抗冻剂对速冻南瓜泥品质影响及其机理探究

为研究果胶、胶原肽及海藻糖组成的新型复配抗冻剂对速冻南瓜泥品质的影响并探究其机理,以析水率、粒径、Zeta电位值表征产品稳定性,采用质构特性、色度、可溶性固形物含量评价产品品质,并结合扫描电子显微镜与激光扫描共聚焦显微镜观察样品微观结构。结果显示,抗冻剂可显著减缓冻藏过程中速冻南瓜泥的析水率、平均粒径的升高趋势,以及L*、a*、b*、硬度、内聚性、可溶性固形物含量、Zeta电位绝对值的降低趋势,并且能够有效保护速冻南瓜泥的超微结构,使大分子分布均匀。     

黄原胶对冷冻熟面冻藏品质的影响

研究添加黄原胶对冷冻熟面质构特性和蒸煮品质的影响,并采用差示扫描量热仪(DSC)和低场核磁共振(NMR)探究了添加黄原胶对冷冻熟面冻藏过程中可冻结水含量和水分分布的影响;利用激光共聚焦显微镜(CLSM)观察了冻藏过程中蛋白质网络结构的变化。结果表明:添加黄原胶可以提高冷冻熟面的硬度、咀嚼性和拉伸性能,降低复煮损失率和吸水率,减缓在冻藏过程中质构品质和蒸煮品质的降低趋势。黄原胶的加入可以使冻藏过程中冷冻熟面的蛋白质网络结构更加连续致密,抑制深层结合水向弱结合水方向的转移,减少可冻结水的含量,从而减少冰晶的形成,减轻因冰晶带来的机械损伤,从而改善冷冻熟面的冻藏品质。     

Influence of pumpkin puree and guar gum on the bioactive,rheological, thermal and sensory properties of ice cream

The effects of pumpkin puree and guar gum on the bioactive, rheological, thermal and sensory properties of ice cream were investigated. The addition of pumpkin puree increased total phenolic content, dietary fibre, and antioxidant activity. Appropriate models described shear thinning and thixotropic behaviours of all mixes. By either adding pumpkin puree or by increasing guar gum concentration, all rheological properties increased except the flow behaviour index. Adding pumpkin puree reduced the freezing point temperature, ice content, frozen water and glass transition temperature but it increased unfreezable water. Increasing guar gum concentration did not alter colour and firmness, whereas the pumpkin puree increased colour, intensity of fruit flavours and firmness.     

Characterisation and stability of quality indices on storage of pumpkin (Cucurbita moschata and Cucurbita maxima) purees

Purees of Cucurbita moschata‘Menina Brasileira’ and of Cucurbita maxima‘Exposição’ pumpkins were produced. A commercial sterilisation test confirmed the effectiveness of the thermal treatment applied in the production. The stability was monitored during storage in ambient conditions. No significant alterations in pH, titratable acidity or soluble solids were noted. Both types of puree have a good concentration of carotenoids, although a slight decrease was detected in the ‘Exposição’ pumpkin puree after 15 days of storage. In relation to the colour of the purees, there were no significant alterations in a*, b* or ΔE during storage. Decreases in L* and WI were detected after 30–60 days of storage, thus suggesting a browning in an initial period. However, the scores given by the sensory assessors remained above 7 in a 9‐point scale, thus showing no significant alterations during storage. The results showed the stability of the pumpkin purees during the 180 days of storage under the proposed conditions.     

贮藏温度对草莓浆理化成分和品质变化的影响

探明贮藏条件对草莓浆理化成分和品质的影响。研究了常温(25℃)、0、4、-18℃冷冻贮藏期间草莓浆花色苷、V_C、可滴定酸、可溶性固形物、风味的变化。结果表明,贮藏60 d,常温和4℃冷藏草莓浆花色苷保留率为12.56%和70.6%,0℃和-18℃冷冻贮藏草莓浆花色苷保留率仍在88%以上,常温和4℃贮藏V_C保留率分别为42.26%和73.21%,0℃和冷冻贮藏V_C保留率均为90%以上;可滴定酸和可溶性固形物在0℃和冷冻贮藏60 d内无显著变化;0℃和冷冻贮藏草莓浆的色泽明显优于常温贮藏;-18℃冷冻贮藏可以较好的保持草莓浆的酸味、甜味等味觉感官品质。经综合评价,0℃和-18℃冷冻环境条件有利于草莓果浆品质的保持,可显著延缓花色苷和V_C的降解,是较合适的草莓浆保藏温度,为草莓浆加工与保藏提供了参考。     

面团冻藏对陕西Biangbiang面条品质变化的影响

该研究以高筋小麦面粉制作面团,分析-18℃ 下不同冻藏时间(0、5、10、20、30 d)对面团的流变学特性,以及冻藏后制作的Biangbiang面条的可冻结水含量、晶型结构、蒸煮特性、质构特性及微观结构的影响.结果表明,面团的黏弹性随着冻藏时间的延长逐渐下降;面团冻藏30 d后制作的Biangbiang面条中可冻结水...     

A PROCESS FOR PRODUCING DEHYDRATED PUMPKIN FLAKES

Single strength pumpkin puree is difficult to drum dry due to its low solids content. It was found in this investigation that the rate of dehydration and quality of the finished product were improved by the addition of corn syrup solids and starch to the puree in amounts sufficient to raise the total solids to around 16%. The quality of pies made from flakes containing added starch and corn syrup solids was also improved over those made from unmodified single strength pumpkin puree. Best results were obtained with pumpkin flakes containing approximately 46% pumpkin solids, 38% corn syrup solids and 16% starch. Based on the average overall acceptable drying conditions and product quality, a ratio of 1 part starch to 2.5–3.0 parts corn syrup solids appeared to be in the optimum range.     

STABILITY of FROZEN STARCH PASTES: EFFECT of FREEZING, STORAGE and XANTHAN GUM ADDITION

ABSTRACT. Starch pastes act as protective systems of the solid elements in precooked frozen foods, minimizing their dehydration and chemical changes during storage. the effect of xanthan gum (0.3 % w/w) on corn starch and wheat flour pastes (10 % w/w), frozen at different freezing rates and stored between -5 and -20C, was analyzed. Freezing modified the quality attributes of the starch pastes increasing exudate production, structure deterioration and rheological changes compared to the unfrozen samples. Starch pastes showed a pseudoplastic behavior and apparent viscosities decreased in frozen samples. High freezing rates led to smaller ice crystals (indirect microscopic observation) and the absence of starch retrogradation. Starch retrogradation and ice recrystallization, both contributed to the deterioration of the frozen paste during storage (spongy structure, marked decrease of apparent viscosity and increase of syneresis). the addition of xanthan gum minimized spongy structure formation, exudate production and rheological changes; however, no protective effect was observed on ice crystal sizes and on amylopectin retrogradation by Differential Scanning Calorimetry.     

聚葡萄糖对冻藏面筋蛋白水合及结构的影响

为提高面筋蛋白的冻藏稳定性,采用核磁共振仪、傅里叶红外光谱仪、差示扫描量热仪、动态流变仪和扫描电子显微镜,研究冻藏条件下添加聚葡萄糖对面筋蛋白体系中水分分布、二级结构、热力学特性、流变学特性及微观结构的影响。结果表明,随冻藏时间延长,添加6%(质量分数)聚葡萄糖的面筋蛋白中弱结合水向自由水的转化量显著减少,抑制了面筋蛋白二级结构中α-螺旋下降及无规则卷曲增大,提高了面筋蛋白的热力学稳定性;冻藏7周时,添加6%(质量分数)聚葡萄糖的面筋蛋白,储能模量和耗能模量下降显著小于对照,且面筋蛋白三维网络结构较均匀,孔径较小,连续性较好。结果表明,聚葡萄糖能有效减弱冻藏对面筋网络的破坏,提升面筋蛋白的冻藏稳定性。     

Kinetics of quality changes of pumpkin (Curcurbita maxima L.) stored under isothermal and non-isothermal frozen conditions

The effects of freezing process and frozen storage at isothermal (−7, −15 and −25 °C) and non-isothermal (accelerated life testing with step-stress methodology; temperature range from −30 to −5 °C) conditions on pumpkin quality were investigated. Storage temperature conditions were selected to embrace the limits practiced in the cold chain. Quality changes, such as texture, colour CIE Lab and vitamin C (ascorbic acid) content, were evaluated for both frozen storage regimes. The freezing process (that included a pre-blanching step) and subsequent frozen storage had significant impacts on all quality parameters analysed.A fractional conversion kinetic model was adequate in colour, texture and vitamin C data fits. The storage temperature effect was successfully described by the Arrhenius law.This study shows that non-isothermal frozen storage has a marked effect on pumpkin quality.     

Microbial growth and the effects of mild acidification and preservatives in refrigerated sweet potato puree

Refrigerated sweet potato puree is a convenient form of sweet potato that can be used as an ingredient in formulated foods. The microbiology of refrigerated sweet potato puree during storage for up to 5 weeks was evaluated. Because the puree was made by comminuting steam-cooked sweet potatoes before refrigeration, no naturally occurring vegetative bacterial cells were detected during a 4-week period of refrigerated storage at 4 degrees C. However, if postprocessing microbial contamination of the puree were to occur, contaminating microorganisms such as Listeria monocytogenes could grow during refrigerated storage. The effects of acidification or the addition of potassium sorbate and sodium benzoate on a population of L. monocytogenes inoculated into refrigerated (4 degrees C) sweet potato puree were determined. Inoculation of the refrigerated puree with L. monocytogenes at 10(6) CFU/ml resulted in a 3-log increase after 3 weeks storage of nonsupplemented puree. Supplementation of the sweet potato puree with 0.06% (wt/vol) sorbic acid or benzoic acid plus mild acidification of the sweet potato puree with citric acid to pH 4.2 prevented growth of L. monocytogenes during storage at 4 degrees C.     

Effect of modifying pumpkin preparation on oral processing of breads

There is an increasing demand for texture sensations of bread during mastication, with reformulation being needed. This study investigated how bread structure influences oral processing behavior and texture perception. Variations in bread structure were created by manipulating ingredient additions, including pumpkin content and pumpkin processing methods. Results indicated that the physical, chemical, and structural properties drove the oral processing behaviors, and texture sensations were highly correlated with bolus properties. At the beginning and middle of the mastication, bolus from breads with low pumpkin-content required more saliva and exhibited greater hardness, lower adhesiveness, and a higher proportion of small-piece particles than the bolus from high pumpkin-content breads. Bolus from pumpkin pulp breads required more saliva, and was softer, stickier, and generated particles with a lower degree of degradation than the bolus from pumpkin puree breads. However, at the end period, the bolus properties tended to change to similar values. Low pumpkin content breads were initially perceived chewy, whereas high pumpkin content, soft. The dominance rate for soft sensation was higher and lasted longer in breads with pumpkin puree than in breads with pumpkin pulp. Finally, six bread samples were all perceived as hydrated, sticky, and crumbly. This study contributes to a better understanding of the impact of reformulation on oral behavior and sensory properties.     

Protein Structural Changes During Preparation and Storage of Surimi

The changes in protein structure associated with the preparation and frozen storage of surimi were investigated. Raw surimi was prepared by repeatedly washing Alaska pollock flesh with chilled water. The product was either slowly frozen or underwent rapid freezing using liquid air; in either case it was then subjected to frozen storage at ‐20 °C for 24 mo. Fourier transform infrared/attenuated total reflectance (FTIR/ATR) spectroscopy showed that during preparation of surimi, the a‐helix content increased with increased number of washing cycles. Differential scanning calorimetry (DSC) revealed a shift in the thermal transition of actin to a higher temperature during surimi preparation. Electrophoresis, FTIR/ATR spectroscopy, and DSC results revealed a loss of myofibrillar proteins from surimi after 3 washing cycles, suggesting that 3 washing cycles were adequate to prepare surimi. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) showed relatively minor changes in protein subunit structure with some loss of the myosin light chains (MLC); myosin heavy chain (MHC), actin, and tropomyosin were found to be relatively stable. Native‐PAGE showed no major changes in surimi after 24 mo storage at ‐20 °C. FTIR/ ATR spectroscopy indicated a significant decrease in a‐helix relative to p‐sheet structure in surimi after 2 y of storage at ‐20 °C. The loss of α‐helical content was more significant in slowly frozen surimi compared with rapid‐frozen surimi samples. DSC results revealed a shift in the thermal transition of actin to lower temperatures during frozen storage of surimi.     

Effect of Combining Mechanically Harvested Green and Ripe Puree and Sliced Fruit, Processing Methodology and Frozen Storage on Quality of Strawberries

Small green and ripe mechanically harvested strawberries were processed into puree and combined with 60 and 80% sliced ripe fruit to determine the effects of holding after harvest, percent green fruit in puree, processing procedure and storage on quality of frozen sliced strawberries. Green and ripe fruit puree added to the sliced strawberries resulted in higher viscosity and lower ascorbic acid, total anthocyanins and red color as compared to packs with 100% sliced ripe fruit. The mixtures of sliced ripe fruit and up to 40% puree were rated acceptable by a sensory panel. Heating the puree may be beneficial to color during long-term storage. Holding of fresh strawberries for 24 hr at 24°C after cleaning decreased the ascorbic acid, viscosity of syrup and color of the frozen pack. Storage of the frozen product decreased ascorbic acid and color.     

海藻酸丙二醇酯对全麦冷冻面团冻藏稳定性和烘焙特性的影响

本文研究了海藻酸丙二醇酯（Propylene glycol alginate,PGA）对全麦冷冻面团冻藏期间稳定性的影响,并探究了冷冻面团烘焙面包品质的变化。将0.3%的PGA加入全麦面团,通过测定冷冻面团冻藏1、2、3、4和5周后发酵特性、流变特性、蛋白质二级结构、微观结构以及面包的比容、质构特性、内部纹理结构和老化程度等,研究冷冻面团冻藏期间的稳定性。结果表明,随着冻藏时间的延长,添加PGA的冷冻面团在冻藏5周后具有较好的保水性,其发酵特性及流变特性相对于对照组均有所改善。冻藏5周后,对照组与PGA组其面包比容分别下降了19.872%和14.153%;面包硬度分别升高了64.186%和36.386%;气孔表面积分率分别下降了3.497%和2.300%;老化焓值分别上升了65.142%和42.416%。添加PGA能延缓冷冻面团冻藏期间β-折叠含量的上升和β-转角相对含量的下降。电镜扫描图（SEM）显示,随着冻藏时间的延长,PGA组的冷冻面团孔洞数目相比对照组明显减少且大小均匀,面筋网络结构完整性和连续性提高。研究结果表明PGA可以有效地延缓冷冻面团在冻藏期间的品质劣变,维持冷冻面团的稳定性并提高面包的烘焙特性。     

Comparison of high pressure treatment and thermal pasteurization effects on the quality and shelf life of guava puree

The effects of high pressures and thermal pasteurization on the survival of microorganisms, enzyme inactivation and quality changes of guava puree during storage at 4°C were investigated and compared with untreated samples. After treatment at a pressure of 600MPa and 25°C for 15 min, the microorganisms in guava puree were inactivated to less than 10 cfu mL⁻¹ and the product exhibited no change in colour, pectin, cloud and ascorbic acid content as compared with fresh samples. The inactivation of enzymes in guava puree by thermal pasteurization was greater than by high pressures. The microbial count in guava puree reduced to 200 cfu mL⁻¹ and the product showed marked changes in viscosity, turbidity and colour when heated at 88–90°C for 24s. The content of pectin, cloud and ascorbic acid as well as colour in untreated and high pressurized (400MPa) guava puree gradually decreased, whereas these changes were not observed in pasteurized (88–90°C) and high pressurized (6000MPa) puree during storage at 4°C for 60 days. The guava puree treated at 600MPa and 25°C for 15 min retained good quality similar to the freshly extracted puree after storage at 4°C for 40 days.     

Impact of Mechanical and Microstructural Properties of Potato Puree-Food Additive Complexes on Extrusion-Based 3D Printing

This paper studies the applicability of extrusion-based 3D printing for constructing novel shapes from potato puree and the effects of four additives (agar, alginate, lecithin, and glycerol) added separately at three concentrations (0.5, 1, 1.5%) on the internal strength, mechanical properties, microstructure, and color of potato puree. The printability of the potato puree and the mixtures was assayed by examining the consistency of the extrusions and the stability and accuracy of the printed patterns. The results indicate that better printing was achieved at a nozzle height of 0.5 cm and a nozzle diameter of 4 mm, with concentrations of alginate and agar between 0.5–1.5% and 0.5–1%, respectively, providing the best printability and end product stability, which was attributed to their respective high mechanical characteristics and specific mechanical energy (SME) values. Scanning electron microscopy (SEM) revealed that more convolutions were induced in the potato puree upon the addition of agar or alginate, which increased the puree stability. 3D printing did not significantly affect the surface color parameters of the final product. This study showed that the 3D printing process is a critical factor for initializing the production of customized healthy products.     

Gelation of Persimmon Puree and Its Prevention by Enzymatic Treatment

Fresh persimmon puree showed a rheological behavior corresponding to a weak gel, where storage modulus (G′) prevailed over loss modulus (G″). In a temperature sweep test (from 25–80–25 °C), G′ values increased at temperatures above 60 °C and continued increasing during the subsequent cooling step showing a wide scattering. These changes indicated a gelation phenomena that resulted in a more rigid and irregular gel structure. The gelation was lower in the acidified puree (pH 4.4) than in the puree at its natural pH (5.9). The addition of ethylenediaminetetraacetate sodium avoided the increase of G′ during the heating and reduced the G′ increase in the cooling step. Thus, gelation in persimmon puree occurred by a heat-set gelation influenced by pH, and also by cold-set gelation depending on an ionotropic mechanism. The incubation of persimmon puree with Viscozyme L (1 g/L, 25 °C, 30 min) allowed to obtain a more fluid product able to tolerate a thermal processing at 85 °C without gelation. During the incubation with Viscozyme L, the pH of the persimmon puree decreased monotonically as a consequence of its pectinmetylesterase activity, and the continuous measurement of pH could be used to monitor this process.     

菠菜粉对芋头粉糊化和菠菜芋泥流变特性与感官特性的影响

针对婴幼儿辅食中蔬菜补充不足的问题,以菠菜粉和芋头粉为原料制备菠菜芋泥,探究了菠菜粉对芋头粉糊化特性的影响,以及芋头粉添加量为5、10和15 g/100 mL时菠菜粉的添加量对菠菜芋泥流变特性与感官特性的影响。结果表明,菠菜粉的添加降低了芋头粉的峰值黏度、谷值黏度、最终黏度,改善了高温加工过程中芋头粉糊的稳定性,抑制了淀粉的回生。菠菜粉的添加提高了菠菜芋泥的储能模量（G'）和表观黏度。感官评价结果显示,菠菜粉的添加提高了菠菜芋泥的搅动阻力、滞留感和稠厚感,降低了其流动性。流变特性与勺搅拌阻力呈现出最强的正相关性,与口腔内流动性呈现出最强的负相关性。芋头粉添加量为10 g/100 mL的菠菜芋泥的流变特性符合婴幼儿果蔬泥的要求。在开发菠菜芋泥产品时,可通过增加菠菜含量来达到预期的感官指标。控制芋头含量并提高菠菜含量,有助于婴幼儿摄入适量的膳食纤维。     

Effect of pasteurisation on sensory quality of natural soursop puree under different storage conditions

Pasteurisation effects on natural soursop (Annona muricata L.) puree were evaluated in terms of appearance, colour, flavour, odour, consistency and overall acceptability for 12 weeks. The packaging and storage temperature combinations used were laminated aluminium foil (LAF), lacquered can (LC) and high density polyethylene plastic bottle (HDPE) at ambient temperature (28–38°C), 15, 4 and −20°C. Results showed pasteurisation at 79°C for 69 s significantly improved the sensory colour, flavour, appearance and overall acceptability of the puree. Pasteurised puree packed in LAF at 4°C had the highest score for almost every attribute evaluated. Overall, all samples were found acceptable by judges during the 12 week storage period. The better stability, in terms of colour, consistency and flavour characteristics, of pasteurised puree packed in foil at 4°C than the frozen control could be an additional and cheap advantage for storage and transport.