Influence of yeast and frozen storage on rheological, structural and microbial quality of frozen sweet dough

The aim of the present study was to investigate the effect of yeast content and frozen storage (9 weeks at −40 °C) on the structural and rheological parameters, and fermentative activity of frozen sweet dough. Two types of dough were studied (to estimate dough shelf life): simple yeasted dough (SY) and double yeasted dough (DY). Fermentative activity (yeast viability, gassing power, and dough volume), rheological and textural parameters were assessed for frozen sweet doughs.These effects were explored by different and complementary methods: Fourier transform infrared (FTIR), dynamic rheology, texture profile analysis (TPA) and differential scanning calorimetry (DSC).The data showed that the longer the frozen storage time at −40 °C, the higher the decreased of frozen sweet dough quality. The rheological attributes such as hardness, ΔS, springiness, tan δ and yeast activity declined significantly during frozen storage. This modification led to lower specific volume of frozen sweet dough during proofing.The observed changes of the frozen sweet doughs rheological properties after thawing may be attributed to the damage on the gluten cross-linking, mainly produced by the ice crystallization during frozen storage. The storage effect was particularly concentrated in the first 27 days of storage.     

Improving freeze tolerance of yeast and dough properties for enhancing frozen dough quality - A review of effective methods

BackgroundFrozen dough technology could effectively extend the shelf life of bread to ensure the freshness, which is widely used and gradually replace the traditional bread production. However, during the production and storage of frozen dough, a series of problems could take place, such as inhibition of yeast activity, damage of the structure of the dough, leading to the deterioration of dough quality.Scope and approachThis review summarizes the factors that affect the final quality of frozen dough, including yeast activity, dough structure and dough properties. Some effective methods for improving freeze tolerance of yeast, dough structure and dough properties are discussed, including addition of various additives, use of genetic engineering technique, optimization of freezing and storage conditions, and employment of novel freezing technology.Key findings and conclusionsThe addition of additives can not only improve the freeze tolerance of yeast but also maintain the rheological and thermophysical properties of dough. Through the modification of gene, freeze tolerance and fermentation ability of yeast can be improved. Optimizing freezing and storage conditions ensures the activity of yeast as well as dough network structure so that freezing damage due to ice crystals can be minimized. In addition, novel freezing technology such as ultrasound-assisted freezing can simultaneously accelerate the freezing process as well as generate fine and uniform ice crystals, thus protecting dough network structure.     

Frozen Sangak dough and bread properties: Impact of pre-fermentation and freezing rate

The impact of pre-fermentation time and freezing rate on Sangak frozen dough and bread quality were studied. The pre-fermented doughs for 0, 30, 60, 90, or 120 min were frozen under –20, –25, or –30°C in air blast freezer. After 24 h storage at –18°C, dough samples were baked after final fermentation. The yeast viability, gassing power, and dough development for fresh and frozen Sangak doughs were determined. Crust color, density, and shear stress of bread obtained from fresh and frozen Sangak dough were evaluated. The results showed that yeast survival initially increased and then decreased with increasing freezing rate. The maximum yeast survival was observed at short pre-fermentation (30 min). A direct relationship was observed between gassing power, dough development, and yeast viability. From bread quality point-of-view, short pre-fermentation and higher freezing rate led to a more desirable bread.     

Effects of refrigeration,freezing and replacement of milk fat by inulin and whey protein concentrate on texture profile and sensory acceptance of synbiotic guava mousses

The effects of refrigeration, freezing and substitution of milk fat by inulin and whey protein concentrate (WPC) on the texture and sensory features of synbiotic guava mousses supplemented with the probiotic, Lactobacillus acidophilus La-5, and the prebiotic fibre oligofructose, were studied. The frozen storage (−18 ± 1 °C), followed by thawing at 4 °C before the analyses, and the complete replacement of the milk fat by inulin plus WPC, led to significant differences in the instrumental texture parameters of mousses (P < 0.05). Nonetheless, these changes did not affect the sensory acceptability of the products studied. The frozen storage may be employed to extend the shelf-life of synbiotic guava mousses. Additionally, to obtain a texture profile similar to the traditional product, the simultaneous addition of inulin and WPC is recommended only for the partial replacement of milk fat in refrigerated and frozen mousses, and the total proportion of both ingredients together should not exceed 2.6%.     

Double freezing of cod fillets: Influence on sensory,physical and chemical attributes of battered and breaded fillet portions

Fillet samples were processed on board a research vessel from cod (Gadus morhua) in different states of rigor mortis. In addition, headed and gutted fish in different states of rigor were frozen and, after ten days of frozen storage, the fish were thawed, processed into fillets and refrozen. During subsequent frozen storage at –24°C of breaded and battered portions processed from the different fillet batches several quality attributes were tested using sensory, physical, and chemical methods. The measurements indicated differences in the quality attributes depending on refreezing and rigor states. Especially the sensory texture attributes gumminess and, with some restrictions, firmness were found to be suitable for distinguishing single frozen (SF) from double frozen (DF) samples. This finding was supported by the outcome of the measurement of penetration force where generally a significantly (p < 0.05) higher force was necessary to penetrate the DF compared to SF samples. DF samples were generally lighter (higher L*) than SF samples. The colour difference δE between both sample types was at least very clear and therefore visible. However, no clear differences between SF and DF samples were found when evaluating the flavour attributes and using instrumental texture profile analysis for texture characterisation. Also, all chemical parameters measured did not allow to clearly distinguish between single and double frozen samples. Therefore, it can be stated that, at least when using cod as raw material for processing battered and breaded portions, the different methods for preparing the fillet blocks will, if at all, only affect the textural quality of the final products.     

回软对紫薯类月饼TPA参数及感官品质的影响

分析紫薯类月饼回软过程中硬度、回复性、凝聚性等质构剖面分析(texture profile analysis,TPA)参数的变化及其与感官品质的相关性。结果发现:在72 h的回软过程中,紫薯类月饼TPA参数的变化均呈现先增大后减小的趋势;其中,紫薯莲蓉月饼(紫薯和莲蓉馅料质量各占50%)TPA参数峰值出现在回软24 h,紫薯月饼(紫薯馅料100%)TPA参数峰值出现在回软48 h;紫薯莲蓉月饼的TPA参数总体低于紫薯月饼。分别在回软12、24、48 h及72 h对紫薯类月饼进行感官评定,结果表明,72 h感官评分最高,且感官评分与相应TPA参数呈现极显著负相关性(P≤0.01),说明回软过程有助于提高紫薯类月饼的感官品质,且TPA参数可以客观评价紫薯类月饼的感官品质。     

Effect of high hydrostatic pressure to sweet potato flour on dough properties and characteristics of sweet potato‐wheat bread

The effect of high hydrostatic pressure (HHP, 100–400 MPa) for 20 min at 25 °C to sweet potato flour (SPF) on dough properties and characteristics of sweet potato‐wheat bread was investigated. The particle size of SPF after HHP was decreased significantly. The obvious rupture was observed in granules of SPF after HHP at 300 and 400 MPa by scanning electron microscopy (SEM). After HHP, significant differences on endothermic peak temperatures (T_P) of SPF were observed by differential scanning calorimetric (DSC), of which the enthalpy change (ΔH) had a slight increase, expect that at 200 MPa. Gas retention of dough with SPF after HHP increased markedly from 1199 (0.1 MPa) to 1246 ml (100 MPa). Specific loaf volume of bread with SPF at 400 MPa was increased significantly, while the hardness and chewiness were reduced. Thus, SPF treated with HHP at 400 MPa could be potentially used in wheat bread production.     

冷冻速率对面团发酵和烘焙性质的影响

研究了冷冻速率对冷冻面团体系中酵母发酵(包括酵母产气力、酵母存活率)和面团微结构的影响;以及对冷冻面团烘焙性质的影响(包括面包比容,面包评分和面包保质期).结果显示冷冻速率同时影响酵母活力和面团的超微结构,进而影响面包的品质和体积,综合考虑,确定面团在-32℃下快速冷冻至-18℃(冷冻速率约-5℃/min),并在-18℃下冻藏,较适合冷冻面团的生产.     

基于感官评价的加热不燃烧卷烟原料品种(系)筛选

为筛选适宜生产加热不燃烧卷烟烟叶原料的烤烟品种,在云南省5个试点(玉溪、保山、红河、临沧、文山)种植5个烤烟品种(系)(云烟207、云烟99、云烟116、KRK26、红花大金元),按加热不燃烧卷烟感官评价方法进行初烤烟中部叶的感官质量评价,并检测烟叶化学成分和香味物质含量(质量分数)。结果表明:①云烟99和云烟207的香气香味、劲头、谐调性和刺激性表现相对较好,适宜作为加热不燃烧卷烟烟叶原料的候选品种(系),而云烟116的感官评价指标表现相对较差。②烟叶常规化学成分和香味物质中,氮含量与香气香味、劲头、谐调性、口感等指标呈显著正相关,总糖和还原糖含量与谐调性、口感等指标呈显著负相关,酮类化合物含量与香气香味和口感指标呈显著正相关,酯类化合物含量与刺激性和口感指标呈显著负相关。这些烟叶成分可作为筛选其他适宜烟叶原料品种时重点分析的物质成分。     

Microbiological and sensory quality of stored croissant‐type bakery products depending on external (sorbic acid) and internal (dough,aw value) conditions

The work presents some results from the evaluation of microbiological (total bacterial count, coliform bacteria, moulds and yeasts) and sensory (shape, odour, colour, taste, consistency, crust, soft inside, etc.) quality and of the a_w value and pH during the 90‐day storage (interval of 0, 30, 45, 60, 75 and 90 days) under laboratory conditions at 20 ± 2°C in eight types of the bakery croissant‐type product with the nougat cream differing by the type of dough (brioche, croissant( a_w value of the cream, and by the presence or absence of sorbic acid in the spirit spray applied onto the surface of products. The above‐indicated parameters were examined also in the nougat cream samples (on the zero and 90^th day of storage). The chosen quality parameters permitted the level of the durability influence of croissants depending on external (sorbic acid) as well as internal (recipe, a_w) conditions to be estimated.     

Effect of freezing on sensory quality, shear force and water loss in beef M. longissimus dorsi

The objective of this study was to determine how sensory quality, shear force and water loss differ between beef stored either chilled or frozen before cooking. Meat tenderness was analysed instrumentally and sensorially using both a consumer panel and a semi-trained panel. Both M. longissimus dorsi (LD) from eight young Holstein bulls were cut into eight samples, weighed, vacuum packed and aged at 4 °C for 2, 7 or 14 days. After ageing, the frozen samples were kept at −20 °C prior to heat treatment. Water holding capacity was recorded as purge or thawing loss and cooking loss or as combined loss. Sensory analyses were performed on samples aged 7 days. Peak force values declined with ageing time and freezing. Frozen meat aged 2 days had the same peak force values as chilled meat aged 7 days. Total energy was the same for both treatments at day 2 and 7, whereas at day 14 frozen samples showed significantly higher values than chilled samples. The sensory panel experienced the chilled meat to be more tender, juicier and having a more intense meat taste than the frozen meat, whereas the consumers could not find any significant difference in degree of liking. Water holding capacity was lower for the frozen samples. The results indicate that conclusions from studies concerning sensory quality of beef will depend on whether the meat has been kept chilled or frozen before testing.     

Effect of addition of cryoprotectants on the mechanical properties, colour and sensory attributes of fresh and frozen/thawed mashed potatoes

Cryoprotectants such as hydrocolloids (amidated low-methoxyl (ALM) and high methoxyl (HM) pectins), kappa- and iota-carrageenans (k-C and i-C), xanthan gum (XG)) and dairy proteins [whey protein (WP), sodium caseinate (SC)] were added to mashed potatoes to investigate ways of improving the effects of freezing and thawing. It was found that each hydrocolloid and protein, depending on concentration, affected the mechanical properties [instrumental textural profile analysis (ITPA), cone penetration (CP) test], the total colour difference (ΔE*) with respect to fresh control (FC) and the sensory attributes of fresh (F) and frozen/thawed (F/T) mashed potatoes in a different way. In the F/T samples, adding 5 and 8 g kg⁻¹ ALM, 3, 5 and 8 g kg⁻¹ k-C, 1.5, 3, 5 and 8 g kg⁻¹ i-C and 1.5, 5 and 15 g kg⁻¹ WP significantly increased ITPA consistency. Also, adding 2.5 and 5 g kg⁻¹ XG significantly increased ITPA consistency of the F/T product. In both F and F/T samples, k-C provided the highest ITPA consistency and also high CP average force evidencing a stronger synergistic effect in κ-C/denatured milk protein systems, although the excessive thickening and stickiness provided was judged undesirable by the panellists. Adding 8 g kg⁻¹ HM pectin had a disruptive effect on the mashed potatoes and decreased both ITPA consistency and CP average force. In all cases, freezing and thawing reinforced the gel structure of the products as compared to F and FC counterparts. The ΔE* values were higher in F samples containing ALM and HM pectins. Dairy proteins affected the taste and odour of the mashed potatoes and were judged unacceptable in the sensory analysis. Samples containing 0.5 and 1.5 g kg⁻¹ added XG were preferred organoleptically due to the creamy mouthfeel it produced. ITPA consistency correlated well with sensory texture attributes.     

玛咖采后贮藏过程中质构与色泽变化的研究

目的:旨在揭示玛咖块根采后贮藏期间质构与色泽变化状况,为利用仪器分析代替感官评价测定玛咖块根质地品质提供理论依据。方法:利用质构仪采用质地多面分析（Texture Profile Analysis,TPA）法,研究不同温度贮藏期间玛咖块根采后质地参数变化的规律。结果:在4、20℃两个贮藏温度下,玛咖块根硬度值先下降后缓慢上升,其他各项质地参数变化规律总体均呈现下降趋势;硬度与凝聚性、咀嚼度以及颜色饱和度值呈现极显著的正相关性,而与粘附性呈负相关性;咀嚼度与硬度、凝聚性呈极显著正相关性;反映玛咖表面色泽状况的指标-颜色饱和度值与硬度、弹性呈极显著正相关,与咀嚼度、凝聚性呈显著正相关,但与粘附性呈显著负相关。结论:玛咖块根4℃贮藏的质地变化速度明显缓慢于20℃贮藏的值,说明玛咖在低温下贮运更易保持质构品质,这些质构参数指标可应用于检测玛咖质地的变化,为玛咖的货架期提供一定的理论指导,但其与感官评价指标的相关性还有待进一步分析。      

Selection of dietary fibres for sucrose replacement in functional Chhana‐murki (Indian Cottage cheese‐based dessert) and their effect on sensory,physical and instrumental texture parameters

With a wide range of beneficial effects on human health, various dietary fibres such as microcrystalline cellulose (MCC), inulin, oat fibre and wheat fibre were screened based on their bulking ability in the functional Chhana‐murki (FCM) with respect to sensory and physical properties. Sensory scores were maximum for MCC at 7.5% having optimum moisture content and water activity and minimum hardness, whereas oat and wheat fibres increased the hardness of the product while decreasing the moisture content and water activity thus lowering the sensory scores. Further, replacement of MCC with inulin in 1:1 ratio improved the product characteristics.     

Influence of some prefermentative treatments on aroma composition and sensory evaluation of white Godello wines

The influence of the static settling time and the addition of ammonium salts on basic parameters, aroma composition and tasting of white Godello wines have been studied. The statistical analysis showed a significant influence of those treatments on several analytical parameters. The static settling time proved to be very influential on total acidity, free sulphur dioxide, esters, terpenols and fatty acids, while the addition of ammonium salts showed a significant effect on higher alcohols and ethyl lactate. According to the odour active value (OAV), 14 out of 47 studied volatile components had OAV >1 in all the analysed wines, while six volatile components showed OAV >1 only for some of them. Ethyl octanoate, isoamyl acetate and ethyl hexanoate showed the highest OAV values. During the tasting session, the two studied factors became relevant, being better valued the wine made with must containing higher limpidity and with the addition of diammonium hydrogen phosphate.     

基于主成分分析和质构分析的甘薯泥品质综合评价

目的 利用主成分分析和综合评价建立方便、快捷的甘薯泥加工品质综合评价方法.方法 采用质构分析和多元统计学方法相结合,对7个甘薯泥的基本成分和质构品质进行了相关性和主成分分析,并进行综合评价.结果 不同品种甘薯泥的基本成分在淀粉含量和水分含量上都有显著差异(P<0.05).甘薯泥的基本成分、感官评分和质构品质指标间有部分...     

Effect of using transglutaminase on physical,chemical and sensory properties of set-type yoghurt

This study was conducted in order to evaluate the effects of transglutaminase (TGase) addition on some properties of set-type yoghurts such as titratable acidity, lactic acid, tyrosine, viscosity, gel firmness, syneresis, aroma compounds, sensory analysis, and micro-structural properties. The enzyme was added to yoghurt-milk at different production steps (after homogenization, after pasteurization and together with starter culture addition) and two different incubation times (10 min and 1 h) were used. Five TGase treated yoghurt samples and control sample were analyzed on 1st, 10th, and 20th days of storage. TGase addition did not cause significant changes on chemical properties of yoghurts. However, enzyme addition after pasteurization increased the gel strength and decreased the syneresis. Results of electron microscope showed that enzyme addition led proteins to be distributed more evenly in gel network due to the formation of cross-links between proteins.     

不同温度冻藏对军曹鱼片品质的影响

研究不同冻藏温度(－ 10、－ 18、－ 30℃)对军曹鱼片部分理化指标、质构特性及感官品质的影响。结果表明,冻藏温度对军曹鱼片的解冻汁液流失率、蒸煮损失率、盐溶蛋白含量、Ca2+-ATPase 活性和TBA 值(硫代巴比妥酸)均有显著性影响(P ＜ 0.05)。冻藏时间越长、冻藏温度越高,汁液流失率、蒸煮损失率、TBA 值增加越大,盐溶蛋白含量、Ca2+-ATPase 活性下降也越多,即保水性降低、蛋白质变性程度增大、脂肪氧化加快。TPA(质构分析)发现军曹鱼片的硬度和耐嚼性随着冻藏时间的延长均呈显著增加趋势(P ＜ 0.05),而回复性则显著下降(P ＜ 0.05);冻藏温度越低,相应的硬度和耐嚼性就越小,而回复性则越大。感官评价表明冻藏导致军曹鱼片的品质下降,冻藏温度越高,品质劣变就越严重。采用较低的温度(－ 30℃)冻藏可以最大限度的保持军曹鱼片的品质。     

Effect of inulin and Lactobacillus paracasei on sensory and instrumental texture properties of functional chocolate mousse

BACKGROUND: This study evaluated the effect of a potentially probiotic bacteria (Lactobacillus paracasei subsp. paracasei LBC 82), added solely or together with the prebiotic ingredient inulin on instrumental texture attributes and sensory properties of a functional chocolate mousse during storage at 4 ± 1 °C for up to 28 days. RESULTS: The addition of Lactobacillus paracasei resulted in a firmer and more adhesive chocolate mousse. This effect was intensified with the presence of inulin in the synbiotic formulation (5.24 N and ? 0.956 N, respectively, for firmness and adhesiveness after 28 days of storage) (P < 0.05). L. paracasei population did not vary (P > 0.05) during storage (always between 7.27 and 7.35 log cfu g^?1), both for the probiotic and the synbiotic mousses. Synbiotic mousse differed from control and probiotic mousses during storage with respect to the color attribute. Moreover, both probiotic and synbiotic mousses presented taste, aroma and texture perceptions which were different from one another and from the control mousse after 14 and 21 days of storage. CONCLUSION: The use of inulin, together with the potentially probiotic strain of Lactobacillus paracasei subsp. paracasei, is advantageous, conferring potentially symbiotic potential to the chocolate mousse, as well as favorable texture and sensory properties. Copyright © 2008 Society of Chemical Industry