Cereal Chem. 81(2):232-236The effect of hydration level on processing properties and the effects of hydration level, concentration of buckwheat bran flour and drying temperature on the physical and cooking quality of spaghetti were determined. Specific mechanical energy transferred to the dough during extrusion decreased 69% for semolina and 79% for semolina containing 30%, w/w, buckwheat bran flour, as hydration level increased 29-32% absorption. Little or no postdrier checking occurred in spaghetti made from semolina or spaghetti containing buckwheat bran flour when dried at high (70°C) or ultrahigh temperature (90°C). When dried at low temperature (40°C), tolerance to postdrier checking of spaghetti decreased as buckwheat bran flour increased 0-30% (w/w). Hydration level before extrusion did not affect cooking loss of spaghetti made from semolina. However, cooking loss was greater from spaghetti made with semolinabuckwheat bran flour that was hydrated to 32% compared with 29-31% absorption. Cooked firmness of spaghetti containing buckwheat bran flour decreased from 0.588-0.471 Nm as hydration increased from 29-32% absorption. Cooking loss was lower and cooked firmness was greater when spaghetti containing buckwheat bran flour was dried at ultrahigh than at low temperature.

The 2001 durum wheat crop grown in the Northern Plains was surveyed for microbial loads, mycotoxins, and quality. Correlations among these factors were identified. Effects of cleaning, milling, and pasta processing on microbial loads and deoxynivalenol (DON) concentrations were determined. Aerobic plate counts (APCs), mold and yeast counts (MYCs), internal mold infection (IMI), and internal Fusarium infection (IFI) were lowest in grain samples from Montana and highest in grain from northeastern North Dakota. DON and 15-acetyldeoxynivalenol (15-ADON) were not detected in samples from Montana. Nivalenol was not detected in any samples. DON in North Dakota samples ranged from none detected to 23 micrograms/g. 15-ADON was detected in a few North Dakota samples, with a maximum of 0.8 microgram/g. DON positively correlated with APCs, MYCs, IFI, damaged kernels, total defects, U.S. grade number, and tombstone kernel content and negatively correlated with test weight, vitreous kernel content, and kernel weight. APCs, MYCs, and DON concentrations were lower in semolina than whole grain. Processing semolina into spaghetti did not change DON concentrations. APCs for spaghetti were reduced 2.2 to 4.1 logs from those for semolina, whereas MYCs were reduced 0.1 to 1.7 log. Some APCs in durum flour and semolina were higher than certain industry specifications would allow, although other factors were acceptable. However, microbial loads in the spaghetti were all within specifications found in the available literature.

Specific mechanical energy (SME), mechanical energy, extrusion rate and temperature of extruded spaghetti were monitored to determine the effects of semolina, hydration level and nontraditional ingredients on pasta extrusion using a semi-commercial pasta press with a fixed screw speed of 25 rpm. SME transferred to the dough during extrusion and the temperature of extruded spaghetti were greater with strong than with weak gluten semolina and at low than at high absorption levels. When compared with semolina hydrated to 300 g kg −1 absorption, SME transferred to the dough was 13 kJ kg −1 lower for semolina mixed with buckwheat (Fagopyrum esculentum Moench.) bran flour, 47 kJ kg −1 lower for semolina mixed with flaxseed (Linum usitativissimum L.) flour and 7 kJ kg −1 lower for semolina mixed with wheat (Triticum turgidum var. durum L.) bran. Weak gluten semolina, high absorption levels and non-traditional ingredients reduced the mechanical energy required for extrusion more than they reduced extrusion rate. The target temperature for extruded spaghetti was 45 • C. The temperature of extruded spaghetti containing flaxseed flour was below 45 • C whereas the temperature of spaghetti containing wheat bran was above 45 • C, regardless of semolina type or absorption level. INTRODUCTIONSeveral studies have reported on the effects of processing conditions on physical and cooking quality of pasta. 1 -3 Water absorption of semolina and temperature of the extrusion barrel have been shown to affect brightness, yellowness, cooked firmness, cooked weight and cooking loss of pasta. 1,2 Abecassis et al. 3 reported that extrusion speed, temperature and pressure in the extruder affected pasta quality. They found that increasing the hydration level of semolina from 440 to 480 g kg −1 (dry basis) and the rotational speed of the screw from 15 to 30 rpm enhanced the cooking quality of pasta. Each study cited above used a single source of commercial semolina.Information seems to be lacking concerning the effects of gluten strength on the extrusion properties of hydrated semolina. Strength of pasta dough is determined by gluten strength of the protein in the semolina and by the level of hydration. 3,4 Dough strength can affect the amount of mechanical energy required to extrude and the rate of extrusion. 5 Abecassis et al. 3 reported that an increase in dough temperature or in hydration level decreased dough strength and subsequently decreased specific mechanical energy (SME) transferred to the pasta during extrusion.