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Freezing and thawing are heat transfer processes, involving chemical changes which may greatly affect product quality. Due to sparse literature on freeze–thawed cycles and its effects on soups quality, the effect of freeze–thaw cycles on the nutritional quality of selected Nigerian soups has to be investigated. Soups (Ila, Ewedu, Ogbono, and Kuka) were prepared using standard recipes. The soups were packaged in plastic and aluminum containers, frozen at −20°C, and thawed with microwave oven, hot water (100°C), and at ambient condition for four cycles of 5‐day interval. After each cycle, chemical compositions of the samples were determined using AOAC methods. Data were analyzed using ANOVA at P = 0.05. Moisture, protein, fat, crude fiber, ash, and carbohydrate contents of the freeze–thawed soups were 63.6–88.6%, 3.6–8.8%, 1.0–6.1%, 0.8–1.2%, 1.8–4.6%, and 0.9–15.6%, respectively. Mineral contents were iron (5.0–6.8 mg/100 g), calcium (68.1–190.8 mg/100 g), sodium (144.4–231.7 mg/100 g), potassium (200.4–302.1 mg/100 g), and phosphorus (228.0–337.2 mg/100 g). Vitamins were vitamin A (29.5–59.9 mg/100 g), vitamin B (10.1–36.4 mg/100 g), and vitamin E (28.4–90.2 mg/100 g). Microwave‐thawed plastic soups had limited nutritional losses when compared with other thawing methods, and should not be extended beyond the third cycle because of increasing reduction in fat and protein, indicating deterioration.

No abstract

Acha is a less utilized cereal grain in Africa. Scaling up of the processing technology of acha seeds is desirable if accurate information on effect of processing on its properties is available. This study investigated the effect of cooking duration on the chemical and physical properties of acha seeds. Cooking times (2.5, 5, 7.5 and 10 minutes) at 100oC were used. The volume, length, breadth, thickness, porosity, density, sphericity, aspect ratio, specific heat capacity, thermal conductivity, thermal diffusivity, moisture, protein, fat, ash, crude fibre and carbohydrate were determined using standard methods. Data were analysed using ANOVA at p = 0.05. The results obtained revealed that varietal difference had a significant effect on volume, length, breadth, thickness, true density, bulk density, porosity, sphericity and aspect ratio. The moisture content, ash, protein, crude fibre, fat, carbohydrate, specific heat capacity, thermal conductivity and thermal diffusivity varied from 8.80 - 56.17 %, 0.32 - 1.87%, 1.92 - 11.50%, 0.29 - 1.58%, 0.32 - 2.81%, 40.94 - 76.26%, 1.66 -2.97 kJkg-1K-1, 0.26 -0.43 Wm-1K-1 and 0.85 x 10-7 - 1.17 x 10-7 ms-2 respectively, as significantly influenced by cooking time. Cooking for 7.5 minutes was appropriate using the moisture uptakes and thermal properties as criteria.

Selected Nigerian soups were freeze dried with the aim of establishing their storage stabilities and reconstitution potentials. Freshly prepared soups were freeze‐dried under vacuum for 12–14 hr. Sorption isotherms were determined at 27 °C using gravimetric method at water activities (aw) of 0.1 − 0.8. Reconstitution potentials were determined at 30 and 100 °C using gravimetric methods. Data were analyzed using SPSS for the best fit model equations (Peleg, GAB, Oswin, and Langmuir). The rehydration ratios of the freeze dried soups ranged from 1.00 to 9.11 g absorbed water/g dry matter. Soups were optimally reconstituted at 30 °C for 30 min and at 100 °C for 5 min. The equilibrium moisture contents of freeze dried soups ranged from 8.84 to 27.50%. The GAB model was the best estimator for predicting the monolayer moisture contents of the soups, which ranged from 7.87 to 9.82% (dry basis), and were within the acceptable limit of 10% dry basis for good storage stability. Practical applications Traditionally, soups are generally reheated several times in the day to prevent spoilage, while in modern homes, most soups are kept under frozen condition to preserve them and to avoid nutritional loses which can arise as a result of periodical heating once used, but these methods of soup preservation had been shown to lead to losses of nutrients. Development of shelf stable soups that requires little energy to preserve them for considerable length of time is desirable. Freeze drying (FD) is a gentle technique, which retains the nutritional and sensory properties of food products and their final products can be reconstituted easily by simple addition of liquid. The moisture sorption isotherms, which describe water activity food products are of special interest in the design of Nigerian soups FD process and are also required for the prediction of soups storage stability, shelf life, and calculation of drying time.