EXTRUSION COOKING OF SWEET POTATO ROOTS1

An extruded product was prepared using a mixture of sweet potato roots (SP), high protein wheat flour (WF), oil and water. The mixture was extruded in a Wenger X-5 extruder. The best physical characteristics of the extruded product were obtained using drum dried baked sweet potato powder (DDSPP) and WF in the ratio of 3:1, oil content of 4.0% and an initial moisture content of 12.32%. This combination yielded a 4.33 fold expansion of the product. Physical measurements on the extruded product were: diameter, bulk density, expansion, and percent rehydration. The carotenoid content of the extruded product did not change considerably from that of DDSPP. The use of DDSPP: WF ratio of 3:1 represented 89.86% utilization of raw SP roots on a fresh weight basis.     

SINGLE-SCREW EXTRUSION OF PORK AND SOY FLOUR BLEND

This study examined the rheological properties of defatted soy flour and lean pork blend of various moisture contents extruded in a single-screw extruder and the sensory texture property of extruded meat analogs as the first step to develop commercial low-cost meat analogs that not only resemble real meats but have excellent sensory textures. Additional work was also conducted to examine the effect of moisture content of soy flour under the extrusion condition (high temperature and pressure) on the fiber structure and overall texturization of the extrudate as a result of changes in chemical bonds between soy proteins. The mixture of soy meal with ground lean pork showed significant decrease in viscosity as compared with either soy meal or ground meat alone. The best sensory texture was obtained for the pork-soy flour blend with 41. 3% moisture content at screw speed of 180 rpm under the feeding-metering-die temperature setting of 140–170–80C.     

DESTRUCTION OF POTATO PEEL TRYPSIN INHIBITOR BY PEELING AND EXTRUSION COOKING

Potato peels, a by-product of potato processing, can serve as a source of concentrated dietary fiber, but potato trypsin inhibitors (TI) in peels could reduce nutritional quality. Peels prepared by two methods (abrasion or steam) were extruded at 110C or 150C with feed moistures of either 30% or 35%. Prior to extrusion, abrasion and steam peels contained 45.57 and 8.06 TIU/g, respectively. Extrusion reduced TI activity by 75–85% in abrasion peels, but no reductions were observed for steam peels. TI may not pose a nutritional problem for steam peels with or without extrusion. Abrasion peels should be extruded, or processed by another thermal method, prior to use in foods.     

EFFECT OF SONIC ENERGY ON THE AIR DRYING OF APPLE AND SWEET POTATO CUBES

Cubes (2 cc) of apple and sweet potato were dried with and without sound energy in air at velocities of 5 – 20 fps and temperatures of 125 – 175°F. A stem jet or electronic whistle provided sound energy at 9,800 and 13,000 Hz with an intensity up to 135 dB. Results indicated that sonic energy had no effect on drying rate under all experimental conditions.     

EXTRUSION COOKING OF RICE: EFFECT OF AMYLOSE CONTENT AND BARREL TEMPERATURE ON PRODUCT PROFILE

The effect of amylose content (5.0–28.6%) of rice and barrel temperature (80–120C) on extrusion system parameters torque and net specific mechanical energy and extrudate characteristics extrudate bulk density (ED), water solubility index, expansion ratio (ER) and Warner–Bratzler shear stress were studied using a twin‐screw extruder. The feed rate (15 kgh^?1), moisture content (20.0% ± 0.2) of feed and the screw speed (400 rpm) were kept constant. ED and ER of the product suggested that a barrel temperature of 120C was desirable to generate an expanded extrudate rice product from low‐amylose rice cultivar. Experimental data on system parameters and extrudate characteristics fit to second‐degree polynomial regression equations (r ≥ 0.904, P ≤ 0.01) with the amylose content of rice and barrel temperature of the extruder.     

PRODUCTION AND PROXIMATE COMPOSITION OF A HYDROPONIC SWEET POTATO FLOUR DURING EXTENDED STORAGE

In developing countries, where limited transport infrastructure exists, processing the sweet potato (Ipomoea batatas (L.) Lam) into flour provides an alternative to the difficulties associated with storage and transport of the raw roots. The objectives of this study were: (1) to process hydroponic sweet potato roots into flour; and (2) to evaluate the nutritive composition and the color of the processed hydroponic sweet potato flour during storage. The TU–82–155 hydroponic sweet potatoes were processed into flour and stored for five months at room and refrigerated temperatures. The sweet potato flour contained 3.0%, 4.5%, 1.0%, 1.0%, 90.6% moisture, ash, fat, protein, and carbohydrate, respectively, with no significant changes during storage. The *L values for the sweet potato flour increased as storage time increased, but the *a and *b values decreased. Hydroponic sweet potato roots could be processed into flour and stored at 4C or 21C to 25C for five months without deterioration in quality.     

甘薯纤维提取工艺及应用研究

对利用甘薯渣提取纤维的工艺以及甘薯纤维的理化特性进行研究.结果表明:采用甘薯渣制糖残渣提取纤维为适宜工艺.对甘薯纤维理化特性的测定表明,甘薯纤维是一种优良的食物纤维.甘薯纤维在焙烤食品生产的应用结果表明,为保证产品的质量,其添加量不能过多,在面包和蛋糕中的添加量分别不能超过7%和6%.     

MODELING THE TEMPERATURE EFFECT ON THE FLOW BEHAVIOR OF SWEET POTATO PUREE1

A study was conducted to investigate the effect of temperature on viscosity of sweet potato (SP) puree. Rheological data of the puree were measured using a Bohlin VOR Rheometer. Shear rates employed ranged from 0.01–921 s^?1. Thermal scans were run at 15, 25, 40, 60, 75, and 90C. The puree exhibited “shear thinning” behavior with a yield stress value of 10 Pa at each temperature tested. The characteristic of the flow behavior of the puree was determined by fitting the experimental data to Herschel-Bulkley, Casson and Modified Casson models. The model with the best fit was then used to represent the combined effect of shear rate and temperature on the apparent viscosity of SP puree in a model based upon the Modified Casson model. The model was validated using data for SP puree samples at 50C. Results showed that, within the experimental conditions used in this study, the model could adequately predict apparent viscosities of sweet potato puree processed at different temperatures.     

EFFECTS OF SOY PROTEIN AND FREEZING TREATMENTS ON COOKING LOSS AND COMPOSITION OF BEEF PATTIES

All-beef and soy-extended patties were frozen to −18°C in either 24, 48, 72 or 96h and stored at −23, −18 or −7°C for 6, 9, 12, 18 or 24 months. The addition of soy resulted in a substantial reduction in cooking loss for patties cooked from the frozen state with a greater retention of moisture in cooked patties. Freezing reduced cooking loss for soy-extended patties, but increased cooking loss for all-beef patties. Faster freezing (-18°C in 24 h vs. −18°C in 96 h) reduced cooking loss and produced higher moisture values in all-beef patties. Patties stored at –7°C lost more moisture during cooking. Increased frozen storage time had a minimal effect on cooking losses, moisture and fat levels. Where it is essential for frozen patties to sustain minimal cooking losses with maximal moisture in cooked patties, the inclusion of soy protein concentrate, faster freezing, and storage at –18°C or colder are suggested.     

酸碱挤压联合作用对膳食纤维组成的影响

研究了酸碱预处理与挤压联合对大豆纤维进行加工的作用，结果表明：酸的浓度和强度以及碱浓度和水的数量对可溶性纤维（SDF）的转化都有利。变化主要发生在半纤维素部分，而纤维素所受影响很小。     

不同加热温度和时间对食用调和油品质的影响

研究了在130℃、150℃和170℃下,加热0～12h对食用调和油的酸价（AV）、过氧化值（POV）及丙二醛（MAD）含量的影响.结果表明：食用调和油的AV、POV随加热温度和时间的增加而增加,MAD含量随加热温度的增加而增加,随时间的延长开始增加,达到一最大值后又下降.     

紫甘薯米酒生产工艺的研究

以紫甘薯、糯米为主要原料，将二者混合进行发酵。通过一系列单因子试验和正交试验确定出紫甘薯米酒生产的较佳工艺条件为：发酵时间51h，糯米与紫甘薯的质量比为10：1，混合物料与酒曲的质量比为7：1，发酵温度为28℃。