Chiang Mai Journal of Science

     The negative binomial regression model (NBRM) is a widely used approach for analyzing non-negative count data, particularly when overdispersion is present. Parameter estimation in this model typically relies on the maximum likelihood estimator (MLE), which can produce unstable and unreliable results under multicollinearity. To address this issue, we present a hybrid version of the Kibria-Lukman estimator adapted for NBRM. We evaluate the efficacy of our proposed estimator compared to established methods via simulation studies and a practical application for estimating CO₂ emissions from vehicles in Canada. Our results show that the hybrid Kibria-Lukman estimator is more accurate and stable than traditional methods. This makes it a promising way to deal with multicollinearity in count data analysis.

     The increasing demand for biopolymers in the food industry has increased interest in using alternative resources. Kefiran, which is produced by microorganisms found in kefir grains, is a versatile exopolysaccharide (EPS) that can form gel, an important biopolymer for the food manufacturing. In this study, kefiran extracted by using an EPS isolation method was characterized by rheological analysis according to power law model and determination of functional properties and texture profile analysis. The effects on apparent viscosity (η_a) and flow properties of kefiran concentrations ranging from 1.1 to 3.1% (w/v) were investigated. The results indicated that kefiran solutions at low concentrations exhibited behavior close to Newtonian, whereas at higher concentrations, they showed pseudoplastic (shear-thinning) behavior. This shear-thinning behavior is attributed to hydrogen bonding between hydroxyl groups and water molecules, which contributes to the formation of an entangled polymer network. The results showed that isolated kefiran at a high degree of purity (93.0%) was able to possess good texture profile properties and with a high degree of water holding capacity (WHC) (90.3%), and bloom strength value (53.0 g). Kefiran had a gelling temperature of 14 °C. This study confirms that extracted polysaccharide can be especially used as a gelling agent in fermented dairy products and can also be successfully used as a texture improver biopolymer in food systems.

     Soaking is a crucial preparatory step that strongly influences the texture and sensory quality of cooked glutinous rice. In northern Thailand, the indigenous Lanna practice of partially reusing soaking water, termed wild fermentative soaking, is traditionally believed to enhance the eating quality of glutinous rice. This study investigated the effects of soaking duration (8, 16, and 24 hours) and successive reuse of soaking water (first, second, and third batches) on the physicochemical, microbiological, and sensory properties of two Thai glutinous rice varieties, Kor Khor 6 (RD6) and Sanpatong (SPT). The results showed that extended soaking and water reuse significantly reduced rice hardness while increasing adhesiveness, springiness, and microbial activity. RD6 was more responsive to soaking duration, whereas reused soaking water accelerated fermentation, shortening the time needed to achieve comparable texture level. Microbial analysis revealed a progressive increase in lactic acid bacteria and titratable acidity, with a corresponding decline in pH, especially in reused soaking water. These microbial and biochemical changes were strongly correlated with improvements in textural attributes. Although texture preference did not differ significantly among treatments, correlation analysis showed modest positive associations between adhesiveness (r = 0.28) and gumminess (r = 0.23) with perceived texture. Prolonged soaking beyond 16 hours led to diminished aroma and reduced consumer appeal. Principal component analysis confirmed that early fermentation stages were associated with desirable sensory characteristics, while over-fermentation negatively impacted product quality. These findings indicate that moderate fermentative soaking, particularly an 8-hour soak using reused water, significantly improves texture and sensory appeal of glutinous rice. This approach offers a practical, culturally grounded technique for improving rice quality in both traditional and industrial applications.