Acidity/Rancidity Levels, Chemical Studies, Bacterial Count/Flora of Fermented and Unfermented Silver Catfish (<i>Chrysichthys nigrodigitatus</i>)

The keeping quality and shelf life of fermented and unfermented Chrysichthys nigrodigitatus were monitored in this study. Four kilograms of fresh Chrysichthys nigrodigitatus was minced into fine particles (with an initial pH of 7.2 before distribution into 8 samples). Samples 1-4 are unfermented cooked while Samples 5-8 were fermented, not cooked. All the 8 prepared samples barely lasted for two weeks, while samples 1, 3 and 7 lasted for six weeks. Total Volatile Base (TVB) ranged higher (24.12 - 29.43) mg/100gm in Samples 1-4 than (14.23 - 18.09) mg/100gm recorded in Samples 5-8. In Samples 1-4, FFA values were not significantly (P > 0.05) different;also followed a narrow range of (6.14 - 6.45)% while higher range of (6.42 - 12.27)% recorded in samples (5-8). Peroxide values (PV) increased in all the 8 samples in the second, fourth and sixth week, however higher values were recorded in Samples 5-8. Acidity generally increased with length (weeks) of fermentation with a gradual drop in pH from 7.2 (in the fresh fish) to pH 4.5 (sample 7), the worst sample at six weeks. Sample 4 with bacteria load of 5.05 × 105 at second week and sample 7 (8.2 × 105) at sixth week became unfit for consumption having exceeded the 5.0 × 105 ICMSF standard for safe fish product. Five bacteria species (Lactobacillus sp, Proteus spp, Staphylococcus aureus, Staphylococcus epidermis, Bacillus sp) with the exception of Proteus spwere not represented in sample 1 (due to salt content). Strong positive correlation (r = 0.97, P < 0.01) exists between PV and FFA. Acidityof the fermented products increased over the weeks with strong negative correlation (r = -0.121, P < 0.01) exists between pH and FFA. Acidity (i.e drop in PH) with increasing rancidity since (r = -0.313, P < 0.05) exists between PV and pH.

Indigenous Methods of Processing Shea Butter and Perceptions about Rancidity in Northern Ghana

This study aimed at the geographical variation in methods of processing shea butter that has been passed on from generation to generation and storage procedures （materials and containers used/perceived shelf life of the products used for preservation and local perceptions about rancidity）. Little variation was found in indigenous processing methods, utilization and storage across most of the three regions. Only among the Dagomba tribe in the Northern region did women intentionally use shrubs to add yellow colour to butter particularly that for the market. The use of onions and lemon/lime leaves to prevent rancidity and also improve the taste and smell of butter was found to be practiced by only one missionary group. Perception about shelf life of the butter was found to vary widely among the processors and consumers （3 months to 2 years）. Though this was the main focus of the study, most of the indigenous processors and consumers apart from the missionary group had little experience as far as this problem was concerned. This was due to the fact that most of them consumed the butter within one or two months after processing and so the product is not kept long enough to give any appreciable signs of rancidity.

Aflatoxin Contamination and Rancidity in Locally Processed Commercial Fish Feeds and Ingredients along the Value Chain in Wakiso and Kampala Districts, Uganda

Aflatoxin contamination and rancidity in locally processed commercial fish feeds and ingredients along value chains is a Public and Animal health hazard. The study established the level of aflatoxin contamination, peroxide value (PV), Anisidine value (AnV), and their associated factors at storage areas among farmers, processors, traders, factories, and landing sites in the Wakiso and Kampala districts. The value chain actors were purposively selected in a cross-sectional study based on access to the feed store and the use of locally processed commercial fish feeds on farms. Data collected were statistically analyzed in SPSS version 20. All the samples (45) were positive for aflatoxin contamination and PV with 51% (23/45) of samples being contaminated with “above acceptable” aflatoxin levels and 66.6% (30/45) of samples with “above acceptable” PV. The overall percentage of “above acceptable” AnV was 11/29 (37.9%). Samples from factories were within acceptable contamination levels. Multivariate logistic regression analysis revealed no significant difference between aflatoxin contamination, peroxide, and Anisidine value with storage factors for locally processed commercial fish feeds and ingredients. The study recommended the purchase of fish feeds from factories and a larger study on storage factors responsible for aflatoxin contamination and rancidity in fish feeds in Uganda.

The Effect of Processing Variables on Antioxidative Capacity of Mangosteen Peel （Garcinia mangostana L.） Extract

Mangosteen peel （Garcinia mangostana L.） is well known as an excellent source of antioxidative compounds. The objective of this study was to determine the most suitable processing condition for ethanolic extraction of mangosteen peel. The experimental factors included raw material prepared as fresh and dried forms, material-to-solvent ratio varying at 1：3, 1：4, 1：5, 1：6, 1：9 and 1：12, and contacting time at 1, 3, 6, 9, 12 and 16 hours. Antioxidative capacity of all extracts were evaluated and compared according to DPPH radical scarvenging assay, trolox equivalent antioxidant capacity （TEAC assay） and total phenolic compounds. It was found that the extract from dried mangosteen peel had significantly stronger antioxidative capacity than that from fresh mangosteen peel （P 〈 0.05）. The suitable ethanolic extraction was found at the material-to-solvent ratio of 1：6 and 12 hours of contacting time. Mangosteen peel extracts prepared from fresh peel, dried peel, boiled and dried peel were also tested for oxidative rancidity reduction in lard at accelerated temperature of 60 ~C. The antioxidative rancidity was measured by acid value, totox value and thiobarbituric acid test. Commercial rosemary extract and BHT were compared at the equivalent concentration of 1,000 mg/kg. The results showed that the extract from dried mangosteen peel provided antioxidative capacity slightly stronger than fresh mangosteen peel extract, similar to rosemary extract but still poorer than BHT.

Nano-Microencapsulation and Controlled Release of Linoleic Acid in Biopolymer Matrices: Effects of the Physical State, Water Activity, and Quercetin on Oxidative Stability

In this study, linoleic acid (LA) was encapsulated in the presence or absence of quercetin into a dual polymer system of whey protein and kappa-carrageenan using power ultrasound. Atomic Force Microscopy (AFM) and FlowCam imaging technology were used for imaging and size determination of nano-and micro-capsules. Differential scanning calorimeter (DSC) was used to determine the glass transition temperature (Tg) of the freeze-dried nanocapsules. In order to examine the effect of water activity (aw) on the release profile of the encapsulated LA, the nanocapsules were equilibrated over saturated salt solution conditions corresponding to the range of aw between 0.333 and 0.769 in evacuated desiccators at room temperature. Gravimetric measurements of the steady state linoleic acid (LA) contents were conducted. The anti-oxidant activity of quercetin and the stability of encapsulated LA toward long term and thermally induced rancidity was investigated. The capsules were in the nanosize regime and 83% of the LA was effectively encapsulated. Furthermore, at aw of 0.764, the highest percentage of LA (74%) was released from the expelling nanocapsules. Quercetin was found to exhibit protective antioxidant effect against time-dependent oxidation and thermally induced rancidity of LA. Water activity values of 0.662 and 0.764 provided ideal humidity and pressure conditions for sustained release of nanoencapsulated LA at room temperature.