retention of aroma,taste,and color of spicy essential oil during thermal processing and storage,which was superior to that of both treatments alone.Three thermal processing means all caused the significant damage to the sensory quality of spicy essential oil,especially the high temperature and high pressure sterilization(121°C,20 min).TPP and M significantly increased the stability of the sensory quality of spicy essential oil in all three thermal processing processes.The spicy essential oil treated by combined technology retained the best sensory quality during thermal processing,having the strongest flavoring and coloring effects on three food products,and the flavor was highly stable during food storage.(6)Based on the studies of part 3 and 4,CEO was selected as research object to investigate the regulating effect of high voltage electrostatic field-cinnamon essential oil emulsion combined treatment(HVEF+CEOE)on the antimicrobial ability and the compatibility between added objects of CEO,and the antimicrobial and antiseptic effects of regulated CEO on minced pork(high-fat and high-protein system)and carrot juice(highwater and high-carbohydrate system)were studied.The results showed that HVEF+CEOE had a stronger sterilization ability compared with HVEF+CEO.In the actual food system,the Pickering emulsion resulted in a significant reduction of the negative effect of CEO on the original sensory qualities of minced pork and carrot juice,and a significant increase in the solubility of CEO in carrot juice.Meanwhile,HVEF+CEOE substantially improved the antimicrobial and antiseptic effects of CEO on two food products,allowing CEO to extend their shelf life from about 3 d and 1～2 d to about 7 d and 4 d.(7)To simultaneously break through the application problems of the poor stability of the sensory quality and low adaptability to added objects of spice essential oils,a double-layer active film was constructed using 3D printing,while with cinnamon essential oil emulsion(CEOE)was added as antimicrobial functional substance and banana peel carbon dots(CDs)were served as ultraviolet ray and oxygen barrier material.The results showed that the addition of CEOE and CDs had a significant effect on the chemical structure,microstructure,crystallization state,and surface wettability of the film.When the filling rate of CEO-loaded functional layer was 60%,the bilayer active film had the best comprehensive performance,including good mechanical properties,water vapor and UV barrier properties,antibacterial and antioxidant activities,and the best CEO slow-release effect.The bilayer active film significantly improved the stability of sensory quality of spicy essential oil microcapsules under room temperature storage.In addition,the film significantly extended the shelf life of mango in non-contact mode and was more effective when combined with HVEF. |
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