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Use of different Storage Packaging Materials
Kaced et al (1984) compared cotton and polyethylene bags for pearl millet flour storage.
The fat acidity increased more rapidly in pearl millet flour sample that was stored in cotton bags than the one, which was stored in the polyethylene bags. The fat acidity for flours stored in cotton and polyethylene bags increased from 0.4 to 2.2 and 1.5 g KOH kg-1 meal, respectively within 150 h of storage. This effect was explained as being due to the cotton bags allowing moisture entry as was indicated by a marked increase in flour moisture level, which favours lipase hydrolytic activity hence an increased fat acidity.
Nevertheless, the increases in fat acidity indicate that triglyceride deterioration is not adequately curbed by either cotton bag or polyethylene bag. Moreover, storing products that are prone to triglyceride deterioration in polyethylene bags may not be a wise idea, especially if the storage duration spans several months. This is because polyethylene may contain a plasticiser that gives the bag its flexibility (Potter and Hotchkiss, 1995). The plasticiser could react with the triglyceride deterioration products leading to undesirable effects on both the packaging material and perhaps the food product stored in them (Potter and Hotchkiss, 1995). Polyethylene bags are most likely to be impermeable to triglyceride deterioration volatiles (Potter and Hotchkiss, 1995). This may lead to trapping and accumulation of these volatiles of disagreeable odours. Cotton or paper bags that would permit the escape of volatiles could be preferred for storing whole pearl millet flour. Cotton and paper bags may also be of economical importance to both the consumer and the environment.
Acid-Soaking
Chavan and Kachare (1994) used 0.05 M hydrochloric acid solution to soak pearl millet grain for 12 h at ambient temperature. This method was aimed at lowering the pH to inactivate the lipase enzymes. The grain was washed with tap water and dried to 10% moisture before milling. The flour was stored in cloth bags at ambient conditions. It was analysed for changes in fat acidity during 30 days storage. They found that fat acidity of untreated flour increased by about 6-fold. The fat acidity of acid-soaked grain flour increased by about 1.5-fold. This indicates that this treatment inhibited the hydrolysis of triglycerides quite substantially. Hydrochloric acid, however, introduced questionable effects such as bleaching of the flour and imparted a sour taste to the flour (Chavan and Kachare, 1994). These effects could also result in objectionable sensory quality in food products made from the flour.
Antioxidants
Antioxidants are compounds that retard autoxidation of triglycerides (Eskin and Przybylski, 2001). Antioxidants can be classified into two broad categories, namely primary and secondary ones. Primary antioxidants act by inhibiting the radical propagation stages in the triglyceride oxidation process (Eskin and Przybylski, 2001).
Examples of primary antioxidants include butylated hydroxy anisole (BHA), tocopherols and a range of phenolics. Secondary antioxidants may act as oxygen scavengers, chelating agents and/or hydrogen donors to the primary antioxidants (Eskin and Przybylski, 2001). An example of secondary antioxidant could be ascorbic acid.
Ascorbic acid acts by scavenging for oxygen or chelating pro-oxidant metal ions (Eskin and Przybylski, 2001). Kapoor and Kapoor (1990) studied the effects of adding BHA, butylated hydroxy toluene and ascorbic acid to whole pearl millet flour on its shelf life. They found that addition of these antioxidants resulted only in a slight decrease in the peroxide level in comparison to the control sample during storage. This indicates their ineffectiveness in preventing triglycerides deterioration. Another important issue is that the use of synthetic chemicals such as BHA has also been met with skeptism from consumers many of whom today demand food products without synthetic additives (Eskin and Przybylski, 2001).
CHAPTER 1: INTRODUCTION
1.1 STATEMENT OF PROBLEM
1.2 LITERATURE REVIEW
1.3 OBJECTIVES
1.4 HYPOTHESES
CHAPTER 2: RESEARCH
Abstract
2.1 INTRODUCTION
2.2 MATERIALS AND METHODS
2.3 RESULTS AND DISCUSSION
2.4 CONCLUSIONS
2.5. REFERENCES
CHAPTER 3: GENERAL DISCUSSION
3.1 Principles, strengths and weaknesses of lipid extraction, lipid quality assays, degree of cook and sensory evaluations
3.2 Effect of thermal treatments on lipid quality, degree of cook and sensory evaluations
3.3 Practicalities and energy demand estimation of thermal treatments as processing techniques in the production of whole pearl millet flour in rural areas of Namibia
CHAPTER 4: CONCLUSIONS AND RECOMMENDATIONS
CHAPTER 5: REFERENCES
PRESENTATION ON THE RESEARCH
