Crust morphology and crispness development during deep-fat frying of potato

Crust formation is an important factor in determining the crispness of French fries. This study aimed at unravelling detailed structural and textural properties of the crust in relation to crispness during frying as a function of the process temperature and time. X-ray tomography showed a larger overall pore volume at higher frying times, while a lower final moisture content mainly resulted in an increase in the amount of large pores. Texture analysis revealed that the increase in porosity, due to the increased formation of pores, results in a more crispy behaviour after frying with oil of up to 180 °C. At temperatures above 180 °C crispness is actually found to decrease again, which is explained by the increased plastic behaviour of the crust. This may be related to the reduced glass transition temperature of the crust because of increased sugar degradation at a very high temperature.     

Effect of pre-drying and par-frying conditions on the crispness of French fries

An experimental design was used to study the effect of pre-drying (to 10, 15 and 20% weight loss) and par-frying conditions (160, 170 and 180 °C) on the crispness of French fries. Par-frying time was adjusted with a software program to obtain equal moisture content and internal texture for all samples. Crispness was evaluated with a sensory panel. Furthermore, samples were analysed with a texture analyser and with confocal scanning laser microscopy (CSLM). Par-frying at 180 °C resulted in a crispier product than at 160 and 170 °C. Pre-drying to 20% weight loss lead to blisters and reduced crispness in comparison with pre-drying to 10 and 15% weight loss. Instrumental texture measurements showed a good correlation with sensory crispness. Large differences in cell structure, such as blisters, could be observed with CSLM. CSLM was useful to explain results from the instrumental and sensory texture evaluation.     

冷冻及微波复热条件对预油炸面拖食品脆性的影响

利用微波工作站实时测定预油炸冷冻面拖食品在冷冻和微波复热过程中内部温度的变化,研究了不同冷冻方式、冷冻速率、冻藏温度及微波复热参数条件对产品脆性的影响.对微波预油炸面拖食品微波复热过程中功率和时间时产品脆性的影响也进行了探讨.结果表明,冷冻速率和冷藏温度与产品脆性存在正相关,相同温度下强制通风冷冻的产品脆性高,强制通风样品的超微结构较自然降温样品平整致密,水分阻隔性能力强.     

Computational approaches to investigate how biological macromolecules can be protected in extreme conditions

ABSTRACT:  Water is required to hydrate molecules, but under cold conditions water freezes and under dehydrating conditions water evaporates—thus presenting a dilemma for organisms that live in extreme environments. Organisms have developed various strategies for protection against extreme temperatures and dehydration. In this review, we describe how the interaction of water and 2 natural cryoprotectants, namely glycerol and sugars, can be studied at the molecular level. Techniques using infrared spectroscopy and computation are described. In the case of glycerol, H-bonding of water to the OH groups of glycerol limits the amount of water available to form ice and prevents crystallization at low temperatures. For aldohexopyranose sugars, the different isomeric forms have different water H-bonding networks, which are consistent with isomeric-dependent activities. By studying the strategies used in nature, derivatives for use in food preservation can be more readily developed.     

Screening and characterization of bacteria that can utilize ammonium and nitrate ions simultaneously under controlled cultural conditions

Eighteen bacterial stock cultures were examined for their ability to utilize NH(4)(+) and NO(3)(-) simultaneously in a medium containing NH(4)NO(3) with shaking using a test tube capped with a cotton stopper. Pseudomonas aeruginosa NBRC 12689 utilized 1 mg/ml of NH(4)NO(3) most rapidly of the cultures tested. The bacterium could completely utilize 5 mg/ml of NH(4)NO(3) within 3 d, 6 mg/ml of NH(4)Cl within 3 d, and 20 mg/ml of NaNO(3) within 2 d under optimum conditions. The addition of Fe(2+) to the NH(4)NO(3) medium markedly promoted the utilization of the two ions. When the Pseudomonas strain utilized 5 mg/ml of NH(4)NO(3) completely, the total nitrogen in the culture including its cells decreased to 41% of that of the NH(4)NO(3) originally provided. GC-MS analysis showed that the removed nitrogen was probably denitrified. When the bacterium was incubated in the NH(4)NO(3) medium with shaking in a vial sealed with a rubber stopper, N(2) accumulated, but not N(2)O at the final phase of cultivation. On the other hand, both N(2) and N(2)O were detected in the NaNO(3) medium. We concluded that the bacterium removed NH(4)(+) from NH(4)NO(3) as a nitrogen source for its cell components, together with the denitrification of NO(3)(-) under controlled shaking conditions. In addition, NH(4)(+) promoted the cell growth of the bacterium and denitrification to N(2), preventing the accumulation of N(2)O.     

板栗糯米饼的微波膨化工艺和酥脆度改善方法的研究

本实验以面粉、糯米粉及板栗粉为主要原料,将糯米粉、面粉、板栗粉、土豆淀粉混合后使用微波膨化技术制作成膨化板栗饼。首先通过单因素实验了解不同因素对产品感官品质的影响,然后采用正交实验进一步对关键因素进行优化,确定了膨化板栗饼制作的最佳工艺条件为:原料(面粉、板栗粉、糯米粉)配比为4∶6∶8,原料初始含水量为20%,土豆淀粉的添加量为7%,微波炉膨化时间为100s,功率为520W,设定温度为150℃。在此工艺条件下所得产品膨化度为2.9,制得口感较佳的膨化板栗饼。      

Cadmium uptake by a green alga can be predicted by equilibrium modelling

Short-term uptake of cadmium by a wild-type (2137) and a cell wall-less strain (CW-2) of Chlamydomonas reinhardtii was examined as a function of Cd speciation in a well-defined, aqueous medium. Internalization fluxes were determined for free cadmium concentrations ranging from 5 x 10(-10) M to 5 x 10(-4) M in the presence of ligands forming both labile and inert hydrophilic complexes. A first-order biological internalization, as predicted by the free ion activity model (FIAM), was observed for both strains. The maximum Cd internalization flux, Jmax, for the wild-type strain was 5-fold higher (1.3 x 10(-11) mol cm(-2) min(-1)) than for the CW-2 strain (2.3 x 10(-12) mol cm(-2) min(-1)) and was not influenced by the presence of competitors such as Ca in the experimental solution. The conditional stability constant for the adsorption of Cd to transport sites of the CW-2 strain was 5-fold higher (10(6.7) M(-1)) than for the wild-type strain (10(6) M(-1)). Competition experiments demonstrated that Mo, Mn, Cu, Co, Zn, Ni, Ca, and Pb inhibited, at least partially, Cd uptake, while no inhibition was observed for similar concentrations of Mg and Fe. The stability constant for the competitive binding of Ca to the Cd transport site was determined to be 10(4.5) M(-1). Cu and Zn competed with Cd uptake sites with stability constants of 10(5.6) and 10(5.2) M(-1), respectively. Protons also appeared to compete with Cd uptake sites as uptake could generally be predicted quantitatively in their presence. Finally, in the presence of low concentrations (<20 mg L(-1)) of Suwannee River fulvic acid, Cd internalization fluxes could be predicted from [Cd2+], in accordance with the FIAM.     

Aflatoxin can be degraded by the mycelium of aspergillus parasiticus.

Aflatoxins B1, B2, G1, and G2 were degraded by the 8- and 16-day old but not by the 4-day old mycelium of a toxigenic strain of Aspergillus parasiticus. The 16-day old mycelium degraded the toxin more rapidly than did the 8-day old mycelium. Degradation of toxin by the mycelium was similar at pH 2.5 and 6.0.     

Estimation of crispness and consumer acceptance of fried potato chips by mechanical and acoustic measurements

Fried potato chips retaining various moisture contents (MCs) (2.21–9.20%) were analysed to estimate the intensity of crispness and consumer acceptance by texture and acoustic measurements. The MC of the chips was highly correlated with the mechanical maximum force (MMF) in the texture measurement, total area (MTA) and number of sound peaks (NSP) in the acoustic measurement. The intensities of crispness and consumer acceptance decreased as the MC of potato chips increased. For the predictive models established, the combined use of mechanical and acoustic parameters was shown to better predict sensory crispness intensity [R² = 0.975, root mean square error of prediction (RMSEP) = 0.138] and consumer overall liking (R² = 0.966, RMSEP = 0.111) than either parameter alone. Based on the instrumental‐sensory crispness equivalent table established, the estimated values of the MTA were below 71.24, while the NSP should be above 22.81 to meet ‘slightly like’ category of consumer acceptance.     

印染污水六成可循环利用

8月11日，在慈溪一家印染企业的污水池旁，由兵科院宁波分院研发成功的“污水资源化”工程样机，向各地的企业代表展示其污水处理新技术。这种把污水处理和资源化利用合在一起的工艺技术在国内属于首创，处理后的水可循环利用。使企业废水减排60％，还可节约大量用水成本。[编者按]     

Cyclic pressure applied to cows' teats by teatcup liners can be determined simply and noninvasively

Liner overpressure is a quantitative variable indicating the extent to which the vacuum difference across the liner during phase d (the liner compression phase) of milking machine pulsation exceeds the vacuum difference that would be just sufficient to stop milk flow from the teat. Previously defined methods of determining liner overpressure have required modifications to the milking machine, complex instrumentation, or both. Our method of measuring derived overpressure (OP) offers relatively simple instrumentation and realistic milking machine characteristics. We determined derived OP by measuring the duration of milk flow within a pulsation cycle, and then comparing that duration with the shape of the pulsation curve to deduce the pulsation chamber vacuum level corresponding to that duration. Derived OP by our method yielded measurements of OP that differed by less than 2.0 kPa from those determined by the most practical previous method, for 2 trial liners. Derived OP can serve as a method for comparing and evaluating liners, and the method we developed may also be applied to automatic control of the milking process.     

Fresh and cooked color of dark-cutting beef can be altered by post-rigor enhancement with lactic acid

Fresh and cooked color of dark-cutting (DC) beef strip loins (mean pH = 6.56) enhanced with 0.25, 0.50, 0.75 or 1.00% lactic acid (LA) were compared to non-enhanced DC and normal pH (NpH; mean pH = 5.43) strip loins. Even though NpH steaks received the most (P < 0.05) desirable fresh color scores, color scores for steaks from DC sections enhanced with 0.25% LA approached those of NpH steaks after the first day of retail display. Discoloration scores were also similar (P > 0.05) among NpH and 0.25% LA-enhanced DC steaks throughout the 5 d of display. Fresh steaks from NpH strip loins were redder, as evidenced by greater (P < 0.05) a^* values and lower (P < 0.05) hue angles, than DC steaks and DC steaks enhanced with LA, regardless of concentration. However, cooked color scores and proportions of denatured myoglobin were similar (P > 0.05) between untreated NpH steaks and DC steaks enhanced with 0.25% LA. Results from this study indicate that enhancing DC beef with LA may lead to the brightening of the fresh color and prevention of the persistent red cooked color, approaching that of NpH beef.     

馒头的微波烹制工艺与特性研究

采用正交试验研究加水量、醒发时间、微波剂量和烹制时间对微波烹制馒头感官品质的影响,确定最佳工艺参数,并对比分析微波和蒸汽2种不同烹制方式下馒头的微观形貌、质构特性和消化特性。试验表明,微波烹制馒头的适宜工艺参数为:加水量为50 g/100 g小麦粉,醒发时间为35 min,采用2.76 W/g的微波剂量,烹制时间为2.5 min。在此工艺条件下所制作的馒头感官品质与蒸汽烹制馒头较为接近。与蒸汽烹制馒头相比,微波烹制馒头的口感稍劣;内部微观结构较为粗糙,孔洞均匀性稍差,孔壁较厚,局部区域略呈聚集状,部分网络结构有轻微程度的断裂;硬度、黏聚性和咀嚼度较大,弹性较小;淀粉消化率较高,蛋白质消化特性与之相近。     

大豆营养面包的研制

大豆经过发芽处理消除了不良风味及抗营养因子,添加到面粉中制成豆大豆面包,提高了面包的品质和营养价值,可以替代牛乳生产高级营养面包。     

Characterization of crispness of French fries by fracture and acoustic measurements,effect of pre-frying and final frying times

The influence of pre-frying and final frying time on the crispness of French fries was evaluated by simultaneous analysis of the fracture and acoustic properties during instrumental simulation of human chewing. The analysis of the frequency distribution of the force and sound events corresponding to the crust of the French fry reflected an effect of both pre-frying and final frying time on instrumental crispness. Up to 60 s pre-frying, an increase in the number and magnitude of force and sound events was found, which reflect an increase in crispness. The increase in final frying time increased crispness, but it cannot counterbalance a lack of pre-frying. The moisture content of the whole French fries cannot explained the effect of pre-frying on crispness. Conversely, the effect of pre-frying can be explained when considering only the moisture content of the crust. Pre-frying may allow an easier loss of water from the crust during final frying, which will enhance its crispness.     

Growth and egg production of layer pullets can be affected by the method of supplying energy and protein sources

BACKGROUND: The effects of different methods of offering energy (ES) and protein (PS) sources on growth and egg production of layer pullets were assessed. From 9 to 22 weeks of age, 320 layer chickens (Isa Brown) were allocated to four treatments: 1, control (balanced diet); 2, E60:P40 (ES and PS in balanced diet sequentially during 60 and 40% of daily photoperiod respectively); 3, E40:P60 (ES and PS in balanced diet sequentially during 40 and 60% of daily photoperiod respectively); 4, EPFC (free choice between ES and PS in separate troughs). RESULTS: Sequential or free choice feeding between ES and PS to point of lay decreased feed intake and delayed onset of egg production (P < 0.05). Control pullets had higher body weight at first egg than E60:P40 and E40:P60 birds (P < 0.05). Pullets in the E40:P60 group consumed less ES and more PS than those in other groups (P < 0.05). During the laying period, E40:P60 birds had higher egg production and egg mass than E60:P40 birds. EPFC pullets had lower feed efficiency than control and E40:P60 pullets. CONCLUSION: Offering PS during 60% of the photoperiod to point of lay may decrease feed intake without affecting egg production. Copyright © 2009 Society of Chemical Industry